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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 120 journals)
Showing 1 - 30 of 30 Journals sorted alphabetically
Acta Astronautica     Hybrid Journal   (Followers: 483)
Advances in Aerospace Engineering     Open Access   (Followers: 66)
Advances in Aerospace Science and Technology     Open Access   (Followers: 7)
Advances in Astronautics Science and Technology     Hybrid Journal  
Advances in Space Research     Full-text available via subscription   (Followers: 454)
Aeronautical Journal, The     Hybrid Journal   (Followers: 10)
Aerospace     Open Access   (Followers: 57)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 14)
Aerospace Science and Technology     Hybrid Journal   (Followers: 422)
Aerospace Scientific Journal     Open Access   (Followers: 15)
Aerospace Systems     Hybrid Journal   (Followers: 3)
Aerospace technic and technology     Open Access   (Followers: 2)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal  
AIAA Journal     Hybrid Journal   (Followers: 1175)
Air Force Magazine     Full-text available via subscription   (Followers: 11)
Air Medical Journal     Hybrid Journal   (Followers: 8)
Annual of Navigation     Open Access   (Followers: 22)
Artificial Satellites     Open Access   (Followers: 23)
ASTRA Proceedings     Open Access   (Followers: 2)
Astrodynamics     Hybrid Journal   (Followers: 1)
Aviation     Open Access   (Followers: 15)
Aviation Advances & Maintenance     Open Access   (Followers: 3)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 10)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 26)
Aviation Week     Full-text available via subscription   (Followers: 437)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 33)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 29)
Chinese Journal of Aeronautics     Open Access   (Followers: 20)
Ciencia y Poder Aéreo     Open Access   (Followers: 2)
Civil Aviation High Technologies     Open Access   (Followers: 5)
Control Systems     Hybrid Journal   (Followers: 317)
Cosmic Research     Hybrid Journal   (Followers: 4)
COSPAR Colloquia Series     Full-text available via subscription   (Followers: 11)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 24)
Elsevier Astrodynamics Series     Full-text available via subscription   (Followers: 12)
Fatigue of Aircraft Structures     Open Access   (Followers: 15)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 12)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 255)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 276)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 383)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 39)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 39)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 36)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 2)
International Journal of Aerospace Engineering     Open Access   (Followers: 80)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 23)
International Journal of Aerospace Sciences     Open Access   (Followers: 30)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 7)
International Journal of Aviation Management     Hybrid Journal   (Followers: 8)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 7)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 4)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 12)
International Journal of Micro Air Vehicles     Full-text available via subscription   (Followers: 11)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 13)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 11)
International Journal of Space Structures     Full-text available via subscription   (Followers: 17)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 10)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 5)
International Journal of Turbo and Jet-Engines     Hybrid Journal   (Followers: 6)
Investigación Pecuaria     Open Access   (Followers: 3)
Journal of Aerodynamics     Open Access   (Followers: 17)
Journal of Aeronautical Materials     Open Access   (Followers: 9)
Journal of Aeronautics & Aerospace Engineering     Open Access   (Followers: 28)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 68)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 16)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 20)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 32)
Journal of Aerospace Technology and Management     Open Access   (Followers: 7)
Journal of Aircraft     Hybrid Journal   (Followers: 338)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 8)
Journal of Airline and Airport Management     Open Access   (Followers: 12)
Journal of Astrobiology & Outreach     Open Access   (Followers: 3)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 11)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 2)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 1)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 204)
Journal of KONBiN     Open Access   (Followers: 3)
Journal of Navigation     Hybrid Journal   (Followers: 279)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 609)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 7)
Journal of Space Weather and Space Climate     Open Access   (Followers: 27)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 770)
Journal of Spatial Science     Hybrid Journal   (Followers: 3)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 7)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 8)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 1)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 16)
Life Sciences in Space Research     Hybrid Journal   (Followers: 3)
MAD - Magazine of Aviation Development     Open Access   (Followers: 2)
Mekanika : Jurnal Teknik Mesin i     Open Access   (Followers: 1)
Microgravity Science and Technology     Hybrid Journal   (Followers: 2)
New Space     Hybrid Journal   (Followers: 6)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
npj Microgravity     Open Access   (Followers: 3)
Open Aerospace Engineering Journal     Open Access   (Followers: 1)
Population Space and Place     Hybrid Journal   (Followers: 9)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 3)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 16)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 45)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 79)
Propulsion and Power Research     Open Access   (Followers: 67)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 17)
RocketSTEM     Free   (Followers: 6)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 24)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 1)
Space and Polity     Hybrid Journal   (Followers: 4)
Space Policy     Hybrid Journal   (Followers: 30)
Space Research Today     Full-text available via subscription   (Followers: 48)
Space Safety Magazine     Free   (Followers: 51)
Space Science International     Open Access   (Followers: 192)
Space Science Reviews     Hybrid Journal   (Followers: 97)
SpaceNews     Free   (Followers: 824)
Spatial Information Research     Hybrid Journal   (Followers: 1)
Technical Soaring     Full-text available via subscription   (Followers: 1)
Transport and Aerospace Engineering     Open Access   (Followers: 1)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 8)
Unmanned Systems     Hybrid Journal   (Followers: 5)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 2)

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Journal Prestige (SJR): 0.305
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Number of Followers: 57  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2226-4310
Published by MDPI Homepage  [233 journals]
  • Aerospace, Vol. 8, Pages 11: Evolution of Emission Species in an
           Aero-Engine Turbine Stator

    • Authors: André A.V. Perpignan, Stella Grazia Tomasello, Arvind Gangoli Rao
      First page: 11
      Abstract: Future energy and transport scenarios will still rely on gas turbines for energy conversion and propulsion. Gas turbines will play a major role in energy transition and therefore gas turbine performance should be improved, and their pollutant emissions decreased. Consequently, designers must have accurate performance and emission prediction tools. Usually, pollutant emission prediction is limited to the combustion chamber as the composition at its outlet is considered to be “chemically frozen”. However, this assumption is not necessarily valid, especially with the increasing turbine inlet temperatures and operating pressures that benefit engine performance. In this work, Computational Fluid Dynamics (CFD) and Chemical Reactor Network (CRN) simulations were performed to analyse the progress of NOx and CO species through the high-pressure turbine stator. Simulations considering turbulence-chemistry interaction were performed and compared with the finite-rate chemistry approach. The results show that progression of some relevant reactions continues to take place within the turbine stator. For an estimated cruise condition, both NO and CO concentrations are predicted to increase along the stator, while for the take-off condition, NO increases and CO decreases within the stator vanes. Reaction rates and concentrations are correlated with the flow structure for the cruise condition, especially in the near-wall flow field and the blade wakes. However, at the higher operating pressure and temperature encountered during take-off, reactions seem to be dependent on the residence time rather than on the flow structures. The inclusion of turbulence-chemistry interaction significantly changes the results, while heat transfer on the blade walls is shown to have minor effects.
      Citation: Aerospace
      PubDate: 2021-01-04
      DOI: 10.3390/aerospace8010011
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 12: Axial Flow Compressor Stability Enhancement:
           Circumferential T-Shape Grooves Performance Investigation

    • Authors: Marco Porro, Richard Jefferson-Loveday, Ernesto Benini
      First page: 12
      Abstract: This work focuses its attention on possibilities to enhance the stability of an axial compressor using a casing treatment technique. Circumferential grooves machined into the case are considered and their performances evaluated using three-dimensional steady state computational simulations. The effects of rectangular and new T-shape grooves on NASA Rotor 37 performances are investigated, resolving in detail the flow field near the blade tip in order to understand the stall inception delay mechanism produced by the casing treatment. First, a validation of the computational model was carried out analysing a smooth wall case without grooves. The comparisons of the total pressure ratio, total temperature ratio and adiabatic efficiency profiles with experimental data highlighted the accuracy and validity of the model. Then, the results for a rectangular groove chosen as the baseline case demonstrated that the groove interacts with the tip leakage flow, weakening the vortex breakdown and reducing the separation at the blade suction side. These effects delay stall inception, improving compressor stability. New T-shape grooves were designed keeping the volume as a constant parameter and their performances were evaluated in terms of stall margin improvement and efficiency variation. All the configurations showed a common efficiency loss near the peak condition and some of them revealed a stall margin improvement with respect to the baseline. Due to their reduced depth, these new configurations are interesting because they enable the use of a thinner light-weight compressor case as is desirable in aerospace applications.
      Citation: Aerospace
      PubDate: 2021-01-04
      DOI: 10.3390/aerospace8010012
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 13: Quasi-3D Aerodynamic Analysis Method for
           Blended-Wing-Body UAV Configurations

    • Authors: Pericles Panagiotou, Thomas Dimopoulos, Stylianos Dimitriou, Kyros Yakinthos
      First page: 13
      Abstract: The current study presents a low-fidelity, quasi-3D aerodynamic analysis method for Blended-Wing-Body (BWB) Unmanned Aerial Vehicle (UAV) configurations. A tactical BWB UAV experimental prototype is used as a reference platform. The method utilizes 2D panel method analyses and theoretical aerodynamic calculations to rapidly compute lift and pitching moment coefficients. The philosophy and the underlying theoretical and semi-empirical equations of the proposed method are extensively described. Corrections related to control surfaces deflection and ground effect are also suggested, so that the BWB pitching stability and trimming calculations can be supported. The method is validated against low-fidelity 3D aerodynamic analysis methods and high-fidelity, Computational Fluid Dynamics (CFD) results for various BWB configurations. The validation procedures show that the proposed method is considerably more accurate than existing low-fidelity ones, can provide predictions for both lift and pitching moment coefficients and requires far less computational resources and time when compared to CFD modeling. Hence, it can serve as a valuable aerodynamics and stability analysis tool for BWB UAV configurations.
      Citation: Aerospace
      PubDate: 2021-01-06
      DOI: 10.3390/aerospace8010013
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 14: Climate Impact Mitigation Potential of
           Formation Flight

    • Authors: Tobias Marks, Katrin Dahlmann, Volker Grewe, Volker Gollnick, Florian Linke, Sigrun Matthes, Eike Stumpf, Majed Swaid, Simon Unterstrasser, Hiroshi Yamashita, Clemens Zumegen
      First page: 14
      Abstract: The aerodynamic formation flight, which is also known as aircraft wake-surfing for efficiency (AWSE), enables aircraft to harvest the energy inherent in another aircraft’s wake vortex. As the thrust of the trailing aircraft can be reduced during cruise flight, the resulting benefit can be traded for longer flight time, larger range, less fuel consumption, or cost savings accordingly. Furthermore, as the amount and location of the emissions caused by the formation are subject to change and saturation effects in the cumulated wake of the formation can occur, AWSE can favorably affect the climate impact of the corresponding flights. In order to quantify these effects, we present an interdisciplinary approach combining the fields of aerodynamics, aircraft operations and atmospheric physics. The approach comprises an integrated model chain to assess the climate impact for a given air traffic scenario based on flight plan data, aerodynamic interactions between the formation members, detailed trajectory calculations as well as on an adapted climate model accounting for the saturation effects resulting from the proximity of the emissions of the formation members. Based on this approach, we derived representative AWSE scenarios for the world’s major airports by analyzing and assessing flight plans. The resulting formations were recalculated by a trajectory calculation tool and emission inventories for the scenarios were created. Based on these inventories, we quantitatively estimated the climate impact using the average temperature response (ATR) as climate metric, calculated as an average global near surface temperature change over a time horizon of 50 years. It is shown, that AWSE as a new operational procedure has a significant mitigation potential on climate impact. For a global formation flight scenario, we estimated the average relative change of climate response to range between 22% and 24% while the relative fuel saving effects sum up to 5–6%.
      Citation: Aerospace
      PubDate: 2021-01-08
      DOI: 10.3390/aerospace8010014
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 15: Effect of Increased Cabin Recirculation
           Airflow Fraction on Relative Humidity, CO2 and TVOC

    • Authors: Victor Norrefeldt, Florian Mayer, Britta Herbig, Ria Ströhlein, Pawel Wargocki, Fang Lei
      First page: 15
      Abstract: In the CleanSky 2 ComAir study, subject tests were conducted in the Fraunhofer Flight Test Facility cabin mock-up. This mock-up consists of the front section of a former in-service A310 hosting up to 80 passengers. In 12 sessions the outdoor/recirculation airflow ratio was altered from today’s typically applied fractions to up to 88% recirculation fraction. This leads to increased relative humidity, carbon dioxide (CO2) and Total Volatile Organic Compounds (TVOC) levels in the cabin air, as the emissions by passengers become less diluted by outdoor, dry air. This paper describes the measured increase of relative humidity, CO2 and TVOC level in the cabin air for the different test conditions.
      Citation: Aerospace
      PubDate: 2021-01-13
      DOI: 10.3390/aerospace8010015
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 16: Proof of Concept Study for Fuselage Boundary
           Layer Ingesting Propulsion

    • Authors: Arne Seitz, Anaïs Luisa Habermann, Fabian Peter, Florian Troeltsch, Alejandro Castillo Pardo, Biagio Della Corte, Martijn van Sluis, Zdobyslaw Goraj, Mariusz Kowalski, Xin Zhao, Tomas Grönstedt, Julian Bijewitz, Guido Wortmann
      First page: 16
      Abstract: Key results from the EU H2020 project CENTRELINE are presented. The research activities undertaken to demonstrate the proof of concept (technology readiness level—TRL 3) for the so-called propulsive fuselage concept (PFC) for fuselage wake-filling propulsion integration are discussed. The technology application case in the wide-body market segment is motivated. The developed performance bookkeeping scheme for fuselage boundary layer ingestion (BLI) propulsion integration is reviewed. The results of the 2D aerodynamic shape optimization for the bare PFC configuration are presented. Key findings from the high-fidelity aero-numerical simulation and aerodynamic validation testing, i.e., the overall aircraft wind tunnel and the BLI fan rig test campaigns, are discussed. The design results for the architectural concept, systems integration and electric machinery pre-design for the fuselage fan turbo-electric power train are summarized. The design and performance implications on the main power plants are analyzed. Conceptual design solutions for the mechanical and aero-structural integration of the BLI propulsive device are introduced. Key heuristics deduced for PFC conceptual aircraft design are presented. Assessments of fuel burn, NOx emissions, and noise are presented for the PFC aircraft and benchmarked against advanced conventional technology for an entry-into-service in 2035. The PFC design mission fuel benefit based on 2D optimized PFC aero-shaping is 4.7%.
      Citation: Aerospace
      PubDate: 2021-01-13
      DOI: 10.3390/aerospace8010016
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 17: The Efficacy of Operational Bird Strike

    • Authors: Isabel Metz, Joost Ellerbroek, Thorsten Mühlhausen, Dirk Kügler, Stefan Kern, Jacco Hoekstra
      First page: 17
      Abstract: Involving air traffic controllers and pilots into the bird strike prevention process is considered an essential step to increase aviation and avian safety. Prior to implementing operational measures such as real-time warning systems, it is vital to evaluate their feasibility. This paper studies the efficacy of a bird strike advisory system for air traffic control. In addition to the potential safety benefit, the possible impact on airport operations is analyzed. To this end, a previously developed collision avoidance algorithm underlying the system was tested in fast-time Monte Carlo simulations involving various air traffic and bird densities to obtain representative conclusions for different operational conditions. The results demonstrate the strong safety potential of operational bird strike prevention in case of precise bird movement prediction. Unless airports operate close to their capacity limits while bird abundance is high, the induced delays remain tolerable. Prioritization of hazardous strikes involving large individuals as well as flocks of birds are expected to support operational feasibility in all conditions.
      Citation: Aerospace
      PubDate: 2021-01-14
      DOI: 10.3390/aerospace8010017
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 18: Unmanned Aerial Vehicle Pitch Control Using
           Deep Reinforcement Learning with Discrete Actions in Wind Tunnel Test

    • Authors: Daichi Wada, Sergio A. Araujo-Estrada, Shane Windsor
      First page: 18
      Abstract: Deep reinforcement learning is a promising method for training a nonlinear attitude controller for fixed-wing unmanned aerial vehicles. Until now, proof-of-concept studies have demonstrated successful attitude control in simulation. However, detailed experimental investigations have not yet been conducted. This study applied deep reinforcement learning for one-degree-of-freedom pitch control in wind tunnel tests with the aim of gaining practical understandings of attitude control application. Three controllers with different discrete action choices, that is, elevator angles, were designed. The controllers with larger action rates exhibited better performance in terms of following angle-of-attack commands. The root mean square errors for tracking angle-of-attack commands decreased from 3.42° to 1.99° as the maximum action rate increased from 10°/s to 50°/s. The comparison between experimental and simulation results showed that the controller with a smaller action rate experienced the friction effect, and the controllers with larger action rates experienced fluctuating behaviors in elevator maneuvers owing to delay. The investigation of the effect of friction and delay on pitch control highlighted the importance of conducting experiments to understand actual control performances, specifically when the controllers were trained with a low-fidelity model.
      Citation: Aerospace
      PubDate: 2021-01-14
      DOI: 10.3390/aerospace8010018
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 19: Numerical Analysis of Flow across Brush
           Elements Based on a 2-D Staggered Tube Banks Model

    • Authors: Xiaolei Song, Meihong Liu, Xiangping Hu, Xueliang Wang, Taohong Liao, Junfeng Sun
      First page: 19
      Abstract: In order to improve efficiency in turbomachinery, brush seal replaces labyrinth seals widely in the secondary air system. A 2-d staggered tube bank model is adopted to simulate the gas states and the pressure character in brush seal, and computational fluid dynamics (CFD) is used to solve the model in this paper. According to the simulation results, the corrected formula of the Euler number and dimensionless pressure are given. The results show that gas expands when flow through the bristle pack, and the gas expansion closes to an isotherm process. The dynamic pressure increases with decreasing static pressure. The Euler number can reflect the seal performance of brush seals in leakage characteristics. Compared with increasing the number of rows, the reduction of the gap is a higher-efficiency method to increase the Euler number. The Euler number continually increases as the gap decreases. However, with the differential pressure increasing, Euler number first increases and then decreases as the number of rows increases. Finally, the pressure distribution on the surface of end rows is asymmetric, and it may increase the friction between the bristles and the back plate.
      Citation: Aerospace
      PubDate: 2021-01-15
      DOI: 10.3390/aerospace8010019
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 20: Review of State-of-the-Art Green
           Monopropellants: For Propulsion Systems Analysts and Designers

    • Authors: Ahmed E. S. Nosseir, Angelo Cervone, Angelo Pasini
      First page: 20
      Abstract: Current research trends have advanced the use of “green propellants” on a wide scale for spacecraft in various space missions; mainly for environmental sustainability and safety concerns. Small satellites, particularly micro and nanosatellites, evolved from passive planetary-orbiting to being able to perform active orbital operations that may require high-thrust impulsive capabilities. Thus, onboard primary and auxiliary propulsion systems capable of performing such orbital operations are required. Novelty in primary propulsion systems design calls for specific attention to miniaturization, which can be achieved, along the above-mentioned orbital transfer capabilities, by utilizing green monopropellants due to their relative high performance together with simplicity, and better storability when compared to gaseous and bi-propellants, especially for miniaturized systems. Owing to the ongoing rapid research activities in the green-propulsion field, it was necessary to extensively study and collect various data of green monopropellants properties and performance that would further assist analysts and designers in the research and development of liquid propulsion systems. This review traces the history and origins of green monopropellants and after intensive study of physicochemical properties of such propellants it was possible to classify green monopropellants to three main classes: Energetic Ionic Liquids (EILs), Liquid NOx Monopropellants, and Hydrogen Peroxide Aqueous Solutions (HPAS). Further, the tabulated data and performance comparisons will provide substantial assistance in using analysis tools—such as: Rocket Propulsion Analysis (RPA) and NASA CEA—for engineers and scientists dealing with chemical propulsion systems analysis and design. Some applications of green monopropellants were discussed through different propulsion systems configurations such as: multi-mode, dual mode, and combined chemical–electric propulsion. Although the in-space demonstrated EILs (i.e., AF-M315E and LMP-103S) are widely proposed and utilized in many space applications, the investigation transpired that NOx fuel blends possess the highest performance, while HPAS yield the lowest performance even compared to hydrazine.
      Citation: Aerospace
      PubDate: 2021-01-15
      DOI: 10.3390/aerospace8010020
      Issue No: Vol. 8, No. 1 (2021)
  • Aerospace, Vol. 8, Pages 1: Advanced Materials and Technologies for
           Compressor Blades of Small Turbofan Engines

    • Authors: Dmytro Pavlenko, Yaroslav Dvirnyk, Radoslaw Przysowa
      First page: 1
      Abstract: Manufacturing costs, along with operational performance, are among the major factors determining the selection of the propulsion system for unmanned aerial vehicles (UAVs), especially for aerial targets and cruise missiles. In this paper, the design requirements and operating parameters of small turbofan engines for single-use and reusable UAVs are analysed to introduce alternative materials and technologies for manufacturing their compressor blades, such as sintered titanium, a new generation of aluminium alloys and titanium aluminides. To assess the influence of severe plastic deformation (SPD) on the hardening efficiency of the proposed materials, the alloys with the coarse-grained and submicrocrystalline structure were studied. Changes in the physical and mechanical properties of materials were taken into account. The thermodynamic analysis of the compressor was performed in a finite element analysis system (ANSYS) to determine the impact of gas pressure and temperature on the aerodynamic surfaces of compressor blades of all stages. Based on thermal and structural analysis, the stress and temperature maps on compressor blades and vanes were obtained, taking into account the physical and mechanical properties of advanced materials and technologies of their processing. The safety factors of the components were established based on the assessment of their stress-strength characteristics. Thanks to nomograms, the possibility of using the new materials in five compressor stages was confirmed in view of the permissible operating temperature and safety factor. The proposed alternative materials for compressor blades and vanes meet the design requirements of the turbofan at lower manufacturing costs.
      Citation: Aerospace
      PubDate: 2020-12-22
      DOI: 10.3390/aerospace8010001
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 2: Parametric Modeling of a Long-Range Aircraft
           under Consideration of Engine-Wing Integration

    • Authors: Matthias Schulze, Jens Neumann, Thomas Klimmek
      First page: 2
      Abstract: The purpose of this paper is to investigate the influence of the engine position and mass as well as the pylon stiffness on the aeroelastic stability of a long-range wide-body transport aircraft. As reference configuration, DLR’s (German Aerospace Center/Deutsches Zentrum für Luft und Raumfahrt) generic aircraft configuration DLR-D250 is taken. The structural, mass, loads, and optimization models for the reference and a modified configuration with different engine and pylon parameters are set up using DLR’s automatized aeroelastic design process cpacs-MONA. At first, the cpacs-MONA process with its capabilities for parametric modeling of the complete aircraft and in particular the set-up of a generic elastic pylon model is unfolded. Then, the influence of the modified engine-wing parameters on the flight loads of the main wing is examined. The resulting loads are afterward used to structurally optimize the two configurations component wise. Finally, the results of post-cpacs-MONA flutter analyses performed for the two optimized aircraft configurations with the different engine and pylon characteristics are discussed. It is shown that the higher mass and the changed position of the engine slightly increased the flutter speed. Although the lowest flutter speeds for both configurations occur at a flutter phenomenon of the horizontal tail-plane outside of the aeroelastic stability envelope.
      Citation: Aerospace
      PubDate: 2020-12-23
      DOI: 10.3390/aerospace8010002
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 3: Design and Optimization of Ram Air-Based
           Thermal Management Systems for Hybrid-Electric Aircraft

    • Authors: Hagen Kellermann, Michael Lüdemann, Markus Pohl, Mirko Hornung
      First page: 3
      Abstract: Ram air-based thermal management systems (TMS) are investigated herein for the cooling of future hybrid-electric aircraft. The developed TMS model consists of all components required to estimate the impacts of mass, drag, and fuel burn on the aircraft, including the heat exchangers, coldplates, ducts, pumps, and fans. To gain a better understanding of the TMS, one- and multi-dimensional system sensitivity analyses were conducted. The observations were used to aid with the numerical optimization of a ram air-based TMS towards the minimum fuel burn of a 180-passenger short-range turboelectric aircraft with a power split of up to 30 electric power. The TMS was designed for the conditions at the top of the climb. For an aircraft with the maximum power split, the additional fuel burn caused by the TMS is 0.19. Conditions occurring at a hot-day takeoff represent the most challenging off-design conditions for TMS. Steady-state cooling of all electric components with the designed TMS is possible during a hot-day takeoff if a small puller fan is utilized. Omitting the puller fan and instead oversizing the TMS is an alternative, but the fuel burn increase on the aircraft level grows to 0.29.
      Citation: Aerospace
      PubDate: 2020-12-23
      DOI: 10.3390/aerospace8010003
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 4: LEO Object’s Light-Curve Acquisition System
           and Their Inversion for Attitude Reconstruction

    • Authors: Fabrizio Piergentili, Gaetano Zarcone, Leonardo Parisi, Lorenzo Mariani, Shariar Hadji Hossein, Fabio Santoni
      First page: 4
      Abstract: In recent years, the increase in space activities has brought the space debris issue to the top of the list of all space agencies. The fact of there being uncontrolled objects is a problem both for the operational satellites in orbit (avoiding collisions) and for the safety of people on the ground (re-entry objects). Optical systems provide valuable assistance in identifying and monitoring such objects. The Sapienza Space System and Space Surveillance (S5Lab) has been working in this field for years, being able to take advantage of a network of telescopes spread over different continents. This article is focused on the re-entry phase of the object; indeed, the knowledge of the state of the object, in terms of position, velocity, and attitude during the descent, is crucial in order to predict as accurately as possible the impact point on the ground. A procedure to retrieve the light curves of orbiting objects by means of optical data will be shown and a method to obtain the attitude determination from their inversion based on a stochastic optimization (genetic algorithm) will be proposed.
      Citation: Aerospace
      PubDate: 2020-12-23
      DOI: 10.3390/aerospace8010004
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 5: A Conceptional Approach of
           Resin-Transfer-Molding to Rosin-Sourced Epoxy Matrix Green Composites

    • Authors: Sicong Yu, Xufeng Zhang, Xiaoling Liu, Chris Rudd, Xiaosu Yi
      First page: 5
      Abstract: In this concept-proof study, a preform-based RTM (Resin Transfer Molding) process is presented that is characterized by first pre-loading the solid curing agent onto the preform, and then injecting the liquid nonreactive resin with an intrinsically low viscosity into the mold to infiltrate and wet the pre-loaded preform. The separation of resin and hardener helped to process inherently high viscosity resins in a convenient way. Rosin-sourced, anhydrite-cured epoxies that would normally be regarded as unsuited to liquid composite molding, were thus processed. Rheological tests revealed that by separating the anhydrite curing agent from a formulated RTM resin system, the remaining epoxy liquid had its flowtime extended. C-scan and glass transition temperature tests showed that the preform pre-loaded with anhydrite was fully infiltrated and wetted by the liquid epoxy, and the two components were diffused and dissolved with each other, and finally, well reacted and cured. Composite laminates made via this approach exhibited roughly comparable quality and mechanical properties with prepreg controls via autoclave or compression molding, respectively. These findings were verified for both carbon and ramie fiber composites.
      Citation: Aerospace
      PubDate: 2020-12-28
      DOI: 10.3390/aerospace8010005
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 6: Target Tracking Enhancement by
           Three-Dimensional Cooperative Guidance Law Imposing Relative Interception

    • Authors: Xiaoma Liu, Yang Han, Peng Li, Hongwu Guo, Wenqi Wu
      First page: 6
      Abstract: The problem that two cooperative missiles intercept a maneuvering target while imposing a desired relative geometry is investigated in the paper. Firstly, a three-dimensional (3D) estimation model for cooperative target tracking is proposed and the observability of the missile-target range measurement is analyzed. In order to enhance the estimation performance, a two-level cooperative interception guidance architecture is proposed which combines a coordination algorithm with a novel 3D fixed-time convergent guidance law considering line of sight (LOS) angle constraints, such that the desired relative geometry can be imposed quickly and steadily by a dynamic strategy. The effectiveness and superiority of the proposed guidance law is evidenced through the numerical simulations comparing with other guidance laws.
      Citation: Aerospace
      PubDate: 2020-12-28
      DOI: 10.3390/aerospace8010006
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 7: Numerical Simulations on Unsteady Nonlinear
           Transonic Airfoil Flow

    • Authors: Diliana Friedewald
      First page: 7
      Abstract: Large-amplitude excitations need to be considered for gust load analyses of transport aircraft in cruise flight conditions. Nonlinear amplitude effects in transonic flow are, however, only marginally taken into account. The present work aims at closing this gap by means of systematic unsteady Reynolds-averaged Navier-Stokes simulations. The RAE2822 airfoil is analyzed for a variety of sinusoidal gust excitations at different transonic Mach numbers. Responses are evaluated with respect to lift and moment coefficients, their derivatives and the unsteady shock motion. A strong dependency on inflow Mach number and excitation frequency is observed. Generally, amplitude effects decrease with lower Mach numbers or higher excitation frequencies. The unsteady nonlinear simulations predict lower maximum lift values and lower lift and moment derivatives compared to their linear counterparts for lower frequencies in combination with large-amplitude excitations. For the mid-frequency range, trends are not as clear. Additionally, it is shown that the variables of harmonic distortion and maximum shock motion might not be reasonable indicators to predict a nonlinear response.
      Citation: Aerospace
      PubDate: 2020-12-29
      DOI: 10.3390/aerospace8010007
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 8: Correction: Tanaka, T., et al. Dual-Satellite
           Lunar Global Navigation System Using Multi-Epoch Double-Differenced
           Pseudorange Observations. Aerospace 2020, 7, 122

    • Authors: Toshiki Tanaka, Takuji Ebinuma, Shinichi Nakasuka
      First page: 8
      Abstract: The authors regret that this paper [1] contains typographical errors in the sentence between Equation (16) and Equation (17), as well as in Equations (18), (20), (21), (34), (36) and (37), with respect to the point that they use the wrong notations t1 − tN, while the correct notations are tk − tk+N−1 [...]
      Citation: Aerospace
      PubDate: 2020-12-30
      DOI: 10.3390/aerospace8010008
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 9: Novel 3U Stand-Alone CubeSat Architecture for
           Autonomous Near Earth Asteroid Fly-By

    • Authors: Stefano Casini, Iosto Fodde, Bert Monna, Angelo Cervone, Eberhard Gill
      First page: 9
      Abstract: The purpose of this work is to present a novel CubeSat architecture, aimed to explore Near Earth Asteroids. The fast growth in small satellite commercial-off-the-shelf technologies, which characterized the last decade of space industry, is exploited to design a 3U CubeSat able to provide a basic scientific return sufficient to improve the target asteroid dataset. An overview of the current available technologies for each subsystem is presented, followed by a component selection driven by the mission constraints. First a typical asteroid fly-by mission is introduced together with the system and performance requirements. Then each characterizing subsystem is critically analyzed, and the proposed configuration is presented, showing the mission feasibility within only 3.9 kg of wet mass and 385 m/s of total ΔV.
      Citation: Aerospace
      PubDate: 2020-12-30
      DOI: 10.3390/aerospace8010009
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 8, Pages 10: Amphibious Aircraft Developments:
           Computational Studies of Hydrofoil Design for Improvements in

    • Authors: Arjit Seth, Rhea P. Liem
      First page: 10
      Abstract: Amphibious aircraft designers face challenges to improve takeoffs and landings on both water and land, with water-takeoffs being relatively more complex for analyses. Reducing the water-takeoff distance via the use of hydrofoils was a subject of interest in the 1970s, but the computational power to assess their designs was limited. A preliminary computational design framework is developed to assess the performance and effectiveness of hydrofoils for amphibious aircraft applications, focusing on the water-takeoff performance. The design framework includes configuration selections and sizing methods for hydrofoils to fit within constraints from a flying-boat amphibious aircraft conceptual design for general aviation. The position, span, and incidence angle of the hydrofoil are optimized for minimum water-takeoff distance with consideration for the longitudinal stability of the aircraft. The analyses and optimizations are performed using water-takeoff simulations, which incorporate lift and drag forces with cavitation effects on the hydrofoil. Surrogate models are derived based on 2D computational fluid dynamics simulation results to approximate the force coefficients within the design space. The design procedure is evaluated in a case study involving a 10-seater amphibious aircraft, with results indicating that the addition of the hydrofoil achieves the purpose of reducing water-takeoff distance by reducing the hull resistance.
      Citation: Aerospace
      PubDate: 2020-12-30
      DOI: 10.3390/aerospace8010010
      Issue No: Vol. 8, No. 1 (2020)
  • Aerospace, Vol. 7, Pages 119: Experimental Studies into the Analysis
           Required for the Durability Assessment of 7075 and 6061 Cold Spray Repairs
           to Military Aircraft

    • Authors: Rhys Jones, Neil Matthews, Daren Peng, R. K. Singh Raman, Nam Phan
      First page: 119
      Abstract: This paper presents an experimental study into the analysis required for the durability assessment of 7075 and 6061 cold spray repairs to military aircraft. To this end, it is first shown that provided the bulk stress in a 7075 cold spray coating can be kept beneath approximately 150 MPa, then the coating should not crack. A range of examples are presented in which the interface between the coating and the substrate only fails subsequent to crack growth in the substrate. We also show that failure of cold spray repaired/coated panels can also be due to the nucleation and growth of cracks in the substructure immediately adjacent to the coated/repaired region. As such, when performing a durability analysis for a cold spray repair, the growth of such small naturally occurring cracks, both at the interface and immediately adjacent to the ends of the coating, need to be accounted for.
      Citation: Aerospace
      PubDate: 2020-08-19
      DOI: 10.3390/aerospace7090119
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 120: Future Directions for Electric Propulsion

    • Authors: Ethan Dale, Benjamin Jorns, Alec Gallimore
      First page: 120
      Abstract: The research challenges for electric propulsion technologies are examined in the context of s-curve development cycles. It is shown that the need for research is driven both by the application as well as relative maturity of the technology. For flight qualified systems such as moderately-powered Hall thrusters and gridded ion thrusters, there are open questions related to testing fidelity and predictive modeling. For less developed technologies like large-scale electrospray arrays and pulsed inductive thrusters, the challenges include scalability and realizing theoretical performance. Strategies are discussed to address the challenges of both mature and developed technologies. With the aid of targeted numerical and experimental facility effects studies, the application of data-driven analyses, and the development of advanced power systems, many of these hurdles can be overcome in the near future.
      Citation: Aerospace
      PubDate: 2020-08-20
      DOI: 10.3390/aerospace7090120
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 121: Beyond Contrail Avoidance: Efficacy of
           Flight Altitude Changes to Minimise Contrail Climate Forcing

    • Authors: Teoh, Schumann, Stettler
      First page: 121
      Abstract: : Contrail cirrus introduce a short-lived but significant climate forcing that could be mitigated by small changes in aircraft cruising altitudes. This paper extends a recent study to evaluate the efficacy of several vertical flight diversion strategies to mitigate contrail climate forcing, and estimates impacts to air traffic management (ATM). We use six one-week periods of flight track data in the airspace above Japan (between May 2012 and March 2013), and simulate contrails using the contrail cirrus prediction model (CoCiP). Previous studies have predominantly optimised a diversion of every contrail-forming flight to minimise its formation or radiative forcing. However, our results show that these strategies produce a suboptimal outcome because most contrails have a short lifetime, and some have a cooling effect. Instead, a strategy that reroutes 15.3% of flights to avoid long-lived warming contrails, while allowing for cooling contrails, reduces the contrail energy forcing (EFcontrail) by 105% [91.8, 125%] with a total fuel penalty of 0.70% [0.66, 0.73%]. A minimum EFtotal strategy (contrails + CO2), diverting 20.1% of flights, reduces the EFcontrail by the same magnitude but also reduces the total fuel consumption by 0.40% [0.31, 0.47%]. For the diversion strategies explored, between 9% and 14% of diversions lead to a loss of separation standards between flights, demonstrating a modest scale of ATM impacts. These results show that small changes in flight altitudes are an opportunity for aviation to significantly and rapidly reduce its effect on the climate.
      Citation: Aerospace
      PubDate: 2020-08-21
      DOI: 10.3390/aerospace7090121
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 122: Dual-Satellite Lunar Global Navigation
           System Using Multi-Epoch Double-Differenced Pseudorange Observations

    • Authors: Toshiki Tanaka, Takuji Ebinuma, Shinichi Nakasuka
      First page: 122
      Abstract: In view of the upcoming missions to obtain resources from the lunar surface, it is essential to have highly-accurate navigation systems to locate surface vehicles in shadowed regions. In response, we propose a dual-satellite lunar navigation system that is based on a multi-epoch double-differenced pseudorange observations (MDPO) algorithm. We used multi-epoch observations in a new way that reduces the number of navigation satellites required. In addition, the double-differenced pseudorange is used in order to eliminate the bias effects of the satellite and user clocks that conventional dual-satellite navigation algorithms did not fully take into account. Furthermore, a pre-known lunar digital elevation model is used to reduce the number of observations. The theoretical behavior of the MDPO algorithm was confirmed by simulation and the results indicate that user position accuracy can be several tens of meters with 95% probability (2drms) within a one-minute observation.
      Citation: Aerospace
      PubDate: 2020-08-24
      DOI: 10.3390/aerospace7090122
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 123: Numerical Simulation of the Anti-Icing
           Performance of Electric Heaters for Icing on the NACA 0012 Airfoil

    • Authors: Sho Uranai, Koji Fukudome, Hiroya Mamori, Naoya Fukushima, Makoto Yamamoto
      First page: 123
      Abstract: Ice accretion is a phenomenon whereby super-cooled water droplets impinge and accrete on wall surfaces. It is well known that the icing may cause severe accidents via the deformation of airfoil shape and the shedding of the growing adhered ice. To prevent ice accretion, electro-thermal heaters have recently been implemented as a de- and anti-icing device for aircraft wings. In this study, an icing simulation method for a two-dimensional airfoil with a heating surface was developed by modifying the extended Messinger model. The main modification is the computation of heat transfer from the airfoil wall and the run-back water temperature achieved by the heater. A numerical simulation is conducted based on an Euler–Lagrange method: a flow field around the airfoil is computed by an Eulerian method and droplet trajectories are computed by a Lagrangian method. The wall temperature distribution was validated by experiment. The results of the numerical and practical experiments were in reasonable agreement. The ice shape and aerodynamic performance of a NACA 0012 airfoil with a heater on the leading-edge surface were computed. The heating area changed from 1% to 10% of the chord length with a four-degree angle of attack. The simulation results reveal that the lift coefficient varies significantly with the heating area: when the heating area was 1.0% of the chord length, the lift coefficient was improved by up to 15%, owing to the flow separation instigated by the ice edge; increasing the heating area, the lift coefficient deteriorated, because the suction peak on the suction surface was attenuated by the ice formed. When the heating area exceeded 4.0% of the chord length, the lift coefficient recovered by up to 4%, because the large ice near the heater vanished. In contrast, the drag coefficient gradually decreased as the heating area increased. The present simulation method using the modified extended Messinger model is more suitable for de-icing simulations of both rime and glaze ice conditions, because it reproduces the thin ice layer formed behind the heater due to the runback phenomenon.
      Citation: Aerospace
      PubDate: 2020-08-27
      DOI: 10.3390/aerospace7090123
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 124: Mathematical Modelling of Gimballed
           Tilt-Rotors for Real-Time Flight Simulation

    • Authors: Anna Abà, Federico Barra, Pierluigi Capone, Giorgio Guglieri
      First page: 124
      Abstract: This paper introduces a novel gimballed rotor mathematical model for real-time flight simulation of tilt-rotor aircraft and other vertical take-off and landing (VTOL) concepts, which improves the previous version of a multi-purpose rotor mathematical model developed by ZHAW and Politecnico di Torino as part of a comprehensive flight simulation model of a tilt-rotor aircraft currently implemented in the Research and Didactics Simulator of ZHAW and used for research activities such as handling qualities studies and flight control systems development. In the novel model, a new formulation of the flapping dynamics is indroduced to account for the gimballed rotor and better suit current tilt-rotor designs (XV-15, V-22, AW-609). This paper describes the mathematical model and provides a generic formulation as well as a specific one for 3-blades proprotors. The method expresses the gimbal attitude but also considers the variation of each blade’s flapping due to the elasticity of the blades, so that the rotor coning angle can be represented. A validation of the mathematical model is performed against the available literature on the XV-15 Tilt-rotor aircraft and a comparison between the previous model is provided to show the improvements achieved. The results show a good correlation between the model and the reference data and the registered performance allow real-time flight simulation with pilot and hardware in the loop.
      Citation: Aerospace
      PubDate: 2020-08-28
      DOI: 10.3390/aerospace7090124
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 125: Real Time Measurement of Airplane Flutter
           via Distributed Acoustic Sensing

    • Authors: Ezzat G. Bakhoum, Cheng Zhang, Marvin H. Cheng
      First page: 125
      Abstract: This research group has recently used the new technology Distributed Acoustic Sensing (DAS) for the monitoring and the measurement of airplane flutter. To the authors’ knowledge, this is the first such use for this new technology. Traditionally, the measurement of airplane flutter requires the mounting of a very large number of sensors on the wing being monitored, and extensive wiring must be connected to all these sensors. The new system and technology introduced in this paper dramatically reduces the hardware requirements in such an application: all the traditional sensors and wiring are replaced with one fiber optic cable with a diameter of 2 mm. An electro-optical system with the size of a desktop PC monitors simultaneously one or more of such fiber optic cables and detects/characterizes any mechanical disturbances on the cables. Theoretical and experimental results are given.
      Citation: Aerospace
      PubDate: 2020-08-29
      DOI: 10.3390/aerospace7090125
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 126: Vision-Based Spacecraft Pose Estimation via

    • Authors: Thaweerath Phisannupawong, Patcharin Kamsing, Peerapong Torteeka, Sittiporn Channumsin, Utane Sawangwit, Warunyu Hematulin, Tanatthep Jarawan, Thanaporn Somjit, Soemsak Yooyen, Daniel Delahaye, Pisit Boonsrimuang
      First page: 126
      Abstract: The capture of a target spacecraft by a chaser is an on-orbit docking operation that requires an accurate, reliable, and robust object recognition algorithm. Vision-based guided spacecraft relative motion during close-proximity maneuvers has been consecutively applied using dynamic modeling as a spacecraft on-orbit service system. This research constructs a vision-based pose estimation model that performs image processing via a deep convolutional neural network. The pose estimation model was constructed by repurposing a modified pretrained GoogLeNet model with the available Unreal Engine 4 rendered dataset of the Soyuz spacecraft. In the implementation, the convolutional neural network learns from the data samples to create correlations between the images and the spacecraft’s six degrees-of-freedom parameters. The experiment has compared an exponential-based loss function and a weighted Euclidean-based loss function. Using the weighted Euclidean-based loss function, the implemented pose estimation model achieved moderately high performance with a position accuracy of 92.53 percent and an error of 1.2 m. The in-attitude prediction accuracy can reach 87.93 percent, and the errors in the three Euler angles do not exceed 7.6 degrees. This research can contribute to spacecraft detection and tracking problems. Although the finished vision-based model is specific to the environment of synthetic dataset, the model could be trained further to address actual docking operations in the future.
      Citation: Aerospace
      PubDate: 2020-08-30
      DOI: 10.3390/aerospace7090126
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 127: Leader–Follower Synchronization of
           Uncertain Euler–Lagrange Dynamics with Input Constraints

    • Authors: Muhammad Ridho Rosa
      First page: 127
      Abstract: This paper addresses the problem of leader–follower synchronization of uncertain Euler–Lagrange systems under input constraints. The problem is solved in a distributed model reference adaptive control framework that includes positive μ-modification to address input constraints. The proposed design has the distinguishing features of updating the gains to synchronize the uncertain systems and of providing stable adaptation in the presence of input saturation. By using a matching condition assumption, a distributed inverse dynamics architecture is adopted to guarantee convergence to common dynamics. The design is studied analytically, and its performance is validated in simulation using spacecraft dynamics.
      Citation: Aerospace
      PubDate: 2020-08-30
      DOI: 10.3390/aerospace7090127
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 128: Procedures for the Integration of Drones
           into the Airspace Based on U-Space Services

    • Authors: Víctor Alarcón, Manuel García, Francisco Alarcón, Antidio Viguria, Ángel Martínez, Dominik Janisch, José Joaquín Acevedo, Ivan Maza, Aníbal Ollero
      First page: 128
      Abstract: A safe integration of drones into the airspace is fundamental to unblock the potential of drone applications. U-space is the drone traffic management solution for Europe, intended to handle a large number of drones in the airspace, especially at very low level (VLL). This paper presents the procedures we have designed and tested in real flights in the SAFEDRONE European project to pave the way for a safe integration of drones into the airspace using U-space services. We include three important aspects: Design of procedures related to no-fly zones, ensure separation with manned aircraft, and autonomous non-cooperative detect-and-avoid (DAA) technologies. A specific U-space architecture has been designed and implemented for flight campaigns with up to eight drones with different configurations and a manned aircraft. From this experience, specific recommendations about procedures to exit and avoiding no-fly zones are presented. Additionally, it has been concluded that the use of surveillance information of manned aircraft will allow a more efficient use of the airspace while maintaining a proper safety level, avoiding the creation of large geofence areas.
      Citation: Aerospace
      PubDate: 2020-09-01
      DOI: 10.3390/aerospace7090128
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 129: A Preliminary Investigation of Maintenance
           Contributions to Commercial Air Transport Accidents

    • Authors: Fatima Najeeb Khan, Ayiei Ayiei, John Murray, Glenn Baxter, Graham Wild
      First page: 129
      Abstract: Aircraft maintenance includes all the tasks needed to ensure an aircraft’s continuing airworthiness. Accidents that result from these maintenance activities can be used to assess safety. This research seeks to undertake a preliminary investigation of accidents that have maintenance contributions. An exploratory design was utilized, which commenced with a content analysis of the accidents with maintenance contributions (n = 35) in the official ICAO accident data set (N = 1277), followed by a quantitative ex-post facto study. Results showed that maintenance contributions are involved in 2.8 ± 0.9% of ICAO official accidents. Maintenance accidents were also found to be more likely to have one or more fatalities (20%), compared to all ICAO official accidents (14.7%). The number of accidents with maintenance contributions per year was also found to have reduced over the period of the study; this rate was statistically significantly greater than for all accidents (5%/year, relative to 2%/year). Results showed that aircraft between 10 and 20 years old were most commonly involved in accidents with maintenance contributions, while aircraft older than 18 years were more likely to result in a hull loss, and aircraft older than 34 years were more likely to result in a fatality.
      Citation: Aerospace
      PubDate: 2020-09-02
      DOI: 10.3390/aerospace7090129
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 130: Airlift Maintenance and Sustainment: The
           Indirect Costs

    • Authors: Kourousis
      First page: 130
      Abstract: This article aims to present and discuss a set of technical matters affecting the maintenance and sustainment cost of military transport aircraft (airlifters). An overview of the military aviation technical support system is provided, in conjunction with a high level discussion on the life cycle cost. Four technical support pillars are defined as part of this analysis: supply, restoration and upgrade, engineering and regulatory compliance. A focused discussion on airlift sustainment factors, based on past experience, is used to identify technical considerations that can be used for the evaluation of new aircraft. A number of technical considerations which are key for cost purposes are identified and mapped against the defined technical support pillars, related to engineering and technical support and airworthiness management aspects. Important practical technical considerations are identified, discussed and critiqued under an independent lens. This article can stimulate discussion of the maintenance and sustainment costs of airlifters, both within military aviation operators and the defence industry community but also within the civil aircraft maintenance industry.
      Citation: Aerospace
      PubDate: 2020-09-02
      DOI: 10.3390/aerospace7090130
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 131: The Two-Point Boundary-Value Problem for
           Rocket Trajectories

    • Authors: Luís M. B. C. M. B. C. Campos, Paulo J. S. Gil
      First page: 131
      Abstract: The two dimensional gravity turn problem is addressed allowing for the effects of variable rocket mass due to propellant consumption, thrust and thrust vector angle, lift and drag forces at an angle-of-attack and atmospheric mass density varying with altitude; Coriolis and centrifugal forces are neglected. Three distinct analytical solutions are obtained for constant: propellant flow rate, thrust, thrust vector angle, angle-of-attack and acceleration of gravity; the lift and drag are assumed to be proportional to the square of velocity, and the mass density is assumed to decrease exponentially with altitude. The method III uses power series of time for the horizontal (downrange) and vertical (altitude) coordinates; the method II replaces the altitude as variable by the atmospheric mass density and method I by its inverse. Thus the three solutions have distinct properties, e.g., I and III converge best close to lift-off and II close to burn-out. The three solutions: I, II, III, can be applied in isolation (or matched in combination) to the single-point boundary-value problem (SPBVP) of finding the trajectory with given initial conditions at launch. They can also be used as pairs in six distinct ways (I + II, I + III, II + III or reverse orders) to solve the two-point boundary-value problem (TPBVP), viz.: from given conditions at launch achieve one (not more) specified condition at burn-out, e.g., ã desired horizontal velocity for payload release. Each of the six distinct combinations of methods of addressing the TPBVP shares three features: (i) it can determine if there is a solution, viz. if the rocket has enough performance to reach the desired burn-out condition; (ii) if the desired burn-out condition is achievable it can calculate the complete trajectory from launch to burn-out; (iii) it can determine the range of achievable burn-out conditions, e.g., the minimum and maximum possible horizontal velocity at burn-out for given initial conditions at launch.
      Citation: Aerospace
      PubDate: 2020-09-02
      DOI: 10.3390/aerospace7090131
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 132: Deep Neural Network Feature Selection
           Approaches for Data-Driven Prognostic Model of Aircraft Engines

    • Authors: Khumprom, Grewell, Yodo
      First page: 132
      Abstract: Predicting Remaining Useful Life (RUL) of systems has played an important role in various fields of reliability engineering analysis, including in aircraft engines. RUL prediction is critically an important part of Prognostics and Health Management (PHM), which is the reliability science that is aimed at increasing the reliability of the system and, in turn, reducing the maintenance cost. The majority of the PHM models proposed during the past few years have shown a significant increase in the amount of data-driven deployments. While more complex data-driven models are often associated with higher accuracy, there is a corresponding need to reduce model complexity. One possible way to reduce the complexity of the model is to use the features (attributes or variables) selection and dimensionality reduction methods prior to the model training process. In this work, the effectiveness of multiple filter and wrapper feature selection methods (correlation analysis, relief forward/backward selection, and others), along with Principal Component Analysis (PCA) as a dimensionality reduction method, was investigated. A basis algorithm of deep learning, Feedforward Artificial Neural Network (FFNN), was used as a benchmark modeling algorithm. All those approaches can also be applied to the prognostics of an aircraft gas turbine engines. In this paper, the aircraft gas turbine engines data from NASA Ames prognostics data repository was used to test the effectiveness of the filter and wrapper feature selection methods not only for the vanilla FFNN model but also for Deep Neural Network (DNN) model. The findings show that applying feature selection methods helps to improve overall model accuracy and significantly reduced the complexity of the models.
      Citation: Aerospace
      PubDate: 2020-09-04
      DOI: 10.3390/aerospace7090132
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 133: Large Constellations of Small Satellites: A
           Survey of Near Future Challenges and Missions

    • Authors: Giacomo Curzi, Dario Modenini, Paolo Tortora
      First page: 133
      Abstract: Constellations of satellites are being proposed in large numbers; most of them are expected to be in orbit within the next decade. They will provide communication to unserved and underserved communities, enable global monitoring of Earth and enhance space observation. Mostly enabled by technology miniaturization, satellite constellations require a coordinated effort to face the technological limits in spacecraft operations and space traffic. At the moment in fact, no cost-effective infrastructure is available to withstand coordinated flight of large fleets of satellites. In order for large constellations to be sustainable, there is the need to efficiently integrate and use them in the current space framework. This review paper provides an overview of the available experience in constellation operations and statistical trends about upcoming constellations at the moment of writing. It highlights also the tools most often proposed in the analyzed works to overcome constellation management issues, such as applications of machine learning/artificial intelligence and resource/infrastructure sharing. As such, it is intended to be a useful resource for both identifying emerging trends in satellite constellations, and enabling technologies still requiring substantial development efforts.
      Citation: Aerospace
      PubDate: 2020-09-07
      DOI: 10.3390/aerospace7090133
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 134: A Generalized Approach to Operational,
           Globally Optimal Aircraft Mission Performance Evaluation, with Application
           to Direct Lift Control

    • Authors: Sam de de Wringer, Carmine Varriale, Oliviero
      First page: 134
      Abstract: A unified approach to aircraft mission performance assessment is presented in this work. It provides a detailed and flexible formulation to simulate a complete commercial aviation mission. Based on optimal control theory, with consistent injection of rules and procedures typical of aeronautical operations, it relies on generalized mathematical and flight mechanics models, thereby being applicable to aircraft with very distinct configurations. It is employed for an extensive evaluation of the performance of a conventional commercial aircraft, and of an unconventional box-wing aircraft, referred to as the PrandtlPlane. The PrandtlPlane features redundant control surfaces, and it is able to employ Direct Lift Control. To demonstrate the versatility of the performance evaluation approach, the mission-level benefits of using Direct Lift Control as an unconventional control technique are assessed. The PrandtlPlane is seen to be competitive in terms of its fuel consumption per passenger per kilometer. However, this beneficial fuel performance comes at the price of slower flight. The benefits of using Direct Lift are present but marginal, both in terms of fuel consumption and flight time. Nonetheless, enabling Direct Lift Control results in a broader range of viable trajectories, such that the aircraft no longer requires cruise-climb for maximum fuel economy.
      Citation: Aerospace
      PubDate: 2020-09-09
      DOI: 10.3390/aerospace7090134
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 135: A Method for Improved Flight Testing of
           Remotely Piloted Aircraft Using Multisine Inputs

    • Authors: Roger Larsson, Alejandro Sobron, David Lundström, Martin Enqvist
      First page: 135
      Abstract: Unless a segregated airspace and the corresponding clearances can be afforded, flight testing of remotely piloted aircraft is often done near the ground and within visual line-of-sight. In addition to the increased exposure to turbulence, this setup also limits the available time for test manoeuvres on each pass, especially for subscale demonstrators with a relatively high wing loading and flight speed. A suitable testing procedure, efficient excitation signals and a robust system identification method are therefore fundamental. Here, the authors use ground-based flight control augmentation to inject multisine signals with low correlation between the different inputs. Focusing on initial flight-envelope expansion, where linear regression is common, this paper also describes the improvement of an existing frequency-domain method by using an instrumental variable (IV) approach to better handle turbulence and measurement noise and to enable real-time identification analysis. Both simulations and real flight tests on a subscale demonstrator are presented. The results show that the combination of multisine input signals and the enhanced frequency-domain method is an effective way of improving flight testing of remotely piloted aircraft in confined airspace.
      Citation: Aerospace
      PubDate: 2020-09-10
      DOI: 10.3390/aerospace7090135
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 136: In-Flight Test Campaign to Validate PIO
           Detection and Assessment Tools

    • Authors: Michael Jones, Marc Alexander, Marc Höfinger, Miles Barnett, Perry Comeau, Arthur Gubbels
      First page: 136
      Abstract: This paper describes a joint research campaign conducted by the German Aerospace Center (DLR) and the National Research Council Canada (NRC) to explore methods and techniques to expose rotorcraft pilot-induced oscillations (PIOs) during flight testing. A flight test campaign was conducted at NRC using the Bell 205 experimental aircraft. Results show that, particularly for the lateral axis, ADS-33 tasks can be successfully applied to expose PIO tendencies. Novel subjective and objective criteria were used during the test campaign. PIO prediction boundaries of the objective phase-aggression criteria (PAC) detection algorithm were validated through results obtained. This was the first use of PAC with data recorded in-flight. To collect subjective feedback, the aircraft–pilot coupling (APC) scale was used. This was the first use of the novel scale in-flight and received favourable feedback from the evaluation pilot. Modifications to ADS-33 mission tasks were found to successfully improve the ability to consistently expose PIOs.
      Citation: Aerospace
      PubDate: 2020-09-10
      DOI: 10.3390/aerospace7090136
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 137: Aircraft Pilots Workload Analysis: Heart
           Rate Variability Objective Measures and NASA-Task Load Index Subjective

    • Authors: Andrea Alaimo, Antonio Esposito, Calogero Orlando, Andre Simoncini
      First page: 137
      Abstract: Workload and fatigue of aircraft pilots represent an argument of great interest in the framework of human factors and a pivotal point to be considered in aviation safety. 75% of aircraft accidents are related to human errors that, in most cases, are due to high level of mental workload and fatigue. There exist several subjective or objective metrics to quantify the pilots’ workload level, with both linear and nonlinear relationships reported in the literature. The main research objective of the present work is to analyze the relationships between objective and subjective workload measurements by looking for a correlation between metrics belonging to the subjective and biometric rating methods. More particularly, the Heart Rate Variability (HRV) is used for the objective analysis, whereas the NASA-TLX questionnaire is the tool chosen for the subjective evaluation of the workload. Two different flight scenarios were considered for the studies: the take-off phase with the initial climb and the final approach phase with the landing. A Maneuver Error Index (MEI) is also introduced to evaluate the pilot flight performance according to mission requirements. Both qualitative and quantitative correlation analyses were performed among the MEI, subjective and objective measurements. Monotonic relationships were found within the HRV indexes, and a nonlinear relationship is proposed among NASA-TLX and HRV indexes. These findings suggest that the relationship between workload, biometric data, and performance indexes are characterized by intricate patterns of nonlinear relationships.
      Citation: Aerospace
      PubDate: 2020-09-16
      DOI: 10.3390/aerospace7090137
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 138: Strain Measurement on Cracks Using Fiber
           Bragg Gratings for Use in Aircraft Composite Skin Repairs

    • Authors: Aris A. Ikiades
      First page: 138
      Abstract: Fiber Bragg grating (FBG) sensors have been widely used for measurements of strain and temperature in a host of different applications, including aerospace in composite wings, fuselage structures, and other critical components. Here, we report on a method to measure highly localized intense stress fields, generated at the initialization point of a crack, or crack-tip, using Fiber Bragg Gratings (FBG) inscribed in highly photosensitive hydrogenated germanium and boron co-doped fiber. From the spectral characteristics of short and long FBGs, bonded on a test aluminum coupon with a crack, which simulated damaged skins of an aircraft, the local stresses near the cracks were measured and assessed. As a case study, bespoke composite repair patches were designed and bonded on a coupon, incorporating a number of gratings to monitor the stress distribution with applied force in the composite patch, near the crack.
      Citation: Aerospace
      PubDate: 2020-09-22
      DOI: 10.3390/aerospace7090138
      Issue No: Vol. 7, No. 9 (2020)
  • Aerospace, Vol. 7, Pages 103: Thermoelastic Response of Closed Cylindrical
           Shells in a Supersonic Gas Flow

    • Authors: Marine Mikilyan
      First page: 103
      Abstract: The work is devoted to the investigation of flutter oscillations and the stability of the closed cylindrical shell in supersonic gas flow in an inhomogeneous temperature field. It is assumed that supersonic gas flows on the outside of the shell with an unperturbed velocity U, directed parallel to the cylinder generatrix. Under the action of an inhomogeneous temperature field the shell bulges out, this deformed state is accepted as unperturbed, and the stability of this state is studied. The main nonlinear equations and relationships describing the behavior of the examined system are derived. The formulated boundary value problem is solved using the Galerkin method. The joint influence of the flow and the temperature field on the relationship between the amplitude of nonlinear oscillations of a cylindrical shell and the speed of the flowing stream is studied. The critical velocity values are calculated from the corresponding linear system and are given in tables. The numerical results show that: (a) the surrounding flow significantly affects the nature of the investigated relationship; (b) a certain interval of supersonic velocity exists where it is impossible to excite steady-state flutter oscillations (the silence zone); (c) the dependence of amplitude on the supersonic velocity can be either multivalued or single-valued.
      Citation: Aerospace
      PubDate: 2020-07-22
      DOI: 10.3390/aerospace7080103
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 104: OpenAP: An Open-Source Aircraft Performance
           Model for Air Transportation Studies and Simulations

    • Authors: Junzi Sun, Jacco M. Hoekstra, Joost Ellerbroek
      First page: 104
      Abstract: Air traffic simulations serve as common practice to evaluate different concepts and methods for air transportation studies. The aircraft performance model is a key element that supports these simulation-based studies. It is also an important component for simulation-independent studies, such as air traffic optimization and prediction studies. Commonly, contemporary studies have to rely on proprietary aircraft performance models that restrict the redistribution of the data and code. To promote openness and research comparability, an alternative open performance model would be beneficial for the air transportation research community. In this paper, we introduce an open aircraft performance model (OpenAP). It is an open-source model that is based on a number of our previous studies, which were focused on different components of the aircraft performance. The unique characteristic of OpenAP is that it was built upon open aircraft surveillance data and open literature models. The model is composed of four main components, including aircraft and engine properties, kinematic performances, dynamic performances, and utility libraries. Alongside the performance model, we are publishing an open-source toolkit to facilitate the use of this model. The main objective of this paper is to describe each main component, their connections, and how they can be used for simulation and research in practice. Finally, we analyzed the performance of OpenAP by comparing it with an existing performance model and sample flight data.
      Citation: Aerospace
      PubDate: 2020-07-23
      DOI: 10.3390/aerospace7080104
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 105: State-of-the-Art and Advancement Paths for
           Inductive Pulsed Plasma Thrusters

    • Authors: Kurt Polzin, Adam Martin, Justin Little, Curtis Promislow, Benjamin Jorns, Joshua Woods
      First page: 105
      Abstract: An inductive pulsed plasma thruster (IPPT) operates by pulsing high current through an inductor, typically a coil of some type, producing an electromagnetic field that drives current in a plasma, accelerating it to high speed. The IPPT is electrodeless, with no direct electrical connection between the externally applied pulsed high-current circuit and the current conducted in the plasma. Several different configurations were proposed and tested, including those that produce a plasma consisting of an accelerating current sheet and those that use closed magnetic flux lines to help confine the plasma during acceleration. Specific impulses up to 7000 s and thrust efficiencies over 50% have been measured. The present state-of-the-art for IPPTs is reviewed, focusing on the operation, modeling techniques, and major subsystems found in various configurations. Following that review is documentation of IPPT technology advancement paths that were proposed or considered.
      Citation: Aerospace
      PubDate: 2020-07-24
      DOI: 10.3390/aerospace7080105
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 106: Static Aeroelastic Beam Model Development
           for Folding Winglet Design

    • Authors: Bereket Sitotaw Kidane, Enrico Troiani
      First page: 106
      Abstract: Wing shape adaptability during flight is the next step towards the greening of aviation. The shape of the wing is typically designed for one cruise point or a weighted average of several cruise points. However, a wing is subjected to a variety of flight conditions, which results in the aircraft flying sub-optimally during a portion of the flight. Shape adaptability can be achieved by tuning the shape of the winglet during flight. The design challenge is to combine a winglet structure that is able to allow the required adaptable shape while preserving the structural integrity to carry the aerodynamic loads. The shape changing actuators must work against the structural strains and the aerodynamic loads. Analyzing the full model in the preliminary design phase is computationally expensive; therefore, it is necessary to develop a model. The goal of this paper is to derive an aeroelastic model for a wing and winglet in order to reduce the computational cost and complexity of the system in designing a folding winglet. In this paper, the static aeroelastic analysis is performed for a regional aircraft wing at sea level and service ceiling conditions with three degree and eight degree angle of attack. MSC Nastran Aeroelastic tool is used to develop a Finite Element Model (FEM), i.e., beam model and the aerodynamic loads are calculated based on a doublet lattice panel method (DLM).
      Citation: Aerospace
      PubDate: 2020-07-25
      DOI: 10.3390/aerospace7080106
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 107: Comparative Analysis and Optimization of
           Technical and Weight Parameters of Turbo-Electric Propulsion Systems

    • Authors: Mykhaylo Filipenko, Stefan Biser, Martin Boll, Matthias Corduan, Mathias Noe, Peter Rostek
      First page: 107
      Abstract: According to Flightpath 2050, the aviation industry is aiming to substantially reduce emissions over the coming decades. One possible solution to meet these ambitious goals is by moving to hybrid-electric drivetrain architectures which require the electric components to be extremely lightweight and efficient at the same time. It has been claimed in several publications that cryogenic and in particular superconducting components can help to fulfill such requirements that potentially cannot be achieved with non-cryogenic components. The purpose of this work was to make a fair comparison between a cryogenic turbo-electric propulsion system (CEPS) and a non-cryogenic turbo-electric propulsion system (TEPS) on a quantitative level. The results on the CEPS were presented in detail in a previous publication. The focus of this publication is to present the study on the TEPS, which in conclusion allows a direct comparison. For both systems the same top-level aircraft requirements were used that were derived within the project TELOS based on an exemplary mission profile and the physical measures of a 220-passenger aircraft. Our study concludes that a CEPS could be 10% to 40% lighter than a TEPS. Furthermore, a CEPS could have a total efficiency gain of up to 18% compared to a similar TEPS.
      Citation: Aerospace
      PubDate: 2020-07-27
      DOI: 10.3390/aerospace7080107
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 108: Lifetime Considerations for Electrospray

    • Authors: Anirudh Thuppul, Peter L. Wright, Adam L. Collins, John K. Ziemer, Richard E. Wirz
      First page: 108
      Abstract: Ionic liquid electrospray thrusters are capable of producing microNewton precision thrust at a high thrust–power ratio but have yet to demonstrate lifetimes that are suitable for most missions. Accumulation of propellant on the extractor and accelerator grids is thought to be the most significant life-limiting mechanism. In this study, we developed a life model to examine the effects of design features, operating conditions, and emission properties on the porous accelerator grid saturation time of a thruster operating in droplet emission mode. Characterizing a range of geometries and operating conditions revealed that modifying grid aperture radius and grid spacing by 3–7% can significantly improve thruster lifetime by 200–400%, though a need for explicit mass flux measurement was highlighted. Tolerance analysis showed that misalignment can result in 20–50% lifetime reduction. In addition, examining the impact of electron backstreaming showed that increasing aperture radius produces a significant increase in backstreaming current compared to changing grid spacing. A study of accelerator grid bias voltages revealed that applying a reasonably strong accelerator grid potential (in the order of a kV) can minimize backstreaming current to negligible levels for a range of geometries.
      Citation: Aerospace
      PubDate: 2020-07-29
      DOI: 10.3390/aerospace7080108
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 109: Plant Model-Based Fault Detection during
           Aircraft Takeoff Using Non-Deterministic Finite-State Automata

    • Authors: Settele, Weber, Knoll
      First page: 109
      Abstract: In this note, the application of a plant model-based fault detection method for nonlinear control systems on aircraft takeoff is introduced. This method utilizes non-deterministic finite-state automata, which approximate the fault-free dynamics of the plant. The aforementioned automaton is computed in a preliminary step while during evolution of the plant the automaton is continually evaluated to detect discrepancies between the actual and the nominal dynamics. In this way the fault detection module itself can be implemented on simpler hardware on board of the plant. Moreover, an implementation technique is presented that allows the use of the proposed fault detection method when the plant dynamics is given only by means of a graphical programming script. The great potential and practicality of the used method are demonstrated on a simulated takeoff manoeuvre of a battery-electrically driven aircraft.
      Citation: Aerospace
      PubDate: 2020-07-31
      DOI: 10.3390/aerospace7080109
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 110: Dynamic Lifecycle Cost Modeling for
           Adaptable Design Optimization of Additively Remanufactured Aeroengine

    • Authors: Lydia Lawand, Massimo Panarotto, Petter Andersson, Ola Isaksson, Michael Kokkolaras
      First page: 110
      Abstract: Additive manufacturing (AM) is being used increasingly for repair and remanufacturing of aeroengine components. This enables the consideration of a design margin approach to satisfy changing requirements, in which component lifespan can be optimized for different lifecycle scenarios. This paradigm requires lifecycle cost (LCC) modeling; however, the LCC models available in the literature consider mostly the manufacturing of a component, not its repair or remanufacturing. There is thus a need for an LCC model that can consider AM for repair/remanufacturing to quantify corresponding costs and benefits. This paper presents a dynamic LCC model that estimates cumulative costs over the in-service phase and a nested design optimization problem formulation that determines the optimal component lifespan range to minimize overall cost while maximizing performance. The developed methodology is demonstrated by means of an aeroengine turbine rear structure.
      Citation: Aerospace
      PubDate: 2020-07-31
      DOI: 10.3390/aerospace7080110
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 111: Numerical/Experimental Validation of
           Thin-Walled Composite Box Beam Optimal Design

    • Authors: Enrico Cestino, Giacomo Frulla, Paolo Piana, Renzo Duella
      First page: 111
      Abstract: Thin-walled composite box beam structural configuration is representative of a specific high aspect ratio wing structure. The optimal design procedure and lay-up definition including appropriate coupling necessary for aerospace applications has been identified by means of “ad hoc” analytical formulation and by application of commercial code. The overall equivalent bending, torsional and coupled stiffness are derived and the accuracy of the simplified beam model is demonstrated by the application of Altair Optistruct. A simple case of a coupled cantilevered beam with load at one end is introduced to demonstrate that stiffness and torsion angle distribution does not always correspond to the trends that one would intuitively expect. The maximum of torsional stiffness is not obtained with fibers arranged at 45° and, at the maximum torsional stiffness, there is no minimum rotation angle. This observation becomes essential in any design process of composite structures where the constraints impose structural couplings. Furthermore, the presented theory is also extended to cases in which it is necessary to include composite/stiffened hybrid configurations. Good agreement has been found between the theoretical simplified beam model and numerical analysis. Finally, the selected composite configuration was compared to an experimental test case. The numerical and experimental validation is presented and discussed. A good correlation was found confirming the validity of the overall optimization for the optimal lay-up selection and structural configuration.
      Citation: Aerospace
      PubDate: 2020-07-31
      DOI: 10.3390/aerospace7080111
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 112: A Comparison of Isolated and Ducted
           Fixed-Pitch Propellers Under Non-Axial Inflow Conditions

    • Authors: Michael Cerny, Christian Breitsamter
      First page: 112
      Abstract: A strong interest in highly-efficient, small-scale propeller configurations can be recognized, especially due to the currently growing number of and usage possibilities for unmanned aerial vehicles (UAVs). Although a variety of different propulsion concepts already exist on the market or are discussed in the literature, there is still a demand for a systematic investigation to compare such configurations, in particular, small-scale propellers with a fixed pitch, which are analyzed in this work. Therefore, different configurations of small-scale propellers with a fixed pitch are analyzed in this paper. They were operated as isolated single propellers and as ducted propellers in a cylindrical wing. Furthermore, due to their flight envelope, UAVs are likely to operate at highly inclined inflow conditions and even under reverse inflow. These non-axial inflow conditions have a major influence on the flow field around a propeller. In order to investigate this influence, all analyses were performed at a range of inflow angles in relation to the propeller axis from αdisc=0∘ to 180∘.
      Citation: Aerospace
      PubDate: 2020-08-03
      DOI: 10.3390/aerospace7080112
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 113: Multi-Axis Inputs for Identification of a
           Reconfigurable Fixed-Wing UAV

    • Authors: Piotr Lichota
      First page: 113
      Abstract: Designing a reconfiguration system for an aircraft requires a good mathematical model of the object. An accurate model describing the aircraft dynamics can be obtained from system identification. In this case, special maneuvers for parameter estimation must be designed, as the reconfiguration algorithm may require to use flight controls separately, even if they usually work in pairs. The simultaneous multi-axis multi-step input design for reconfigurable fixed-wing aircraft system identification is presented in this paper. D-optimality criterion and genetic algorithm were used to design the flight controls deflections. The aircraft model was excited with those inputs and its outputs were recorded. These data were used to estimate stability and control derivatives by using the maximum likelihood principle. Visual match between registered and identified outputs as well as relative standard deviations were used to validate the outcomes. The system was also excited with simultaneous multisine inputs and its stability and control derivatives were estimated with the same approach as earlier in order to assess the multi-step design.
      Citation: Aerospace
      PubDate: 2020-08-05
      DOI: 10.3390/aerospace7080113
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 114: Oxygen–Methane Torch Ignition System
           for Aerospace Applications

    • Authors: Olexiy Shynkarenko, Domenico Simone
      First page: 114
      Abstract: A new ignition system, based on a CH4/O2 torch has been developed by the Chemical Propulsion Laboratory of the University of Brasilia. Designed to ignite a hybrid rocket, this device has been improved to be used in testing of solid and liquid ramjet engines under development in our lab. The capability to provide multiple ignitions and to cool-down its combustion chamber walls by using a swirled injection of the oxidizer, along with a very low weight to power ratio, makes this device versatile. The igniter is controlled by a feedback system, developed by our group, which guarantees the possibility of operating in different design conditions enabling, therefore, complete integration with systems of different nature. The main characteristics of the igniter and the design solutions are presented including some considerations about the tests performed to evaluate the quality and performance of the ignition system.
      Citation: Aerospace
      PubDate: 2020-08-07
      DOI: 10.3390/aerospace7080114
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 115: Unsupervised Anomaly Detection in Flight
           Data Using Convolutional Variational Auto-Encoder

    • Authors: Milad Memarzadeh, Bryan Matthews, Ilya Avrekh
      First page: 115
      Abstract: The modern National Airspace System (NAS) is an extremely safe system and the aviation industry has experienced a steady decrease in fatalities over the years. This is in part due the airlines, manufacturers, FAA, and research institutions all continually working to improve the safety of the operations. However, the current approach for identifying vulnerabilities in NAS operations leverages domain expertise using knowledge about how the system should behave within the expected tolerances to known safety margins. This approach works well when the system has a well-defined operating condition. However, the operations in the NAS can be highly complex with various nuances that render it difficult to assess risk based on pre-defined safety vulnerabilities. Moreover, state-of-the-art machine learning models that are developed for event detection in aerospace data usually rely on supervised learning. However, in many real-world problems, such as flight safety, creating labels for the data requires specialized expertise that is time consuming and therefore largely impractical. To address this challenge, we develop a Convolutional Variational Auto-Encoder (CVAE), an unsupervised deep generative model for anomaly detection in high-dimensional time-series data. Validating on Yahoo’s benchmark data as well as a case study of identifying anomalies in commercial flights’ take-offs, we show that CVAE outperforms both classic and deep learning-based approaches in precision and recall of detecting anomalies.
      Citation: Aerospace
      PubDate: 2020-08-08
      DOI: 10.3390/aerospace7080115
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 116: Identification of Fixed-Wing Micro Aerial
           Vehicle Aerodynamic Derivatives from Dynamic Water Tunnel Tests

    • Authors: Sibilski, Nowakowski, Rykaczewski, Szczepaniak, Żyluk, Sibilska-Mroziewicz, Garbowski, Wróblewski
      First page: 116
      Abstract: A micro air vehicle (MAV) is a class of miniature unmanned aerial vehicles that has a size restriction and may be autonomous. Fixed-wing MAVs are very attractive for outdoor surveillance missions since they generally offer better payload and endurance capabilities than rotorcraft or flapping-wing vehicles of equal size. This research paper describes the methodology applying indicial function theory and artificial neural networks for identification of aerodynamic derivatives for fixed-wing MAV. The formulation herein proposed extends well- known aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to strake wing planforms. Using results from dynamic water tunnel tests and indicial functions approach allowed to identify MAV aerodynamic derivatives. The experiments were conducted in a water tunnel in the course of dynamic tests of periodic oscillatory motion. The tests program range was set at high angles of attack and a wide scope of reduced frequencies of angular movements. Due to a built-in propeller, the model’s structure test program was repeated for a turned-on propelled drive system. As a result of these studies, unsteady aerodynamics characteristics and aerodynamic derivatives of the micro-aircraft were identified as functions of state parameters. At the Warsaw University of Technology and the Air Force Institute of Technology, a “Bee” fixed wings micro aerial vehicle with an innovative strake-wing outline and a propeller placed in the wing gap was worked. This article is devoted to the problems of identification of aerodynamic derivatives of this micro-aircraft. The result of this research was the identification of the aerodynamic derivatives of the fixed wing MAV “Bee” as non-linear functions of the angle of attack, and reduced frequency. The identification was carried out using the indicial function approach.
      Citation: Aerospace
      PubDate: 2020-08-13
      DOI: 10.3390/aerospace7080116
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 117: Postscript for Special Issue “Advances in
           Hybrid Rocket Technology and Related Analysis Methodologies”

    • Authors: Carmine Carmicino
      First page: 117
      Abstract: Since the Editorial [...]
      Citation: Aerospace
      PubDate: 2020-08-14
      DOI: 10.3390/aerospace7080117
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 118: Aerostructural Design Exploration of a Wing
           in Transonic Flow

    • Authors: Nicolas P. Bons, Joaquim R. R. A. Martins
      First page: 118
      Abstract: Multidisciplinary design optimization (MDO) has been previously applied to aerostructural wing design problems with great success. Most previous applications involve fine-tuning a well-designed aircraft wing. In this work, we broaden the scope of the optimization problem by exploring the design space of aerostructural wing design optimization. We start with a rectangular wing and optimize the aerodynamic shape and the sizing of the internal structure to achieve minimum fuel burn on a transonic cruise mission. We use a multi-level optimization procedure to decrease computational cost by 40%. We demonstrate that the optimization can transform the rectangular wing into a swept, tapered wing typical of a transonic aircraft. The optimizer converges to the same wing shape when starting from a different initial design. Additionally, we use a separation constraint at a low-speed, high-lift condition to improve the off-design performance of the optimized wing. The separation constraint results in a substantially different wing design with better low-speed performance and only a slight decrease in cruise performance.
      Citation: Aerospace
      PubDate: 2020-08-14
      DOI: 10.3390/aerospace7080118
      Issue No: Vol. 7, No. 8 (2020)
  • Aerospace, Vol. 7, Pages 167: Constructive Aerodynamic Interference in a
           Network of Weakly Coupled Flutter-Based Energy Harvesters

    • Authors: Emmanuel Beltramo, Martín E. Pérez Segura, Bruno A. Roccia, Marcelo F. Valdez, Marcos L. Verstraete, Sergio Preidikman
      First page: 167
      Abstract: Converting flow-induced vibrations into electricity for low-power generation has received growing attention over the past few years. Aeroelastic phenomena, good candidates to yield high energy performance in renewable wind energy harvesting (EH) systems, can play a pivotal role in providing sufficient power for extended operation with little or no battery replacement. In this paper, a numerical model and a co-simulation approach have been developed to study a new EH device for power generation. We investigate the problem focusing on a weakly aerodynamically coupled flutter-based EH system. It consists of two flexible wings anchored by cantilevered beams with attached piezoelectric layers, undergoing nonlinear coupled bending–torsion limit cycle oscillations. Besides the development of individual EH devices, further issues are posed when considering multiple objects for realizing a network of devices and magnifying the extracted power due to nonlinear synergies and constructive interferences. This work investigates the effect of various external conditions and physical parameters on the performance of the piezoaeroelastic array of devices. From the viewpoint of applications, we are most concerned about whether an EH can generate sufficient power under a variable excitation. The results of this study can be used for the design and integration of low-energy wind generation technologies into buildings, bridges, and built-in sensor networks in aircraft structures.
      Citation: Aerospace
      PubDate: 2020-11-24
      DOI: 10.3390/aerospace7120167
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 168: Sensitivity Analysis and Flight Tests
           Results for a Vertical Cold Launch Missile System

    • Authors: Głębocki, Jacewicz
      First page: 168
      Abstract: In vertical cold launch the missile starts without the function of the main engine. Over the launcher, the attitude of the missile is controlled by a set of lateral thrusters. However, a quick turn might be disturbed by various uncertainties. This study discusses the problem of the influences of disturbances and the repeatability of lateral thrusters’ ignition on the pitch maneuver quality. The generic 152.4 mm projectile equipped in small, solid propellant lateral thrusters was used as a test platform. A six degree of freedom mathematical model was developed to execute the Monte-Carlo simulations of the launch phase and to prepare the flight test campaign. The parametric analysis was performed to investigate the influence of system uncertainties on quick turn repeatability. A series of ground laboratory trials was accomplished. Thirteen flight tests were completed on the missile test range. The flight parameters were measured using an onboard inertial measurement unit and a ground vision system. It was experimentally proved that the cold vertical launch maneuver could be realized properly with at least two lateral motors. It was found that the initial roll rate of the projectile and the lateral thrusters’ igniters’ uncertainties could affect the pitch angle achieved and must be minimized to reduce the projectile dispersion.
      Citation: Aerospace
      PubDate: 2020-11-28
      DOI: 10.3390/aerospace7120168
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 169: How Well Can Persistent Contrails Be

    • Authors: Klaus Gierens, Sigrun Matthes, Susanne Rohs
      First page: 169
      Abstract: Persistent contrails and contrail cirrus are responsible for a large part of aviation induced radiative forcing. A considerable fraction of their warming effect could be eliminated by diverting only a quite small fraction of flight paths, namely those that produce the highest individual radiative forcing (iRF). In order to make this a viable mitigation strategy it is necessary that aviation weather forecast is able to predict (i) when and where contrails are formed, (ii) which of these are persistent, and (iii) how large the iRF of those contrails would be. Here we study several data bases together with weather data in order to see whether such a forecast would currently be possible. It turns out that the formation of contrails can be predicted with some success, but there are problems to predict contrail persistence. The underlying reason for this is that while the temperature field is quite good in weather prediction and climate simulations with specified dynamics, this is not so for the relative humidity in general and for ice supersaturation in particular. However we find that the weather model shows the dynamical peculiarities that are expected for ice supersaturated regions where strong contrails are indeed found in satellite data. This justifies some hope that the prediction of strong contrails may be possible via general regression involving the dynamical state of the ambient atmosphere.
      Citation: Aerospace
      PubDate: 2020-12-02
      DOI: 10.3390/aerospace7120169
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 170: The Contrail Mitigation Potential of
           Aircraft Formation Flight Derived from High-Resolution Simulations

    • Authors: Simon Unterstrasser
      First page: 170
      Abstract: Formation flight is one potential measure to increase the efficiency of aviation. Flying in the upwash region of an aircraft’s wake vortex field is aerodynamically advantageous. It saves fuel and concomitantly reduces the carbon foot print. However, CO2 emissions are only one contribution to the aviation climate impact among several others (contrails, emission of H2O and NOx). In this study, we employ an established large eddy simulation model with a fully coupled particle-based ice microphysics code and simulate the evolution of contrails that were produced behind formations of two aircraft. For a large set of atmospheric scenarios, these contrails are compared to contrails behind single aircraft. In general, contrails grow and spread by the uptake of atmospheric water vapour. When contrails are produced in close proximity (as in the formation scenario), they compete for the available water vapour and mutually inhibit their growth. The simulations demonstrate that the contrail ice mass and total extinction behind a two-aircraft formation are substantially smaller than for a corresponding case with two separate aircraft and contrails. Hence, this first study suggests that establishing formation flight may strongly reduce the contrail climate effect.
      Citation: Aerospace
      PubDate: 2020-12-05
      DOI: 10.3390/aerospace7120170
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 171: Using Convolutional Neural Networks to
           Automate Aircraft Maintenance Visual Inspection

    • Authors: Anil Doğru, Soufiane Bouarfa, Ridwan Arizar, Reyhan Aydoğan
      First page: 171
      Abstract: Convolutional Neural Networks combined with autonomous drones are increasingly seen as enablers of partially automating the aircraft maintenance visual inspection process. Such an innovative concept can have a significant impact on aircraft operations. Though supporting aircraft maintenance engineers detect and classify a wide range of defects, the time spent on inspection can significantly be reduced. Examples of defects that can be automatically detected include aircraft dents, paint defects, cracks and holes, and lightning strike damage. Additionally, this concept could also increase the accuracy of damage detection and reduce the number of aircraft inspection incidents related to human factors like fatigue and time pressure. In our previous work, we have applied a recent Convolutional Neural Network architecture known by MASK R-CNN to detect aircraft dents. MASK-RCNN was chosen because it enables the detection of multiple objects in an image while simultaneously generating a segmentation mask for each instance. The previously obtained F1 and F2 scores were 62.67% and 59.35%, respectively. This paper extends the previous work by applying different techniques to improve and evaluate prediction performance experimentally. The approach uses include (1) Balancing the original dataset by adding images without dents; (2) Increasing data homogeneity by focusing on wing images only; (3) Exploring the potential of three augmentation techniques in improving model performance namely flipping, rotating, and blurring; and (4) using a pre-classifier in combination with MASK R-CNN. The results show that a hybrid approach combining MASK R-CNN and augmentation techniques leads to an improved performance with an F1 score of (67.50%) and F2 score of (66.37%).
      Citation: Aerospace
      PubDate: 2020-12-07
      DOI: 10.3390/aerospace7120171
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 172: Assessing the Climate Impact of Formation

    • Authors: Katrin Dahlmann, Sigrun Matthes, Hiroshi Yamashita, Simon Unterstrasser, Volker Grewe, Tobias Marks
      First page: 172
      Abstract: An operational measure that is inspired by migrant birds aiming toward the mitigation of aviation climate impact is to fly in aerodynamic formation. When this operational measure is adapted to commercial aircraft it saves fuel and is, therefore, expected to reduce the climate impact of aviation. Besides the total emission amount, this mitigation option also changes the location of emissions, impacting the non-CO2 climate effects arising from NOx and H2O emissions and contrails. Here, we assess these non-CO2 climate impacts with a climate response model to assure a benefit for climate not only due to CO2 emission reductions, but also due to reduced non-CO2 effects. Therefore, the climate response model AirClim is used, which includes CO2 effects and also the impact of water vapor and contrail induced cloudiness as well as the impact of nitrogen dioxide emissions on the ozone and methane concentration. For this purpose, AirClim has been adopted to account for saturation effects occurring for formation flight. The results of the case studies show that the implementation of formation flights in the 50 most popular airports for the year 2017 display an average decrease of fuel consumption by 5%. The climate impact, in terms of average near surface temperature change, is estimated to be reduced in average by 24%, with values of individual formations between 13% and 33%.
      Citation: Aerospace
      PubDate: 2020-12-08
      DOI: 10.3390/aerospace7120172
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 173: Design Space Exploration of a Jet Engine
           Component Using a Combined Object Model for Function and Geometry

    • Authors: Jakob R. Müller, Massimo Panarotto, Ola Isaksson
      First page: 173
      Abstract: The design of aircraft and engine components hinges on the use of computer aided design (CAD) models and the subsequent geometry-based analyses for evaluation of the quality of a concept. However, the generation (and variation) of CAD models to include radical or novel design solutions is a resource intense modelling effort. While approaches to automate the generation and variation of CAD models exist, they neglect the capture and representation of the product’s design rationale—what the product is supposed to do. The design space exploration approach Function and Geometry Exploration (FGE) aims to support the exploration of more functionally and geometrically different product concepts under consideration of not only geometrical, but also teleological aspects. The FGE approach has been presented and verified in a previous presentation. However, in order to contribute to engineering design practice, a design method needs to be validated through application in industrial practice. Hence, this publication reports from a study where the FGE approach has been applied by a design team of a Swedish aerospace manufacturers in a conceptual product development project. Conceptually different alternatives were identified in order to meet the expected functionality of a guide vane (GV). The FGE was introduced and applied in a series of workshops. Data was collected through participatory observation in the design teams by the researchers, as well as interviews and questionnaires. The results reveal the potential of the FGE approach as a design support to: (1) Represent and capture the design rationale and the design space; (2) capture, integrate and model novel solutions; and (3) provide support for the embodiment of novel concepts that would otherwise remain unexplored. In conclusion, the FGE method supports designers to articulate and link the design rationale, including functional requirements and alternative solutions, to geometrical features of the product concepts. The method supports the exploration of alternative solutions as well as functions. However, scalability and robustness of the generated CAD models remain subject to further research.
      Citation: Aerospace
      PubDate: 2020-12-08
      DOI: 10.3390/aerospace7120173
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 174: Validation of Numerical Models of a
           Rotorcraft Crashworthy Seat and Subfloor

    • Authors: Paolo Astori, Mauro Zanella, Matteo Bernardini
      First page: 174
      Abstract: The present work explores some critical aspects of the numerical modeling of a rotorcraft seat and subfloor equipped with energy-absorbing stages, which are paramount in crash landing conditions. To limit the vast complexity of the problem, a purely vertical impact is considered as a reference scenario for an assembly made of a crashworthy helicopter seat and a subfloor section, including an anthropomorphic dummy. A preliminary lumped mass model is used to drive the design of the experimental drop test. Some additional static and dynamic tests are carried out at the coupon and sub-component levels to characterize the seat cushion, the seat pan and the honeycomb elements that were introduced in the structure as energy absorbers. The subfloor section is designed and manufactured with a simplified technique, yet representative of this structural component. Eventually, a finite element model representing the full drop test was created and, together with the original lumped mass model, finally validated against the experimental test, outlining the advantage of using both the numerical techniques for design assistance.
      Citation: Aerospace
      PubDate: 2020-12-10
      DOI: 10.3390/aerospace7120174
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 175: Traffic Network Identification Using
           Trajectory Intersection Clustering

    • Authors: Ingrid Gerdes, Annette Temme
      First page: 175
      Abstract: The current airspace route system consists mainly of pre-defined routes with a low number of intersections to facilitate air traffic controllers to oversee the traffic. Our aim is a method to create an artificial and reliable route network based on planned or as-flown trajectories. The application possibilities of the resulting network are manifold, reaching from the assessment of new air traffic management (ATM) strategies or historical data to a basis for simulation systems. Trajectories are defined as sequences of common points at intersections with other trajectories. All common points of a traffic sample are clustered, and, after further optimization, the cluster centers are used as nodes in the new main-flow network. To build almost-realistic flight trajectories based on this network, additional parameters such as speed and altitude are added to the nodes and the possibility to take detours into account to avoid congested areas is introduced. As optimization criteria, the trajectory length and the structural complexity of the main-flow system are used. Based on these criteria, we develop a new cost function for the optimization process. In addition, we show how different traffic situations are covered by the network. To illustrate the capabilities of our approach, traffic is exemplarily divided into separate classes and class-dependent parameters are assigned. Applied to two real traffic scenarios, the approach was able to emulate the underlying route systems with a difference in median trajectory length of 0.2%, resp. 0.5% compared to the original routes.
      Citation: Aerospace
      PubDate: 2020-12-10
      DOI: 10.3390/aerospace7120175
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 176: Modelling Flexibility and Qualification
           Ability to Assess Electric Propulsion Architectures for Satellite

    • Authors: Massimo Panarotto, Olivia Borgue, Ola Isaksson
      First page: 176
      Abstract: The higher satellite production rates expected in new megaconstellation scenarios involve radical changes in the way design trade-offs need to be considered by electric propulsion companies. In relative comparison, flexibility and qualification ability will have a higher impact in megaconstellations compared to traditional businesses. For these reasons, this paper proposes a methodology for assessing flexible propulsion architectures by taking into account variations in market behavior and qualification activities. Through the methodology, flexibility and qualification ability can be traded against traditional engineering attributes (such as functional performances) in a quantitative way. The use of the methodology is illustrated through an industrial case related to the study of xenon vs. krypton architectures for megaconstellation businesses. This paper provides insights on how to apply the methodology in other case studies, in order to enable engineering teams to present and communicate the impact of alternative architectural concepts to program managers and decision-makers.
      Citation: Aerospace
      PubDate: 2020-12-11
      DOI: 10.3390/aerospace7120176
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 177: Application of the HPCMP CREATETM-AV Kestrel
           to an Integrated Propeller Prediction

    • Authors: Pooneh Aref, Mehdi Ghoreyshi, Adam Jirasek, Jürgen Seidel
      First page: 177
      Abstract: This article presents the results of a computational investigation of an integrated propeller test case using the HPCMP CREATETM-AV Kestrel simulation tools. There is a renewed interest in propeller-driven aircraft for unmanned aerial vehicles, electric aircraft, and flying taxies. Computational resources can significantly accelerate the generation of aerodynamic models for these vehicles and reduce the development cost if the prediction tools can accurately predict the aircraft/propeller aerodynamic interactions. Unfortunately, limited propeller experimental data are available to validate computational methods. An American Institute of Aeronautics and Astronautics (AIAA) workshop was therefore established to address this problem. The objective of this workshop was to generate an open access-powered wind tunnel test database for computational validation of propeller effects on the wing aerodynamics, specifically for wing-tip-mounted propellers. The propeller selected for the workshop has four blades and a diameter of 16.2 in. The wing has a root and tip chord of 11.6 and 8.6 in, respectively. Two different simulation approaches were used: one using a single grid including wind tunnel walls and the second using a subset grid overset to an adaptive Cartesian grid that fills the space between the near-body grid and wind tunnel walls. The predictions of both approaches have been compared with available experimental data from the Lockheed Martin low-speed wind tunnel to investigate the grid resolution required for accurate prediction of flowfield data. The results show a good agreement for all tested conditions. The measured and predicted data show that wing aerodynamic performance is improved by the spinning tip-mounted propeller.
      Citation: Aerospace
      PubDate: 2020-12-11
      DOI: 10.3390/aerospace7120177
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 178: Analysis of Aircraft Maintenance Related
           Accidents and Serious Incidents in Nigeria

    • Authors: Khadijah Abdullahi Habib, Cengiz Turkoglu
      First page: 178
      Abstract: The maintenance of aircraft presents considerable challenges to the personnel that maintain them. Challenges such as time pressure, system complexity, sparse feedback, cramped workspaces, etc., are being faced by these personnel on a daily basis. Some of these challenges cause aircraft-maintenance-related accidents and serious incidents. However, there is little formal empirical work that describes the influence of aircraft maintenance to aircraft accidents and incidents in Nigeria. This study, therefore, sets out to explore the contributory factors to aircraft-maintenance-related incidents from 2006 to 2019 and accidents from 2009 to 2019 in Nigeria, to achieve a deeper understanding of this safety critical aspect of the aviation industry, create awareness amongst the relevant stakeholders and seek possible mitigating factors. To attain this, a content analysis of accident reports and mandatory occurrence reports, which occurred in Nigeria, was carried out using the Maintenance Factors and Analysis Classification System (MxFACS) and Hieminga’s maintenance incidents taxonomy. An inter-rater concordance value was used to ascertain research accuracy after evaluation of the data output by subject matter experts. The highest occurring maintenance-related incidents and accidents were attributed to “removal/installation”, working practices such as “accumulation of dirt and contamination”, “inspection/testing”, “inadequate oversight from operator and regulator”, “failure to follow procedures” and “incorrect maintenance”. To identify the root cause of these results, maintenance engineers were consulted via a survey to understand the root causes of these contributory factors. The results of the study revealed that the most common maintenance-related accidents and serious incidents in the last decade are “collision with terrain” and “landing gear events’’. The most frequent failures at systems level resulting in accidents are the “engines” and “airframe structure”. The maintenance factors with the highest contribution to these accidents are “operator and regulatory oversight”, “inadequate inspection” and “failure to follow procedures”. The research also highlights that the highest causal and contributory factors to aviation incidents in Nigeria from 2006 to 2019 are “installation/removal issues”, “inspection/testing issues”, “working practices”, “job close up”, “lubrication and servicing”, all of which corresponds to studies by other researchers in other countries.
      Citation: Aerospace
      PubDate: 2020-12-11
      DOI: 10.3390/aerospace7120178
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 179: Trajectory Design of Perseus: A CubeSat
           Mission Concept to Phobos

    • Authors: Ravi teja Nallapu, Graham Dektor, Nalik Kenia, James Uglietta, Shota Ichikawa, Mercedes Herreras-Martinez, Akshay Choudhari, Aman Chandra, Stephen Schwartz, Erik Asphaug, Jekanthan Thangavelautham
      First page: 179
      Abstract: The Martian satellites Phobos and Deimos hold many unanswered questions that may provide clues to the origin of Mars. These moons are low Δv stopover sites to Mars. Some human missions to Mars typically identify Phobos and Deimos as staging bases for Mars surface exploration. Astronauts could base initial operations there in lieu of repeated voyages to and from the planet surface, to refuel transiting spacecraft, to teleoperate robotics and other critical machinery, and to develop habitable infrastructure ahead of human landings. Despite their strategic and scientific significance, there has been no successful dedicated mission to either moon. For this reason, we propose Perseus, a geological imaging CubeSat mission to Phobos. Perseus, a 27U, 54kg CubeSat will return thermal and visible images at resolutions better than currently available over most of Phobos’ surface. This includes visible images at 5m/pixel and thermal images at 25m/pixel of Phobos’ surface. The Perseus mission is nominally intended to be a co-orbital mission, where the spacecraft will encounter Phobos on its Martian orbit. However, a hyperbolic rendezvous mission concept, to image Phobos on a hyperbolic flyby, is also considered to reduce the risks associated with orbit capture and to reduce mission costs. This paper presents the preliminary feasibility, science objectives, and technological development challenges of achieving these science goals. We then formulate two rendezvous concepts as a series of three nonlinear optimization problems that span the design tree of mission concepts. The tree’s root node is the heliocentric cruise problem, which identifies the near-optimal launch and arrival windows for the Perseus spacecraft. The leaf nodes of the design tree are the two rendezvous concepts that identify near-optimal co-orbital and hyperbolic trajectories for Phobos’ reconnaissance. The design problems are solved using evolutionary algorithms, and the performance of the selected mission concepts is then examined. The results indicate that a co-orbital encounter allows about one encounter per day with about 6 min per encounter. The hyperbolic encounter, on the other hand, allows a single encounter where the spacecraft will spend about 2 min in the imaging region with respect to Phobos. The spacecraft will obtain higher resolution images of Phobos on this feasible region than have ever been seen for most of the surface. These detailed images will help identify candidate landing sites and provide critical data to derisk future surface missions to Phobos.
      Citation: Aerospace
      PubDate: 2020-12-15
      DOI: 10.3390/aerospace7120179
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 180: Deployment of Solar Sails by Joule Effect:
           Thermal Analysis and Experimental Results

    • Authors: Gianluigi Bovesecchi, Sandra Corasaniti, Girolamo Costanza, Fabrizio Paolo Piferi, Maria Elisa Tata
      First page: 180
      Abstract: Space vehicles may be propelled by solar sails exploiting the radiation pressure coming from the sun and applied on their surfaces. This work deals with the adoption of Nickel-Titanium Shape Memory Alloy (SMA) elements in the sail deployment mechanism activated by the Joule Effect, i.e., using the same SMA elements as a resistance within suitable designed electrical circuits. Mathematical models were analyzed for the thermal analysis by implementing algorithms for the evaluation of the temperature trend depending on the design parameters. Several solar sail prototypes were built up and tested with different number, size, and arrangement of the SMA elements, as well as the type of the selected electrical circuit. The main parameters were discussed in the tested configurations and advantages discussed as well.
      Citation: Aerospace
      PubDate: 2020-12-16
      DOI: 10.3390/aerospace7120180
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 181: Energy Transition in Aviation: The Role of
           Cryogenic Fuels

    • Authors: Arvind Gangoli Rao, Feijia Yin, Henri G.C. Werij
      First page: 181
      Abstract: Aviation is the backbone of our modern society. In 2019, around 4.5 billion passengers travelled through the air. However, at the same time, aviation was also responsible for around 5% of anthropogenic causes of global warming. The impact of the COVID-19 pandemic on the aviation sector in the short term is clearly very high, but the long-term effects are still unknown. However, with the increase in global GDP, the number of travelers is expected to increase between three- to four-fold by the middle of this century. While other sectors of transportation are making steady progress in decarbonizing, aviation is falling behind. This paper explores some of the various options for energy carriers in aviation and particularly highlights the possibilities and challenges of using cryogenic fuels/energy carriers such as liquid hydrogen (LH2) and liquefied natural gas (LNG).
      Citation: Aerospace
      PubDate: 2020-12-18
      DOI: 10.3390/aerospace7120181
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 182: Advanced Passenger Movement Model Depending
           On the Aircraft Cabin Geometry

    • Authors: Marc Engelmann, Tim Kleinheinz, Mirko Hornung
      First page: 182
      Abstract: The aircraft cabin and boarding procedures are steadily increasing focus points for both aircraft manufacturers and airlines, as they play a key part in the customer experience. In the German research project AVACON (AdVAnced Aircraft CONcepts), the boarding procedure is assessed using the PAXelerate boarding simulation. As the project demands an increased level of detail concerning the passenger movement model, this publication introduces an improved methodology. Additions to the model include the development of a method capable of describing the passenger walking speed in dependence of the surrounding objects, their proximity as well as the location of other passengers within the cabin. The validation of the model is performed using the AVACON research baseline and an Airbus A320. The model is then applied to an altered version of the Airbus A320 with an extended aisle and to a COVID-19 safe distance scenario. Regarding the results, an extended aisle width delivers boarding times reduced by up to 3%, whereas the COVID-19 assessment delivers a 67% increase in boarding times. Concluding, the integration of the newly developed model empowers PAXelerate to simulate a more detailed boarding process and enables a better understanding of the influence of cabin layout changes to an aircraft’s boarding performance.
      Citation: Aerospace
      PubDate: 2020-12-20
      DOI: 10.3390/aerospace7120182
      Issue No: Vol. 7, No. 12 (2020)
  • Aerospace, Vol. 7, Pages 153: Polyatomic Ion-Induced Electron Emission
           (IIEE) in Electrospray Thrusters

    • Authors: Jared M. Magnusson, Adam L. Collins, Richard E. Wirz
      First page: 153
      Abstract: To better characterize the lifetime and performance of electrospray thrusters, electron emission due to electrode impingement by the propellant cation 1-ethyl-3-methylimidazolium (EMI+) has been evaluated with semi-empirical modeling techniques. Results demonstrate that electron emission due to grid impingement by EMI+ cations becomes significant once EMI+ attains a threshold velocity of ∼9e5cm/s. The mean secondary electron yield, γ¯, exhibits strong linearity with respect to EMI+ velocity for typical electrospray operating regimes, and we present a simple linear fit equation corresponding to thruster potentials greater than 1kV. The model chosen for our analysis was shown to be the most appropriate for molecular ion bombardments and is a useful tool in estimating IIEE yields in electrospray devices for molecular ion masses less than ∼scientific−notation=false1000u and velocities greater than ∼e6cm/s. Droplet-induced electron emission (DIEE) in electrospray thrusters was considered by treating a droplet as a macro-ion, with low charge-to-mass ratio, impacting a solid surface. This approach appears to oversimplify back-spray phenomena, meaning a more complex analysis is required. While semi-empirical models of IIEE, and the decades of solid state theory they are based upon, represent an invaluable advance in understanding secondary electron emission in electrospray devices, further progress would be gained by investigating the complex surfaces the electrodes acquire over their lifetimes and considering other possible emission processes.
      Citation: Aerospace
      PubDate: 2020-10-24
      DOI: 10.3390/aerospace7110153
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 154: A Performance-Based Airspace Model for
           Unmanned Aircraft Systems Traffic Management

    • Authors: Nichakorn Pongsakornsathien, Suraj Bijjahalli, Alessandro Gardi, Angus Symons, Yuting Xi, Roberto Sabatini, Trevor Kistan
      First page: 154
      Abstract: Recent evolutions of the Unmanned Aircraft Systems (UAS) Traffic Management (UTM) concept are driving the introduction of new airspace structures and classifications, which must be suitable for low-altitude airspace and provide the required level of safety and flexibility, particularly in dense urban and suburban areas. Therefore, airspace classifications and structures need to evolve based on appropriate performance metrics, while new models and tools are needed to address UTM operational requirements, with an increasing focus on the coexistence of manned and unmanned Urban Air Mobility (UAM) vehicles and associated Communication, Navigation and Surveillance (CNS) infrastructure. This paper presents a novel airspace model for UTM adopting Performance-Based Operation (PBO) criteria, and specifically addressing urban airspace requirements. In particular, a novel airspace discretisation methodology is introduced, which allows dynamic management of airspace resources based on navigation and surveillance performance. Additionally, an airspace sectorisation methodology is developed balancing the trade-off between communication overhead and computational complexity of trajectory planning and re-planning. Two simulation case studies are conducted: over the skyline and below the skyline in Melbourne central business district, utilising Global Navigation Satellite Systems (GNSS) and Automatic Dependent Surveillance-Broadcast (ADS-B). The results confirm that the proposed airspace sectorisation methodology promotes operational safety and efficiency and enhances the UTM operators’ situational awareness under dense traffic conditions introducing a new effective 3D airspace visualisation scheme, which is suitable both for mission planning and pre-tactical UTM operations. Additionally, the proposed performance-based methodology can accommodate the diversity of infrastructure and vehicle performance requirements currently envisaged in the UTM context. This facilitates the adoption of this methodology for low-level airspace integration of UAS (which may differ significantly in terms of their avionics CNS capabilities) and set foundations for future work on tactical online UTM operations.
      Citation: Aerospace
      PubDate: 2020-10-28
      DOI: 10.3390/aerospace7110154
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 155: A Simulation-Based Performance Analysis Tool
           for Aircraft Design Workflows

    • Authors: Agostino De Marco, Vittorio Trifari, Fabrizio Nicolosi, Manuela Ruocco
      First page: 155
      Abstract: A simulation-based approach for take-off and landing performance assessments is presented in this work. In the context of aircraft design loops, it provides a detailed and flexible formulation that can be integrated into a wider simulation methodology for a complete commercial aviation mission. As a matter of fact, conceptual and preliminary aircraft design activities require iterative calculations to quickly make performance predictions on a set of possible airplane configurations. The goal is to search for a design that best fits all top level aircraft requirements among the results of a great number of multi-disciplinary analyses, as fast as possible, and with a certain grade of accuracy. Usually, such a task is carried out using statistical or semi-empirical approaches which can give pretty accurate results in no time. However, those prediction methods may be inappropriate when dealing with innovative aircraft configurations or whenever a higher level of accuracy is necessary. Simulation-based design has become crucial to make the overall process affordable and effective in cases where higher fidelity analyses are required. A common example when flight simulations can be effectively used to support a design loop is given by aircraft mission analyses and performance predictions. These usually include take-off, climb, en route, loiter, approach, and landing simulations. This article introduces the mathematical models of aircraft take-off and landing and gives the details of how they are implemented in the software library JPAD. These features are not present in most of the currently available pieces of preliminary aircraft design software and allow one to perform high fidelity, simulation-based take-off and landing analyses within design iterations. Although much more detailed than classical semi-empirical approaches, the presented methodologies require very limited computational effort. An application of the proposed formulations is introduced in the second part of the article. The example considers the Airbus A220-300 as a reference aircraft model and includes complete take-off and landing performance studies, as well as the simulation of both take-off and landing certification noise trajectories.
      Citation: Aerospace
      PubDate: 2020-10-30
      DOI: 10.3390/aerospace7110155
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 156: Climate-Optimized Trajectories and Robust
           Mitigation Potential: Flying ATM4E

    • Authors: Sigrun Matthes, Benjamin Lührs, Katrin Dahlmann, Volker Grewe, Florian Linke, Feijia Yin, Emma Klingaman, Keith P. Shine
      First page: 156
      Abstract: Aviation can reduce its climate impact by controlling its CO2-emission and non-CO2 effects, e.g., aviation-induced contrail-cirrus and ozone caused by nitrogen oxide emissions. One option is the implementation of operational measures that aim to avoid those atmospheric regions that are in particular sensitive to non-CO2 aviation effects, e.g., where persistent contrails form. The quantitative estimates of mitigation potentials of such climate-optimized aircraft trajectories are required, when working towards sustainable aviation. The results are presented from a comprehensive modelling approach when aiming to identify such climate-optimized aircraft trajectories. The overall concept relies on a multi-dimensional environmental change function concept, which is capable of providing climate impact information to air traffic management (ATM). Estimates on overall climate impact reduction from a one-day case study are presented that rely on the best estimate for climate impact information. Specific weather situation that day, containing regions with high contrail impact, results in a potential reduction of total climate impact, by more than 40%, when considering CO2 and non-CO2 effects, associated with an increase of fuel by about 0.5%. The climate impact reduction per individual alternative trajectory shows a strong variation and, hence, also the mitigation potential for an analyzed city pair, depending on atmospheric characteristics along the flight corridor as well as flight altitude. The robustness of proposed climate-optimized trajectories is assessed by using a range of different climate metrics. A more sustainable ATM needs to integrate comprehensive environmental impacts and associated forecast uncertainties into route optimization in order to identify robust eco-efficient trajectories.
      Citation: Aerospace
      PubDate: 2020-10-30
      DOI: 10.3390/aerospace7110156
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 157: A Novel Holistic Index for the Optimization
           of Composite Components and Manufacturing Processes with Regard to
           Quality, Life Cycle Costs and Environmental Performance

    • Authors: Christos V. Katsiropoulos, Spiros G. Pantelakis
      First page: 157
      Abstract: In the present work, a novel holistic component and process optimization index is introduced. The Index is aimed to provide a decision support tool for the optimization of aircraft composite components and manufacturing processes as well as for the selection of the appropriate manufacturing technique of a component when various techniques are considered as manufacturing options. The criteria involved in the index are quality, cost and environmental footprint functions which are considered to be interdependent. In the present concept quality is quantified through measurable technological features which are required for the component under consideration. Cost has been estimated by implementing the Activity Based Concept (ABC) using an in house developed tool. Environmental footprint is assessed by exploiting the ReCiPe method using the ‘open LCA’ software. The weight factor of each of the above criteria in the Index is calculated by using the Multi Criteria Decision (MCD) method Analytic Hierarchy Process (AHP). The Index developed has been applied to support the selection of the appropriate production technique for a typical aeronautical composite part. The alternative manufacturing options considered have been the Automated Fiber Placement (AFP) as well as the classical Autoclave manufacturing technique. By considering quality as the prevailing factor for meeting a decision the index confirms the advantage of the Autoclave process. Yet, by considering the environmental footprint and/or cost to be of equal or higher significance to quality, the implementation of the index demonstrates the clear advantage of AFP process.
      Citation: Aerospace
      PubDate: 2020-10-30
      DOI: 10.3390/aerospace7110157
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 158: Method to Characterize Potential UAS
           Encounters Using Open Source Data

    • Authors: Andrew Weinert
      First page: 158
      Abstract: As unmanned aerial systems (UASs) increasingly integrate into the US national airspace system, there is an increasing need to characterize how commercial and recreational UASs may encounter each other. To inform the development and evaluation of safety critical technologies, we demonstrate a methodology to analytically calculate all potential relative geometries between different UAS operations performing inspection missions. This method is based on a previously demonstrated technique that leverages open source geospatial information to generate representative unmanned aircraft trajectories. Using open source data and parallel processing techniques, we performed trillions of calculations to estimate the relative horizontal distance between geospatial points across sixteen locations.
      Citation: Aerospace
      PubDate: 2020-11-04
      DOI: 10.3390/aerospace7110158
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 159: Utilization of FPGA for Onboard Inference of
           Landmark Localization in CNN-Based Spacecraft Pose Estimation

    • Authors: Kiruki Cosmas, Asami Kenichi
      First page: 159
      Abstract: In the recent past, research on the utilization of deep learning algorithms for space applications has been widespread. One of the areas where such algorithms are gaining attention is in spacecraft pose estimation, which is a fundamental requirement in many spacecraft rendezvous and navigation operations. Nevertheless, the application of such algorithms in space operations faces unique challenges compared to application in terrestrial operations. In the latter, they are facilitated by powerful computers, servers, and shared resources, such as cloud services. However, these resources are limited in space environment and spacecrafts. Hence, to take advantage of these algorithms, an on-board inferencing that is power- and cost-effective is required. This paper investigates the use of a hybrid Field Programmable Gate Array (FPGA) and Systems-on-Chip (SoC) device for efficient onboard inferencing of the Convolutional Neural Network (CNN) part of such pose estimation methods. In this study, Xilinx’s Zynq UltraScale+ MPSoC device is used and proposed as an effective onboard-inferencing solution. The performance of the onboard and computer inferencing is compared, and the effectiveness of the hybrid FPGA-CPU architecture is verified. The FPGA-based inference has comparable accuracy to the PC-based inference with an average RMS error difference of less than 0.55. Two CNN models that are based on encoder-decoder architecture have been investigated in this study and three approaches demonstrated for landmarks localization.
      Citation: Aerospace
      PubDate: 2020-11-05
      DOI: 10.3390/aerospace7110159
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 160: Influence of Satellite Motion Control System
           Parameters on Performance of Space Debris Capturing

    • Authors: Mahdi Akhloumadi, Danil Ivanov
      First page: 160
      Abstract: Relative motion control problem for capturing the tumbling space debris object is considered. Onboard thrusters and reaction wheels are used as actuators. The nonlinear coupled relative translational and rotational equations of motion are derived. The SDRE-based control algorithm is applied to the problem. It is taken into account that the thrust vector has misalignment with satellite center of mass, and reaction wheels saturation affects the ability of the satellite to perform the docking maneuver to space debris. The acceptable range of a set of control system parameters for successful rendezvous and docking is studied using numerical simulations taking into account thruster discreteness, actuators constrains, and attitude motion of the tumbling space debris.
      Citation: Aerospace
      PubDate: 2020-11-06
      DOI: 10.3390/aerospace7110160
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 161: Multifidelity Sensitivity Study of Subsonic
           Wing Flutter for Hybrid Approaches in Aircraft Multidisciplinary Design
           and Optimisation

    • Authors: Marco Berci, Francesco Torrigiani
      First page: 161
      Abstract: A comparative sensitivity study for the flutter instability of aircraft wings in subsonic flow is presented, using analytical models and numerical tools with different multidisciplinary approaches. The analyses build on previous elegant works and encompass parametric variations of aero-structural properties, quantifying their effect on the aeroelastic stability boundary. Differences in the multifidelity results are critically assessed from both theoretical and computational perspectives, in view of possible practical applications within airplane preliminary design and optimisation. A robust hybrid strategy is then recommended, wherein the flutter boundary is obtained using a higher-fidelity approach while the flutter sensitivity is computed adopting a lower-fidelity approach.
      Citation: Aerospace
      PubDate: 2020-11-12
      DOI: 10.3390/aerospace7110161
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 162: Neuro-Fuzzy Network-Based Reduced-Order
           Modeling of Transonic Aileron Buzz

    • Authors: Rebecca Zahn, Christian Breitsamter
      First page: 162
      Abstract: In the present work, a reduced-order modeling (ROM) framework based on a recurrent neuro-fuzzy model (NFM) that is serial connected with a multilayer perceptron (MLP) neural network is applied for the computation of transonic aileron buzz. The training data set for the specified ROM is obtained by performing forced-motion unsteady Reynolds-averaged Navier Stokes (URANS) simulations. Further, a Monte Carlo-based training procedure is applied in order to estimate statistical errors. In order to demonstrate the method’s fidelity, a two-dimensional aeroelastic model based on the NACA651213 airfoil is investigated at different flow conditions, while the aileron deflection and the hinge moment are considered in particular. The aileron is integrated in the wing section without a gap and is modeled as rigid. The dynamic equations of the rigid aileron rotation are coupled with the URANS-based flow model. For ROM training purposes, the aileron is excited via a forced motion and the respective aerodynamic and aeroelastic response is computed using a computational fluid dynamics (CFD) solver. A comparison with the high-fidelity reference CFD solutions shows that the essential characteristics of the nonlinear buzz phenomenon are captured by the selected ROM method.
      Citation: Aerospace
      PubDate: 2020-11-13
      DOI: 10.3390/aerospace7110162
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 163: A Test Platform to Assess the Impact of
           Miniaturized Propulsion Systems

    • Authors: Fabrizio Stesina, Sabrina Corpino, Daniele Calvi
      First page: 163
      Abstract: Miniaturized propulsion systems can enable many future CubeSats missions. The advancement of the Technology Readiness Level of this technology passes through the integration in a CubeSat platform and the assessment of the impact and the interactions of the propulsion systems on the actual CubeSat technology and vice versa. The request of power, the thermal environmental, and the electromagnetic emissions generated inside the platform require careful analyses. This paper presents the upgraded design and the validation of a CubeSat test platform (CTP) that can interface a wide range of new miniaturized propulsion systems and gather unprecedented information for these analyses, which can be fused with the commonly used ground support equipment. The CTP features are reported, and the main achievements of the tests are shown, demonstrating the effective capabilities of the platform and how it allows for the investigation of the mutual interactions at system level between propulsion systems and the CubeSat technology.
      Citation: Aerospace
      PubDate: 2020-11-16
      DOI: 10.3390/aerospace7110163
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 164: Static Aeroelasticity Using High Fidelity
           Aerodynamics in a Staggered Coupled and ROM Scheme

    • Authors: Angelos Kafkas, George Lampeas
      First page: 164
      Abstract: Current technology in evaluating the aeroelastic behavior of aerospace structures is based on the staggered coupling between structural and low fidelity linearized aerodynamic solvers, which has inherent limitations, although tried and trusted outside the transonic region. These limitations arise from the assumptions in the formulation of linearized aerodynamics and the lower fidelity in the description of the flowfield surrounding the structure. The validity of low fidelity aerodynamics also degrades fast with the deviation from a typical aerodynamic shape due to the inclusion of various control devices, gaps, or discontinuities. As innovative wings tend to become more flexible and also include a variety of morphing devices, it is expected that using low fidelity linearized aerodynamics in aeroelastic analysis will tend to induce higher levels of uncertainty in the results. An obvious solution to these issues is to use high fidelity aerodynamics. However, using high fidelity aerodynamics incurs a very high computational cost. Various formulations of reduced order models have shown promising results in reducing the computational cost. In the present work, the static aeroelastic behavior of three characteristic aeroelastic problems is obtained using both a full three-dimensional staggered coupled scheme and a time domain Volterra series based reduced order model (ROM). The reduced order model’s ability to remain valid for a wide range of dynamic pressures around a specific Mach number (and Reynolds number regime if viscous flow is considered) and the capability to modify structural parameters such as damping ratios and natural frequencies are highlighted.
      Citation: Aerospace
      PubDate: 2020-11-17
      DOI: 10.3390/aerospace7110164
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 165: Evaluation of Strategies to Reduce the Cost
           Impacts of Flight Delays on Total Network Costs

    • Authors: Judith Rosenow, Philipp Michling, Michael Schultz, Jörn Schönberger
      First page: 165
      Abstract: Competitive price pressure and economic cost pressure constantly force airlines to improve their optimization strategies. Besides predictable operational costs, delay costs are a significant cost driver for airlines. Especially reactionary delay costs can endanger the profitability of such a company. These time-dependent costs depend on the number of sensitive transfer passengers. This cost component is represented by the number of missed flights and the connectivity of onward flights, i.e., the offer of alternative flight connections. The airline has several options to compensate for reactionary delays, for example, by increasing cruising speeds, shortening turnaround times, rebookings and cancellations. The effects of these options on the cost balance of airline total operating costs have been examined in detail, considering a flight-specific number of transfer passengers. The results have been applied to a 24-h rotation schedule of a large German hub airport. We found, that the fast turnaround and increasing cruise speed are the most effective strategies to compensate for passenger-specific delay costs. The results could be used in a multi-criteria trajectory optimization to find a balance between environmentally-driven and cost-index-driven detours and speed adjustments.
      Citation: Aerospace
      PubDate: 2020-11-18
      DOI: 10.3390/aerospace7110165
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 166: On the Design of Aeroelastically Scaled
           Models of High Aspect-Ratio Wings

    • Authors: Frederico Afonso, Mónica Coelho, José Vale, Fernando Lau, Afzal Suleman
      First page: 166
      Abstract: Recently, innovative aircraft designs were proposed to improve aerodynamic performance. Examples include high aspect ratio wings to reduce the aerodynamic induced drag to achieve lower fuel consumption. Such solution when combined with a lightweight structure may lead to aeroelastic instabilities such as flutter at lower air speeds compared to more conventional wing designs. Therefore, in order to ensure safe flight operation, it is important to study the aeroelastic behavior of the wing throughout the flight envelope. This can be achieved by either experimental or computational work. Experimental wind tunnel and scaled flight test models need to exhibit similar aeroelastic behavior to the full scale air vehicle. In this paper, three different aeroelastic scaling strategies are formulated and applied to a flexible high aspect-ratio wing. These scaling strategies are first evaluated in terms of their ability to generate reduced models with the intended representations of the aerodynamic, structural and inertial characteristics. Next, they are assessed in terms of their potential in representing the unsteady non-linear aeroelastic behavior in three different flight conditions. The scaled models engineered by exactly scaling down the internal structure suitably represent the intended aeroelastic behavior and allow the performance assessment for the entire flight envelope. However, since both the flight and wind tunnel models are constrained by physical and budgetary limitations, custom built structural models are more likely to be selected. However, the latter ones are less promising to study the entire flight envelope.
      Citation: Aerospace
      PubDate: 2020-11-18
      DOI: 10.3390/aerospace7110166
      Issue No: Vol. 7, No. 11 (2020)
  • Aerospace, Vol. 7, Pages 139: Computational Evaluation of Control Surfaces
           Aerodynamics for a Mid-Range Commercial Aircraft

    • Authors: Nunzio Natale, Teresa Salomone, Giuliano De Stefano, Antonio Piccolo
      First page: 139
      Abstract: Computational fluid dynamics is employed to predict the aerodynamic properties of the prototypical trailing-edge control surfaces for a small, regional transport, commercial aircraft. The virtual experiments are performed at operational flight conditions, by resolving the mean turbulent flow field around a realistic model of the whole aircraft. The Reynolds-averaged Navier–Stokes approach is used, where the governing equations are solved with a finite volume-based numerical method. The effectiveness of the flight control system, during a hypothetical conceptual pre-design phase, is studied by conducting simulations at different angles of deflection, and examining the variation of the aerodynamic loading coefficients. The proposed computational modeling approach is verified to have good practical potential, also compared with reference industrial data provided by the Leonardo Aircraft Company.
      Citation: Aerospace
      PubDate: 2020-09-25
      DOI: 10.3390/aerospace7100139
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 140: Risk Assessment for UAS Logistic Delivery
           under UAS Traffic Management Environment

    • Authors: Pei-Chi Shao
      First page: 140
      Abstract: Resulting from a mature accomplishment of the unmanned aircraft system (UAS), it is feasible to be adopted into logistic delivery services. The supporting technologies should be identified and examined, accompanying with the risk assessment. This paper surveys the risk assessment studies for UAVs. The expected level of safety (ELS) analysis is a key factor to safety concerns. By introducing the UTM infrastructure, the UAS implementation can be monitored. From the NASA technical capability level (TCL), UAV in beyond visual line of sight (BVLOS) flights would need certain verifications. Two UAS logistic delivery case studies are tested to assert the UAS services. To examine the ELS to ground risk and air risk, the case studies result in acceptable data to support the UAS logistic delivery with adequate path planning in the remote and suburban areas in Taiwan.
      Citation: Aerospace
      PubDate: 2020-09-25
      DOI: 10.3390/aerospace7100140
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 141: Emission Modes in Electrospray Thrusters
           Operating with High Conductivity Ionic Liquids

    • Authors: Nolan M. Uchizono, Adam L. Collins, Anirudh Thuppul, Peter L. Wright, Daniel Q. Eckhardt, John Ziemer, Richard E. Wirz
      First page: 141
      Abstract: Electrospray thruster life and mission performance are strongly influenced by grid impingement, the extent of which can be correlated with emission modes that occur at steady-state extraction voltages, and thruster command transients. Most notably, we experimentally observed skewed cone-jet emission during steady-state electrospray thruster operation, which leads to the definition of an additional grid impingement mechanism that we termed “tilted emission”. Long distance microscopy was used in conjunction with high speed videography to observe the emission site of an electrospray thruster operating with an ionic liquid propellant (EMI-Im). During steady-state thruster operation, no unsteady electrohydrodynamic emission modes were observed, though the conical meniscus exhibited steady off-axis tilt of up to 15. Cone tilt angle was independent over a wide range of flow rates but proved strongly dependent on extraction voltage. For the geometry and propellant used, the optimal extraction voltage was near 1.6kV. A second experiment characterized transient emission behavior by observing startup and shutdown of the thruster via flow or voltage. Three of the four possible startup and shutdown procedures transition to quiescence within ∼475s, with no observed unsteady modes. However, during voltage-induced thruster startup, unsteady electrohydrodynamic modes were observed.
      Citation: Aerospace
      PubDate: 2020-09-25
      DOI: 10.3390/aerospace7100141
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 142: Automated Design of CubeSats using
           Evolutionary Algorithm for Trade Space Selection

    • Authors: Himangshu Kalita, Jekan Thangavelautham
      First page: 142
      Abstract: The miniaturization of electronics, sensors, and actuators has enabled the growing use of nanosatellites for earth observation, astrophysics, and even interplanetary missions. This rise of nanosatellites has led to the development of an inventory of modular, interchangeable commercially-off-the-shelf (COTS) components by a multitude of commercial vendors. As a result, the capability of combining subsystems in a compact platform has considerably advanced in the last decade. However, to ascertain these spacecraft’s maximum capabilities in terms of mass, volume, and power, there is an important need to optimize their design. Current spacecraft design methods need engineering experience and judgements made by of a team of experts, which can be labor intensive and might lead to a sub-optimal design. In this work we present a compelling alternative approach using machine learning to identify near-optimal solutions to extend the capabilities of a design team. The approach enables automated design of a spacecraft that requires developing a virtual warehouse of components and specifying quantitative goals to produce a candidate design. The near-optimal solutions found through this approach would be a credible starting point for the design team that will need further study to determine their implementation feasibility.
      Citation: Aerospace
      PubDate: 2020-09-28
      DOI: 10.3390/aerospace7100142
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 143: Natural Language Processing Based Method for
           Clustering and Analysis of Aviation Safety Narratives

    • Authors: Rodrigo L. Rose, Tejas G. Puranik, Dimitri N. Mavris
      First page: 143
      Abstract: The complexity of commercial aviation operations has grown substantially in recent years, together with a diversification of techniques for collecting and analyzing flight data. As a result, data-driven frameworks for enhancing flight safety have grown in popularity. Data-driven techniques offer efficient and repeatable exploration of patterns and anomalies in large datasets. Text-based flight safety data presents a unique challenge in its subjectivity, and relies on natural language processing tools to extract underlying trends from narratives. In this paper, a methodology is presented for the analysis of aviation safety narratives based on text-based accounts of in-flight events and categorical metadata parameters which accompany them. An extensive pre-processing routine is presented, including a comparison between numeric models of textual representation for the purposes of document classification. A framework for categorizing and visualizing narratives is presented through a combination of k-means clustering and 2-D mapping with t-Distributed Stochastic Neighbor Embedding (t-SNE). A cluster post-processing routine is developed for identifying driving factors in each cluster and building a hierarchical structure of cluster and sub-cluster labels. The Aviation Safety Reporting System (ASRS), which includes over a million de-identified voluntarily submitted reports describing aviation safety incidents for commercial flights, is analyzed as a case study for the methodology. The method results in the identification of 10 major clusters and a total of 31 sub-clusters. The identified groupings are post-processed through metadata-based statistical analysis of the learned clusters. The developed method shows promise in uncovering trends from clusters that are not evident in existing anomaly labels in the data and offers a new tool for obtaining insights from text-based safety data that complement existing approaches.
      Citation: Aerospace
      PubDate: 2020-09-28
      DOI: 10.3390/aerospace7100143
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 144: In-Flight Aircraft Trajectory Optimization
           within Corridors Defined by Ensemble Weather Forecasts

    • Authors: Martin Lindner, Judith Rosenow, Thomas Zeh, Hartmut Fricke
      First page: 144
      Abstract: Today, each flight is filed as a static route not later than one hour before departure. From there on, changes of the lateral route initiated by the pilot are only possible with air traffic control clearance and in the minority. Thus, the initially optimized trajectory of the flight plan is flown, although the optimization may already be based upon outdated weather data at take-off. Global weather data as those modeled by the Global Forecast System do, however, contain hints on forecast uncertainties itself, which is quantified by considering so-called ensemble forecast data. In this study, the variability in these weather parameter uncertainties is analyzed, before the trajectory optimization model TOMATO is applied to single trajectories considering the previously quantified uncertainties. TOMATO generates, based on the set of input data as provided by the ensembles, a 3D corridor encasing all resulting optimized trajectories. Assuming that this corridor is filed in addition to the initial flight plan, the optimum trajectory can be updated even during flight, as soon as updated weather forecasts are available. In return and as a compromise, flights would have to stay within the corridor to provide planning stability for Air Traffic Management compared to full free in-flight optimization. Although the corridor restricts the re-optimized trajectory, fuel savings of up to 1.1 %, compared to the initially filed flight, could be shown.
      Citation: Aerospace
      PubDate: 2020-10-01
      DOI: 10.3390/aerospace7100144
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 145: New Reliability Studies of Data-Driven
           Aircraft Trajectory Prediction

    • Authors: Seyed Mohammad Hashemi, Ruxandra Mihaela Botez, Teodor Lucian Grigorie
      First page: 145
      Abstract: Two main factors, including regression accuracy and adversarial attack robustness, of six trajectory prediction models are measured in this paper using the traffic flow management system (TFMS) public dataset of fixed-wing aircraft trajectories in a specific route provided by the Federal Aviation Administration. Six data-driven regressors with their desired architectures, from basic conventional to advanced deep learning, are explored in terms of the accuracy and reliability of their predicted trajectories. The main contribution of the paper is that the existence of adversarial samples was characterized for an aircraft trajectory problem, which is recast as a regression task in this paper. In other words, although data-driven algorithms are currently the best regressors, it is shown that they can be attacked by adversarial samples. Adversarial samples are similar to training samples; however, they can cause finely trained regressors to make incorrect predictions, which poses a security concern for learning-based trajectory prediction algorithms. It is shown that although deep-learning-based algorithms (e.g., long short-term memory (LSTM)) have higher regression accuracy with respect to conventional classifiers (e.g., support vector regression (SVR)), they are more sensitive to crafted states, which can be carefully manipulated even to redirect their predicted states towards incorrect states. This fact poses a real security issue for aircraft as adversarial attacks can result in intentional and purposely designed collisions of built-in systems that can include any type of learning-based trajectory predictor.
      Citation: Aerospace
      PubDate: 2020-10-09
      DOI: 10.3390/aerospace7100145
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 146: Reusable and Reliable Flight-Control
           Software for a Fail-Safe and Cost-Efficient Cubesat Mission: Design and

    • Authors: Latachi, Rachidi, Karim, Hanafi
      First page: 146
      Abstract: While there is no rigorous framework to develop nanosatellites flight software, this manuscript aimed to explore and establish processes to design a reliable and reusable flight software architecture for cost-efficient student Cubesat missions such as Masat-1. Masat-1 is a 1Unit CubeSat, developed using a systems engineering approach, off-the-shelf components and open-source software tools. It was our aim to use it as a test-bed platform and as an initial reference for Cubesat flight software development in Morocco. The command and data handling system chosen for Masat-1 is a system-on-module-embedded computer running freeRTOS. A real-time operating system was used in order to simplify the real-time onboard management. To ensure software design reliability, modularity, reusability and extensibility, our solution follows a layered service oriented architectural pattern, and it is based on a finite state machine in the application layer to execute the mission functionalities in a deterministic manner. Moreover, a client-server model was elected to ensure the inter-process communication and resources access while using uniform APIs to enhance cross-platform data exchange. A hierarchical fault tolerance architecture was also implemented after a systematic assessment of the Masat-1 mission risks using reliability block diagrams (RBDs) and functional failure mode, effect and criticality analysis (FMECA).
      Citation: Aerospace
      PubDate: 2020-10-10
      DOI: 10.3390/aerospace7100146
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 147: Impact of Hybrid-Electric Aircraft on
           Contrail Coverage

    • Authors: Feijia Yin, Volker Grewe, Klaus Gierens
      First page: 147
      Abstract: Aviation is responsible for approximately 5% of global warming and is expected to increase substantially in the future. Given the continuing expansion of air traffic, mitigation of aviation’s climate impact becomes challenging but imperative. Among various mitigation options, hybrid-electric aircraft (HEA) have drawn intensive attention due to their considerable potential in reducing greenhouse gas emissions (e.g., CO2). However, the non-CO2 effects (especially contrails) of HEA on climate change are more challenging to assess. As the first step to understanding the climate impact of HEA, this research investigates the effects on the formation of persistent contrails when flying with HEA. The simulation is performed using an Earth System Model (EMAC) coupled with a submodel (CONTRAIL), where the contrail formation criterion, the Schmidt–Appleman criterion (SAC), is adapted to globally estimate changes in the potential contrail coverage (PCC). We compared the HEA to conventional (reference) aircraft with the same characteristics, except for the propulsion system. The analysis showed that the temperature threshold of contrail formation for HEA is lower; therefore, conventional reference aircraft can form contrails at lower flight altitudes, whereas the HEA does not. For a given flight altitude, with a small fraction of electric power in use (less than 30%), the potential contrail coverage remained nearly unchanged. As the electric power fraction increased, the reduction in contrail formation was mainly observed in the mid-latitudes (30° N and 40° S) or tropical regions and was very much localized with a maximum value of about 40% locally. The analysis of seasonal effects showed that in non-summer, the reduction in contrail formation using electric power was more pronounced at lower flight altitudes, whereas in summer the changes in PCC were nearly constant with respect to altitude.
      Citation: Aerospace
      PubDate: 2020-10-12
      DOI: 10.3390/aerospace7100147
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 148: Quantifying the Environmental Design Trades
           for a State-of-the-Art Turbofan Engine

    • Authors: Evangelia Maria Thoma, Tomas Grönstedt, Xin Zhao
      First page: 148
      Abstract: Aircraft and engine technology have continuously evolved since their introduction and significant improvement has been made in fuel efficiency, emissions, and noise reduction. One of the major issues that the aviation industry is facing today is pollution around the airports, which has an effect both on human health and on the climate. Although noise emissions do not have a direct impact on climate, variations in departure and arrival procedures influence both CO2 and non-CO2 emissions. In addition, design choices made to curb noise might increase CO2 and vice versa. Thus, multidisciplinary modeling is required for the assessment of these interdependencies for new aircraft and flight procedures. A particular aspect that has received little attention is the quantification of the extent to which early design choices influence the trades of CO2, NOx, and noise. In this study, a single aisle thrust class turbofan engine is optimized for minimum installed SFC (Specific Fuel Consumption). The installed SFC metric includes the effect of engine nacelle drag and engine weight. Close to optimal cycles are then studied to establish how variation in engine cycle parameters trade with noise certification and LTO (Landing and Take-Off) emissions. It is demonstrated that around the optimum a relatively large variation in cycle parameters is allowed with only a modest effect on the installed SFC metric. This freedom in choosing cycle parameters allows the designer to trade noise and emissions. Around the optimal point of a state-of-the-art single aisle thrust class propulsion system, a 1.7 dB reduction in cumulative noise and a 12% reduction in EINOx could be accomplished with a 0.5% penalty in installed SFC.
      Citation: Aerospace
      PubDate: 2020-10-13
      DOI: 10.3390/aerospace7100148
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 149: Integration-In-Totality: The 7th System
           Safety Principle Based on Systems Thinking in Aerospace Safety

    • Authors: Johney Thomas, Antonio Davis, Mathews P. Samuel
      First page: 149
      Abstract: Safety is of paramount concern in aerospace and aviation. Safety has evolved over the years, from the technical era to the human-factors era and organizational era, and finally to the present era of systems-thinking. Building upon three foundational concepts of systems-thinking, a new safety concept called “integration-in-totality principle” is propounded in this article as part of a “seven-principles-framework of system safety”, to act as an integrated framework to visualize and model system safety. The integration-in-totality principle concept addresses the need to have a holistic ‘vertical and horizontal integration’, which is a key tenet of systems thinking. The integration-in-totality principle is illustrated and elucidated with the help of a simple “Rubik’s cube model of integration-in-totality principle” with three orthogonal axes, the ‘axis of perspective’ of vertical integration, and the two ‘axes of perception and performance’ of horizontal integration. Safety analysis along the three axes with a ‘bidirectional synthesis’ and ‘continuum approach’ is further elaborated with relevant case studies, one among them related to the Boeing 737 MAX aircraft twin disasters. Safety is directly linked to quality, reliability and risk, through a self-reinforcing reflexive paradigm, and airworthiness assurance is the process through which safety concepts are embedded in a multidisciplinary aviation environment where the system of systems is seamlessly operating. The article explains how the system safety principle of integration-in-totality is related to reliability and airworthiness of an aerospace system with the help of the ‘V-model of systems engineering’. The article also establishes the linkage between integration-in-totality principle and strategic quality management, thus bridging the gap between two parallel fields of knowledge.
      Citation: Aerospace
      PubDate: 2020-10-14
      DOI: 10.3390/aerospace7100149
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 150: A Novel Control Allocation Method for Yaw
           Control of Tailless Aircraft

    • Authors: Thomas R. Shearwood, Mostafa R. A. Nabawy, William J. Crowther, Clyde Warsop
      First page: 150
      Abstract: Tailless aircraft without vertical stabilisers typically use drag effectors in the form of spoilers or split flaps to generate control moments in yaw. This paper introduces a novel control allocation method by which full three-axis control authority can be achieved by the use of conventional lift effectors only, which reduces system complexity and control deflection required to achieve a given yawing moment. The proposed method is based on synthesis of control allocation modes that generate asymmetric profile and lift induced drag whilst maintaining the lift, pitching moment and rolling moment at the trim state. The method uses low order models for aerodynamic behaviour characterisation based on thin aerofoil theory, lifting surface methodology and ESDU datasheets and is applied to trapezoidal wings of varying sweep and taper. Control allocation modes are derived using the zero-sets of surrogate models for the characterised aerodynamic behaviours. Results are presented in the form of control allocations for a range of trimmed sideslip angles up to 10 degrees optimised for either maximum aerodynamic efficiency (minimum drag for a specific yawing moment) or minimum aggregate control deflection (as a surrogate observability metric). Outcomes for the two optimisation objectives are correlated in that minimum deflection solutions are always consistent with efficient ones. A configuration with conventional drag effector is used as a reference baseline. It is shown that, through appropriate allocation of lift based control effectors, a given yawing moment can be produced with up to a factor of eight less aggregate control deflection and up to 30% less overall drag compared to use of a conventional drag effector.
      Citation: Aerospace
      PubDate: 2020-10-19
      DOI: 10.3390/aerospace7100150
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 151: Evaluation of Time Difference of Arrival

    • Authors: Paolo Marzioli, Fabio Santoni, Fabrizio Piergentili
      First page: 151
      Abstract: Time Difference of Arrival (TDOA) networks could support spacecraft orbit determination or near-space (launcher and suborbital) vehicle tracking for an increased number of satellite launches and space missions in the near future. The evaluation of the geometry of TDOA networks could involve the dilution of precision (DOP), but this parameter is related to a single position of the target, while the positioning accuracy of the network with targets in the whole celestial vault should be evaluated. The paper presents the derivation of the MDOP (minimum dilution of precision), a parameter that can be used for evaluating the performance of TDOA networks for spacecraft tracking and orbit determination. The MDOP trend with respect to distance, number of stations and target altitude is reported in the paper, as well as examples of applications for network performance evaluation or time precision requirement definitions. The results show how an increase in the baseline enables the inclusion of more impactive improvements on the MDOP and the mean error than an increase in the number of stations. The target altitude is demonstrated as noninfluential for the MDOP trend, making the networks uniformly applicable to lower altitude (launchers and suborbital vehicles) and higher altitude (Low and Medium Earth Orbits satellites) spacecraft.
      Citation: Aerospace
      PubDate: 2020-10-20
      DOI: 10.3390/aerospace7100151
      Issue No: Vol. 7, No. 10 (2020)
  • Aerospace, Vol. 7, Pages 152: Large-Scale Path-Dependent Optimization of
           Supersonic Aircraft

    • Authors: John P. Jasa, Benjamin J. Brelje, Justin S. Gray, Charles A. Mader, Joaquim R. R. A. Martins
      First page: 152
      Abstract: Aircraft are multidisciplinary systems that are challenging to design due to interactions between the subsystems. The relevant disciplines, such as aerodynamic, thermal, and propulsion systems, must be considered simultaneously using a path-dependent formulation to assess aircraft performance accurately. In this paper, we construct a coupled aero-thermal-propulsive-mission multidisciplinary model to optimize supersonic aircraft considering their path-dependent performance. This large-scale optimization problem captures non-intuitive design trades that single disciplinary models and path-independent methods cannot resolve. We present optimal flight profiles for a supersonic aircraft with and without thermal constraints. We find that the optimal flight trajectory depends on thermal system performance, showing the need to optimize considering the path-dependent multidisciplinary interactions.
      Citation: Aerospace
      PubDate: 2020-10-20
      DOI: 10.3390/aerospace7100152
      Issue No: Vol. 7, No. 10 (2020)
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