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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
Showing 1 - 30 of 30 Journals sorted by number of followers
AIAA Journal     Hybrid Journal   (Followers: 1021)
SpaceNews     Free   (Followers: 796)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 713)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 580)
Aviation Week     Full-text available via subscription   (Followers: 427)
Aerospace Science and Technology     Hybrid Journal   (Followers: 318)
Advances in Space Research     Hybrid Journal   (Followers: 302)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 294)
Journal of Aircraft     Hybrid Journal   (Followers: 278)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 263)
Control Systems     Hybrid Journal   (Followers: 245)
Acta Astronautica     Hybrid Journal   (Followers: 236)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 192)
Journal of Navigation     Hybrid Journal   (Followers: 189)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 179)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 149)
Space Science International     Open Access   (Followers: 129)
Space Science Reviews     Hybrid Journal   (Followers: 93)
Propulsion and Power Research     Open Access   (Followers: 90)
International Journal of Aerospace Engineering     Open Access   (Followers: 88)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 83)
Advances in Aerospace Engineering     Open Access   (Followers: 77)
Aerospace     Open Access   (Followers: 68)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 67)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 57)
Space Safety Magazine     Free   (Followers: 51)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 47)
Space Research Today     Full-text available via subscription   (Followers: 44)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 44)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 43)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 38)
International Journal of Aerospace Sciences     Open Access   (Followers: 38)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 32)
Journal of Space Weather and Space Climate     Open Access   (Followers: 31)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 31)
Space Policy     Hybrid Journal   (Followers: 31)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 28)
Journal of Aerodynamics     Open Access   (Followers: 27)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 27)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 26)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 25)
International Journal of Aerospace Innovations     Full-text available via subscription   (Followers: 24)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 24)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 23)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 23)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 22)
Fatigue of Aircraft Structures     Open Access   (Followers: 22)
Artificial Satellites     Open Access   (Followers: 22)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 21)
Frontiers in Aerospace Engineering     Open Access   (Followers: 21)
International Journal of Space Structures     Full-text available via subscription   (Followers: 20)
Chinese Journal of Aeronautics     Open Access   (Followers: 20)
Nonlinear Dynamics     Hybrid Journal   (Followers: 20)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 19)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 17)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 16)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 16)
Advances in Aerospace Science and Technology     Open Access   (Followers: 16)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 13)
Aviation     Open Access   (Followers: 13)
Journal of Airline and Airport Management     Open Access   (Followers: 12)
Aeronautical Journal, The     Hybrid Journal   (Followers: 12)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 12)
International Journal of Micro Air Vehicles     Open Access   (Followers: 12)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 11)
Journal of Aerospace Technology and Management     Open Access   (Followers: 11)
Air Force Magazine     Full-text available via subscription   (Followers: 11)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 11)
Aerospace Systems     Hybrid Journal   (Followers: 11)
Population Space and Place     Hybrid Journal   (Followers: 11)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 11)
Journal of Aeronautical Materials     Open Access   (Followers: 10)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 10)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 10)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 9)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 8)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 8)
Aerospace technic and technology     Open Access   (Followers: 8)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 8)
Space and Polity     Hybrid Journal   (Followers: 7)
Civil Aviation High Technologies     Open Access   (Followers: 7)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 7)
RocketSTEM     Free   (Followers: 7)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal   (Followers: 7)
New Space     Hybrid Journal   (Followers: 7)
Air Medical Journal     Hybrid Journal   (Followers: 7)
Life Sciences in Space Research     Hybrid Journal   (Followers: 6)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 6)
International Journal of Aviation Management     Hybrid Journal   (Followers: 6)
Journal of Astrobiology & Outreach     Open Access   (Followers: 6)
Cosmic Research     Hybrid Journal   (Followers: 6)
Unmanned Systems     Hybrid Journal   (Followers: 5)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 5)
Astrodynamics     Hybrid Journal   (Followers: 5)
Journal of Spatial Science     Hybrid Journal   (Followers: 5)
Journal of KONBiN     Open Access   (Followers: 5)
Open Aerospace Engineering Journal     Open Access   (Followers: 4)
npj Microgravity     Open Access   (Followers: 4)
Transport and Aerospace Engineering     Open Access   (Followers: 4)
Microgravity Science and Technology     Hybrid Journal   (Followers: 4)
Ciencia y Poder Aéreo     Open Access   (Followers: 4)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 4)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 3)
Advances in Astronautics Science and Technology     Hybrid Journal   (Followers: 3)
ASTRA Proceedings     Open Access   (Followers: 3)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 3)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 3)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 3)
MAD - Magazine of Aviation Development     Open Access   (Followers: 3)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 2)
Spatial Information Research     Hybrid Journal   (Followers: 2)
Investigación Pecuaria     Open Access   (Followers: 2)
Perspectives of Earth and Space Scientists i     Open Access   (Followers: 2)
Transactions on Aerospace Research     Open Access   (Followers: 2)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 1)
Mekanika : Jurnal Teknik Mesin i     Open Access   (Followers: 1)
Xibei Gongye Daxue Xuebao / Journal of Northwestern Polytechnical University     Open Access   (Followers: 1)

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Journal Prestige (SJR): 0.305
Citation Impact (citeScore): 1
Number of Followers: 68  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2226-4310
Published by MDPI Homepage  [84 journals]
  • Aerospace, Vol. 9, Pages 332: Water Surface Flight Control of a Cross
           Domain Robot Based on an Adaptive and Robust Sliding Mode Barrier Control

    • Authors: Ke Wang, Yong Liu, Chengwei Huang, Wei Bao
      First page: 332
      Abstract: When a cross-domain robot (CDR) flies on the water surface, the large pitch angle and roll angle may lead to water flooding into the robot cabin or even overturning. In addition, the CDR is influenced by some uncertain parameters and external disturbances, such as the water resistance and current. To constrain the robot attitude angle and improve the robustness of the controller, a non-singular terminal sliding mode asymmetric barrier control (NTSMABC) algorithm is proposed. All the uncertain disturbances are regarded as a lump disturbance, and a radial basis function neural network (RBFNN) is designed to compensate for the output of the controllers. Unlike the traditional quadrotors, the robot controls the yaw angle by paddles when the robot flies on the water surface. To prevent the actuator saturation and the robot from rolling over due to excessive yaw angular velocity, an adaptive integral sliding mode barrier control (AISMBC) algorithm is proposed to constrain the yaw angular velocity directly. This algorithm adaptively adjusts the gain of the sliding surface to suppress the influence of the lump disturbance on the robot. Another RBFNN is designed to compensate for the output of the controller. Simulation results demonstrate the effectiveness of the proposed control methods.
      Citation: Aerospace
      PubDate: 2022-06-21
      DOI: 10.3390/aerospace9070332
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 333: Resilient Multi-Source Integrated Navigation
           Method for Aerospace Vehicles Based on On-Line Evaluation of Redundant

    • Authors: Jun Kang, Zhi Xiong, Rong Wang, Bing Hua
      First page: 333
      Abstract: Aerospace vehicle navigation systems are equipped with multi-source redundant navigation sensors. According to the characteristics of the above navigation system configuration, building a resilient navigation framework to improve the accuracy and robustness of the navigation system has become an urgent problem to be solved. In the existing integrated navigation methods, redundant information is only used for backup. So, it cannot use the redundant navigation information to improve the accuracy of the navigation system. In this paper, a resilient multi-source fusion integrated navigation method based on comprehensive information evaluation has been proposed by combining of qualitative analysis and quantitative analysis in information theory. Firstly, this paper proposes a multi-layer evaluation framework of redundant information and carries out quantitative analysis of redundant information with the information disorder analysis theory to improve the reliability of the navigation system. Secondly, a navigation output effectiveness evaluation system has been established to analyze the output of heterogeneous navigation subsystems qualitatively to improve the fusion accuracy. Finally, through the mutual correction of multi-level information evaluation results, the error decoupling between the output parameters of heterogeneous navigation sensors has been realized to improve the robustness of the system. The experimental results show that the method proposed in this paper can adaptively allocate and adjust the weight of navigation information at all levels, realize the “non-stop” work of the navigation system and enhance the resilient of the navigation architecture. The navigation accuracy is improved compared with the existing multi-source fusion algorithm, which reflects the reliability and robustness of this algorithm.
      Citation: Aerospace
      PubDate: 2022-06-22
      DOI: 10.3390/aerospace9070333
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 334: Landing Performance Study for Four Wheels
           Twin Tandem Landing Gear Based on Drop Test

    • Authors: Wei Fang, Lingang Zhu, Youshan Wang
      First page: 334
      Abstract: The drop tests of a twin tandem landing gear with different filling parameters are carried out in two different landing attitudes (level and tail-down). The overload coefficient and power absorption efficiency are obtained. Curves of dynamic oscillation and pressure change for the pitch damper are obtained. The results show that twin tandem landing gear has a good ability to absorb the work of landing impact. Under landing weight, the vertical overload coefficients during level landing and tail-down landing are 1.14 and 1.07, respectively, when the corresponding efficiencies of its buffer system are 80.9% and 83.3%. During tail-down landing, the work absorbed by the pitch damper accounts for only 14.9% of the maximum pitching kinetic energy of the trolley. When the orifice diameter of the pitch damper keeps the same, its peak axial load does not change significantly with the change of its initial pressure. When the initial pressure of the pitch damper keeps the same, the decrease of its orifice diameter is beneficial to the vibration attenuation of the trolley. The smaller recoil channel may lead to a significant increase in the peak pressure of the pitch damper, which should be a consideration in its design.
      Citation: Aerospace
      PubDate: 2022-06-22
      DOI: 10.3390/aerospace9070334
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 335: Aeroelastic Tailoring of the Next Generation
           Civil Tiltrotor Technological Demonstrator Composite Wing

    • Authors: Aniello Daniele Marano, Marika Belardo, Jacopo Beretta, Filomena Starace, Salvatore Orlando, Claudio Punzi, Raffaele Frajese, Nicola Paletta, Luigi Di Palma
      First page: 335
      Abstract: The tiltrotor wing structure is one of the most critical and heavily investigated structures in design due to the fundamental need to consider the interactions between the wing, pylon, and rotor systems to achieve aircraft aeroelastic stability. Indeed, in high-speed forward flight, wing flexural and torsional stiffness have fundamental roles in pitch-whirl stability. Another specific concern of tiltrotors is dynamic mode placement; it is necessary to properly place wing bending modes away from prop-rotor forcing frequencies. The main aeroelastic stability and dynamics requirements and the wing design process flow for the next generation civil tiltrotor are presented in this work. In this context, the use of composite materials plays a fundamental role in the attempt to satisfy the requirements, with the perpetual aim of minimizing the structural weight. An overview of the idealized and adopted models for strength, aeroelasticity, and whirl flutter analysis is provided. The primary focus was on the aeroelastic tailoring process. To satisfy, at the same time, all of the structural dynamic and aeroelastic stability requirements, the best compromise, with an acceptable weight penalty, was the mixture of two methodological solutions: adding unidirectional tape in the zones of the upper and lower skins for flexural out-of-plane frequency and adding a proper number of ±45° fabric layers at the locations of the skin with the highest value of strain energy for in-plane torsional modes. The results show that the proposed method based on modal strain energy analysis enables a tiltrotor aeroelastic tailored wing design. It can be easily employed in similar applications (e.g., vehicle scale-up/down) with the advantage of using the stiffness requirements derived directly from the aeroelastic ones (i.e., structural frequencies). The specific wing achieved aeroelastic clearance by adding only 2.7% of extra mass.
      Citation: Aerospace
      PubDate: 2022-06-23
      DOI: 10.3390/aerospace9070335
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 336: Numerical Simulation of Sintering of DLP
           Printed Alumina Ceramics

    • Authors: Michele De Lisi, Nikolina Kovacev, Usama M. Attia, Khamis Essa
      First page: 336
      Abstract: Digital Light Processing (DLP) technology exhibits the capability of producing components with complex structures for a variety of technical applications. Postprocessing of additively printed ceramic components has been shown to be an important step in determining the final product resolution and mechanical qualities, particularly with regard to distortions and resultant density. The goal of this research is to study the sintering process parameters to create a nearly fully dense, defect-free, ceramic component. A high-solid-loading alumina slurry with suitable rheological and photopolymerisable characteristics for DLP was created. TGA/DSC analysis was used to estimate thermal debinding parameters. The sintering process of the debound parts was studied by employing a numerical model based on thermo-viscoelasticity theory to describe the sintering process. The validated Finite Element Modelling (FEM) code was capable of predicting shrinkage and relative density changes during the sintering cycle, as well as providing meaningful information on the final shape. Archimedes’ principle and scanning electron microscope (SEM) were used to characterise the sintered parts and validate the numerical model. Samples with high relative density (>98.5%) were produced and numerical data showed close matches for predicted shrinkages and relative densities, with less than 2% mismatch between experimental results and simulations. The current model may allow to effectively predict the properties of alumina ceramics produced via DLP and tailor them for specific applications.
      Citation: Aerospace
      PubDate: 2022-06-24
      DOI: 10.3390/aerospace9070336
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 337: Fault-Tolerant Control of a Dual-Stator PMSM
           for the Full-Electric Propulsion of a Lightweight Fixed-Wing UAV

    • Authors: Aleksander Suti, Gianpietro Di Rito, Roberto Galatolo
      First page: 337
      Abstract: The reliability enhancement of electrical machines is one of the key enabling factors for spreading the full-electric propulsion to next-generation long-endurance UAVs. This paper deals with the fault-tolerant control design of a Full-Electric Propulsion System (FEPS) for a lightweight fixed-wing UAV, in which a dual-stator Permanent Magnet Synchronous Machine (PMSM) drives a twin-blade fixed-pitch propeller. The FEPS is designed to operate with both stators delivering power (active/active status) during climb, to maximize performances, while only one stator is used (active/stand-by status) in cruise and landing, to enhance reliability. To assess the fault-tolerant capabilities of the system, as well as to evaluate the impacts of its failure transients on the UAV performances, a detailed model of the FEPS (including three-phase electrical systems, digital regulators, drivetrain compliance and propeller loads) is integrated with the model of the UAV longitudinal dynamics, and the system response is characterized by injecting a phase-to-ground fault in the motor during different flight manoeuvres. The results show that, even after a stator failure, the fault-tolerant control permits the UAV to hold altitude and speed during cruise, to keep on climbing (even with reduced performances), and to safely manage the flight termination (requiring to stop and align the propeller blades with the UAV wing), by avoiding potentially dangerous torque ripples and structural vibrations.
      Citation: Aerospace
      PubDate: 2022-06-24
      DOI: 10.3390/aerospace9070337
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 338: Numerical Investigation of the Aerofoil
           Aerodynamics with Surface Heating for Anti-Icing

    • Authors: Bowen Li, Qiangqiang Sun, Dandan Xiao, Wenqiang Zhang
      First page: 338
      Abstract: The aerodynamics of an aerofoil with surface heating was numerically studied with the objective to build an effective anti-icing strategy and balance the aerodynamics performance and energy consumption. NACA0012, RAE2822 and ONERA W6 aerofoils were adopted as the test cases and the simulations were performed in the subsonic flight condition of commercial passenger aircraft. In the first session, the numerical scheme was firstly validated with the experimental data. A parametric study with different heating temperatures and heating areas was carried out. The lift and drag coefficients both drop with surface heating, especially at a larger angle of attack. It was found that the separation point on the upper surface of the aerofoil is sensitive to heating. Higher heating temperature or larger heating area pushes the shock wave and hence flow separation point moving towards the leading edge, which reduces the low-pressure region of the upper surface and decreases the lift. In the second session, the conclusions obtained are applied to inform the design of the heating scheme for NACA0012. Further guidelines for different flight conditions were proposed to shed light on the optimisation of the heating strategy.
      Citation: Aerospace
      PubDate: 2022-06-24
      DOI: 10.3390/aerospace9070338
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 339: Design of an Integrated Platform for Active
           Debris Removal

    • Authors: Senwei Lv, Haojun Zhang, Yao Zhang, Bowen Ning, Rui Qi
      First page: 339
      Abstract: In research concerning active debris removal, scholars have proposed dozens of schemes for removing debris. However, every scheme has both advantages and disadvantages, and no scheme possesses an overwhelming advantage. This paper proposes an integrated platform scheme which integrates multiple capture and deorbit technologies, such as a tethered net, harpoon, and robotic arm, to improve the success rate in terms of the active removal of debris of different shapes and different sizes. The design of the mechanisms of the integrated platform is presented in detail.
      Citation: Aerospace
      PubDate: 2022-06-25
      DOI: 10.3390/aerospace9070339
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 340: Induction Mechanism of Auditory-Assisted
           Vision for Target Search Localization in Mixed Reality (MR) Environments

    • Authors: Wei Wang, Ning Xu, Sina Dang, Xuefeng Hong, Jue Qu
      First page: 340
      Abstract: In MR (mixed reality) environments, visual searches are often used for search and localization missions. There are some problems with search and localization technologies, such as a limited field of view and information overload. They are unable to satisfy the need for the rapid and precise location of specific flying objects in a group of air and space targets under modern air and space situational requirements. They lead to inefficient interactions throughout the mission process. A human being’s decision and judgment will be affected by inefficient interactions. Based on this problem, we carried out a multimodal optimization study on the use of an auditory-assisted visual search for localization in an MR environment. In the spatial–spherical coordinate system, the target flight object position is uniquely determined by the height h, distance r, and azimuth θ. Therefore, there is an urgent need to study the cross-modal connections between the auditory elements and these three coordinates based on a visual search. In this paper, an experiment was designed to study the correlation between auditory intuitive perception and vision and the cognitive induction mechanism. The experiment included the three cross-modal mappings of pitch–height, volume–distance, and vocal tract alternation–spatial direction. The research conclusions are as follows: (1) Visual cognition is induced by high, medium, and low pitches to be biased towards the high, medium, and low spatial regions of the visual space. (2) Visual cognition is induced by loud, medium, and low volumes to be biased towards the near, middle, and far spatial regions of the visual space. (3) Based on the HRTF application, the vocal track alternation scheme is expected to significantly improve the efficiency of visual interactions. Visual cognition is induced by left short sounds, right short sounds, left short and long sounds, and right short and long sounds to be biased towards the left, right, left-rear, and right-rear directions of visual space. (4) The cognitive load of search and localization technologies is significantly reduced by incorporating auditory factors. In addition, the efficiency and effect of the accurate search and positioning of space-flying objects have been greatly improved. The above findings can be applied to the research on various types of target search and localization technologies in an MR environment and can provide a theoretical basis for the subsequent study of spatial information perception and cognitive induction mechanisms in an MR environment with visual–auditory coupling.
      Citation: Aerospace
      PubDate: 2022-06-25
      DOI: 10.3390/aerospace9070340
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 341: An Improved Fault Identification Method for
           Electromechanical Actuators

    • Authors: Gaetano Quattrocchi, Pier C. Berri, Matteo D. L. Dalla Dalla Vedova, Paolo Maggiore
      First page: 341
      Abstract: Adoption of electromechanical actuation systems in aerospace is increasing, and so reliable diagnostic and prognostics schemes are required to ensure safe operations, especially in key, safety-critical systems such as primary flight controls. Furthermore, the use of prognostics methods can increase the system availability during the life cycle and thus reduce costs if implemented in a predictive maintenance framework. In this work, an improvement of an already presented algorithm will be introduced, whose scope is to predict the actual degradation state of a motor in an electromechanical actuator, also providing a temperature estimation. This objective is achieved by using a properly processed back-electromotive force signal and a simple feed-forward neural network. Good prediction of the motor health status is achieved with a small degree of inaccuracy.
      Citation: Aerospace
      PubDate: 2022-06-25
      DOI: 10.3390/aerospace9070341
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 342: Semi-Physical Simulation of Fan Rotor
           Assembly Process Optimization for Unbalance Based on Reinforcement

    • Authors: Huibin Zhang, Mingwei Wang, Zhiang Li, Jingtao Zhou, Kexin Zhang, Xin Ma, Manxian Wang
      First page: 342
      Abstract: An aero engine fan rotor is composed of a multi-stage disk and multi-stage blades. Excessive unbalance of the aero engine fan rotor after assembly is the main cause of aero engine vibration. In the rotor assembly process, blade sequencing optimization and multi-stage blade set assembly phase optimization are important for reducing the overall rotor unbalance. To address this problem, this paper proposes a semi-physical simulation method based on reinforcement learning to optimize the balance in the fan rotor assembly process. Firstly, based on the mass moments of individual blades, the diagonal mass moment difference is introduced as a constraint to build a single-stage blade sorting optimization model, and reinforcement learning is used to find the optimal sorting path so that the balance of the single-stage blade after sorting is optimal. Then, on the basis of the initial unbalance of the disk and the unbalance of the single-stage blade set, a multi-stage blade assembly phase optimization model is established, and reinforcement learning is used to find the optimal assembly phase so that the overall balance of the rotor is optimal. Finally, based on the collection of data during the assembly of the rotor, the least-squares method is used to fit and calculate the real-time assembly unbalance to achieve a semi-physical simulation of the optimization of balance during the assembly process. The feasibility and effectiveness of the proposed method are verified by experiments.
      Citation: Aerospace
      PubDate: 2022-06-25
      DOI: 10.3390/aerospace9070342
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 343: The Confirmation of Thermal Boundary
           Parameters in an Oxygen Kerosene Fuel-Rich Rocket Engine

    • Authors: Xianggeng Wei, Zhongxu Yang, Shaohua Zhu, Zhixin Zhao, Jinying Ye, Oskar J. Haidn
      First page: 343
      Abstract: The thermal environment is an important factor in the design of liquid rockets. In this paper, theoretical analysis, numerical simulation and experimental testing are conducted to study the boundary thermal characteristics of a GOX/kerosene liquid rocket motor with a total flow rate of 120 g/s and an oxygen-fuel ratio of 1:1. We measured the axial temperature in different positions in the combustor using thermocouples and the heat flux using a flux meter. We found that the heat flux at 182 mm increases by 6.8% when a carbon deposit exists. For the theoretical results, after correcting the thermal conductivity by the volume fraction of carbon deposition, the theoretical heat flux (1.11 MW/m2, using the corrected thermal conductivity) and the numerical result (0.89 MW/m2, considering the injectors) are similar to the experimental value (0.937 MW/m2). This study validates the accuracy of theoretical and simulation calculation in this case, and provides verification data for future numerical calculation, as well as data for setting gas temperature at the wall in the simulation of the gas phase.
      Citation: Aerospace
      PubDate: 2022-06-26
      DOI: 10.3390/aerospace9070343
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 344: Quantifying the Resilience Performance of
           Airport Flight Operation to Severe Weather

    • Authors: Xinglong Wang, Ziyan Chen, Kenan Li
      First page: 344
      Abstract: The increased number of severe weather events caused by global warming in recent years is a major turbulence factor for airport operation and results in more irregular flights. Quantifying the system response status towards turbulence is critical, in order for airports to deal with severe weather. For this reason, we propose a resilience framework that is in compliance with resilience theory to evaluate airport flight operations. In this framework, the departure rate (DPR), normal weather baseline (NWB), and nonnegative general resilience (NGR) were defined and used. Meanwhile, the whole process is divided into five phases before and after disturbance, and the system capacities of susceptibility, absorption, adaptation, and recovery are assessed. In order to clarify the performance of the framework towards various severe weather conditions, an analysis was conducted at Beijing Capital Airport in China based on a dataset that includes both the meteorological terminal aviation weather report (METAR) and flight operations from January to July 2021. The results show that the newly proposed resilience framework can commendably reflect airport flight operation performance. The airport flight operation resilience characteristic is different with severe weather. Compared to sandstorms and snow, airport flight operation with stronger robustness was observed during thunderstorm events. The study also confirms that, as the weather warning level increases, the disruption time increases and response time decreases accordingly. The above results could assist researchers and policy makers in clearly understanding the real-world resilience of airport flight operation, in both theory and practice, and responding to emergent disruptive events effectively.
      Citation: Aerospace
      PubDate: 2022-06-27
      DOI: 10.3390/aerospace9070344
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 345: Layout Design and Verification of a Space
           Payload Distributed Capture and Lock System

    • Authors: Gang Wang, Yimeng Yao, Jingtian Wang, Weiye Huo, Guosheng Xu, Xi Hu
      First page: 345
      Abstract: In this paper, the mechanism scheme and parametric design of a capture and lock system are studied based on the high reliability of locking systems. By analyzing the workflow and boundary conditions of the capture and lock system, a positioning design is carried out by combining it with the layout of a distributed capture and lock system. Based on the error domain for the passive end in the presence of errors in the manipulator, planning for the capture trajectory and configuration of the design for the active end are carried out. The influence of the passive end on the dynamic performance of the system is comprehensively considered to design the configuration of the passive end. According to the structure of the active end, a mathematical model for the capture and lock mechanism is established, and an analysis of the influence of trajectory parameters on the active end is carried out. The layout design of the capture hook for the active end is carried out based on an analysis of the influence of its layout on posture adjustment. The large-tolerance capability of the system layout is verified with a tolerance simulation analysis and a ground simulation capture test.
      Citation: Aerospace
      PubDate: 2022-06-28
      DOI: 10.3390/aerospace9070345
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 346: Parametric Research and Aerodynamic
           Characteristic of a Two-Stage Transonic Compressor for a Turbine Based
           Combined Cycle Engine

    • Authors: Hengtao Shi
      First page: 346
      Abstract: This paper researches the parametric optimization of a two-stage transonic compressor having a large air bypass at partial rotating speed according to flow analysis for a turbine-based combined cycle engine (TBCC). To obtain adequate thrust, the inlet transonic compressor of the turbofan part of the TBCC is required to have a wider frequently used corrected rotating speed range and a larger mass-flow rate at low rotating speed, which is different from a typical transonic compressor. The one-dimensional blade design parameters and flow path of the baseline two-stage transonic compressor are introduced. With the widely used CFD software Numeca, the three-dimensional flow fields of the baseline transonic compressor and effects of the flow path between Stage 1 and Stage 2 on the inlet mass flow rate are analyzed for indicating the further improvement direction. For design speed (NC = 1.0), to improve the efficiency at the design point, parametric research is carried out on Rotor 2 to optimize the shock structure and strength, resulting in enhanced efficiency at the design point due to reduced shock loss of Rotor 2. For partial speed (NC = 0.8 and 0.7), since the flow field analysis indicates that the flow blockage in S1 limits the entire mass flow rate, the parametric redesign of stator S1 aims at obtaining an increased blade throat width to enhance the flow capacity of S1. Simulation confirms the increase in the mass-flow rate and efficiency at partial speed due to the reduction in flow blockage and related viscous losses. Aerodynamic analysis at representative operation points indicates that the modifications of R2 and S1 lead to obvious aerodynamic improvement at all rotating speeds (NC = 1.0 to 0.7), while maintaining sufficient stall margin.
      Citation: Aerospace
      PubDate: 2022-06-28
      DOI: 10.3390/aerospace9070346
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 347: Study on Numerical Algorithm of the N-S
           Equation for Multi-Body Flows around Irregular Disintegrations in Near

    • Authors: Zheng Han, Zhihui Li, Zhiyong Bai, Xuguo Li, Jiazhong Zhang
      First page: 347
      Abstract: There has been a concern that the accurate numerical simulation of multi-body flow, which is caused by the multiple disintegrations of expired spacecraft re-entering into the near space, has a critical bottleneck impact on the falling area of the disintegrated debris. To solve this problem, an O-type grid topology method has been designed for the multi-body flow field of irregular debris formed by multiple disintegrations in near space, and a finite-volume implicit numerical scheme has been constructed for the Navier-Stokes equations to solve the aerodynamic interference characteristics of irregular multi-body flow, and further the N-S equation numerical algorithm has been established for the irregular multi-body flows in near space. The reliability of the method has been verified by the comparison of the present computation and the experiment of the low-density wind tunnel for the two-body flow of sphere, cylinder and square scripts. The objects of this study are from the multiple disintegrations of the Tiangong-1 spacecraft during uncontrolled re-entry into the atmosphere, including propelling cylinders and low-temperature lock cabinets. A series of simulations of multi-body flow mechanisms around different combinations have been carried out with varied shapes and spacing. As a result, it is found that when the distance of irregular debris (e.g., two propelling cylinders) in the near space is in the range of Δy < 3D or Δx < D, there is an obvious multi-body interference between debris, and the flow characteristics are obviously changed. When the distance between the debris in near space reaches a certain level, the influence of mutual interference can be ignored. For example, when the y-direction distance between multiple bodies is greater than 3D, the flow interference tends to be small and can be ignored, and we can regard them as two separate pieces to be carried out by the numerical prediction of flight track and falling area in engineering application. The results provide a practical design criterion for the integrated simulation platform which is used to simulate the multi-physics complex aerodynamics of space vehicles from the free-molecule flow of the outer space to the near-ground continuum flow.
      Citation: Aerospace
      PubDate: 2022-06-28
      DOI: 10.3390/aerospace9070347
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 348: A Novel Direct Optimization Framework for
           Hypersonic Waverider Inverse Design Methods

    • Authors: Jiwon Son, Chankyu Son, Kwanjung Yee
      First page: 348
      Abstract: Waverider is a hypersonic vehicle that improves the lift-to-drag ratio using the shockwave attached to the leading edge of the lifting surface. Owing to its superior aerodynamic performance, it exhibits a viable external configuration in hypersonic flight conditions. Most of the existing studies on waverider employ the inverse design method to generate vehicle configuration. However, the waverider inverse design method exhibits two limitations; inaccurate definition of design space and unfeasible performance estimation during the design process. To address these issues, a novel framework to directly optimize the waverider is proposed in this paper. The osculating cone theory is adopted as a waverider inverse design method. A general methodology to define the design space is suggested by analyzing the design curves of the osculating cone theory. The performance of the waverider is estimated accurately and rapidly via combining a high-fidelity computational fluid dynamics solver and a surrogate model. A comparison study shows that the proposed direct optimization framework enables a more accurate design space and efficient performance estimation. The framework is applied to the multi-objective optimization problem, which maximizes internal volume and minimizes aerodynamic drag. Finally, general characteristics for waverider are presented by analyzing the optimized results with data mining methods such as K-means.
      Citation: Aerospace
      PubDate: 2022-06-29
      DOI: 10.3390/aerospace9070348
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 349: Retrofitting Cost Modeling in Aircraft

    • Authors: Pierluigi Della Vecchia, Massimo Mandorino, Vincenzo Cusati, Fabrizio Nicolosi
      First page: 349
      Abstract: Aircraft retrofitting is a challenging task involving multiple scenarios and stakeholders. Providing a strategy to retrofit an existing platform needs detailed knowledge of multiple aspects, ranging from aircraft performance and emissions, development and conversion costs to the projected operating costs. This paper proposes a methodology to account for retrofitting costs at an industrial level, explaining the activities related to such a process. Costs are mainly derived from three contributions: development costs, conversion costs and equipment acquisition costs. Different retrofitting packages, such as engine conversion and onboard systems electrification, are applied in the retrofitting of an existing 90 PAX regional turbofan aircraft, highlighting the impact on both aircraft performance and industrial costs. Multiple variables and scenarios are considered regarding trade-offs and decision-making, including the number of aircraft to be retrofitted, the heritage of an aircraft and its utilization, the fuel price and the airport charges. The results show that a reduction of 15% in fuel demand and emissions are achievable, considering a fleet of 500 platforms, through a conspicuous investment of around EUR 20 million per aircraft (50% of the estimated price). Furthermore, depending on the scenarios driven by the regulatory authorities, governments or airlines, this paper provides a useful methodology to evaluate the feasibility of retrofitting activities.
      Citation: Aerospace
      PubDate: 2022-06-29
      DOI: 10.3390/aerospace9070349
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 350: Load Identification for the More Electric
           Aircraft Distribution System Based on Intelligent Algorithm

    • Authors: Juan Yang, Xingwang Bao, Zhangang Yang
      First page: 350
      Abstract: Accurate identification of electrical load working status can provide information support to the remote electrical distribution system (EDS) of more electric aircraft (MEA), which could use it to realize redundant switching and protection. This paper presents a method to automatically identify the load status on the remote power distribution unit (RPDU) of MEA by using an intelligent algorithm. The experimental platform is built in an aircraft Electrical Power System (EPS) distribution large-scale test cabin. Four pieces of typical aviation equipment are installed in the test cabin and powered from RPDU. Voltage and current values under 15 working combinations on the RPDU are measured to extract the steady-state V-I trajectory. In total, 750 group samples were collected in the feature parameter database. A generalized regression neural network (GRNN) identification model was established, and the smoothing factor was calculated by using a conventional cross-validation method to train and reach an optimal value. However, the identification results are not ideal. In order to improve the accuracy, the parameter of GRNN was optimized by genetic algorithms. The proposed model shows great performance as accuracy of all 15 classifications reached 100%. The proposed model has advantages of flexible network structure, high fault tolerance, and robustness. It can realize global approximation optimization, avoid local optimization, effectively improve GRNN fitting accuracy, improve model generalization ability, and reduce model training calculation.
      Citation: Aerospace
      PubDate: 2022-06-29
      DOI: 10.3390/aerospace9070350
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 351: The Coupling
           Orbit–Attitude–Structure Evolution of Rubble-Pile Asteroid
           with Earth Flyby in the Restricted Three-Body Problem

    • Authors: Xiangyuan Zeng, Chengfan Feng, Tongge Wen, Qingbo Gan
      First page: 351
      Abstract: Some asteroids flying close to Earth may pose a threat of impact. Among them, the structural and dynamical characteristics of rubble-pile asteroids can be changed because of the tidal force of the Earth in this process. This can provide key information for predicting the dynamical evolution of potentially hazardous asteroids. In this study, the long-term evolution of the coupling orbit–attitude–structure of these small bodies is presented numerically based on the integration of two models. One is the 3D discrete element method, which models the structure and irregular shape of the rubble-pile asteroid. The other is the dynamical model of the circular restricted three-body problem (CRTBP). This provides a more precise dynamical environment of the asteroid orbital deflection, morphological modification, and attitude angles analysis compared to the frequently adopted two-body problem. Parametric studies on the asteroid evolution were performed focusing on its flyby distance and the bulk porosity. Numerical results indicate that the Earth flyby can form different patterns of modification of asteroids, where the rubble-pile structure can be destructed by considering the bulk porosity. The asteroid orbital deflection and attitude variational trends are also summarized based on the simulations of multi-orbital revolutions.
      Citation: Aerospace
      PubDate: 2022-06-30
      DOI: 10.3390/aerospace9070351
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 352: Incremental Backstepping Sliding-Mode
           Trajectory Control for Tailless Aircraft with Stability Enhancer

    • Authors: Zihou He, Jianbo Hu, Yingyang Wang, Jiping Cong, Linxiao Han, Maoyu Su
      First page: 352
      Abstract: This paper presents an incremental backstepping sliding-mode (IBS) controller for trajectory control of a tailless aircraft with unknown disturbances and model uncertainties. The proposed controller is based on a nonlinear dynamic model of the tailless aircraft. A stability enhancer (SE) that limits both the rate and amplitude of the virtual control input is proposed. The stability enhancer consists of two layers. When the virtual control input approaches the edge, the first layer SE would be activated to modify the trajectory tracking error; when the virtual control input exceeds the edge, the second layer SE would reduce the control gains to make sure the virtual control input drops within the edge as soon as possible. With the help of SE, the incremental control method could be extended to outer-loop control without considering the dynamics of the inner-loop system. In addition, an adaptive estimator for state derivatives is proposed, together with IBS, allowing the controller to show excellent robustness. Finally, two simulations are presented. The first simulation shows that the system is insensitive to external disturbances and model uncertainties, and the effectiveness of SE is proved in the second simulation.
      Citation: Aerospace
      PubDate: 2022-06-30
      DOI: 10.3390/aerospace9070352
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 353: Adaptive Local Maximum-Entropy Surrogate
           Model and Its Application to Turbine Disk Reliability Analysis

    • Authors: Jiang Fan, Qinghao Yuan, Fulei Jing, Hongbin Xu, Hao Wang, Qingze Meng
      First page: 353
      Abstract: The emerging Local Maximum-Entropy (LME) approximation, which combines the advantages of global and local approximations, has an unsolved issue wherein it cannot adaptively change the morphology of the basis function according to the local characteristics of the sample, which greatly limits its highly nonlinear approximation ability. In this research, a novel Adaptive Local Maximum-Entropy Surrogate Model (ALMESM) is proposed by constructing an algorithm that adaptively changes the LME basis function and introduces Particle Swarm Optimization to ensure the optimality of the adaptively changed basis function. The performance of the ALMESM is systematically investigated by comparison with the LME approximation, a Radial basis function, and the Kriging model in two explicit highly nonlinear mathematical functions. The results show that the ALMESM has the highest accuracy and stability of all the compared models. The ALMESM is further validated by a highly nonlinear engineering case, consisting of a turbine disk reliability analysis under geometrical uncertainty, and achieves a desirable result. Compared with the direct Monte Carlo method, the relative error of the ALMESM is less than 1%, which indicates that the ALMESM has considerable potential for highly nonlinear problems and structural reliability analysis.
      Citation: Aerospace
      PubDate: 2022-06-30
      DOI: 10.3390/aerospace9070353
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 354: Design of a Half-Bridge Current-Source
           Inverter Topology for Avionic Systems

    • Authors: Eralp Sener, Gurhan Ertasgin
      First page: 354
      Abstract: This paper analyses a new half-bridge current–source inverter for avionic systems. In the circuit, two 28 V batteries are used as inputs. These voltage sources are connected to inductors which create a constant current source. Then only two high-frequency switches are used to waveshape the positive and negative half-cycles. The SCR-based half-bridge allows positive and negative current flow properly. The inverter output uses a CL filter to remove PWM components and to obtain 400 Hz sinewave output. Simulation and HIL experiment results are provided with feedback control to prove the concept of the proposed topology. The study shows that the new current–source topology provides promising results while complying with aviation standards.
      Citation: Aerospace
      PubDate: 2022-07-01
      DOI: 10.3390/aerospace9070354
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 355: Aircraft Emissions, Their Plume-Scale
           Effects, and the Spatio-Temporal Sensitivity of the Atmospheric Response:
           A Review

    • Authors: Kieran N. Tait, Mohammad Anwar H. Khan, Steve Bullock, Mark H. Lowenberg, Dudley E. Shallcross
      First page: 355
      Abstract: Non-CO2 aircraft emissions are responsible for the majority of aviation’s climate impact, however their precise effect is largely dependent on the environmental conditions of the ambient air in which they are released. Investigating the principal causes of this spatio-temporal sensitivity can bolster understanding of aviation-induced climate change, as well as offer potential mitigation solutions that can be implemented in the interim to low carbon flight regimes. This review paper covers the generation of emissions and their characteristic dispersion, air traffic distribution, local and global climate impact, and operational mitigation solutions, all aimed at improving scientific awareness of aviation’s non-CO2 climate impact.
      Citation: Aerospace
      PubDate: 2022-07-04
      DOI: 10.3390/aerospace9070355
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 356: Fixed-Time Circular Impact-Time Guidance
           with Look Angle Constraint

    • Authors: Xiangxiang Li, Wanchun Chen, Zhongyuan Chen, Ting Wang, Heng Shi
      First page: 356
      Abstract: A fixed-time nonlinear circular guidance law that satisfies the impact time constraint is proposed. By utilizing the geometric principle that the length of a circular arc connecting the missile and the target can be analytically calculated, the exact expression of time-to-go is obtained. Thus, the impact time error can be shaped to zero, and the missile can intercept the target at the desired time, which is crucial in a salvo attack. The settling time of the impact time error is proved to be bounded by a fixed time, which does not depend on initial conditions, but is only determined by two guidance parameters. Moreover, the criteria for choosing the guidance parameters values are established analytically, rather than by trial-and-error or empirically, which can provide valuable guidelines for guidance law designers. To address the look angle constraint, deviated pure pursuit (DPP) is employed, and switching logic between guidance laws is provided. Unlike many existing impact time control guidance laws, the formulation of the one proposed is based on nonlinear engagement kinematics, and the implementation does not execute numerical calculations, which can improve the guidance accuracy and reduce computation burdens on the guidance system. A series of nonlinear simulations are implemented to verify the effectiveness of the proposed guidance law.
      Citation: Aerospace
      PubDate: 2022-07-05
      DOI: 10.3390/aerospace9070356
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 357: Identification of Time Variations of Moving
           Loads Applied to Plates Resting on Viscoelastic Foundation Using a
           Meshfree Method

    • Authors: Sogol Behradnia, Amir Khosravifard, Mohammad-Rahim Hematiyan, Yui-Chuin Shiah
      First page: 357
      Abstract: Dynamic identification of the intensity of the moving loads applied to structures is an important task in aerospace, marine, and transportation industries. In the present work, a general technique is presented for identification of the time variations in moving loads applied to plate structures resting on viscoelastic foundation. The identification problem is formulated as an inverse problem, which utilizes dynamic responses. The direct analyses required for the identification problem are performed by a meshfree method based on the moving node technique. In this technique, a node, which travels with the applied force, is utilized in the meshfree method. Since there is no connectivity between the nodes of meshfree methods, this technique can be implemented easily, while reducing the computational labor. Another benefit of this technique is that any simple or complicated trajectory of the moving load can be handled without any additional concerns. Two numerical example problems are solved and the effects of several parameters, including the measurement error, and number of sensors on the accuracy of the results are investigated. Through the examples, it is shown that the presented technique can identify the time variations in moving loads efficiently and accurately.
      Citation: Aerospace
      PubDate: 2022-07-05
      DOI: 10.3390/aerospace9070357
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 358: The Investigation of Plume-Regolith
           Interaction and Dust Dispersal during Chang’E-5 Descent Stage

    • Authors: Haiyan Zhang, Cunhui Li, Jilin You, Xiaoping Zhang, Yi Wang, Liping Chen, Qingfei Fu, Baogui Zhang, Yuming Wang
      First page: 358
      Abstract: The plume-surface interaction that occurs as a result of a variable-thrust engine exhaust plume impinging on soil during landings is critical for future lunar mission design. Unique lunar environmental properties, such as low gravity, high vacuum, and the regolith layer, make this study complex and challenging. In this paper, we build a reliable simulation model, with constraints based on landing photos, to characterize the erosion properties induced by a low-thrust engine plume. We focus on the low-thrust plume-surface erosion process and erosion properties during the Chang’E-5 mission, aiming to determine the erosion difference between high- and low-thrust conditions; this is a major concern, as the erosion process for a low-thrust lunar mission is rarely studied. First, to identify the entire erosion process and its relative effect on the flat lunar surface, a one-to-one rocket nozzle simulation model is built; ground experimental results are utilized to verify the simulated inlet parameters of the vacuum plume flow field. Following that, plume flow is considered using the finite volume method, and the Roberts erosion model, based on excess shear stress, is adopted to describe plume-surface interaction properties. Finally, a Lagrangian framework using the discrete phase model is selected to investigate the dynamic properties of lunar dust particles. Results show that erosion depth, total ejected mass, and the maximum particle incline angle during the Chang’E-5 landing period are approximately 0.2 cm, 335.95 kg, and 4.16°, respectively. These results are not only useful for the Chang’E-5 lunar sample analysis, but also for future lunar mission design.
      Citation: Aerospace
      PubDate: 2022-07-05
      DOI: 10.3390/aerospace9070358
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 359: Mission Architecture to Characterize
           Habitability of Venus Cloud Layers via an Aerial Platform

    • Authors: Rachana Agrawal, Weston Buchanan, Archit Arora, Athul Girija, Maxim De Jong, Sara Seager, Janusz Petkowski, Sarag Saikia, Christopher Carr, David Grinspoon, James Longuski, on behalf of Venus Life Finder Mission Team
      First page: 359
      Abstract: Venus is known for its extreme surface temperature and its sulfuric acid clouds. But the cloud layers on Venus have similar temperature and pressure conditions to those on the surface of Earth and are conjectured to be a possible habitat for microscopic life forms. We propose a mission concept to explore the clouds of Venus for up to 30 days to evaluate habitability and search for signs of life. The baseline mission targets a 2026 launch opportunity. A super-pressure variable float altitude balloon aerobot cycles between the altitudes of 48 and 60 km, i.e., primarily traversing the lower, middle, and part of the upper cloud layers. The instrument suite is carried by a gondola design derived from the Pioneer Venus Large Probe pressure vessel. The aerobot transmits data via an orbiter relay combined with a direct-to-Earth link. The orbiter is captured into a 6-h retrograde orbit with a low, roughly 170-degree, inclination. The total mass of the orbiter and entry probe is estimated to be 640 kg. An alternate concept for a constant float altitude balloon is also discussed as a lower complexity option compared to the variable float altitude version. The proposed mission would complement other planned missions and could help elucidate the limits of habitability and the role of unknown chemistry or possibly life itself in the Venus atmosphere.
      Citation: Aerospace
      PubDate: 2022-07-06
      DOI: 10.3390/aerospace9070359
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 360: Refined Beam Theory for Geometrically
           Nonlinear Pre-Twisted Structures

    • Authors: Yi Hu, Yong Zhao, Haopeng Liang
      First page: 360
      Abstract: This paper proposes a novel fully nonlinear refined beam element for pre-twisted structures undergoing large deformation and finite untwisting. The present model is constructed in the twisted basis to account for the effects of geometrical nonlinearity and initial twist. Cross-sectional deformation is allowed by introducing Lagrange polynomials in the framework of a Carrera unified formulation. The principle of virtual work is applied to obtain the Green–Lagrange strain tensor and second Piola–Kirchhoff stress tensor. In the nonlinear governing formulation, expressions are given for secant and tangent matrices with linear, nonlinear, and geometrically stiffening contributions. The developed beam model could detect the coupled axial, torsional, and flexure deformations, as well as the local deformations around the point of application of the force. The maximum difference between the present deformation results and those of shell/solid finite element simulations is 6%. Compared to traditional beam theories and finite element models, the proposed method significantly reduces the computational complexity and cost by implementing constant beam elements in the twisted basis.
      Citation: Aerospace
      PubDate: 2022-07-06
      DOI: 10.3390/aerospace9070360
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 361: A Review of Spatial Robotic Arm Trajectory

    • Authors: Ye Dai, Chaofang Xiang, Yuan Zhang, Yupeng Jiang, Wenyin Qu, Qihao Zhang
      First page: 361
      Abstract: With space technology development, the spatial robotic arm plays an increasingly important role in space activities. Spatial robotic arms can effectively replace humans to complete in-orbit service tasks. The trajectory planning is the basis of robotic arm motion. Its merit has an essential impact on the quality of the completed operation. The research on spatial robotic arm trajectory planning has not yet formed a broad framework categorization, so it is necessary to analyze and deeply summarize the existing research systematically. This paper introduces the current situation of space obstacle avoidance trajectory planning and motion trajectory planning. It discusses the basic principle and practical application of the spatial robotic arm trajectory planning method. The future development trend has also been prospected.
      Citation: Aerospace
      PubDate: 2022-07-06
      DOI: 10.3390/aerospace9070361
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 362: A Survey of Precision Formation Relative
           State Measurement Technology for Distributed Spacecraft

    • Authors: Zhang Zhang, Lei Deng, Jiaqi Feng, Liang Chang, Dong Li, Yilin Qin
      First page: 362
      Abstract: High-precision relative-state measurement technology is one of the key technologies for achieving the precision formation flying of distributed spacecraft. This paper conducts a comprehensive analysis of the precision formation-flying projects of distributed spacecraft in various countries. In the context of practical application, the specific mission configuration, orbit distribution, measurement technology, and payload of the project are summarized. On this basis, the relative state measurement techniques are outlined for the first time, using non-autonomous measurement techniques, autonomous measurement techniques, and new composite relative measurement techniques. A detailed analysis of GNSS (Global Navigation Satellite System)—relative measurement, laser measurement, infrared measurement, RF measurement, visible light visual measurement, and multiple composite measurement methods is conducted. The applicable scenarios of each measurement method are thoroughly discussed from several aspects, such as the technical scheme, system design, accuracy requirements, advantages, and shortcomings. In addition, this paper proposes the concept of adopting a multidisciplinary optimization architecture from the perspective of the overall design of the precision formation of the distributed spacecraft. It enables relative-state measurement payload selection and property indicator optimization, on the premise of optimizing the overall formation performance. Finally, the optimization direction and future development trend of the spacecraft precision formation flight project and relative state measurement technology are established.
      Citation: Aerospace
      PubDate: 2022-07-06
      DOI: 10.3390/aerospace9070362
      Issue No: Vol. 9, No. 7 (2022)
  • Aerospace, Vol. 9, Pages 280: Space Environment Evaluation and
           Low-Earth-Orbit Demonstration of a Communication Component with a
           Commercial Transceiver Integrated Circuit

    • Authors: Toshihiro Kameda, Akihiro Nagata, Yohei Kimura, Ryujin Imai, Pragyan Shrestha, Keisuke Kimura, Atsushi Yasuda, Hiromasa Watanabe
      First page: 280
      Abstract: A software-controllable, consumer-grade, single-chip transceiver integrated circuit (IC) has multiple applications because it can generate a continuous-wave beacon while providing the basic functions of frequency shift keying digital communication as well. In addition, such ICs are low-cost. The above characteristics are advantageous for CubeSats with limited space and for university satellites with development cost constraints. In this study, we conduct radiation tolerance evaluation and Doppler shift tolerance tests to evaluate the feasibility of a single-chip consumer transceiver IC for space applications. In the radiation tolerance evaluation test, we compare the IC radiation tolerance to that of a single-chip microcomputer implemented in space and confirm the good resistance of the former based on the predictive analysis of the single-event upset incidence. Through the Doppler frequency shift tolerance test, we confirm suitable receiving sensitivity. Furthermore, we develop a transceiver IC as a CubeSat-class satellite component and successfully establish communication in an in-orbit demonstration, where the transceiver IC is employed as a CubeSat communication module released from the International Space Station. Thus, the feasability of space utilization of the consumer communication IC is demonstrated, which has implications for the development of more flexible and challenging system designs using newly introduced consumer devices.
      Citation: Aerospace
      PubDate: 2022-05-24
      DOI: 10.3390/aerospace9060280
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 281: Optimal Aggressive Constrained Trajectory
           Synthesis and Control for Multi-Copters

    • Authors: Tsung-Liang Liu, Kamesh Subbarao
      First page: 281
      Abstract: In this paper, we propose a novel time and control effort optimal aggressive trajectory synthesis and control design methodology. The trajectory synthesis is a modified minimum snap design but with specific position and orientation constraints on a multi-copter, such as flying through tight spaces (windows) at specific orientations. The paper also introduces a means to stitch together multiple flight segments, enforce smoothness, and minimize segment times as well as the overall time, thereby resulting in very aggressive and feasible trajectories. A novel analysis for a specific scenario when no yaw angle specifications are provided is conducted, wherein a trade-off results in additional aggressiveness. The control algorithms to follow these trajectories are based on an inverse dynamics approach. Several candidate high-fidelity simulations are performed to verify the effectiveness of the proposed approach.
      Citation: Aerospace
      PubDate: 2022-05-24
      DOI: 10.3390/aerospace9060281
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 282: Multi-Layer Fault-Tolerant Robust Filter for
           Integrated Navigation in Launch Inertial Coordinate System

    • Authors: Jun Kang, Zhi Xiong, Rong Wang, Ling Zhang
      First page: 282
      Abstract: As to an aerospace vehicle, the flight span is large and the flight environment is complex. More than that, the existing navigation algorithms cannot meet the needs to provide accurate navigation parameters for aerospace vehicles, which results in the decline of navigation accuracy. This paper proposes a multi-layer, fault-tolerant robust filtering algorithm of aerospace vehicle in the launch inertial coordinate system to address this problem. Firstly, the launch inertial coordinate system is used as the reference coordinate system for navigation calculation, and the state equation and measurement equation of the navigation system are established in this coordinate system to improve the modeling accuracy of the navigation system. On this basis, a multi-layer, fault-tolerant robust filtering algorithm is designed to estimate and compensate the unknown input in the state equation in real time and adjust the noise variance matrix in the measurement equation adaptively. Simulation results show that the errors about the integrated navigation system output parameters are reduced, through this algorithm, which improves the attitude, velocity and position estimation accuracy of the integrated navigation system. In addition, the algorithm enhances the fault tolerance and robustness of the filtering algorithm.
      Citation: Aerospace
      PubDate: 2022-05-24
      DOI: 10.3390/aerospace9060282
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 283: Spacecraft Staring Attitude Control for
           Ground Targets Using an Uncalibrated Camera

    • Authors: Chao Song, Caizhi Fan, Haibo Song, Mengmeng Wang
      First page: 283
      Abstract: Previous staring attitude control techniques utilize the geographic location of a ground target to dictate the direction of the camera’s optical axis, while the assembly accuracy and the internal structure of the spaceborne camera are not considered. This paper investigates the image-based staring controller design of a video satellite in the presence of uncertain intrinsic and extrinsic camera parameters. The dynamical projection model of the ground target on the image plane is firstly established, and then we linearly parameterize the defined projection errors. Furthermore, a potential function and a self-updating rule are introduced to estimate the parameters online by minimizing the projection errors. As the parameters are updating constantly, an adaptive control algorithm is developed, so that the errors between the current and the desired projections of the ground target converge to zero. The stability is proved using Barbalat’s lemma. Simulation results show that the designed controller can successfully move the target’s projection to the desired coordinate even though the camera parameters are unknown.
      Citation: Aerospace
      PubDate: 2022-05-24
      DOI: 10.3390/aerospace9060283
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 284: Low-Cost Satellite Launch
           System—Aerodynamic Feasibility Study

    • Authors: Aleksander Olejnik, Łukasz Kiszkowiak, Piotr Zalewski, Adam Dziubiński
      First page: 284
      Abstract: In recent decades, the rapid development of alternative methods for launching satellites into space has been observed. The main purpose of this work is to obtain reliable information about aerodynamic properties, which will be useful in the preliminary design of a low-cost satellite launch system based on a system consisting of a carrier aircraft and a space rocket orbiter. The numerical geometry of the aircraft carrier was developed as a result of the digitization process of the external surface of a real aircraft. Aerodynamic analysis was performed using specialized software based on solving partial differential equations using the finite volumes method. The results of the aerodynamic analysis were presented in a quantitative and qualitative manner. Furthermore, in order to confirm the correctness of the chosen method, the obtained results were compared with the results of experimental tests carried out in a wind tunnel. This will also prove that the adopted method is sufficient for solving this type of problem. The main advantage of the presented method is obtainment of reliable results in a relatively short time, which is extremely important during the preliminary design stage. The results presented in this paper will certainly be helpful for all researchers involved in the development of new and low-cost methods for launching small satellites into LEO.
      Citation: Aerospace
      PubDate: 2022-05-24
      DOI: 10.3390/aerospace9060284
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 285: The PAPI Lights-Based Vision System for
           Aircraft Automatic Control during Approach and Landing

    • Authors: Dariusz Nowak, Grzegorz Kopecki, Damian Kordos, Tomasz Rogalski
      First page: 285
      Abstract: The paper presents the concept of a component of an aircraft’s automatic flight control system, controlling the airplane when in longitudinal motion (i.e., pitch angle, sink rate, airspeed channels) during automatic landing, from a final approach until a touchdown. It is composed of two key parts: a vision system and an automatic landing system. The first part exploits dedicated image-processing algorithms to identify the number of red and white PAPI lights appearing on an onboard video camera. Its output data—information about an aircraft’s position on a vertical profile of a landing trajectory—is used as one of the crucial inputs to the automatic landing system (the second part), which uses them to control the landing. The control algorithms implemented by the automatic landing system are based on the fuzzy logic expert system and were developed to imitate the pilot’s control actions during landing an aircraft. These two parts were teamed together as a component of a laboratory rig, first as pure software algorithms only, then as real hardware modules with downloaded algorithms. In two test campaigns (software in the loop and hardware in the loop) they controlled an aircraft model in a simulation environment. Selected results, presenting both control efficiency and flight precision, are given in the final section of the paper.
      Citation: Aerospace
      PubDate: 2022-05-25
      DOI: 10.3390/aerospace9060285
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 286: Optimization of the Conceptual Design of a
           Multistage Rocket Launcher

    • Authors: Pedro Orgeira-Crespo, Guillermo Rey, Carlos Ulloa, Uxia Garcia-Luis, Pablo Rouco, Fernando Aguado-Agelet
      First page: 286
      Abstract: The design of a vehicle launch comprises many factors, including the optimization of the climb path and the distribution of the mass in stages. The optimization process has been addressed historically from different points of view, using proprietary software solutions to obtain an ideal mass distribution among stages. In this research, we propose software for the separate optimization of the trajectory of a launch rocket, maximizing the payload weight and the global design, while varying the power plant selection. The launch is mathematically modeled considering its propulsive, gravitational, and aerodynamical aspects. The ascent trajectory is optimized by discretizing the trajectory using structural and physical constraints, and the design accounts for the mass and power plant of each stage. The optimization algorithm is checked against various real rockets and other modeling algorithms, obtaining differences of up to 9%.
      Citation: Aerospace
      PubDate: 2022-05-25
      DOI: 10.3390/aerospace9060286
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 287: Trim Flap System Design for Improving
           Ballistic-Lifting Entry Performance of the Tianwen-1 Mars Probe

    • Authors: Xinli Li, Yansong Li, Dayong Hu, Wei Rao, Yufeng Qi, Qiang Yang, Gang Wang
      First page: 287
      Abstract: The trim flap is an aerodynamic control surface capable of allowing Mars entry vehicles to improve landing performance during the most dangerous entry, descent, and landing (EDL) phase. In present work, a deployable trim flap system was proposed to meet the aerodynamical trim requirement of the Tianwen-1 Mars probe, which provided a mass-saving alternative to the conventional use of the center-of-gravity (CG) offset of ballast mass. In order to guide the trim flap design, theoretical and finite element (FE) models were established to predict and evaluate the deployment performance. Then, a full-scale physical prototype was manufactured for deployment experiments to verify the design effectiveness as well as validate the theoretical and FE models. Results predicted by theoretical and FE models were in good agreement with deployment experiments. Furthermore, the effects of three factors on the deployment performance were investigated, including the non-linear behavior of the damping, acceleration environment, and backshell flexibility. The manufactured prototype was installed on the Tianwen-1 Mars probe, saving more than 300 kg when compared to the conventional use of ballast mass CG offset, and assisted Tianwen-1 in achieving a successful landing, making China the first country in the world to utilize the trim flap technology for Mars EDL.
      Citation: Aerospace
      PubDate: 2022-05-25
      DOI: 10.3390/aerospace9060287
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 288: Effects on Taxiing Conflicts at
           Intersections by Pilots’ Sensitive Speed Adjustment

    • Authors: Kai Yang, Hongyu Yang, Jianwei Zhang, Rui Kang
      First page: 288
      Abstract: The pilot is the main person in charge of taxiing safety while moving on the airport surface. The visual separation and speed adjustment are directly related to safety and efficiency of airport surface operation. According to the actual taxiing procedures and airport control rules in China, this paper proposes a novel microscopic simulation model based on the pilots’ visual separation. This model is also built by refining the aircraft taxiing procedures at intersections. The observation range, the separation judgment, pilots’ visual distance, rate of proximity and the intention for speed governing are discussed as parameters in the model. The rules for aircraft separation judgment, pilots’ autonomous speed governing, and position updates are also set up and discussed. The proposed simulation can accurately simulate the acceleration and deceleration intentions under different motion trends while reproducing the motion process including the following acceleration, following deceleration and delayed deceleration caused by separation changes. The results demonstrate that the number of conflicts can be reduced to 50% based on visual separation adjustment of 50 s when the convergence angle is 30°. The pilot’s visual distance is inversely proportional to the fluctuation range of the speed of the rear aircraft, the proximity rate of the front and rear aircraft and the probability of conflict. The simulation results of this model conform to the actual taxiing routes and control rules, which provides technical support for improving the safety level of airport surface operation and presents certain reference value and practicability.
      Citation: Aerospace
      PubDate: 2022-05-25
      DOI: 10.3390/aerospace9060288
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 289: Experimental Study of Measuring the Wrinkle
           of Solar Sails

    • Authors: Jie Zou, Dongxu Li, Jie Wang, Ye Yu
      First page: 289
      Abstract: Conducting a wrinkling analysis for a membrane structure of complex boundary conditions is quite difficult. This paper develops a numerical calculation method for completing a wrinkling analysis of a square membrane structure and a trapezoidal membrane structure with static corner forces. Furthermore, an experimental system for measuring the wrinkle is designed and established to verify the correctness of the method. The difference between simulation analysis results and experimental results is quite small for small corner forces, which means the method used for the wrinkling analysis under small loads is effective.
      Citation: Aerospace
      PubDate: 2022-05-26
      DOI: 10.3390/aerospace9060289
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 290: A Generic Mission-Level Flight Control
           Surface EMA Power Consumption Simulation Tool

    • Authors: Jingcheng Fu, Albert S. J. van Heerden, David Judt, Craig Lawson
      First page: 290
      Abstract: The use of electromechanical actuators (EMAs) for aeronautical applications promises substantial benefits regarding efficiency and operability. To advance the design of power electronics and secondary power supply, there is a need for the ability to swiftly study the effects of aircraft mission and operational aspects on the actuator energy consumption. Pursuant to this, the aim of the work presented in this paper is twofold: (i) to build a generic mission-level flight control surface EMA power consumption simulation framework and (ii) to apply this framework to a case study involving a small all-electric aircraft, in which selected factors that impact energy consumption are investigated. The core of the framework comprises physics-based EMA power estimators, linked with a six-degree-of-freedom flight dynamics and control simulation module. The case study results show that the actuator power consumption correlates positively with the proportional gains in the flight control system but is inversely proportional to the trajectory radius and linearly dependent on turbulence intensity. The developed framework could aid in the selection of the actuator, as well as in the optimisation of airborne electronics and secondary power supply.
      Citation: Aerospace
      PubDate: 2022-05-26
      DOI: 10.3390/aerospace9060290
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 291: Aerodynamic Modelling of the Airfoil
           Immersed in Two-Dimensional Jet Flow

    • Authors: Xu Li, Zhou Zhou
      First page: 291
      Abstract: In order to study the aerodynamic interaction of the airfoil and jet flow, the free streamline model and the panel method are combined to develop a fast calculation method for the airfoil in two-dimensional inviscid jet flow. The vortex strength and position of the jet boundary are determined by using the free streamline model and the constant total pressure difference assumption, the circulation of the airfoil is solved by the vortex panel method, and the whole process is coupled by relaxation iteration. Firstly, the convergence and effectiveness of the present method are verified. Next, the influence of the length ratio of jet height to airfoil chord, the velocity ratio of jet velocity to freestream velocity, and the ground effect on airfoil aerodynamics are studied. The results show that the aerodynamic characteristics of the airfoil in finite width jet flow and in freestream have a large difference, and it is important to consider the jet deflection for jet/airfoil interaction. In jet flow, the velocity ratio can be regarded as an aerodynamic similarity parameter for the airfoil. When the jet flow is deflected, the airfoil will not only generate lift but also drag, and the ground effect can be used to decrease drag. The developed method in this paper can not only capture the jet deflection but also has higher calculation efficiency than Computational Fluid Dynamic (CFD), which is beneficial for the preliminary design of a powered-lift device.
      Citation: Aerospace
      PubDate: 2022-05-26
      DOI: 10.3390/aerospace9060291
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 292: Simultaneous Pressure and Displacement
           Measurement on Helicopter Rotor Blades Using a Binocular
           Stereophotogrammetry PSP System

    • Authors: Chunhua Wei, Chenglin Zuo, Xianhui Liao, Guoshuai Li, Lingrui Jiao, Di Peng, Lei Liang
      First page: 292
      Abstract: A simultaneous surface pressure and displacement measurement method that integrates pressure-sensitive paint (PSP) and binocular stereophotogrammetry is proposed. The assays were completed on the Φ4 m rotor test stand at China Aerodynamic Research and Development Center (CARDC). A single-shot lifetime approach was utilized to acquire the instantaneous pressure field on a rotor blade coated with PSP. At the same time, the PSP feature points were used to obtain the 3D coordinates of stereo cameras, which yielded the blade displacement field. The experimental results showed that the displacement measuring accuracy was better than 0.2 mm, and the pressure measurement accuracy was not affected, with Standard Deviation (STD) values below 700 Pa. The advantages of the proposed system are its simple structure, low cost, high accuracy and high test efficiency, which will offer a practical solution for the exploration of fluid–structure interplay. Hence, such a system is a prospective for the wind tunnel tests of helicopter rotor blades.
      Citation: Aerospace
      PubDate: 2022-05-27
      DOI: 10.3390/aerospace9060292
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 293: Influence of Mass Flow Rate on the
           Atomization Characteristics of Screw Conveyor Swirl Injectors

    • Authors: Xianggeng Wei, Yiming Feng, Jinying Ye, Na Li, Oskar J. Haidn
      First page: 293
      Abstract: This study conducted cold flow experimental research on the influence of mass flow rate on the atomization characteristics of screw conveyer swirl injectors in an opening environment. The Phase Doppler Particle Analyzer (PDPA) and high-speed photography were utilized to obtain experimental data. The results showed that the mass flow rate greatly influenced the atomization establishment and working characteristics of the injectors. The design point selection of the injectors exerted significant influence on the flow range and the performances of the injectors in a steady-state operation. The Sauter mean diameter of the atomization field continued to decrease with the increase in the mass flow rate. As the distance to the injector exit increased, the Sauter mean diameter continued to decrease, and finally tended to be stable. The average particle diameter obtained by the current image-processing method was greater than that by PDPA; therefore, the image-processing method needs improvement.
      Citation: Aerospace
      PubDate: 2022-05-27
      DOI: 10.3390/aerospace9060293
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 294: Review of Deep Reinforcement Learning
           Approaches for Conflict Resolution in Air Traffic Control

    • Authors: Zhuang Wang, Weijun Pan, Hui Li, Xuan Wang, Qinghai Zuo
      First page: 294
      Abstract: Deep reinforcement learning (DRL) has been widely adopted recently for its ability to solve decision-making problems that were previously out of reach due to a combination of nonlinear and high dimensionality. In the last few years, it has spread in the field of air traffic control (ATC), particularly in conflict resolution. In this work, we conduct a detailed review of existing DRL applications for conflict resolution problems. This survey offered a comprehensive review based on segments as (1) fundamentals of conflict resolution, (2) development of DRL, and (3) various applications of DRL in conflict resolution classified according to environment, model, algorithm, and evaluating indicator. Finally, an open discussion is provided that potentially raises a range of future research directions in conflict resolution using DRL. The objective of this review is to present a guidance point for future research in a more meaningful direction.
      Citation: Aerospace
      PubDate: 2022-05-28
      DOI: 10.3390/aerospace9060294
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 295: Structural Damage Assessment Using
           Multiple-Stage Dynamic Flexibility Analysis

    • Authors: Yun Sun , Qiuwei Yang, Xi Peng
      First page: 295
      Abstract: Vibration-based damage assessment technology is a hot topic in aerospace engineering, civil engineering, and mechanical engineering. In this paper, a damage assessment approach using multiple-stage dynamic flexibility analysis is proposed for structural safety monitoring. The proposed method consists of three stages. The content of Stage I is to determine the number of damaged elements in the structure by the rank of dynamic flexibility change. The content of Stage II is to determine damage locations by the minimum rank of flexibility correlation matrices. Finally, the damage extents of those damaged elements are calculated in Stage III. The proposed approach fully uses the filtering ability of matrix rank analysis for data noise. A 27-bar truss structure and a steel frame structure are used as the numerical and experimental examples to demonstrate the proposed method, respectively. From the numerical and experimental results, it is found that structure damages can be successfully identified through the multiple-stage dynamic flexibility analysis. By comparative study, the proposed method has more powerful antinoise ability and higher calculation accuracy than the generalized flexibility method. The proposed method may be a promising tool for structural damage assessment.
      Citation: Aerospace
      PubDate: 2022-05-29
      DOI: 10.3390/aerospace9060295
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 296: Nonlinear Control of a Single Tail Tilt
           Servomotor Tri-Rotor Ducted VTOL-UAV

    • Authors: Yanpeng Hu, Jin Guo, Pei Ying, Guannan Zeng, Nanyu Chen
      First page: 296
      Abstract: This paper explores a novel single tail tilt servomotor tri-rotor ducted vertical takeoff and landing unmanned aerial vehicle system(VTOL-UAV), and proposes a compound control method combining disturbance observer, model predictive control (MPC) and sliding mode nonlinear dynamic inversion (NDI), and realizes the robust tracking control of the VTOL-UAV trajectory under compound disturbance. Specifically, the inner loop adopts nonlinear dynamic inverse which improved by sliding mode to realize the pseudo linearization of the system. The outer loop adopts the model predictive control based on the E-SSPC (State Space Predictive Controller based on the Error model) method, on this basis, the sliding mode disturbance observer based on fast Super-twisting algorithm is introduced into the position loop to observe and compensate the disturbance in real time, which improves the robustness of the outer loop system. Numerical simulation experiments verify the effectiveness and robustness of the control method. Finally, the flight test of the VTOL-UAV is carried out.
      Citation: Aerospace
      PubDate: 2022-05-31
      DOI: 10.3390/aerospace9060296
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 297: Development of POLON—A Green
           Microsatellite Propulsion Module Utilizing 98% Hydrogen Peroxide

    • Authors: Jakub Gramatyka, Przemysław Paszkiewicz, Damian Grabowski, Adrian Parzybut, Daria Bodych, Krzysztof Wróblewski, Paweł Surmacz, Krzysztof Pietrzak
      First page: 297
      Abstract: The following paper presents the key design and test activities associated with the development of POLON—a green microsatellite propulsion module using 98% Hydrogen Peroxide (HTP). POLON, which stands for “Polish Propulsion Module”, is the first step toward the development of a full, ready-to-be-commercialized satellite propulsion system at the Łukasiewicz—Institute of Aviation (Ł-IoA). The development of an entire microsatellite propulsion system within the frame of the POLON project effort is the natural milestone on the Ł-IoA green propulsion roadmap, which so far embodied research on fundamental HTP chemistry, work on elementary propulsion technologies, as well as the development of individual propulsion components. Within this article, POLON propulsion development logic is introduced first, and the major challenges associated with utilizing HTP for an orbital propulsion system are described. Consequently, the specific R&D activities aimed at mitigating the identified issues and risks are discussed. Those cover analytical as well as experimental work, including, but not limited to, HTP compatibility studies with candidate construction materials, waterhammer effect studies, HTP catalyst testing and evaluation, and propellant tank manufacturing studies. The initial results for those activities are presented and, finally, further development plans are discussed.
      Citation: Aerospace
      PubDate: 2022-05-31
      DOI: 10.3390/aerospace9060297
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 298: Design and Experimental Comparison of PID,
           LQR and MPC Stabilizing Controllers for Parrot Mambo Mini-Drone

    • Authors: Mohamed Okasha, Jordan Kralev, Maidul Islam
      First page: 298
      Abstract: Parrot Mambo mini-drone is a readily available commercial quadrotor platform to understand and analyze the behavior of a quadrotor both in indoor and outdoor applications. This study evaluates the performance of three alternative controllers on a Parrot Mambo mini-drone in an interior environment, including Proportional–Integral–Derivative (PID), Linear Quadratic Regulator (LQR), and Model Predictive Control (MPC). To investigate the controllers’ performance, initially, the MATLAB®/Simulink™ environment was considered as the simulation platform. The successful simulation results finally led to the implementation of the controllers in real-time in the Parrot Mambo mini-drone. Here, MPC surpasses PID and LQR in ensuring the system’s stability and robustness in simulation and real-time experiment results. Thus, this work makes a contribution by introducing the impact of MPC on this quadrotor platform, such as system stability and robustness, and showing its efficacy over PID and LQR. All three controllers demonstrate similar tracking performance in simulations and experiments. In steady state, the maximal pitch deviation for the PID controller is 0.075 rad, for the LQR, it is 0.025 rad, and for the MPC, it is 0.04 rad. The maximum pitch deviation for the PID-based controller is 0.3 rad after the take-off impulse, 0.06 rad for the LQR, and 0.17 rad for the MPC.
      Citation: Aerospace
      PubDate: 2022-06-01
      DOI: 10.3390/aerospace9060298
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 299: Capture Dynamics and Control of a Flexible
           Net for Space Debris Removal

    • Authors: Man Ru, Ying Zhan, Bin Cheng, Yu Zhang
      First page: 299
      Abstract: Space debris severely threatens the safety of spacecraft in near-earth orbit. Dragging space debris into the atmosphere to burn is an effective way to remove it. In this paper, the authors focus on capturing irregular and rotating debris via a flexible net. The net capture dynamics, including the constitutive dynamics of the flexible net and the nonlinear contact dynamics with the debris, are established to simulate the movements of the flexible net. The debris dynamics, comprising translational and rotational dynamics, are constructed to simulate its motions throughout the whole process. In addition, an active control scheme is applied to designing the controllers of the flexible net. The presented method can be used to simulate the capture and post-capture process of irregular and rotating debris. Moreover, compared with the previous space debris capture mechanism, the presented flexible net can be opened or closed repeatedly; thus, the proposed flexible net has more potential to capture many pieces of debris in one mission. Numerical simulations show that the flexible net has an excellent capture capability with the presented control scheme. The flexible net can capture the debris rotating with an angular velocity of 6.28 rad/s. Moreover, the debris can be fully enveloped and further dragged away along the expected trajectory. The critical indicator results show that the wrapping of the debris is stable; thus, this method is feasible for future missions.
      Citation: Aerospace
      PubDate: 2022-06-01
      DOI: 10.3390/aerospace9060299
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 300: Surrogate-Based Optimization Design for
           Air-Launched Vehicle Using Iterative Terminal Guidance

    • Authors: Jiaxin Li, Donghui Wang, Weihua Zhang
      First page: 300
      Abstract: In recent years, the penetration of low-cost air-launched vehicles for nano/micro satellites has significantly increased worldwide. Conceptual design and overall parameters optimization of the air-launched vehicle has become an exigent task. In the present research, a modified surrogate-based sequential approximate optimization (SAO) framework with multidisciplinary simulation is proposed for overall design and parameters optimization of a solid air-launched vehicle system. In order to reduce the large computation costs of time-consuming simulation, a local density-based radial basis function is applied to build the surrogate model. In addition, an improved particle swarm algorithm with adaptive control parameters is proposed to ensure the efficiency and reliability of the optimization method. According to the LauncherOne air-launched vehicle, the overall optimization design problem aims to improve payload capacity with the same lift-off mass. Reasonable constraints are imposed to ensure the orbit injection accuracy and stability of the launch vehicle. The influences of the vehicle configuration, optimization method, and terminal guidance are considered and compared for eight different cases. Finally, the effect on the speed of optimization convergence of employing a terminal guidance module is investigated. The payload capability of the optimized configurations increased by 27.52% and 23.35%, respectively. The final estimated results and analysis show the significant efficiency of the proposed method. These results emphasize the ability of SAO to optimize the parameters of an air-launched vehicle at a lower computation cost.
      Citation: Aerospace
      PubDate: 2022-06-01
      DOI: 10.3390/aerospace9060300
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 301: Dynamic Response of a Composite Fan Blade
           Excited Instantaneously by Multiple MFC Actuators

    • Authors: Yong Chen, Lu Jin, Xu Tang, Dandan Huang, Jiguo Zhang
      First page: 301
      Abstract: The vibration characteristics of a composite fan blade are much more complex than those of a solid titanium fan blade due to the anisotropic material properties and complex excitations coming from unsteady flow and mechanically induced vibration. In this study, the dynamic response measurement of a wide-chord composite fan blade was carried out to study the vibration characteristics using multiple macro fiber composite (MFC) actuators, which can generate complex excitation forces with different frequencies and peak values at different locations. The measured mode shapes and natural frequencies were compared with the finite element simulation results. Based on these results, the responses of the blade under the instantaneous excitation of three MFC actuators with different combinations of several natural frequencies were measured and compared. The results show that the responses of the blade excited by different combinations of MFC actuators with different frequencies were significantly different from those excited by a single MFC actuator. The superposition of different mode shapes may cause the change of the vibration stress state, which indicates that the high cycle fatigue location of the blade under complex excitations may change to an unexpected location. The results will be helpful in understanding the vibration characteristics of the composite blades under complex excitations, and the MFC actuator could be a potential tool in vibration active control.
      Citation: Aerospace
      PubDate: 2022-06-02
      DOI: 10.3390/aerospace9060301
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 302: Congestion Recognition of the Air Traffic
           Control Sector Based on Deep Active Learning

    • Authors: Xianghua Tan, Yushi Sun, Weili Zeng, Zhibin Quan
      First page: 302
      Abstract: The air traffic control sector (ATCS) is the basic unit of the airspace system. If we can identify the congestion of an ATCS, it will help provide decision support for planning and daily operations. However, current methods mainly characterize congestion from the static structure and the dynamic operational features, resulting in poor generalization and operability. To this end, we propose a deep learning method from the perspective of complex networks. It takes aircraft as nodes to construct an aircraft network and utilizes the complexity indices to characterize it. So, the problem of identifying congestion becomes the complexity of the aircraft network. Inspired by active learning methods, we construct a deep active learning (DAL) model for congestion recognition. It adopts an iterative semi-supervised approach to reduce the number of labeled samples while ensuring recognition performance. To make full use of a large number of unlabeled samples, the sparse autoencoder is employed to characterize all labeled samples and unlabeled samples. The hidden layer of the deep neural network is constructed by stacking. In the process of active learning iteration, minimum confidence, marginal sampling, and information entropy are introduced as measures to select samples from the unlabeled sample set with significantly different features from the labeled sample set. The model is applied to three representative sectors in China’s airspace as cases. Results suggest that DAL can reduce the labeled sample set’s redundancy and achieve the desired performance with the smallest number of samples. Additionally, DAL is superior to the existing mainstream methods in the four objective evaluation indices.
      Citation: Aerospace
      PubDate: 2022-06-02
      DOI: 10.3390/aerospace9060302
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 303: Attitude Maneuver and Stability Control of
           Hyper-Agile Satellite Using Reconfigurable Control Moment Gyros

    • Authors: Zhi Qu, Gaofei Zhang, Ziyang Meng, Kai Xu, Ruiqin Xu, Jiaojiao Di
      First page: 303
      Abstract: Addressing the problems of insurmountable unknown frictional disturbance and balancing the trade−off between high maneuverability and stability during attitude maneuver are important in low−cost miniaturized single control moment gyro clusters (SGCMGs) for hyper-agile satellite. This paper proposes a new concept of reconfigurable octagonal cone-type SGCMGs by considering practical engineering requirements of hyper-agile satellites. Firstly, the momentum characteristics of typical configurations are quantitatively explained, and the evaluation metrics for SGCMGs based on norm L∞ and norm L2 are defined, respectively. Secondly, a reconfiguration design of SGCMGs from octagonal cone-type into pyramid−type is proposed by analyzing the unknown disturbance mechanism based on SGCMGs. When the hyper-agile satellite is supported to perform fast attitude maneuvers, all units of SGCMGs can work together to output rough and large torque. On the other hand, when the maneuvering ends with stable pointing control, gimbles of one pyramid−type SGCMGs are locked down and fine torque is outputted using another pyramid−type SGCMGs. This will greatly reduce the difficulty of controller design and improve the satellite attitude performance indices. The superiority of the control strategy and selection of the proposed actuator is verified by experiments.
      Citation: Aerospace
      PubDate: 2022-06-03
      DOI: 10.3390/aerospace9060303
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 304: Fault-Tolerant Control for Hexacopter UAV
           Using Adaptive Algorithm with Severe Faults

    • Authors: Ngoc Phi Nguyen, Nguyen Xuan Mung, Le Nhu Ngoc Thanh Ha, Sung Kyung Hong
      First page: 304
      Abstract: In this paper, a fault-tolerant control method is proposed for a hexacopter under uncertainties. The proposed method is based on adaptive-sliding-mode control (ASMC) and a control allocation scheme. First, a mathematical model of the hexacopter is employed with model uncertainties. Next, the control allocation strategy is combined with ASMC to handle actuator faults, which can distribute the virtual control signal to redundant actuators. A modified fault-tolerant control is proposed to overcome this virtual input saturation. Finally, the system stability is validated using the Lyapunov theory. The performance of the proposed method is compared with that of normal ASMC. The simulation results show that the suggested strategy can realize quicker compensation under faulty conditions.
      Citation: Aerospace
      PubDate: 2022-06-03
      DOI: 10.3390/aerospace9060304
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 305: Lifetime Extension of Ultra Low-Altitude
           Lunar Spacecraft with Low-Thrust Propulsion System

    • Authors: Jingxi Liu, Bo Xu, Chengzhang Li, Muzi Li
      First page: 305
      Abstract: Due to the non-spherical perturbation of the Moon, the lifetime of ultra low-altitude Lunar spacecraft may be quite short. In this paper, we analyze the lifetime of about 50 km-altitude Lunar spacecraft with different initial orbit. The lifetime in low inclination orbits is much shorter than the ones in the near polar orbits. To extend the lifetime and keep the spacecraft in an appropriate range, an orbit maintenance strategy based on low-thrust propulsion system is proposed. The influence of the orbit initial conditions (e.g., semi-major axis, inclination, right ascension of the ascending node) on lifetime extension are discussed and the effect of the low-thrust magnitude in orbit maintenance is analyzed. According to the numerical simulation results, the lifetime of about 50 km-altitude 100 kg Lunar spacecraft with 10 kg fuel and 20 mN thruster can be extended from 7.958 days to over a 109.1725 days, which demonstrates the effectiveness of the strategy. Furthermore, a global perspective for ultra low-altitude Lunar spacecraft lifetime extension problem is provided in this paper, which can be applied to Moon mission designs extensively.
      Citation: Aerospace
      PubDate: 2022-06-03
      DOI: 10.3390/aerospace9060305
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 306: Mars Exploration Using Sailplanes

    • Authors: Adrien Bouskela, Alexandre Kling, Tristan Schuler, Sergey Shkarayev, Himangshu Kalita, Jekan Thangavelautham
      First page: 306
      Abstract: We present the preliminary design of sailplanes, used for Mars exploration. The sailplanes mitigate the weight and energy storage limitations traditionally associated with powered flight by instead exploiting atmospheric wind gradients for dynamic soaring, and slope/thermal updrafts for static soaring. Equations of motion for the sailplanes were combined with wind profiles from the Mars Regional Atmospheric Modeling System (MRAMS) for two representative sites: Jezero crater, Perseverance’s landing site, and over a section of the Valles Marineris canyon. Optimal flight trajectories were obtained from the constrained optimization problem, using the lift coefficient and the roll angle as control parameters. Numerical results for complete dynamic soaring cycles demonstrated that the total sailplane energy at the end of a soaring cycle increases by 6.8–11%. The absence of a propulsion system, allowing for a compact form factor, means the sailplanes can be packaged into CubeSats and deployed as secondary payloads at a relatively low cost; providing scientific data over locations inaccessible by current landers and rovers. Various sailplane deployment methods are considered, including rapid deployment during Entry, Descent, and Landing (EDL) of a Mars Science Laboratory-class (MSL) vehicle and slow deployment using a blimp.
      Citation: Aerospace
      PubDate: 2022-06-03
      DOI: 10.3390/aerospace9060306
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 307: Study on the Characteristics of Boundary
           Layer Flow under the Influence of Surface Microstructure

    • Authors: Hongqing Lv, Shan Liu, Jiahao Chen, Baoli Li
      First page: 307
      Abstract: The energy consumption of a vehicle is closely related to the resistance it receives, and it is of great significance to study the drag reduction of a vehicle to promote energy conservation and emissions reductions. Boundary layer control drag reduction is mainly achieved by controlling the coherent structure in turbulence and reducing its burst intensity and frequency. It can be divided into an active control drag reduction and passive control drag reduction. In passive drag reduction, the advantages of the surface groove drag reduction are relatively obvious. In this paper, the large eddy simulation method is used to study the boundary layer flow with triangular groove and rectangular groove plates along the flow direction under subsonic flow, and to explore the influence of a surface micro-groove structure on the boundary layer flow. The simulation results show that the fluid inside the groove can be blocked by the triangular groove which can keep the low-velocity fluid at the bottom of the groove, and that it can increase the thickness of the viscous bottom layer as well as reduce the velocity gradient at the wall. The spanwise stress component of the Reynolds stress in the triangular groove boundary layer and the burst of turbulence on the wall are inhibited, and the spanwise flow in the boundary layer is blocked. In the subsonic range, about 10% shear force can be reduced because there are secondary vortices induced by the upper flow vortices at the top of the groove wall, and these secondary vortices can restrain the rising of the low-speed strip in the groove and reduce the burst of turbulence. The rectangular groove creates a weak blocking effect on the fluid inside the groove, which can only inhibit spanwise pulsation under subsonic speed. The wall shear stress cannot be reduced when the flow velocity is low, and it even increases.
      Citation: Aerospace
      PubDate: 2022-06-03
      DOI: 10.3390/aerospace9060307
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 308: Recognition of the Airspace Affected by the
           Presence of Volcanic Ash from Popocatepetl Volcano Using Historical
           Satellite Images

    • Authors: José Carlos Jiménez-Escalona, José Luis Poom-Medina, Julie Roberge, Ramon S. Aparicio-García, José Eduardo Avila-Razo, Oliver Marcel Huerta-Chavez, Rodrigo Florencio Da Silva
      First page: 308
      Abstract: A volcanic eruption can produce large ash clouds in the atmosphere around a volcano, affecting commercial aviation use of the airspace around the volcano. Encountering these ash clouds can cause severe damage to different parts of the aircraft, mainly the engines. This work seeks to contribute to the development of methods for observing the dispersion of volcanic ash and to complement computational methods that are currently used for the prediction of ash dispersion. The method presented here is based on the frequency of occurrence of the regions of airspace areas affected by ash emission during a volcanic eruption. Popocatepetl volcano, 60 km east of Mexico City is taken as a case study. A temporal wind analysis was carried out at different atmospheric levels, to identify the direction towards which the wind disperses ash at different times of the year. This information showed two different trends, related to seasons in the direction of dispersion: the first from November to May and the second from July to September. To identify the ash cloud and estimate its area, a set of 920 MODIS images that recorded Popocatepetl volcanic activity between 2000 and 2021 was used. These satellite images were subjected to a semi-automatic, digital pre-processing of binarization by thresholds, according to the level of the brightness temperature difference between band 31 (11 µm) and band 32 (12 µm), followed by manual evaluation of each binarized image. With the information obtained by the processing of the MODIS image, an information table was built with the geographical position of each pixel characterized by the presence of ash for each event. With these data, the areas around Popocatepetl volcano with the highest frequency of affectation by ash emissions were identified during the period analyzed. This study seeks to complement the results obtained by numerical models that make forecasts of ash dispersions and that are very important for the prevention of air navigation risks.
      Citation: Aerospace
      PubDate: 2022-06-07
      DOI: 10.3390/aerospace9060308
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 309: Remaining Useful Life Estimation of Cooling
           Units via Time-Frequency Health Indicators with Machine Learning

    • Authors: Raúl Llasag Rosero, Catarina Silva, Bernardete Ribeiro
      First page: 309
      Abstract: Predictive Maintenance (PM) strategies have gained interest in the aviation industry to reduce maintenance costs and Aircraft On Ground (AOG) time. Taking advantage of condition monitoring data from aircraft systems, Prognostics and Health Maintenance (PHM) practitioners have been predicting the life span of aircraft components by applying Remaining Useful Life (RUL) concepts. Additionally, in prognostics, the construction of Health Indicators (HIs) plays a significant role when failure advent patterns are strenuous to be discovered directly from data. HIs are typically supported by data-driven models dealing with non-stationary signals, e.g., aircraft sensor time-series, in which data transformations from time and frequency domains are required. In this paper, we build time-frequency HIs based on the construction of the Hilbert spectrum and propose the integration of a physics-based model with a data-driven model to predict the RUL of aircraft cooling units. Using data from a major airline, and considering two health degradation stages, the advent of failures on aircraft systems can be estimated with data-driven Machine Learning models (ML). Specifically, our results reveal that the analyzed cooling units experience a normal degradation stage before an abnormal degradation that emerges within the last flight hours of useful life.
      Citation: Aerospace
      PubDate: 2022-06-08
      DOI: 10.3390/aerospace9060309
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 310: Sound-Quality-Based Decision Making in
           Multiobjective Optimisation of Operations for Sustainable Airport

    • Authors: Umberto Iemma, Francesco Centracchio
      First page: 310
      Abstract: The paper deals with a community-oriented approach to the multiobjective optimisation of sustainable takeoff and landing procedures of commercial aircraft. The objective functions to be minimised are defined as the measure of area surrounding the airport where the Sound Exposure Level (SEL) is higher than 60 dBA, and the amount of fuel burned during the procedure. The first merit factor is a measure of the number of citizens affected by a potentially harmful noise level, whereas the second is proportional to the chemical emissions. The novelty of the present approach is the use of a criterion based on sound quality for the selection of the optimal procedure from the Pareto front set. The spectrum of the noise produced by each non-dominated solution is compared to a reference spectrum, the target sound. This is synthesised to meet the acceptance requirements that emerged by a campaign of psychometric tests. The rationale underlying the research is tightly linked to the expected transformation of civil aviation, with the advent of new air transport solutions in urban and suburban environments. The breakthrough nature of the emerging scenarios requires a drastic renewal of the approaches used in the management of operations, and the present work represents a contribution to this evolution. The optimisation is attained adopting a global, deterministic method, and numerical results are obtained for single- and twin-aisle aircraft.
      Citation: Aerospace
      PubDate: 2022-06-08
      DOI: 10.3390/aerospace9060310
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 311: Probabilistic Risk Assessment in Space
           Launches Using Bayesian Network with Fuzzy Method

    • Authors: Xing Pan, Song Ding, Wenjin Zhang, Tun Liu, Liqin Wang, Lijing Wang
      First page: 311
      Abstract: Space launch projects are extremely risky, and any equipment failure or human error may lead to disastrous consequences. Probabilistic risk assessment (PRA) is beneficial to qualitative analysis of risk, but it has not been paid enough attention in risk analysis for space launch systems (SLSs). Compared with most qualitative risk analysis in this field, this paper proposes a risk analysis framework based on Bayesian network (BN) with fuzzy method, which is suitable for probabilistic risk analysis of SLS. This method establishes a risk analysis model of SLS based on statistics and expert experience and reduces the uncertainty of the model by using fuzzy theory. By predicting the system risk probabilities, diagnosing the key risk causes, determining the risk conduction path, and performing a sensitivity analysis, the proposed risk analysis framework is aimed at alleviating this drawback to deal more effectively with the uncertainties in the field of space launches. A case study of space launches demonstrates and verifies the proposed method, and it also provides guidance for similar engineering projects.
      Citation: Aerospace
      PubDate: 2022-06-09
      DOI: 10.3390/aerospace9060311
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 312: The ORIGIN Space Instrument for Detecting
           Biosignatures and Habitability Indicators on a Venus Life Finder Mission

    • Authors: Niels F. W. Ligterink, Kristina A. Kipfer, Salome Gruchola, Nikita J. Boeren, Peter Keresztes Schmidt, Coenraad P. de Koning, Marek Tulej, Peter Wurz, Andreas Riedo
      First page: 312
      Abstract: Recent and past observations of chemical and physical peculiarities in the atmosphere of Venus have renewed speculations about the existence of life in its clouds. To find signs of Venusian life, a dedicated astrobiological space exploration mission is required, and for this reason the Venus Life Finder mission is currently being prepared. A Venus Life Finder mission will require dedicated and specialized instruments to hunt for biosignatures and habitability indicators. In this contribution, we present the ORIGIN space instrument, a laser desorption/laser ablation ionization mass spectrometer. This instrument is designed to detect large, non-volatile molecules, specifically biomolecules such as amino acids and lipids. At the same time, it can also be used in ablation mode for elemental composition analysis. Recent studies with this space prototype instrument of amino acids, polycyclic aromatic hydrocarbons, lipids, salts, metals, sulphur isotopes, and microbial elemental composition are discussed in the context of studies of biosignatures and habitability indicators in Venus’s atmosphere. The implementation of the ORIGIN instrument into a Venus Life Finder mission is discussed, emphasizing the low weight and low power consumption of the instrument. An instrument design and sample handling system are presented that make optimal use of the capabilities of this instrument. ORIGIN is a highly versatile instrument with proven capabilities to investigate and potentially resolve many of the outstanding questions about the atmosphere of Venus and the presence of life in its clouds.
      Citation: Aerospace
      PubDate: 2022-06-09
      DOI: 10.3390/aerospace9060312
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 313: Trajectory Tracking Based on Active
           Disturbance Rejection Control for Compound Unmanned Aircraft

    • Authors: Bohai Deng, Jinfa Xu
      First page: 313
      Abstract: The compound unmanned aircraft is provided with three primary flight modes, which are helicopter flight mode in low forward speed flight, airplane flight mode in high forward speed flight and transition flight mode in middle forward speed flight. For the different flight modes, an appropriate flight control law is the need to ensure good flying qualities. In this paper, a trajectory tracking control system based on the active disturbance rejection controller (ADRC) for the compound unmanned aircraft is proposed to adapt the full flight modes. A flight dynamics model and a Simulink simulation model of the compound unmanned aircraft are developed. The transition flight control strategy is analyzed and synthesized to meet the requirement of control strategy in the full flight modes. The internal uncertainties and external disturbance of the UAV are estimated with an extended state observer to compensate control input. A genetic algorithm-particle swarm optimization (GA-PSO) algorithm is utilized to optimize the controller parameters. The simulation of route tracking and spiral climb with different flight modes is conducted, which demonstrates the tracking ability, interference rejection, robustness and effectiveness of the developed controller in the full flight modes.
      Citation: Aerospace
      PubDate: 2022-06-09
      DOI: 10.3390/aerospace9060313
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 314: A Preliminary Top-Down Parametric Design of
           Electromechanical Actuator Position Control

    • Authors: Jean-Charles Maré
      First page: 314
      Abstract: A top-down process is proposed and virtually validated for the position control of electromechanical actuators (EMA) that use conventional cascade controllers. It aims at facilitating the early design phases of a project by providing a straightforward mean that requires simple algebraic calculations only, from the specified performance and the top-level EMA design parameters. This makes it possible to include realistic control considerations in the preliminary sizing and optimisation phase. The position, speed and current controllers are addressed in sequence. This top-down process is based on the generation and use of charts that define the optimal position gain, speed loop second-order damping factor and natural frequency with respect to the specified performance of the position loop. For each loop, the control design formally specifies the required dynamics and the digital implementation of the following inner loop. A noncausal flow chart summarises the equations used and the interdependencies between data. This potentially allows changing which ones are used as inputs. The process is virtually validated using the example of a flight control actuator. This is achieved with resort to the simulation of a realistic lumped-parameter model, which includes any significant functional and parasitic effects. The virtual tests are run following a bottom–up approach to highlight the pursuit and rejection performance. Using low-, medium- and high-excitation magnitudes, they show the robustness of the controllers against nonlinearities. Finally, the simulation results confirm the soundness of the proposed process.
      Citation: Aerospace
      PubDate: 2022-06-09
      DOI: 10.3390/aerospace9060314
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 315: Research on Dual-Arm Control of Lunar
           Assisted Robot Based on Hierarchical Reinforcement Learning under
           Unstructured Environment

    • Authors: Weiyan Ren, Dapeng Han, Zhaokui Wang
      First page: 315
      Abstract: When a lunar assisted robot helps an astronaut turn over or transports the astronaut from the ground, the trajectory of the robot’s dual arms should be automatically planned according to the unstructured environment on the lunar surface. In this paper, a dual-arm control strategy model of a lunar assisted robot based on hierarchical reinforcement learning is proposed, and the trajectory planning problem is modeled as a two-layer Markov decision process. In the training process, a reward function design method based on the idea of the artificial potential field method is proposed, and the reward information is fed back in a dense reward method, which significantly reduces the invalid exploration space and improves the learning efficiency. Large-scale tests are carried out in both simulated and physical environments, and the results demonstrate the effectiveness of the method proposed in this paper. This research is of great significance in respect of human–robot interaction, environmental interaction, and intelligent control of robots.
      Citation: Aerospace
      PubDate: 2022-06-10
      DOI: 10.3390/aerospace9060315
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 316: A Prognostic and Health Management Framework
           for Aero-Engines Based on a Dynamic Probability Model and LSTM Network

    • Authors: Yufeng Huang, Jun Tao, Gang Sun, Hao Zhang, Yan Hu
      First page: 316
      Abstract: In this study, a prognostics and health management (PHM) framework is proposed for aero-engines, which combines a dynamic probability (DP) model and a long short-term memory neural network (LSTM). A DP model based on Gaussian mixture model-adaptive density peaks clustering algorithm, which has the advantages of an extremely short training time and high enough precision, is employed for modelling engine fault development from the beginning of engine service, and principal component analysis is introduced to convert complex high-dimensional raw data into low-dimensional data. The model can be updated from time to time according to the accumulation of engine data to capture the occurrence and evolution process of engine faults. In order to address the problems with the commonly used data driven methods, the DP + LSTM model is employed to estimate the remaining useful life (RUL) of the engine. Finally, the proposed PHM framework is validated experimentally using NASA’s commercial modular aero-propulsion system simulation dataset, and the results indicate that the DP model has higher stability than the classical artificial neural network method in fault diagnosis, whereas the DP + LSTM model has higher accuracy in RUL estimation than other classical deep learning methods.
      Citation: Aerospace
      PubDate: 2022-06-10
      DOI: 10.3390/aerospace9060316
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 317: A New Method for Remote Sensing Satellite
           Observation Effectiveness Evaluation

    • Authors: Zhi Li, Yunfeng Dong, Peiyun Li, Hongjue Li, Yingjia Liew
      First page: 317
      Abstract: The number of remote sensing satellites has increased rapidly in parallel with the advancement of space technology and the rising demand in the space industry. Consequently, the observation effectiveness evaluation of remote sensing satellites has received extensive attention. As the core content of the effectiveness evaluation, index systems are usually established and screened using qualitative or quantitative methods. They can hardly satisfy the construction principles such as completeness and independence simultaneously. To address this issue, we propose a new method for remote sensing satellite observation effectiveness evaluation that considers various principles. Firstly, a three-layer evaluation index system structure is constructed. The principle of completeness, hierarchy, and measurability of the index system is ensured by decomposition, clustering, and preliminary screening. Secondly, the principal component contribution rate is obtained through principal component analysis. Finally, we introduce a comprehensive scoring method (ICCLR) based on the combination of independence coefficient and principal component comprehensive loss rate. It realizes the screening of an index system from the index set containing correlation relationships. The validity and optimality of the proposed method are verified through experiments and analysis of three typical tasks.
      Citation: Aerospace
      PubDate: 2022-06-11
      DOI: 10.3390/aerospace9060317
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 318: Numerical Prediction of Unsteady
           Aerodynamics of a Ducted Fan Unmanned Aerial Vehicle in Hovering

    • Authors: Hongming Cai, Zhuoran Zhang, Shuanghou Deng
      First page: 318
      Abstract: Recently, ducted fan unmanned aerial vehicles (UAVs) have attracted considerable attention due to their potential for application in both civil and military missions. Compared with free propellers, the presence of duct can in principle decrease the flow contraction after propeller, and gives the potential to fly efficiently with high security, compact structure, and low noise. In the present study, a ducted fan UAV is designed using the open source code OpenProp. The computational fluid dynamics (CFD) simulation model using sliding mesh technique is established and validated as a reliable tool for highly vortical flows by propeller thrust experiment. The effect of the duct, revolution speed, and distance between propellers on the aerodynamic characteristics of the ducted fan UAV is evaluated in detail. Results show that the unducted coaxial upper and lower propellers generate 3.8%, 4.3% more thrust than the unducted single propellers, respectively, and the unducted upper and lower propellers generate 55.9%, 34.9% more thrust than ducted propellers, respectively. The ducted fan UAV generates 5.7% more thrust and consumes 39.1% less power than the unducted coaxial propellers. The thrust of the ducted fan UAV increases first and then follows with a decreased tendency as the distance between propellers increases.
      Citation: Aerospace
      PubDate: 2022-06-11
      DOI: 10.3390/aerospace9060318
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 319: The Enabling Technologies for a Quasi-Zero
           Emissions Commuter Aircraft

    • Authors: Danilo Ciliberti, Pierluigi Della Vecchia, Vittorio Memmolo, Fabrizio Nicolosi, Guido Wortmann, Fabrizio Ricci
      First page: 319
      Abstract: The desire for greener aircraft pushes both academic and industrial research into developing technologies, manufacturing, and operational strategies providing emissions abatement. At time of writing, there are no certified electric aircraft for passengers’ transport. This is due to the requirements of lightness, reliability, safety, comfort, and operational capability of the fast air transport, which are not completely met by the state-of-the-art technology. Recent studies have shown that new aero-propulsive technologies do not provide significant fuel burn reduction, unless the operational ranges are limited to short regional routes or the electric storage capability is unrealistically high, and that this little advantage comes at increased gross weight and operational costs. Therefore, a significant impact into aviation emissions reduction can only be obtained with a revolutionary design, which integrates disruptive technologies starting from the preliminary design phase. This paper reviews the recent advances in propulsions, aerodynamics, and structures to present the enabling technologies for a low emissions aircraft, with a focus on the commuter category. In fact, it is the opinion of the European Community, which has financed several projects, that advances on the small air transport will be a fundamental step to assess the results and pave the way for large greener airplanes.
      Citation: Aerospace
      PubDate: 2022-06-12
      DOI: 10.3390/aerospace9060319
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 320: Identification Strategy Design with the
           Solution of Wavelet Singular Spectral Entropy Algorithm for the
           Aerodynamic System Instability

    • Authors: Mingming Zhang, Pan Kong, Anping Hou, Aiguo Xia, Wei Tuo, Yongzhao Lv
      First page: 320
      Abstract: In order to effectively identify the signs of instability in the aerodynamic system of an axial compressor, a wavelet singular spectral entropy algorithm incorporated within the wavelet transform, singular value decomposition and information entropy is proposed to describe the distribution complexity of the spatial modalities in the flow field. This kind of identification design can accurately distinguish the boundary between the stable and unstable states of the internal flow field from the view of a dynamic system. On the basis of the information entropy algorithm, the wavelet singular spectral entropy algorithm is designed to integrate with the advantages of wavelet transform analysis on the time-frequency localization and singular value decomposition for signal processing and data mining together. So that the quantitative analysis of the definition of rebuilding a system image can be achieved by the solution of wavelet singular spectral entropy. This method can automatically extract the transient information of the space mode in the time-frequency domain. It effectively avoids the shortcoming that the feature extraction on spatial information cannot be accomplished from multiple angles with the single information entropy algorithm. In the data processing of instability signals under different speeds, the wavelet singular spectral entropy algorithm shows a greater advantage in the early warning for compressor stall. The result shows that the value of the wavelet singular spectral shows an obvious mutation when the aerodynamic system approaches the instability boundary. According to the threshold set, the identification hybrid algorithm can detect the stall precursor about 23~96 r in advance. Compared to the single information entropy algorithm, the hybrid wavelet singular spectral entropy algorithm is able to shift to an earlier precursor identification by about 11~82 r. This established hybrid identification algorithm accounts for the nonlinearity of the aerodynamic system, providing a new perspective for the nonlinear system instability identification.
      Citation: Aerospace
      PubDate: 2022-06-13
      DOI: 10.3390/aerospace9060320
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 321: Efficient Modeling of Heat Conduction across
           Thin Surface Coatings on 3D Anisotropic Substrate

    • Authors: Yui-Chuin Shiah, Po-Wen Huang, Mohammad-Rahim Hematiyan, Nguyen Anh Tuan
      First page: 321
      Abstract: In aerospace applications, surface coatings have been widely applied for variouspurposes. One typical example is the use of thermal barrier coating (TBC) applied on anisotropic substrate for enhancing the heat resistance of the substrate under severe operational environments. Numerical modeling of thin coatings usually present difficulties for most techniques, due to their dimensional orders being far below that of the substrate. This paper presents a numerical methodology to efficiently model the heat conduction across thin layered coatings on 3D, generally anisotropic, media by the boundary element method (BEM). In the modeling, singularities of the surface-integrals are weakened by using Green’s Second Identity, where a newly introduced function is solved by the finite volume method. Using the proposed approach, the heat conduction problem can be efficiently analyzed, despite the great difference in dimensional orders in comparison with that of the substrate beneath, by simply employing very coarse surface meshes. Such analysis shows great efficiency in calculating the nearly singular boundary integrals for the modeling. Finally, two benchmark examples of thermal barrier coatings are analyzed to illustrate the effectiveness of this approach.
      Citation: Aerospace
      PubDate: 2022-06-13
      DOI: 10.3390/aerospace9060321
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 322: A Routing Optimization Method for LEO
           Satellite Networks with Stochastic Link Failure

    • Authors: Guohong Zhao, Zeyu Kang, Yixin Huang, Shufan Wu
      First page: 322
      Abstract: In this paper, for an Low-Earth Orbit (LEO) satellite network with inter-satellite links, a routing optimization method is developed in the case of stochastic link failure. First, a discrete-time strategy is used for the satellite network to acquire several static topological graphs during a cycle. Based on the static topological graphs regarding stochastic link failure, a constraint model is established that constructs the task revenue, switching times and routing cost as indicators. Then, an improved Genetic Algorithm based on A* is proposed to optimize the topology under the constraint model. In particular, to reduce the cost of computation, a new generation strategy for the initial solution is presented which combines the roulette wheel operator and the A* algorithm. Finally, the effectiveness of the proposed method is illustrated by a group of numerical simulations for the network with stochastic link failure.
      Citation: Aerospace
      PubDate: 2022-06-14
      DOI: 10.3390/aerospace9060322
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 323: Midcourse Iterative Guidance Method for the
           Impact Time and Angle Control of Two-Pulse Interceptors

    • Authors: Yifan Deng, Jinlei Ren, Xu Wang, Yuanli Cai
      First page: 323
      Abstract: To address the need for flexible energy management and impact angle control in the midcourse guidance of modern long-range antiballistic interceptors, an impact time and angle guidance law is designed for the exoatmospheric midcourse flight of antiballistic interceptors, which covers two pulse sections and two coast sections. The problem is described as an optimal control model with discontinuities in the system equations at interior points, and an iterative guidance method is used to efficiently solve the two-point boundary value problem. Simulation results demonstrate the effectiveness of the proposed guidance law; the obtained miss distance accuracy has an order of magnitude of 1 m, and the impact angle accuracy has a 1° order of magnitude while the angle can be achieved.
      Citation: Aerospace
      PubDate: 2022-06-15
      DOI: 10.3390/aerospace9060323
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 324: Progress of Stewart Vibration Platform in
           Aerospace Micro–Vibration Control

    • Authors: Zepeng He, Xiangchao Feng, Yeqing Zhu, Zhibo Yu, Zhen Li, Yan Zhang, Yinhang Wang, Pengfei Wang, Liangyu Zhao
      First page: 324
      Abstract: In order to support the development of high–precision spacecraft, the current state of the Stewart vibration isolation platform in the field of aerospace micro–vibration was surveyed. First, based on analyses of the causes and characteristics of spacecraft micro–vibration, the principles, characteristics, advantages and disadvantages of four vibration isolation technologies are summarized. Second, the development process of the Stewart vibration isolation platform, from structural proposal and theoretical calculation to application in various fields, is introduced. Then, the current state of kinematics, dynamics and braking control algorithms of the Stewart platform is investigated, and related work on rigid/flexible platforms in the field of aerospace micro–vibration is introduced in detail. Finally, the idea that the Stewart platform can be fabricated by 4D printing technology is proposed. The novel Stewart platform can be combined with artificial intelligence algorithms and advanced control strategies, allowing for further development in the direction of an integrated omnidirectional, full–frequency and multi–function platform with variable stiffness.
      Citation: Aerospace
      PubDate: 2022-06-15
      DOI: 10.3390/aerospace9060324
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 325: Performance Comparison of Control Strategies
           for a Variable-Thrust Solid-Propellant Rocket Motor

    • Authors: Jihyoung Cha, Élcio Jeronimo de Oliveira
      First page: 325
      Abstract: This paper deals with a performance comparison of the control algorithm for a variable-thrust solid-propellant rocket motor (VTSRM). To do this, we develop a simulation model of a VTSRM considering characteristic changes in the combustor and design control systems for pressure and thrust. We use three types of control algorithms for the pressure control: classical PID control, feedback linearization control, and fuzzy PID control, and two control algorithms for thrust control: classical PID control and fuzzy PID control. Finally, we compare the performance of each control system through a numerical simulation using step responses. Through this work, we check that feedback linearization is better in pressure control, and fuzzy PID control is more appropriate in thrust control. Especially using fuzzy PID control, we can get fast settling with a small undershoot even if the system is a nonminimum phase system.
      Citation: Aerospace
      PubDate: 2022-06-16
      DOI: 10.3390/aerospace9060325
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 326: Numerical Investigation on the Heat Transfer
           of n-Decane in a Horizontal Channel with Axially Nonuniform Heat Flux
           under Supercritical Pressure

    • Authors: Jin Zhang, Qilin Zhou, Xudong Zhao, Yuguang Jiang, Wei Fan
      First page: 326
      Abstract: Regenerative cooling is considered promising in the thermal protection of hypersonic propulsion devices such as SCRamjet. However, the heat transfer deterioration (HTD) of hydrocarbon fuel is a severe threat to the thermal structure safety, especially under axially nonuniform heat flux caused by the thermal load difference in different components. In this work, the heat transfer of trans-critical n-decane in a mini-horizontal channel is numerically investigated. The influences of the axially nonuniform heat flux on the heat transfer is focused on. Two types of HTD are recognized and analyzed. The first type of HTD is induced by the near-wall flow acceleration and the local thickening of the viscous sublayer. The second type of HTD is closely related to the expansion of the low thermal conductivity λ and specific heat cp region, which is seriously worsened under axially nonuniform heat flux, especially when the heat flux peak locates where Tw ≥ Tpc. The minimum HTC deteriorates by 40.80% and the Tw_max increases from 857 K to 1071 K by 27.5%. The maximum fluctuation in pressure drop is 6.8% in the variation in heat flux distribution with Φ = 2. This work is expected to offer a reference to the proper match of fuel temperature distribution and the engine heat flux boundary in SCRamjet cooling system design.
      Citation: Aerospace
      PubDate: 2022-06-17
      DOI: 10.3390/aerospace9060326
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 327: Vibro-Acoustic Modelling of Aeronautical
           Panels Reinforced by Unconventional Stiffeners

    • Authors: Giovanni Fasulo, Pasquale Vitiello, Luigi Federico, Roberto Citarella
      First page: 327
      Abstract: The purpose of this work is to characterise the vibro-acoustic behaviour of rectangular flat panels reinforced by “unconventional” stiffeners. Such panels are being increasingly employed in the aircraft industry in the case of composite fuselage, so that the assessment of the most efficient and accurate numerical techniques and modelling procedures to correctly predict their dynamic and acoustic behaviour is required. To this end, an analytical method, available from literature, has been initially employed to investigate on the main attributes of sound transmission loss properties of stiffened panels driven by an acoustic diffuse field excitation. Based on existing commercial codes, different numerical techniques have been implemented and deeply examined to assess their potentiality and restrictions. Among them, the Hybrid method has been eventually identified as the best compromise in terms of accuracy and computational effort. The drawbacks of deterministic and even Hybrid numerical approaches for medium–high frequency vibro-acoustic analysis when dealing with large structures, make use of the pure SEA approach compulsory. In particular, a refined tuning of a specific feature made available within the employed SEA analysis environment when dealing with reinforced shells is implemented as a potential solution to overcome the complexity in correctly modelling the examined unconventionally stiffened panels.
      Citation: Aerospace
      PubDate: 2022-06-17
      DOI: 10.3390/aerospace9060327
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 328: Effect of Lifting Gas Diffusion on the
           Station-Keeping Performance of a Near-Space Aerostat

    • Authors: Jun Li, Linyu Ling, Jun Liao, Zheng Chen, Shibin Luo
      First page: 328
      Abstract: During the long-endurance flight of a near-space aerostat, the characteristics of lifting gas diffusion have a great influence on the flight altitude adjustment and station-keeping performance. Thus, in this study, a lifting gas diffusion model and a dynamic model that consider thermal effects, which had not been studied in similar models before, were developed. The dynamic model and thermal model were validated by historic flight data, and the calculated lifting gas diffusion results were compared with the experimental data of other researchers. The variations in the flight endurance, flight altitude, lifting gas diffusion rate, and diffusion coefficient of a near-space aerostat were analyzed. The effects of the ratio of porosity to tortuosity and envelope radiation properties on the mass of the lifting gas and flight altitude were considered in detail. To analyze the effect mechanism of the ratio of porosity to tortuosity and the envelope radiation properties, the envelope and gas temperature, as well as the gas pressure, were studied. The results show that the lifting gas diffusion rate and diffusion coefficient are very sensitive to the change in the ratio of porosity to tortuosity and envelope temperature. The results obtained from the analysis of the lifting gas diffusion can lay a solid foundation for improving the flight performance of near-space aerostats and for providing improved design considerations for aerostats.
      Citation: Aerospace
      PubDate: 2022-06-18
      DOI: 10.3390/aerospace9060328
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 329: Flight Anomaly Detection via a Deep Hybrid

    • Authors: Kun Qin, Qixin Wang, Binbin Lu, Huabo Sun, Ping Shu
      First page: 329
      Abstract: In the civil aviation industry, security risk management has shifted from post-accident investigations and analyses to pre-accident warnings in an attempt to reduce flight risks by identifying currently untracked flight events and their trends and effectively preventing risks before they occur. The use of flight monitoring data for flight anomaly detection is effective in discovering unknown and potential flight incidents. In this paper, we propose a time-feature attention mechanism and construct a deep hybrid model for flight anomaly detection. The hybrid model combines a time-feature attention-based convolutional autoencoder with the HDBSCAN clustering algorithm, where the autoencoder is constructed and trained to extract flight features while the HDBSCAN works as an anomaly detector. Quick access record (QAR) flight data containing information of aircraft landing at Kunming Changshui International and Chengdu Shuangliu International airports are used as the experimental data, and the results show that (1) the time-feature-based convolutional autoencoder proposed in this paper can better extract the flight features and further discover the different landing patterns; (2) in the representation space of the flights, anomalous flight objects are better separated from normal objects to provide a quality database for subsequent anomaly detection; and (3) the discovered flight patterns are consistent with those at the airports, resulting in anomalies that could be interpreted with the corresponding pattern. Moreover, several examples of anomalous flights at each airport are presented to analyze the characteristics of anomalies.
      Citation: Aerospace
      PubDate: 2022-06-19
      DOI: 10.3390/aerospace9060329
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 330: MC-New: A Program to Calculate Newtonian
           Aerodynamic Coefficients Based on Monte-Carlo Integration

    • Authors: Michiko Ahn Furudate
      First page: 330
      Abstract: A computer program, MC-New, to calculate Newtonian aerodynamics is presented. The aerodynamic coefficients of a geometry expressed by an analytic function are calculated in a Monte-Carlo integration manner, in which the local forces on the randomly chosen sample points are summed up. The verification study and the accuracy analysis show that the program can provide good approximations of exact solutions. The example results of the parametric study on the Apollo-like entry capsule geometry are presented, showing the potential capability of the MC-New program as an efficient open-source tool for designing hypersonic vehicles.
      Citation: Aerospace
      PubDate: 2022-06-20
      DOI: 10.3390/aerospace9060330
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 331: Energy System Optimization and Simulation
           for Low-Altitude Solar-Powered Unmanned Aerial Vehicles

    • Authors: Ke Li, Yansen Wu, Abu Bakar, Shaofan Wang, Yuangan Li, Dongsheng Wen
      First page: 331
      Abstract: The accurate calculation of energy system parameters makes a great contribution to the long-term low-altitude flight of solar-powered aircraft. The purpose of this paper is to propose a design method for optimization and management of the low-altitude and long-endurance Unmanned Aerial Vehicles (UAV) energy system. In terms of optimization, the power input and output generated by solar panels and cruise thrust are calculated, and the energy balance of the UAV during flight is analyzed. In addition, in order to meet the energy consumption requirements of UAV during day and night flight, the influence of local environmental conditions (such as morning and evening clouds and night interference) on the aircraft is considered, and the remaining time indicator is designed to ensure long-term flight stability. Battery capacity is also estimated by the remaining time. This paper will describe extended criteria for optimization and extension methods to improve the stability and robustness of aircraft flight performance for multiple consecutive days. In addition, a design method for the UAV has been developed, which simulates and optimizes the parameters of the solar-powered UAV so that it has a wingspan of 5 m and a relative battery mass of 3 kg. The simulation in this paper describes in detail the aircraft taking off from 7 a.m. on the first day to verify the aircraft’s full day and night flight capability, and achieving the aircraft’s long flight on 22 June to meet the mission requirements of multi-day flights. It also analyzed and verified the performance at the edge of the 48 h flight time window on 21 April, which differs from the lighting in August. Finally, a flight experiment was completed on 9 August. The feasibility of the proposed method and process is verified in this paper along with the performance of the designed UAV, which will provide more guidance for future work.
      Citation: Aerospace
      PubDate: 2022-06-20
      DOI: 10.3390/aerospace9060331
      Issue No: Vol. 9, No. 6 (2022)
  • Aerospace, Vol. 9, Pages 263: Aircraft-Type-Specific Impact of Speed
           Brakes on Lift and Drag

    • Authors: Judith Rosenow, Thomas Sachwitz, Shumpei Kamo, Gong Chen, Hartmut Fricke
      First page: 263
      Abstract: The increasing influence of current research in air traffic management on daily flight operations leads to a stronger consideration of individually optimized aircraft trajectories. However, in the dichotomy between ecological, economic, and safety-based optimization goals, four-dimensionally optimized trajectories are subject to severe constraints in terms of position and speed. To fully assess the performance envelope of these trajectories, precise modelling of the influence of secondary control surfaces on flight performance is necessary. In particular, the use of speed brakes can significantly influence the descent and speed profile and allows the implementation of different cost indices. In this study, we present a modelling approach of the influence of extended speed brakes on flight performance and apply this method in a simulation environment for trajectory modelling of twelve different aircraft types. In doing so, we can determine an almost linear influence of the additional fuel requirement from the effective area of the speed brakes. The results can be implemented in any flight performance model and enable more precise modelling of future aircraft trajectories. Specifically, optimization targets regarding the required time of arrival, or the cost index and the consideration of the dynamic impact of atmospheric conditions in the trajectory optimization, only becomes possible through the calculation of the influence of the speed brake on lift and drag.
      Citation: Aerospace
      PubDate: 2022-05-12
      DOI: 10.3390/aerospace9050263
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 264: Design, Analysis, and Testing of a Scaled
           Propeller for an Innovative Regional Turboprop Aircraft

    • Authors: Danilo Ciliberti, Fabrizio Nicolosi
      First page: 264
      Abstract: This paper describes the design, numerical analyses, and wind tunnel tests of the scaled model of a propeller serving as a propulsive element for the experimental tests of an advanced regional turboprop aircraft with engines installed on the horizontal tailplane tips. The design has been performed by complying with the thrust similarity from the full-scale aircraft propulsive requirements. Numerical analyses with a high-fidelity aerodynamic solver confirmed that the initial design made with XROTOR would achieve the expected performance. Finally, a strengthened version of the propeller has been manufactured via 3D printing and tested in the wind tunnel. Test data include measurements of thrust as well as propeller normal force at different angles of attack. Good agreement between numerical and experimental results has been observed, enabling the propeller to be used confidently in the aircraft wind tunnel powered test campaign.
      Citation: Aerospace
      PubDate: 2022-05-13
      DOI: 10.3390/aerospace9050264
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 265: A Modal Interpretation for Aeroelastic
           Stability Enhancement of Mistuned Bladed Disks

    • Authors: Xin Liu, Yu Fan, Lin Li, Xiaoping Yu
      First page: 265
      Abstract: Understanding the mechanism of the aeroelastic stability improvement induced by mistuning is essential for the design of bladed disks in aero-engines. In this paper, a quantitative interpretation is given. It starts by projecting the mistuned aeroelastic modes into the space spanned by the tuned modes. In this way, the mistuned aeroelastic damping can be expressed by the superposition of the tuned damping. Closed-form expressions are found, providing clear interpretations of several frequently reported trends in the literature. Further, a prediction approach is proposed, where the analysis of aeroelastic coupling only needs to be performed once, and it is decoupled from the analysis of the mistuning effect. The advantages are two-fold. First, the design of the mistuning pattern is accelerated. Second, this allows one to introduce more accurate data or models of aeroelastic damping. An empirical bladed disk with NASA-ROTOR37 profile is used as an example, and the alternate, wave, and random patterns are considered.
      Citation: Aerospace
      PubDate: 2022-05-13
      DOI: 10.3390/aerospace9050265
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 266: Long-Term Orbit Prediction and Deorbit
           Disposal Investigation of MEO Navigation Satellites

    • Authors: Min Hu, Yongjing Ruan, Huifeng Zhou, Jiahui Xu, Wen Xue
      First page: 266
      Abstract: With the increase in satellites in the medium Earth orbit (MEO) region, there should be a focus on orbit safety in the MEO region. A safe orbit disposal strategy is necessary to maintain the sustainability of the MEO region. This paper focuses on long-term evolution modeling, safety analysis of MEO objects, and different disposal techniques for end-of-life BDS-2 MEO satellites. On the one hand, a long-term numerical evolution model is established, and mean equinoctial elements are adopted to propagate a long-term orbit. Long-term evolution for the MEO region over 100 years is carried out, including the Galileo, BDS, GPS, and GLONASS constellations. The earliest orbit intersection time with other global navigation satellite system (GNSS) constellations is put forward. On the other hand, a dynamic model and an optimization model for disposal orbit are established, which minimize the eccentricity growth within 200 years and the fuel consumption for maneuvering to the disposal orbit. The bounds for the disposal region of BDS MEO satellites are also proposed, which consider the measurement and control error of BDS MEO satellites and the eccentricity bounds for end-of-life BDS MEO satellites. A genetic algorithm is adopted to optimize the orbital elements for end-of-life BDS MEO satellites. In addition, two disposal cases, namely, upraising and reducing the orbit, for end-of-life BDS MEO satellites are simulated. The long-term evolutions for the disposal of orbital elements within 200 years are implemented, and the fuel consumption is calculated. The results show that the current MEO region is relatively safe and that the eccentricity is the most important factor that influences the long-term evolution of safety analysis for BDS MEO disposal orbits. Upraising the orbit is safe for end-of-life BDS MEO satellites. This investigation provides the theoretical foundation for investigating the long-term evolutionary mechanisms of the MEO region and references disposal strategy analysis for decommissioned navigation satellites, and the spent upper stages for other GNSS constellations.
      Citation: Aerospace
      PubDate: 2022-05-15
      DOI: 10.3390/aerospace9050266
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 267: Experimental Investigation of a Cylindrical
           Air-Breathing Continuous Rotating Detonation Engine with Different Nozzle
           Throat Diameters

    • Authors: Guangyu Wang, Shijie Liu, Haoyang Peng, Weidong Liu
      First page: 267
      Abstract: A continuous detonation engine with various exhaust nozzles, analogous to typical scramjet cavity combustors with variable rear-wall heights, was adopted to perform a succession of cylindrical air-breathing continuous rotating detonation experiments fueled by a non-premixed ethylene/air mixture. The results show that the detonation combustion was observed to self-sustain in the combustor through simultaneous high-speed imaging covering the combustor and isolator. A long test, lasting more than three seconds, was performed in this unique configuration, indicating that the cylindrical isolator–combustor engine exhibits potential for practical applications. Three distinct combustion modes were revealed with varied equivalent ratios (hybrid mode, sawtooth wave mode, and deflagration mode). The diameter of the nozzle throat was critical in the formation of rotating detonation waves. When the nozzle throat diameter was larger than the specific value, the detonation wave could not form and self-sustain. The upstream boundary of the shock train was supposed to be close to the isolator entrance in conditions of a high equivalence ratio and small nozzle throat diameter. In addition, it was verified that periodic high-frequency pressure oscillation could cause substantial impacts on the incoming flow as compared with the steady deflagration with the same combustor pressure.
      Citation: Aerospace
      PubDate: 2022-05-16
      DOI: 10.3390/aerospace9050267
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 268: Thermal Design of Blackbody for On-Board
           Calibration of Spaceborne Infrared Imaging Sensor

    • Authors: Hye-In Kim, Bong-Geon Chae, Pil-Gyeong Choi, Mun-Shin Jo, Kyoung-Muk Lee, Hyun-Ung Oh
      First page: 268
      Abstract: In this study, we propose a thermal design for an on-board blackbody (BB) for spaceborne infrared (IR) sensor calibration. The main function of the on-board BB is to provide highly uniform and precise radiation temperature reference sources from 0 °C to 40 °C during the calibration of the IR sensor. To meet the functional requirements of BB, a BB thermal design using a heater to heat the BB during sensor calibration and heat pipes to transfer residual heat to the radiator after calibration is proposed and investigated both numerically and experimentally. The main features of the proposed thermal design are a symmetric temperature gradient on the BB surface with less than 1 K temperature uniformity, ease of temperature sensor implementation to estimate the representative surface temperature of the BB, a stable thermal interface between the heat pipes and BB, and a fail-safe function under one heat pipe failure. The thermal control performance of the BB is investigated via in-orbit thermal analysis, and its effectiveness is verified via a heat-up test of the BB under ambient conditions. These results indicate that the temperature gradient on the BB surface was obtained at less than 1 K, and the representative surface temperature could be estimated with an accuracy of 0.005 °C via the temperature sensor.
      Citation: Aerospace
      PubDate: 2022-05-16
      DOI: 10.3390/aerospace9050268
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 269: A Clustering Ensemble Method of Aircraft
           Trajectory Based on the Similarity Matrix

    • Authors: Xiao Chu, Xianghua Tan, Weili Zeng
      First page: 269
      Abstract: Performing clustering analysis on a large amount of historical trajectory data can obtain information such as frequent flight patterns of aircraft and air traffic flow distribution, which can provide a reference for the revision of standard flight procedures and the optimization of the division of airspace sectors. At present, most trajectory clustering uses a single clustering algorithm. When other processing remains unchanged, it is difficult to improve the clustering effect by using a single clustering method. Therefore, this paper proposes a trajectory clustering ensemble method based on a similarity matrix. Firstly, a stacked autoencoder is used to learn a small number of features that are sufficiently representative of the trajectory and used as the input to the subsequent clustering algorithm. Secondly, each basis cluster is used to cluster the data set, and then a consistent similarity matrix is obtained by using the clustering results of each basis cluster. On this basis, using the deformation of the matrix as the distance matrix between trajectories, the agglomerative hierarchical clustering algorithm is used to ensemble the results of each basis cluster. Taking the Nanjing Lukou Airport terminal area as an example, the experimental results show that integrating multiple basis clusters eliminates the inherent randomness of a single clustering algorithm, and the trajectory clustering results are more robust.
      Citation: Aerospace
      PubDate: 2022-05-17
      DOI: 10.3390/aerospace9050269
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 270: A Cyber-Physical Prototyping and Testing
           Framework to Enable the Rapid Development of UAVs

    • Authors: Or D. Dantsker, Mirco Theile, Marco Caccamo
      First page: 270
      Abstract: In this work, a cyber-physical prototyping and testing framework to enable the rapid development of UAVs is conceived and demonstrated. The UAV Development Framework is an extension of the typical iterative engineering design and development process, specifically applied to the rapid development of UAVs. Unlike other development frameworks in the literature, the presented framework allows for iteration throughout the entire development process from design to construction, using a mixture of simulated and real-life testing as well as cross-aircraft development. The framework presented includes low- and high-order methods and tools that can be applied to a broad range of fixed-wing UAVs and can either be combined and executed simultaneously or be executed sequentially. As part of this work, seven novel and enhanced methods and tools were developed that apply to fixed-wing UAVs in the areas of: flight testing, measurement, modeling and emulation, and optimization. A demonstration of the framework to quickly develop an unmanned aircraft for agricultural field surveillance is presented.
      Citation: Aerospace
      PubDate: 2022-05-17
      DOI: 10.3390/aerospace9050270
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 271: Aerodynamic Uncertainty Quantification for
           Tiltrotor Aircraft

    • Authors: Ye Yuan, Douglas Thomson, David Anderson
      First page: 271
      Abstract: The tiltrotor has unique flight dynamics due to the aerodynamic interference characteristics. Multiple aerodynamics calculation approaches, such as the CFD method, are utilised to characterise this feature. The calculation process is usually time-consuming, and the obtained results are generally varied from each other. Thus, the uncertainty quantification (UQ) method will be utilised in this research to identify the aerodynamic inaccuracy effect on the handling qualities of the tiltrotor aircraft. The study aims to quantify the influence of the aerodynamic interference on the tiltrotor flight dynamics in different flight states, such as forward speeds and nacelle tilting angles, which can guide the flight dynamics modelling simplification to improve the simulation efficiency. Therefore, uncertainty identification and full factorial numerical integration (FFNI) methods are introduced to scale these aerodynamic uncertainties. The eigenvalue and bandwidth and phase delay requirements are presented as the failure criteria. The UQ calculation indicates that the uncertainties of the aerodynamic calculation significantly affect the handling quality ratings in two flight ranges: the helicopter mode and the conversion and aeroplane modes with higher forward speed (close to the conversion envelope). Furthermore, a sensitivity analysis is performed to identify the mechanism behind these influences. The results demonstrate that aerodynamics affect the pitching attitude, the pitching damping, and the velocity and incidence stability derivatives. However, the effects of the velocity stability and the incidence stability are the reason causing the handling qualities’ degradation in the helicopter mode and high-speed mode, respectively.
      Citation: Aerospace
      PubDate: 2022-05-18
      DOI: 10.3390/aerospace9050271
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 272: Coordinated Formation Guidance Law for
           Fixed-Wing UAVs Based on Missile Parallel Approach Method

    • Authors: Zheng Gong, Zan Zhou, Zian Wang, Quanhui Lv, Jinfa Xu, Yunpeng Jiang
      First page: 272
      Abstract: This paper presents a classic missile-type parallel-approach guidance law for fixed-wing UAVs in coordinated formation flight. The key idea of the proposed guidance law is to drive each follower to follow the virtual target point. Considering the turning ability of each follower, the formation form adopts the semi-perfect rigid form, which does not require the vehicle positions form a rigid formation, and the orientations keep consensus. According to the mission characteristics of the follower following a leader and the leader following a route, three guidance laws for straight, turning, and circling flight are designed. A series of experiments demonstrate the proposed guidance law’s improved response and maneuvering stability. The results of hardware-in-the-loop simulations and real flight tests prove that the proposed guidance law satisfies the practical UAV formation flight control demands.
      Citation: Aerospace
      PubDate: 2022-05-18
      DOI: 10.3390/aerospace9050272
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 273: Performance Evaluation of Multiflight Ground
           Handling Process

    • Authors: Biao Li, Liwen Wang, Zhiwei Xing, Qian Luo
      First page: 273
      Abstract: The ever-increasing high density of flights arouses an urgent requirement to improve the effectiveness and performance of ground handling in airport operation. The implementation of coordinated airport decision-making quantifies the ground handling process into a series of key milestone nodes, which is more conducive for operators to reduce resource consumption and flight delays. An innovative performance evaluation method for the multiflight ground handling process is proposed based on shared information of milestone nodes in the ground handling. A dynamic performance evaluation model is established, which should superimpose the performance evaluation results of the single-flight ground handling process. Meanwhile, the indicators and weights of the single-flight performance evaluation are obtained by combining the ground handling process prediction and expected value. As time evolves, a matrix method for the multiflight ground handling performance evaluation is proposed to combine the logic and evolution of the process. It is shown that the average prediction accuracy of single-flight ground handling process nodes can be increased to 87.63%. The experimental analysis demonstrates that the objectivity, effectiveness and dynamics of the proposed approach can be the basis for short-term tactics in airport.
      Citation: Aerospace
      PubDate: 2022-05-18
      DOI: 10.3390/aerospace9050273
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 274: Track Segment Association Method Based on
           Bidirectional Track Prediction and Fuzzy Analysis

    • Authors: Yupeng Cao, Jiangwei Cao, Zhiguo Zhou
      First page: 274
      Abstract: Due to sensor characteristics, geographical environment, electromagnetic interference, electromagnetic silence, information countermeasures, and other reasons, the phenomenon of track breakages occur in the process of aircraft track data processing. It leads to the change in target label attributes. In order to make the track segment association effect better, we studied several existing time series prediction methods, and proposed a track segment association method based on bidirectional Holt-Winters prediction and fuzzy analysis. This algorithm bidirectionally predicts and extrapolates track segments by the Holt-Winters method, and then uses the fuzzy track segment association algorithm to perform segment association and secondary association. The simulation results of this method show that the track segment association method based on Holt-Winters prediction and fuzzy analysis can effectively solve the track association problem where the target label attributes change before and after track breakage, demonstrating better association ability and robustness. Compared with the fuzzy association method without adding track prediction, our method generally improves the association accuracy by 35%.
      Citation: Aerospace
      PubDate: 2022-05-19
      DOI: 10.3390/aerospace9050274
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 275: Conceptual Design of a Hybrid Hydrogen Fuel
           Cell/Battery Blended-Wing-Body Unmanned Aerial Vehicle—An Overview

    • Authors: Siwat Suewatanakul, Alessandro Porcarelli, Adam Olsson, Henrik Grimler, Ariel Chiche, Raffaello Mariani, Göran Lindbergh
      First page: 275
      Abstract: The manuscript presents the conceptual design phase of an unmanned aerial vehicle, with the objective of a systems approach towards the integration of a hydrogen fuel-cell system and Li-ion batteries into an aerodynamically efficient platform representative of future aircraft configurations. Using a classical approach to aircraft design and a combination of low- and high-resolution computational simulations, a final blended wing body UAV was designed with a maximum take-off weight of 25 kg and 4 m wingspan. Preliminary aerodynamic and propulsion sizing demonstrated that the aircraft is capable of completing a 2 h long mission powered by a 650 W fuel cell, hybridized with a 100 Wh battery pack, and with a fuel quantity of 80 g of compressed hydrogen.
      Citation: Aerospace
      PubDate: 2022-05-19
      DOI: 10.3390/aerospace9050275
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 276: Real-Time Fuel Optimization and Guidance for
           Spacecraft Rendezvous and Docking

    • Authors: Ahmed Mehamed Oumer, Dae-Kwan Kim
      First page: 276
      Abstract: Autonomous rendezvous and docking (RVD) fuel optimization with field-of-view and obstacle avoidance constraints is a nonlinear and nonconvex optimization problem, making it computationally intensive for onboard computation on CubeSats. This paper proposes an RVD fuel optimization and guidance technique suitable for onboard computation on CubeSats, considering the shape, size and computational limitations of CubeSats. The computation time is reduced by dividing the guidance problem into separate orbit and attitude guidance problems, formulating the orbit guidance problem as a convex optimization problem by considering the CubeSat shape, and then solving the orbit guidance problem with a convex optimization solver and the attitude guidance problem analytically by exploiting the attitude geometry. The performance of the proposed guidance method is demonstrated through simulations, and the results are compared with those of conventional methods that perform orbit guidance optimization with attitude quaternion feedback control. The proposed method shows better performance, in terms of fuel efficiency, than conventional methods.
      Citation: Aerospace
      PubDate: 2022-05-20
      DOI: 10.3390/aerospace9050276
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 277: Nonlinear Covariance Analysis-Based Robust
           Rendezvous Trajectory Design by Improved Differential Evolution Method

    • Authors: Kai Jin, Zeyang Yin, Yaolin Lei, Yuanlong Zhang, Xiaolong Zhang
      First page: 277
      Abstract: This paper presents a robust trajectory design method for approaching and rendezvous with a space target considering multi-source uncertainties. A nonlinear covariance analysis method based on the state transition tensor is presented to formulate the propagation of uncertainties including environment parameter uncertainty, actuator error, sensor noise, navigation error and initial state dispersion of the closed-loop GN&C system. Then, the robust trajectory design problem is defined based on the quantified effect of the uncertainties, and an improved self-adaptive differential evolution algorithm is presented to solve the robust trajectory design problem with uncertainties. Finally, four groups of numerical simulations are carried out to show that the designed robust trajectories can satisfy the final state dispersion constraint under multi-source uncertainties.
      Citation: Aerospace
      PubDate: 2022-05-21
      DOI: 10.3390/aerospace9050277
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 278: Model and Optimization of the Tether for a
           Segmented Space Elevator

    • Authors: Shihao Luo, Naigang Cui, Xiaowei Wang, Youhua Fan, Run Shi
      First page: 278
      Abstract: In order to improve the shortcomings of the traditional constant section and gradual section space elevator system, combined with the advantages of constant section and gradual section space elevator system, a model of segmented space elevator system is designed. This model has the characteristics of easier construction, more practical functions, and easier maintenance. The cyclic iterative method is proposed to calculate the stress distribution of the space elevator system. The maximum stress variation and system scale variation of segmented space elevator system with different segment numbers is analyzed and compared with the system scale of constant section and gradual section space elevator system. The results show that the segmented space elevator model can significantly reduce the peak stress of the space elevator system under the condition of limited increase in the system scale, and the peak stress is 56% lower than that of the constant section space elevator model. Considering the number of segments, peak stress, and system scale, the calculation results show that the optimal number of segments is 5 or 6.
      Citation: Aerospace
      PubDate: 2022-05-22
      DOI: 10.3390/aerospace9050278
      Issue No: Vol. 9, No. 5 (2022)
  • Aerospace, Vol. 9, Pages 279: Assessment of Future Airframe and Propulsion
           Technologies on Sustainability of Next-Generation Mid-Range Aircraft

    • Authors: Stanislav Karpuk, Rolf Radespiel, Ali Elham
      First page: 279
      Abstract: The present work demonstrates the impact of future airframe and propulsion technologies on the sustainability of potential future medium-range commercial jets with design specifications similar to the Airbus A320-200. Advanced airframe and engine technologies include laminar flow control (LFC), active load alleviation, new materials and structures, and ultra-high bypass ratio turbofan engines. Two aircraft configurations with various design options were compared to determine potentially the best option for the mission profile, which tends to minimize the environmental impact. Each configuration was designed to balance the equivalent CO2 emissions and Direct Operating Costs. Technology sensitivity analyses were performed to investigate the significance of particular technology combinations and determine the ones that improve aircraft sustainability the most. All studies were performed at a conceptual design level using a multi-fidelity design approach to investigate the system-level effects of the technologies. The open-source aircraft design environment SUAVE was extended and integrated with other aircraft design and analysis tools to obtain all required correlations. The aircraft with advanced technologies showed an average reduction in equivalent CO2 emissions of 36% and a 23% reduction in DOC compared to the reference aircraft for a similar mission profile, although aircraft with future technologies may have a 43% higher production cost. The given results indicate that the application of technologies may be commercially successful if technologies achieve expected performance values, despite high development costs. Finally, the technology sensitivity analysis demonstrated the most significant influence of engine-related technologies and laminar flow control compared to other technologies considered in this research. Depending on design and integration complexities, engine technologies can be more achievable in the near future and can substantially reduce the overall emission level.
      Citation: Aerospace
      PubDate: 2022-05-23
      DOI: 10.3390/aerospace9050279
      Issue No: Vol. 9, No. 5 (2022)
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