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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
Showing 1 - 30 of 30 Journals sorted alphabetically
Acta Astronautica     Hybrid Journal   (Followers: 220)
Advances in Aerospace Engineering     Open Access   (Followers: 74)
Advances in Aerospace Science and Technology     Open Access   (Followers: 14)
Advances in Astronautics Science and Technology     Hybrid Journal   (Followers: 2)
Advances in Space Research     Hybrid Journal   (Followers: 295)
Aeronautical Journal, The     Hybrid Journal   (Followers: 9)
Aerospace     Open Access   (Followers: 64)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 306)
Aerospace Systems     Hybrid Journal   (Followers: 10)
Aerospace technic and technology     Open Access   (Followers: 7)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal   (Followers: 6)
AIAA Journal     Hybrid Journal   (Followers: 1002)
Air Medical Journal     Hybrid Journal   (Followers: 6)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 139)
Artificial Satellites     Open Access   (Followers: 21)
ASTRA Proceedings     Open Access   (Followers: 3)
Astrodynamics     Hybrid Journal   (Followers: 4)
Aviation     Open Access   (Followers: 12)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 7)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 23)
Aviation Week     Full-text available via subscription   (Followers: 411)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 31)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 30)
Chinese Journal of Aeronautics     Open Access   (Followers: 19)
Ciencia y Poder Aéreo     Open Access   (Followers: 3)
Civil Aviation High Technologies     Open Access   (Followers: 6)
Control Systems     Hybrid Journal   (Followers: 235)
Cosmic Research     Hybrid Journal   (Followers: 5)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 25)
Fatigue of Aircraft Structures     Open Access   (Followers: 21)
Frontiers in Aerospace Engineering     Open Access   (Followers: 20)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 177)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 251)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 281)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 43)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 37)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 46)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 4)
International Journal of Aerospace Engineering     Open Access   (Followers: 86)
International Journal of Aerospace Innovations     Full-text available via subscription   (Followers: 23)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 22)
International Journal of Aerospace Sciences     Open Access   (Followers: 36)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 7)
International Journal of Aviation Management     Hybrid Journal   (Followers: 5)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 8)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 9)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 10)
International Journal of Micro Air Vehicles     Open Access   (Followers: 11)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 13)
International Journal of Space Structures     Full-text available via subscription   (Followers: 19)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 11)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 5)
Investigación Pecuaria     Open Access   (Followers: 1)
Journal of Aerodynamics     Open Access   (Followers: 27)
Journal of Aeronautical Materials     Open Access   (Followers: 10)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 66)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 22)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 27)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 57)
Journal of Aerospace Technology and Management     Open Access   (Followers: 10)
Journal of Aircraft     Hybrid Journal   (Followers: 263)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 15)
Journal of Airline and Airport Management     Open Access   (Followers: 11)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 10)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 2)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 2)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 165)
Journal of KONBiN     Open Access   (Followers: 4)
Journal of Navigation     Hybrid Journal   (Followers: 176)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 569)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 8)
Journal of Space Weather and Space Climate     Open Access   (Followers: 30)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 702)
Journal of Spatial Science     Hybrid Journal   (Followers: 4)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 9)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 11)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 3)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 21)
Life Sciences in Space Research     Hybrid Journal   (Followers: 5)
MAD - Magazine of Aviation Development     Open Access   (Followers: 3)
Mekanika : Jurnal Teknik Mesin i     Open Access  
Microgravity Science and Technology     Hybrid Journal   (Followers: 3)
New Space     Hybrid Journal   (Followers: 6)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
npj Microgravity     Open Access   (Followers: 3)
Open Aerospace Engineering Journal     Open Access   (Followers: 4)
Perspectives of Earth and Space Scientists i     Open Access   (Followers: 1)
Population Space and Place     Hybrid Journal   (Followers: 10)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 3)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 16)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 42)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 82)
Propulsion and Power Research     Open Access   (Followers: 89)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
RocketSTEM     Free   (Followers: 5)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 23)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 1)
Space and Polity     Hybrid Journal   (Followers: 6)
Space Policy     Hybrid Journal   (Followers: 30)
Space Research Today     Full-text available via subscription   (Followers: 43)
Space Safety Magazine     Free   (Followers: 50)
Space Science International     Open Access   (Followers: 117)
Space Science Reviews     Hybrid Journal   (Followers: 92)
SpaceNews     Free   (Followers: 779)
Spatial Information Research     Hybrid Journal   (Followers: 1)
Transactions on Aerospace Research     Open Access   (Followers: 1)
Transport and Aerospace Engineering     Open Access   (Followers: 4)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 7)
Unmanned Systems     Hybrid Journal   (Followers: 4)
Xibei Gongye Daxue Xuebao / Journal of Northwestern Polytechnical University     Open Access  
Вісник Національного Авіаційного Університету     Open Access   (Followers: 1)

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Aerospace
Journal Prestige (SJR): 0.305
Citation Impact (citeScore): 1
Number of Followers: 64  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2226-4310
Published by MDPI Homepage  [84 journals]
  • Aerospace, Vol. 9, Pages 226: Impact Pressure Distribution Recognition for
           Large Non-Cooperative Target in Ground Detumbling Experiment

    • Authors: Siqi Peng, Huibo Zhang, Chaoqun Qi, Jialiang Xu, Rui Ma, Shijie Dai
      First page: 226
      Abstract: During the contact between the detumbling end-effector and large non-cooperative target, the recognition of impact pressure distribution is important for estimating the success rate of detumbling mission. To figure out the pressure trends, the ground experiments before the real space mission are necessary. However, due to the drawbacks of the pressure array-like sensor, dynamic characteristics of impact, and unavoidable noise, the accurate dynamic pressure distribution is hard to obtain. In this letter, we propose a recognition method, Impact Pressure Distribution Recognition. The proposed method can quickly generate dynamic impact pressure distribution without limitation on sensor accuracy through pressure data supplement and area correction based on contact model. The analysis results show that our method can efficiently recognize multiple distributed pressure and rebuild the more accurate impact pressure distribution.
      Citation: Aerospace
      PubDate: 2022-04-20
      DOI: 10.3390/aerospace9050226
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 227: Trajectory Clustering for Air Traffic
           Categorisation

    • Authors: Tatjana Bolić, Lorenzo Castelli, Andrea De Lorenzo, Fulvio Vascotto
      First page: 227
      Abstract: Availability of different types of data and advances in data-driven techniques open the path to more detailed analyses of various phenomena. Here, we examine the insights that can be gained through the analysis of historical flight trajectories, using data mining techniques. The goal is to learn about usual (or nominal) choices airlines make in terms of routing, and their relation with aircraft types and operational flight costs. The clustering is applied to intra-European trajectories during one entire summer season, and a statistical test of independence is used to evaluate the relations between the variables of interest. Even though about half of all flights are less than 1000 km long, and mostly operated by one airline, along one trajectory, the analysis shows that, for longer flights, there exists a clear relation between the trajectory clusters and the operating airlines (in about 49% of city pairs) and/or the aircraft types (30%), and/or the flight costs (45%).
      Citation: Aerospace
      PubDate: 2022-04-21
      DOI: 10.3390/aerospace9050227
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 228: The Flying and Adhesion Robot Based on
           Approach and Vacuum

    • Authors: Chengwei Huang, Yong Liu, Bing Bai, Ke Wang
      First page: 228
      Abstract: The conventional flying and adhesion robot adsorbs on the wall by controlling the attitude angle to generate a horizontal-direction force combined with the negative-pressure device at the target position. However, when the robot is in contact with the wall, the wall will generate reaction forces and tilting moments on the robot, which increases the complexity of modeling and controlling the adsorption process. Therefore, inspired by perching mechanisms that geckos and tree frogs can use to jump and adsorb to vertical surfaces such as tree trunks, we propose a natural method based on approach adsorption. The method uses a suitable approaching velocity to achieve stable adsorption at the desired position. We investigate the effects of approach velocity, vacuum-pump flow rate and wall material on the adsorption performance. Furthermore, we design a unidirectional-approach-adsorption system and heading controller and establish a contact and negative-pressure model. The relevant parameters of the adsorption system are identified, and the ground-collision experiments and flight experiments for the flying and adhesion robot were carried out to validate the proposed method.
      Citation: Aerospace
      PubDate: 2022-04-21
      DOI: 10.3390/aerospace9050228
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 229: Results of the Study of the Influence of
           External Cargo Parameters on the Helicopter Controllability

    • Authors: Grigory Babenko, Vadim Efimov, Mikhail Kiselev, Maksim Shkurin
      First page: 229
      Abstract: Helicopters are widely used for air transportation and aerial work with cargo on external cables, one of the most challenging and dangerous uses. The main reason for the flight complication is the change in the controllability characteristics of the helicopter because of the presence of cargo. As of today, flight tests are mainly conducted to determine the feasibility of aerial transportation and aerial work involving external cargo. In addition, they are conducted to determine safe flight regimes when performing such operations. From a flight safety perspective, it is always desirable to know the changes in the control parameters before flight tests are performed. A proposal was made to use theoretical methods, including numerical simulations, to solve these problems. At present, work is progressing to isolate the effects of different cargoes on the external cable suspension and its direct effects on the static and dynamic characteristics of the helicopter’s control and stability. The effect of cargo mass and sail weight on the control efficiency is expressed by the helicopter’s angular acceleration, which is gained by deviating the cyclic pitch handle—a static control and stability indicator. When considering dynamic control and stability, the influence of the length of the external suspension cable on the transition time was investigated. The results obtained were refined for inclusion in all flight manuals for Mi-8 helicopters concerning flights with cargoes attached to the external suspension cables, the size and weight of the suspension cables as well as the methods of instruction and for preparing the crew for flights with upgraded cargo, including instruction via flight simulators.
      Citation: Aerospace
      PubDate: 2022-04-21
      DOI: 10.3390/aerospace9050229
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 230: Air Traffic Complexity Map Based on Linear
           Dynamical Systems

    • Authors: Daniel Delahaye, Adrían García, Julien Lavandier, Supatcha Chaimatanan, Manuel Soler
      First page: 230
      Abstract: This paper presents a new air traffic complexity metric based on linear dynamical systems, of which the goal is to quantify the intrinsic complexity of a set of aircraft trajectories. Previous works have demonstrated that the structure and organization of air traffic are essential factors in the perception of the complexity of an air traffic situation. Usually, they were not able to explicitly address trajectory pattern organization. The new metric, by identifying the organization properties of trajectories in a traffic pattern, captures some of the key factors involved in ATC complexity. The key idea of this work is to find a linear dynamical system which fits a vector field as closely as possible to the observations given by the aircraft positions and speeds. This approach produces an aggregate complexity metric that enables one to identify high (low) complexity regions of the airspace and compare their relative complexity. The metric is very appropriate to compare different traffic situations for any scale (sector or country) by associating a complexity index to each trajectory sample in the airspace. For instance, to compute the complexity for a sector, one must just sum-up the complexity for trajectory samples intersecting such a sector. This computation can also be extended in the time dimension in order to estimate the average complexity in a given airspace for a period of time.
      Citation: Aerospace
      PubDate: 2022-04-22
      DOI: 10.3390/aerospace9050230
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 231: Case Study for Testing the Validity of
           NOx-Ozone Algorithmic Climate Change Functions for Optimising Flight
           Trajectories

    • Authors: Pratik Rao, Feijia Yin, Volker Grewe, Hiroshi Yamashita, Patrick Jöckel, Sigrun Matthes, Mariano Mertens, Christine Frömming
      First page: 231
      Abstract: One possibility to reduce the climate impact of aviation is the avoidance of climate-sensitive regions, which is synonymous with climate-optimised flight planning. Those regions can be identified by algorithmic Climate Change Functions (aCCFs) for nitrogen oxides (NOx), water vapour (H2O) as well as contrail cirrus, which provide a measure of climate effects associated with corresponding emissions. In this study, we evaluate the effectiveness of reducing the aviation-induced climate impact via ozone (O3) formation (resulting from NOx emissions), when solely using O3 aCCFs for the aircraft trajectory optimisation strategy. The effectiveness of such a strategy and the associated potential mitigation of climate effects is explored by using the chemistry–climate model EMAC (ECHAM5/MESSy) with various submodels. A summer and winter day, characterised by a large spatial variability of the O3 aCCFs, are selected. A one-day air traffic simulation is performed in the European airspace on those selected days to obtain both cost-optimised and climate-optimised aircraft trajectories, which more specifically minimised a NOx-induced climate effect of O3 (O3 aCCFs). The air traffic is laterally and vertically re-routed separately to enable an evaluation of the influences of the horizontal and vertical pattern of O3 aCCFs. The resulting aviation NOx emissions are then released in an atmospheric chemistry–climate simulation to simulate the contribution of these NOx emissions to atmospheric O3 and the resulting O3 change. Within this study, we use O3-RF as a proxy for climate impact. The results confirm that the climate-optimised flights lead to lower O3-RF compared to the cost-optimised flights, although the aCCFs cannot reproduce all aspects of the significant impact of the synoptic situation on the transport of emitted NOx. Overall, the climate impact is higher for the selected summer day than for the selected winter day. Lateral re-routing shows a greater potential to reduce climate impact compared to vertical re-routing for the chosen flight altitude. We find that while applying the O3 aCCFs in trajectory optimisation can reduce the climate impact, there are certain discrepancies in the prediction of O3 impact from aviation NOx emissions, as seen for the summer day. Although the O3 aCCFs concept is a rough simplification in estimating the climate impact of a local NOx emission, it enables a reasonable first estimate. Further research is required to better describe the O3 aCCFs allowing an improved estimate in the Average Temperature Response (ATR) of O3 from aviation NOx emissions. A general improvement in the scientific understanding of non-CO2 aviation effects could make climate-optimised flight planning practically feasible.
      Citation: Aerospace
      PubDate: 2022-04-22
      DOI: 10.3390/aerospace9050231
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 232: Optimal Cooperative Line-of-Sight Guidance
           for Defending a Guided Missile

    • Authors: Chendi Li, Jiang Wang, Peng Huang
      First page: 232
      Abstract: This correspondence proposes an optimal cooperative guidance law for protecting a target from a guided missile. The linearized three-body kinematics using the line-of-sight (LOS) triangle concept is formulated, and a new concept called error distance is introduced. A generalized linear quadratic optimization problem is formulated in minimizing weighted energy consumption while regulating the error distance. The analytic guidance command is derived by solving the optimization problem formulated. The main feature of the proposed guidance law lies in that it helps reduce the maneuver capability demand of the defender. Extensive numerical simulations are carried out to demonstrate the effectiveness of the proposed solution.
      Citation: Aerospace
      PubDate: 2022-04-22
      DOI: 10.3390/aerospace9050232
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 233: Special Issue “Hybrid Rocket
           (Volume II)”

    • Authors: Toru Shimada, Carmine Carmicino, Arif Karabeyoglu
      First page: 233
      Abstract: Over the past 40 years, the loss rate for commercial passenger aircrafts has decreased down to about one in ten million, whereas the loss rate for spaceflight has remained high, in the 1% range [...]
      Citation: Aerospace
      PubDate: 2022-04-24
      DOI: 10.3390/aerospace9050233
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 234: Design of Mega-Constellations for Global
           Uniform Coverage with Inter-Satellite Links

    • Authors: Lu Jia, Yasheng Zhang, Jinlong Yu, Xuan Wang
      First page: 234
      Abstract: Constellation configuration design is a prerequisite and critical step in the construction of a mega-constellation system in low Earth orbit. However, the huge number of satellites and the intricate changes in relative positions among them make the configuration design the most challenging part. In this paper, we propose a configuration design scheme for mega-constellations considering collision-avoidance constraints with the objective of uniform global coverage. In this design scheme, the constellation is made up of multiple Walker constellations with the same orbital altitude and different orbital inclination. Moreover, the analytical expression for the minimum distance between any two satellites in the same orbital altitude is derived, and the constellation internal collision-avoidance constraint is established accordingly. Finally, a permanent inter-satellite link design scheme without dynamic reconstruction is presented based on the mega-constellation configuration. Simulation results show that the mega-constellation design scheme introduced in this paper can achieve relatively uniform global coverage (its N Asset Coverage ranges from 18 to 25). The mixed Walker constellation is capable of providing a greater number of N Asset Coverage for most of the world than the Walker constellation of the same satellite order of magnitude. In addition, the inter-satellite link scheme designed in this paper can ensure continuous and stable communication between any satellite nodes.
      Citation: Aerospace
      PubDate: 2022-04-24
      DOI: 10.3390/aerospace9050234
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 235: A Simulated Annealing Algorithm with Tabu
           List for the Multi-Satellite Downlink Schedule Problem Considering Waiting
           Time

    • Authors: Yan Liu, Shengyu Zhang, Haiying Hu
      First page: 235
      Abstract: In the multi-satellite and multi-ground station downlink task scheduling problem, the waiting time from the proposal of the task to the execution will affect its validity. If the satellite has multiple communicable ground stations when the downlink task is proposed, the selection problem needs to be solved first. After the selection, since the available time conflict between tasks of different satellites for the same ground station, the specific start time should be determined. To reduce the waiting time, a simulated annealing algorithm with a tabu list and start time decision (SATLD) is proposed. This method uses a two-stage scheduling strategy. In the first stage, the improved simulated annealing algorithm based on a tabu list is used to select the downlink ground station. The second stage combines downlink scheduling algorithm based on task arrival time (DSA-AT) method and downlink scheduling algorithm based on task requirement time (DSA-RT) method to determine the specific start time of each task of a single ground station. Simulation analysis prove the method has better selection efficiency of downlink task and shorter total task waiting time, and has practical value.
      Citation: Aerospace
      PubDate: 2022-04-25
      DOI: 10.3390/aerospace9050235
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 236: Fault Detection of Aero-Engine Sensor Based
           on Inception-CNN

    • Authors: Xiao Du, Jiajie Chen, Haibo Zhang, Jiqiang Wang
      First page: 236
      Abstract: The aero-engine system is complex, and the working environment is harsh. As the fundamental component of the aero-engine control system, the sensor must monitor its health status. Traditional sensor fault detection algorithms often have many parameters, complex architecture, and low detection accuracy. Aiming at this problem, a convolutional neural network (CNN) whose basic unit is an inception block composed of convolution kernels of different sizes in parallel is proposed. The network fully extracts redundant analytical information between sensors through different size convolution kernels and uses it for aero-engine sensor fault detection. On the sensor failure dataset generated by the Monte Carlo simulation method, the detection accuracy of Inception-CNN is 95.41%, which improves the prediction accuracy by 17.27% and 12.69% compared with the best-performing non-neural network algorithm and simple BP neural networks tested in the paper, respectively. In addition, the method simplifies the traditional fault detection unit composed of multiple fusion algorithms into one detection algorithm, which reduces the complexity of the algorithm. Finally, the effectiveness and feasibility of the method are verified in two aspects of the typical sensor fault detection effect and fault detection and isolation process.
      Citation: Aerospace
      PubDate: 2022-04-25
      DOI: 10.3390/aerospace9050236
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 237: Active Fault-Tolerant Control for Near-Space
           Hypersonic Vehicles

    • Authors: Kai Zhao, Jia Song, Shaojie Ai, Xiaowei Xu, Yang Liu
      First page: 237
      Abstract: Due to the harsh working environment, Near-Space Hypersonic Vehicles (NSHVs) have the characteristics of frequent faults, which seriously affect flight safety. However, most researches focus on active fault-tolerant control for actuator faults. In order to fill the gap of active fault-tolerant control for sensor faults, this paper presents an Active Fault-Tolerant Control (AFTC) strategy for NSHVs based on Active Disturbance Rejection Control (ADRC) combined with fault diagnosis and evaluation. With the proposed AFTC strategy, both sensor faults and actuator faults can be compensated within 0.5 s. Wavelet packet decomposition and Kernel Extreme Learning Machine (KELM) are associated to ensure the high accuracy and real-time ability of fault diagnosis. Simulation results show that the proposed fault diagnosis method can significantly reduce the divergence of diagnosis results by up to 98%. The fault information is used to generate tolerant compensation, which is combined with the ADRC to achieve AFTC. Statistical results indicate that AFTC has significantly lower static error than ADRC. The proposed AFTC method endows NSHVs with the ability to complete missions even when various types of faults appear. Its advantages are demonstrated in comparison with other fault diagnosis and tolerant control methods.
      Citation: Aerospace
      PubDate: 2022-04-25
      DOI: 10.3390/aerospace9050237
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 238: Numerical Modeling of Heat Exchanger Filled
           with Octahedral Lattice Frame Porous Material

    • Authors: Bi Zhao, Jingzhou Zhang, Wenlei Lian
      First page: 238
      Abstract: A numerical investigation into the fluid flow and heat transfer process in a 3D-printed shell-and-tube heat exchanger was carried out. The shell side of the heat exchanger was inserted with octahedral lattice frame porous material to enhance the heat transfer. In order to avoid establishing a complex grid system, the porous material of the shell side was modeled by a porous media model. The non-equilibrium model was adopted for the modeling of the heat exchange between the solid and fluid in porous media. An experimental investigation was carried out to validate the feasibility of this approach. The result indicates that the simplified approach is capable of providing an appropriate prediction of the pressure drop and heat transfer efficiency with moderate computational resources. The average error of pressure loss and heat transfer effectiveness is within 4% and 6.1%.
      Citation: Aerospace
      PubDate: 2022-04-26
      DOI: 10.3390/aerospace9050238
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 239: Form-Finding Analysis of Mesh Reflector of
           Large Parabolic Cylindrical Antenna

    • Authors: Jinbao Chen, Jiayu Dong, Zhicheng Song, Chuanzhi Chen, Jiaqi Li
      First page: 239
      Abstract: In this study, a hybrid iteration force density method (HIFDM) was proposed to ensure both tension uniformity and accuracy of an antenna mesh reflector. Based on a genetic algorithm (GA), the boundary cable tension of the antenna reflector net was optimized, which further improved the precision of the antenna mesh reflector. The static model of the large deployable structure was established using the finite element method (FEM), and thus, an iterative strategy for form-finding of the antenna reflector net was proposed, which considered the influence of the elastic deformation of the deployable structure. The results showed that the HIFDM was effective for the form-finding of the antenna mesh reflector, and the shape precision was improved by further optimization using the GA. Finally, it was noted that the elastic deformation of the deployable structure will reduce the uniformity of cable tension and affect the precision of antenna reflectors. Due to the large-scale and soft stiffness, the large deployable structure had a high sensitivity to cable pretension, and it is important to design a reasonable cable pretension to ensure the accurate shape of antenna mesh reflectors.
      Citation: Aerospace
      PubDate: 2022-04-26
      DOI: 10.3390/aerospace9050239
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 240: Systematic Reliability-Based
           Multidisciplinary Optimization by Parallel Adaptive Importance Candidate
           Region

    • Authors: Mengchuang Zhang, Shasha Xia, Xiaochuan Li, Qin Yao, Yang Xu, Zhiping Yin
      First page: 240
      Abstract: Reliability-based design optimization (RBDO) has become a prevalent design for aeronautical and aerospace engineering. The main problem is that it is impractical in complex cases with multi-failure regions, especially in multi-objective optimization. The active learning method can obtain an adaptive size of samples to get a relatively acceptable accuracy. The problem of RBDO using the traditional active learning Kriging (ALK) method is that the design space is generally still and only one training point is selected, which is not reasonable based on the concept of importance sampling and parallel calculation. As a consequence, the accuracy improvement is limited. In this paper, we investigate the method of obtaining an optimal size of design and reliability to assess space in parallel, simultaneously. A strategy of parallel adaptive candidate (PAIC) region with ALK is proposed and a sequential optimization and reliability assessment (SORA) method is modified to efficiently improve the accuracy. Importance sampling is used as a demonstration for the modified SORA with more accuracy. The method is then verified using mathematical cases and a scooping system of an amphibious aircraft.
      Citation: Aerospace
      PubDate: 2022-04-26
      DOI: 10.3390/aerospace9050240
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 241: An Efficient Blade Design Method of a Ducted
           Fan Coupled with the CFD Modification

    • Authors: Jiahao Guo, Zhou Zhou
      First page: 241
      Abstract: In order to improve the design accuracy of the blade design method of a ducted fan based on the blade element momentum theory, the design was modified by the CFD calculation with higher accuracy to propose an integrated and efficient design method for the rotor and stator. Firstly, a fast blade design method for the ducted fan was established based on the blade element momentum theory, and the initial design of the rotor and stator was carried out. Then, the performance of the designed ducted fan was calculated by the CFD method, and the rotor and stator were modified and redesigned according to the CFD results. Such continuous iterations finally made the design results basically consistent with the CFD results so as to improve the design accuracy. The blade design of different ducted fans shows that the unsteady CFD method based on the sliding mesh has higher accuracy and applicability than the MRF method, and the efficient blade design method established in this paper can meet the thrust demand with a small amount of the CFD modification. The thrust design accuracy of the ducted fan was increased by 11.362%, and the torque design accuracy was increased by 8.141%.
      Citation: Aerospace
      PubDate: 2022-04-26
      DOI: 10.3390/aerospace9050241
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 242: Hybrid Guidance Optimization for Multipulse
           Glideslope Approach with Bearing-Only Navigation

    • Authors: Hao Yuan, Dongxu Li, Jie Wang
      First page: 242
      Abstract: This paper proposes a modified glideslope guidance method that optimizes a hybrid multiobjective of bearing-only navigation error and fuel consumption. The traditional glideslope guidance fixes uniform maneuver intervals and the initial approach velocity as a predetermined value, making this approach inflexible. In this paper, the maneuver intervals and the initial approach velocity were used as optimization variables, and a hybrid cost function was designed. The tradeoff between the two objectives was analyzed with a bearing-only navigation simulation conducted to reveal the navigation performance following different resulting trajectories. The result showed that the optimal scheduled times of maneuvers remained relatively stable under different tradeoff weights, while a strong correlation between the optimal initial approach velocity and the tradeoff weight was revealed. Therefore, when the optimization has to be solved several times online with different tradeoff weights, the initial approach velocity can be the only optimization variable, leaving the scheduled times of maneuvers fixed in the optimal values achieved offline. These findings provide a potential reference for far-approach trajectory design of bearing-only navigation.
      Citation: Aerospace
      PubDate: 2022-04-26
      DOI: 10.3390/aerospace9050242
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 243: Thermal Management System Optimization for a
           Parallel Hybrid Aircraft Considering Mission Fuel Burn

    • Authors: Eytan J. Adler, Benjamin J. Brelje, Joaquim R. R. A. Martins
      First page: 243
      Abstract: Electrified aircraft propulsion enables new aircraft designs with fewer emissions. One challenge of electrified architectures is handling the electrical components’ waste heat. This is because batteries and other electrical components are sensitive to high temperatures and accumulate heat within their structure. In this work, we investigate using a thermoacoustic refrigerator to cool the battery of a parallel hybrid single-aisle commercial transport aircraft. This thermoacoustic refrigeration system is powered by waste heat from the turbofan engine core, whereas a conventional refrigerator consumes electricity from the battery or shaft power offtakes. Compared to a conventional vapor cycle refrigerator, the thermoacoustic refrigeration system results in greater mission fuel burn because of pressure losses attributable to the extraction of heat from the turbofan to drive the thermoacoustic refrigerator. Heat exchangers with very low pressure losses may render the thermoacoustic refrigeration system beneficial compared to conventional refrigeration in certain use cases, such as low-altitude missions.
      Citation: Aerospace
      PubDate: 2022-04-26
      DOI: 10.3390/aerospace9050243
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 244: Nonlinear Slewing Control of a Large
           Flexible Spacecraft Using Reaction Wheels

    • Authors: Massimo Posani, Mauro Pontani, Paolo Gasbarri
      First page: 244
      Abstract: Reorientation maneuvers represent a key task for large satellites. This work considers a space vehicle with solar panels and reaction wheels as actuation devices. Solar panels are modeled as flexural beams, using the modal decomposition technique. An inertia-free nonlinear attitude control algorithm, which enjoys quasi-global stability properties, is employed for the numerical simulation of a large reorientation maneuver. Preliminary analysis with ideal actuation allows sizing the control system and identifying the expected elastic displacements. Then, the actuation dynamics is included, and the actual torque transferred to the vehicle no longer coincides with the commanded one, supplied by the nonlinear control algorithm. Moreover, the solar panels are designed to rotate, in order to maximize the power storage during the maneuver. The numerical results prove that the slewing maneuver is successfully completed in reasonable time and without any saturation of the actuation devices, while the elastic displacements remain modest, in spite of the solar panel rotation aimed at pursuing the Sun direction.
      Citation: Aerospace
      PubDate: 2022-04-26
      DOI: 10.3390/aerospace9050244
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 245: Micro Coaxial Drone: Flight Dynamics,
           Simulation and Ground Testing

    • Authors: Victor H. Dominguez, Octavio Garcia-Salazar, Luis Amezquita-Brooks, Luis A. Reyes-Osorio, Carlos Santana-Delgado, Erik G. Rojo-Rodriguez
      First page: 245
      Abstract: This paper describes the conceptual design of a micro coaxial unmanned aerial vehicle (MCR UAV v3.0) based on its flight dynamics and a simple aerodynamic analysis using computational fluid dynamics (CFD). In addition, a simple linear control is proposed with the pole assignment technique. The methodology proposed in this paper involves a standardized path for designing the novel micro coaxial UAV. This begins by selecting the avionics to create a primary dimensional design for a later transient and stationary CFD analysis. In effect, the mathematical model is obtained using the Newton–Euler formulation and is linearized to obtain the dynamical requirements of the vehicle. The requirements allow us to design the control scheme with a linear control technique. This process is iterative and uses a combination of flight dynamics and CFD. The control technique is based on pole assignment, ensuring a specific phase condition is used in the controller gain for the stabilization of the proposed aerial vehicle. The control scheme is analyzed once the CFD analysis is correctly performed; in this sense, the methodology proposed in this paper is capable of converging as a result of the dimensional design. This design ensures a suitable vehicle performance according to the dynamical requirements. Thus, the micro coaxial UAV is completely designed based on its flight dynamics along with a CFD analysis, generating a robust methodology.
      Citation: Aerospace
      PubDate: 2022-05-01
      DOI: 10.3390/aerospace9050245
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 246: Characterizing an Air-Bearing Testbed for
           Simulating Spacecraft Dynamics and Control

    • Authors: Zheng Huang, Wei Zhang, Ti Chen, Hao Wen, Dongping Jin
      First page: 246
      Abstract: Ground-based testbeds play a critical role in developing and testing different methods of spacecraft dynamics and control. To find the dynamic behavior in such an air-bearing testbed, a detailed characterization of the testbed must be provided via systematic testing approaches. This paper describes a planar air-bearing testbed to develop control methods in spacecraft on-orbit operations. This testbed has an almost frictionless surface and can be used to simulate two-dimensional motions in the microgravity environment, with one rotational and two translational degrees of freedom (DOF). The hardware and software architectures of the testbed are presented in detail and key parameters are characterized by a series of systematic test approaches. In addition, a new visual navigation method was designed as an alternative to the external visual system. Finally, two typical case studies are presented to demonstrate the performance of the developed testbed.
      Citation: Aerospace
      PubDate: 2022-05-01
      DOI: 10.3390/aerospace9050246
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 247: Effects of Surface Errors of Antennas on
           Detection Performance of Space VLBI

    • Authors: Yangyang Zhang, Huijie Liu, Xingfu Liu
      First page: 247
      Abstract: This work investigates the effects of the surface errors of the satellite antenna on the detection performance of the space VLBI system. First, the relationship between the surface errors and the antenna gain loss is analyzed, and then the influence of the gain loss on the detection performance of the VLBI system is analyzed. Both the uniform and nonuniform distributions of errors are studied, and the second-order Taylor expansion is performed on the errors to simplify the calculation. When the errors distribute nonuniformly, the solver SCIP is adopted to solve the corresponding distribution, which leads to the maximum gain loss of the antenna. Taking the VLBI system with two base stations as the object, and each station’s radio telescope is a hoop truss deployable antenna with 30 m aperture, the effects of antenna gain loss on the detection capability of the radio telescope and the delay error of the VLBI system are studied. The study of extreme working conditions will have a higher guiding significance for the overall link analysis of practical projects.
      Citation: Aerospace
      PubDate: 2022-05-01
      DOI: 10.3390/aerospace9050247
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 248: 3D Component Segmentation Network and
           Dataset for Non-Cooperative Spacecraft

    • Authors: Guangyuan Zhao, Xue Wan, Yaolin Tian, Yadong Shao, Shengyang Li
      First page: 248
      Abstract: Spacecraft component segmentation is one of the key technologies which enables autonomous navigation and manipulation for non-cooperative spacecraft in OOS (On-Orbit Service). While most of the studies on spacecraft component segmentation are based on 2D image segmentation, this paper proposes spacecraft component segmentation methods based on 3D point clouds. Firstly, we propose a multi-source 3D spacecraft component segmentation dataset, including point clouds from lidar and VisualSFM (Visual Structure From Motion). Then, an improved PointNet++ based 3D component segmentation network named 3DSatNet is proposed with a new geometrical-aware FE (Feature Extraction) layers and a new loss function to tackle the data imbalance problem which means the points number of different components differ greatly, and the density distribution of point cloud is not uniform. Moreover, when the partial prior point clouds of the target spacecraft are known, we propose a 3DSatNet-Reg network by adding a Teaser-based 3D point clouds registration module to 3DSatNet to obtain higher component segmentation accuracy. Experiments carried out on our proposed dataset demonstrate that the proposed 3DSatNet achieves 1.9% higher instance mIoU than PointNet++_SSG, and the highest IoU for antenna in both lidar point clouds and visual point clouds compared with the popular networks. Furthermore, our algorithm has been deployed on an embedded AI computing device Nvidia Jetson TX2 which has the potential to be used on orbit with a processing speed of 0.228 s per point cloud with 20,000 points.
      Citation: Aerospace
      PubDate: 2022-05-01
      DOI: 10.3390/aerospace9050248
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 249: On the Extrapolation of Stability
           Derivatives to Combined Changes in Airspeed and Angles of Attack and
           Sideslip

    • Authors: Luís M. B. C. Campos, Joaquim M. G. Marques
      First page: 249
      Abstract: The variation in stability derivatives with airspeed and angles of attack and sideslip is determined using only the dependence of the aerodynamic forces and moments on the modulus and direction of the velocity. Analytic extrapolation factors are obtained for all 12 longitudinal plus 12 lateral stability derivatives of linear decoupled motion. The extrapolation factors relate the stability derivatives for two flight conditions with different airspeeds, angles of attack (AoA), and angles of sideslip (AoS). The extrapolation formulas were validated by comparison with results of computational fluid dynamics (CFD) using Reynolds-averaged Navier–Stokes (RANS) equations. The comparison concerns the extrapolated full longitudinal–lateral stability matrix from one landing and one takeoff condition of a V-tailed aircraft, to 10 other landing and takeoff flight cases with different airspeeds, AoAs, and AoSs. Thus, 420 comparisons were made between extrapolated stability derivatives and CFD–RANS results demonstrating the achievable levels of accuracy.
      Citation: Aerospace
      PubDate: 2022-05-03
      DOI: 10.3390/aerospace9050249
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 250: A Counterfactual Framework Based on the
           Machine Learning Method and Its Application to Measure the Impact of
           COVID-19 Local Outbreaks on the Chinese Aviation Market

    • Authors: Linfeng Zhang, Hongwu Tang, Lei Bian
      First page: 250
      Abstract: COVID-19 affects aviation around the world. China’s civil aviation almost recovered to its pre-epidemic levels in the domestic market, but there are still local outbreaks that affect air traffic. This paper proposes measuring the impact of local outbreaks of COVID-19 by the machine learning method and the synthetic control method as a counterfactual control group to measure such an impact. In this study, we use the LightGBM algorithm to construct a counterfactual control group and transform the prediction problem from time series to the fitting problem at the spatial level. We find that machine learning methods can measure such an impact more accurately. We take local outbreaks in Beijing and Dalian as examples, and our measure of their impacts shows that the impact of an outbreak on intercity air traffic can be divided into lag, decline, stable, and recovery periods, and will last for a long period (more than 40 days) unless there are external stimuli, such as legal holidays. The outbreaks reduced the number of passengers in the cities by 90%. Finally, we show the impact on the air traffic network, and find that when a local outbreak happens in a big city, tourist cities or small stations will be greatly affected.
      Citation: Aerospace
      PubDate: 2022-05-04
      DOI: 10.3390/aerospace9050250
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 251: A Civil Aircraft Cockpit Layout Evaluation
           Method Based on Layout Design Principles

    • Authors: Kang Cao, Yongjie Zhang, Yuefan Jiang, Yongqi Zeng, Bo Cui, Wenjun Dong
      First page: 251
      Abstract: As technology continues to leap forward and innovations advance, the systems of civil aircraft are becoming increasingly sophisticated and complex. Accordingly, there is a rising amount of information to be processed by pilots in the cockpit, increasing their cognitive burden, which significantly threatens the safety of flight. Thus, designers have formulated cockpit layout principles relating to importance, frequency of use, functional grouping, and operation sequence on the basis of ergonomics, which can effectively reduce the cognitive burden for pilots. The degree to which the cockpit layout of a model conforms to the four design principles can indicate its ergonomic design level. In accordance with the concepts of the above four cockpit layout principles, evaluation methods for determining their respective conformity to the four design principles were proposed in this paper. These methods use the operational sequence of cockpit system controls used in the normal flight mission of the actual aircraft type as the evaluation data source. Subsequently, the total evaluation results for cockpit layout were obtained using the weighted accumulation method. Lastly, the process for evaluating the cockpit layouts of civil aircraft was illustrated using the cockpits of the A320 series and B737NG series as examples. Based on the final evaluation results, the feasibility and effectiveness of the proposed evaluation method was verified.
      Citation: Aerospace
      PubDate: 2022-05-04
      DOI: 10.3390/aerospace9050251
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 252: Modelling and Stabilisation of an
           Unconventional Airship: A Polytopic Approach

    • Authors: Said Chaabani, Naoufel Azouz
      First page: 252
      Abstract: The paper presents the modelling and stabilisation of an unconventional airship. The complexity of such a new design requires both proper dynamic modelling and control. A complete dynamic model is built here. Based on the developed dynamic model, a nonlinear control law is proposed for this airship to evaluate its sensitivity during manoeuvres above a loading area. The proposed stabilisation controller derives its source from a polytopic quasi-Linear Parameter varying (qLPV) model of the nonlinear system. A controller, which takes into account certain modelling uncertainties and the stability of the system, is analysed using Lyapunov’s theory. Finally, to facilitate the design of the controller, we express the stability conditions using Linear Matrix Inequalities (LMIs). Numerical simulations are presented to highlight the power of the proposed controller.
      Citation: Aerospace
      PubDate: 2022-05-05
      DOI: 10.3390/aerospace9050252
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 253: Spaceborne Atom-Interferometry Gravity
           Gradiometry Design towards Future Satellite Gradiometric Missions

    • Authors: Zhu Zhu, He Liao, Haibo Tu, Xiaochun Duan, Yanbin Zhao
      First page: 253
      Abstract: Atom-interferometry gravity gradiometry has been developed as a promising technique for future gravity gradiometric missions after GOCE due to its greater sensitivity in micro-gravity environments and constant performance over the measurement bandwidth. In this paper, a feasible method of spaceborne atom-interferometry gravity gradiometry is proposed by utilizing the free-fall condition of the cold atoms in space. Compared with GOCE, which shows an in-orbit noise performance of 10~20 mE/Hz1/2, the scheme described in this paper would achieve a high sensitivity of 1.9 mE/Hz1/2 for gravity gradients measurement by reducing the orbital altitude and optimizing the interrogation time for atom interferometry. The results show that the proposed scheme could significantly augment the spectral content of the gravity field in the degree and order of 280~316 and resolve the global gravity field with an improved accuracy of 0.2 cm@100 km and 0.85 cm@80 km in terms of geoid height, and 0.06 mGal@100 km and 0.3 mGal@80 km in terms of gravity anomaly after 1270 days of data collection.
      Citation: Aerospace
      PubDate: 2022-05-06
      DOI: 10.3390/aerospace9050253
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 254: SpaceDrones 2.0—Hardware-in-the-Loop
           Simulation and Validation for Orbital and Deep Space Computer Vision and
           Machine Learning Tasking Using Free-Flying Drone Platforms

    • Authors: Marco Peterson, Minzhen Du, Bryant Springle, Jonathan Black
      First page: 254
      Abstract: The proliferation of reusable space vehicles has fundamentally changed how assets are injected into the low earth orbit and beyond, increasing both the reliability and frequency of launches. Consequently, it has led to the rapid development and adoption of new technologies in the aerospace sector, including computer vision (CV), machine learning (ML)/artificial intelligence (AI), and distributed networking. All these technologies are necessary to enable truly autonomous “Human-out-of-the-loop” mission tasking for spaceborne applications as spacecrafts travel further into the solar system and our missions become more ambitious. This paper proposes a novel approach for space-based computer vision sensing and machine learning simulation and validation using synthetically trained models to generate the large amounts of space-based imagery needed to train computer vision models. We also introduce a method of image data augmentation known as domain randomization to enhance machine learning performance in the dynamic domain of spaceborne computer vision to tackle unique space-based challenges such as orientation and lighting variations. These synthetically trained computer vision models then apply that capability for hardware-in-the-loop testing and evaluation via free-flying robotic platforms, thus enabling sensor-based orbital vehicle control, onboard decision making, and mobile manipulation similar to air-bearing table methods. Given the current energy constraints of space vehicles using solar-based power plants, cameras provide an energy-efficient means of situational awareness when compared to active sensing instruments. When coupled with computationally efficient machine learning algorithms and methods, it can enable space systems proficient in classifying, tracking, capturing, and ultimately manipulating objects for orbital/planetary assembly and maintenance (tasks commonly referred to as In-Space Assembly and On-Orbit Servicing). Given the inherent dangers of manned spaceflight/extravehicular activities (EVAs) currently employed to perform spacecraft maintenance and the current limitation of long-duration human spaceflight outside the low earth orbit, space robotics armed with generalized sensing and control and machine learning architecture have a unique automation potential. However, the tools and methodologies required for hardware-in-the-loop simulation, testing, and validation at a large scale and at an affordable price point are in developmental stages. By leveraging a drone’s free-flight maneuvering capability, theater projection technology, synthetically generated orbital and celestial environments, and machine learning, this work strives to build a robust hardware-in-the-loop testing suite. While the focus of the specific computer vision models in this paper is narrowed down to solving visual sensing problems in orbit, this work can very well be extended to solve any problem set that requires a robust onboard computer vision, robotic manipulation, and free-flight capabilities.
      Citation: Aerospace
      PubDate: 2022-05-06
      DOI: 10.3390/aerospace9050254
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 255: Additive Manufacturing of Novel Hybrid
           Monolithic Ceramic Substrates

    • Authors: Nikolina Kovacev, Sheng Li, Weining Li, Soheil Zeraati-Rezaei, Athanasios Tsolakis, Khamis Essa
      First page: 255
      Abstract: Additive manufacturing (AM) can revolutionise engineering by taking advantage of unconstrained design and overcoming the limitations of traditional manufacturing capabilities. A promising application of AM is in catalyst substrate manufacturing, aimed at the enhancement of the catalytic efficiency and reduction in the volume and weight of the catalytic reactors in the exhaust gas aftertreatment systems. This work addresses the design and fabrication of innovative, hybrid monolithic ceramic substrates using AM technology based on Digital Light Processing (DLP). The designs are based on two individual substrates integrated into a single, dual-substrate monolith by various interlocking systems. These novel dual-substrate monoliths lay the foundation for the potential reduction in the complexity and expense of the aftertreatment system. Several examples of interlocking systems for dual substrates were designed, manufactured and thermally post-processed to illustrate the viability and versatility of the DLP manufacturing process. Based on the findings, the sintered parts displayed anisotropic sintering shrinkage of approximately 14% in the X–Y direction and 19% in the Z direction, with a sintered density of 97.88 ± 0.01%. Finally, mechanical tests revealed the mechanical integrity of the designed interlocks. U-lock and Thread configurations were found to sustain more load until complete failure.
      Citation: Aerospace
      PubDate: 2022-05-07
      DOI: 10.3390/aerospace9050255
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 256: Influence of Fluid Viscosity and
           Compressibility on Nonlinearities in Generalized Aerodynamic Forces for
           T-Tail Flutter

    • Authors: Dominik Schäfer
      First page: 256
      Abstract: The numerical assessment of T-tail flutter requires a nonlinear description of the structural deformations when the unsteady aerodynamic forces comprise terms from lifting surface roll motion. For linear flutter, a linear deformation description of the vertical tail plane (VTP) out-of-plane bending results in a spurious stiffening proportional to the steady lift forces, which is corrected by incorporating second-order deformation terms in the equations of motion. While the effect of these nonlinear deformation components on the stiffness of the VTP out-of-plane bending mode shape is known from the literature, their impact on the aerodynamic coupling terms involved in T-tail flutter has not been studied so far, especially regarding amplitude-dependent characteristics. This term affects numerical results targeting common flutter analysis, as well as the study of amplitude-dependent dynamic aeroelastic stability phenomena, e.g., Limit Cycle Oscillations (LCOs). As LCOs might occur below the linear flutter boundary, fundamental knowledge about the structural and aerodynamic nonlinearities occurring in the dynamical system is essential. This paper gives an insight into the aerodynamic nonlinearities for representative structural deformations usually encountered in T-tail flutter mechanisms using a CFD approach in the time domain. It further outlines the impact of geometrically nonlinear deformations on the aerodynamic nonlinearities. For this, the horizontal tail plane (HTP) is considered in isolated form to exclude aerodynamic interference effects from the studies and subjected to rigid body roll and yaw motion as an approximation to the structural mode shapes. The complexity of the aerodynamics is increased successively from subsonic inviscid flow to transonic viscous flow. At a subsonic Mach number, a distinct aerodynamic nonlinearity in stiffness and damping in the aerodynamic coupling term HTP roll on yaw is shown. Geometric nonlinearities result in an almost entire cancellation of the stiffness nonlinearity and an increase in damping nonlinearity. The viscous forces result in a stiffness offset with respect to the inviscid results, but do not alter the observed nonlinearities, as well as the impact of geometric nonlinearities. At a transonic Mach number, the aerodynamic stiffness nonlinearity is amplified further and the damping nonlinearity is reduced considerably. Here, the geometrically nonlinear motion description reduces the aerodynamic stiffness nonlinearity as well, but does not cancel it.
      Citation: Aerospace
      PubDate: 2022-05-09
      DOI: 10.3390/aerospace9050256
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 257: Maneuvering Spacecraft Orbit Determination
           Using Polynomial Representation

    • Authors: Xingyu Zhou, Tong Qin, Linzhi Meng
      First page: 257
      Abstract: This paper proposed a polynomial representation-based method for orbit determination (OD) of spacecraft with the unknown maneuver. Different from the conventional maneuvering OD approaches that rely on specific orbit dynamic equation, the proposed method needs no priori information of the unknown maneuvering model. The polynomials are used to represent the unknown maneuver. A transformation is made for the polynomials to improve the convergence and robustness. The Extended Kalman Filter (EKF) is used to process incoming observation data by compensating the unknown maneuver using the polynomials. The proposed method is successfully applicated into the OD problem of spacecraft with trigonometric maneuver. Numerical simulations show that the eighth-order polynomials are accurate enough to represent a trigonometric maneuver. Moreover, Monte Carlo simulations show that the position errors are smaller than 1 km, and the maneuver estimated errors are no more than 0.1 mm/s2 using the eighth-order polynomials. The proposed method is accurate and efficient, and has potential applications for tracking maneuvering space target.
      Citation: Aerospace
      PubDate: 2022-05-10
      DOI: 10.3390/aerospace9050257
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 258: Geostationary Orbital Debris Collision
           Hazard after A Collision

    • Authors: Haitao Zhang, Zhi Li, Weilin Wang, Yasheng Zhang, Hao Wang
      First page: 258
      Abstract: Many space objects are densely distributed in the geostationary (GEO) band, and the long-term impact of the collision of GEO spacecraft and space debris on the GEO environment has attracted more and more attention. After summarizing the advantages and disadvantages of the long-term evolution model based on the “Cube” collision probability calculation model, the “Grid” model, a long-term evolution model especially suitable for GEO band, was established. For four types of collision and disintegration events, the “Grid” model was used to study the space environment in the GEO band after collisions between GEO spacecraft and space debris. Future collisions were simulated, and the number of space objects in the next 100 years was counted. Once space debris and massive spacecraft were completely disintegrated after collision, the number of space objects and the collision probability increased sharply, and this caused a collision cascading syndrome. Even if there was no initial disintegration event, collision and disintegration events occurred in the long-term evolution of the GEO band, which led to an increase in the number of space objects. However, the collision probability was much lower, and the number of space objects grew much more slowly without the initial collision.
      Citation: Aerospace
      PubDate: 2022-05-10
      DOI: 10.3390/aerospace9050258
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 259: Angular Displacement Control for Timoshenko
           Beam by Optimized Traveling Wave Method

    • Authors: Huawei Ji, Chuanping Zhou, Jiawei Fan, Huajie Dai, Wei Jiang, Youping Gong, Chuzhen Xu, Ban Wang, Weihua Zhou
      First page: 259
      Abstract: The vibration of flexible structures in spacecraft, such as large space deployable reflectors, solar panels and large antenna structure, has a great impact on the normal operation of spacecraft. Accurate vibration control is necessary, and the control of angular displacement is a difficulty of accurate control. In the traditional control method, the mode space control has a good effect on suppressing low-order modes, but there is control overflow. The effect of traveling wave control on low-order modes is worse than the former, but it has the characteristics of broadband control. It can better control high-order modes and reduce control overflow. In view of the advantages and disadvantages of the two control methods, based on Timoshenko beam theory, this paper uses vector mode function to analyze the modal of spacecraft cantilever beam structure, establishes the system dynamic equation, and puts forward an optimized traveling wave control method. As a numerical example, three strategies of independent mode space control, traditional traveling wave control and optimized traveling wave control are used to control the active vibration of beam angle. By comparing the numerical results of the three methods, it can be seen that the optimal control method proposed in this paper not only effectively suppresses the vibration, but also improves the robustness of the system, reflecting good control performance. An innovation of this paper is that the Timoshenko beam model is adopted, which considers the influence of transverse shear deformation and moment of inertia on displacement and improves the accuracy of calculation, which is important for spacecraft accessory structures with high requirements for angle control. Another innovation is that the optimized traveling wave control method is exquisite in mathematical processing and has good results in global and local vibration control, which is not available in other methods.
      Citation: Aerospace
      PubDate: 2022-05-11
      DOI: 10.3390/aerospace9050259
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 260: Dynamic Response of Structurally Reinforced
           Wing Leading Edge against Soft Impact

    • Authors: Muhammad Azeem Aslam, Saiaf Bin Rayhan, Ke Zhang
      First page: 260
      Abstract: In this current research, a commercial aircraft metallic leading edge structurally reinforced with a Y-shaped and V-shaped plate system is numerically examined to investigate the effectiveness of such reinforcements against soft impacts, more commonly known as bird strikes in the aviation industry. A non-linear finite element code Ansys Explicit is adopted to run the virtual test cases. The computational bird model is presented with the Lagrange algorithm and Mooney–Rivlin hyperelastic material parameters which are validated against the experimental data found in the literature. A second validation of the leading edge deformation pattern is also carried out to ensure the accuracy of the present work. Numerical outcomes suggest that due to the presence of the reinforcement, the leading edge skin is restrained from being drastically deformed and the bird model tears apart into two pieces requiring the leading edge model to absorb much less kinetic energy. Additionally, it is found that both the reinforcements have similar crashworthiness performance against bird impacts. The novelty of the research lies in founding the structural reinforcement as a primary preference to strengthen the vulnerable wing leading edge during bird impacts.
      Citation: Aerospace
      PubDate: 2022-05-11
      DOI: 10.3390/aerospace9050260
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 261: Numerical Simulation of Tiltrotor Flow Field
           during Shipboard Take-Off and Landing Based on CFD-CSD Coupling

    • Authors: Peng Yu, Zhiyuan Hu, Guohua Xu, Yongjie Shi
      First page: 261
      Abstract: Due to the small tilt angle, a tiltrotor operates in non-axial flow conditions during shipboard take-off and landing. The non-uniformity of the blade’s air-load is high, resulting in structural deformation with high fluctuation frequency, affecting the rotor’s aerodynamic characteristics. A new computational fluid-dynamic computational structural dynamics (CFD-CSD) solver is proposed to analyze the effects of the blade’s elastic deformation on the aerodynamic characteristics. This method is suitable for the aeroelastic simulation of shipboard tiltrotor take-offs and landings. The CFD method uses the Reynolds-averaged Navier-Stokes (RANS) equations as the control equation, while the CSD solver is based on the Timoshenko beam model. The solvers are combined with a two-way loose coupling strategy to improve the solution efficiency. The reverse overset assembly technique (ROAT) is utilized to eliminate the effects of orphan mesh points after deformation. The simulation is conducted during take-off and landing at different heights and different tilt angles, using the XV-15 tiltrotor as an example. An analysis of the rotor’s air-load and the mutual interference of the vortex and wake indicates that when the tiltrotor takes off or lands with a small tilt angle, the wing shedding vortex causes the rotor’s wake to roll upward before it reaches the ship’s deck, producing strong thrust fluctuations. The elastic deformation of the blade reduces the fluctuations in the thrust amplitude. This phenomenon is more pronounced in areas of high fluctuations in the blade’s air-load.
      Citation: Aerospace
      PubDate: 2022-05-12
      DOI: 10.3390/aerospace9050261
      Issue No: Vol. 9, No. 5 (2022)
       
  • Aerospace, Vol. 9, Pages 262: Aerodynamic Interference on Trim
           Characteristics of Quad-Tiltrotor Aircraft

    • Authors: Pan Zhou, Renliang Chen, Ye Yuan, Cheng Chi
      First page: 262
      Abstract: The aerodynamic interference between the different components of quad-tiltrotor (QTR) aircraft were considered to analyze its influence on trim characteristics. A comprehensive method with the fixed-wake model was developed for multiple aerodynamic interactions, improving the accuracy of the flight dynamics analysis. Additionally, a more general control strategy was developed to tackle the redundant control issue of the QTR, improving its control efficiency by coordinating the authority relationship of various control surfaces across the flight range. Then, the trim features were calculated in the helicopter mode, conversion mode, and airplane mode, and the relevant results with and without interaction were compared. The results show that the aerodynamic interaction mainly influences the body’s vertical force, longitudinal force, and pitching moment. Furthermore, there are significant differences between collective and longitudinal sticks and pitch attitudes. The interference plays a major role in helicopter and conversion modes with a less-than-30-degree tilt angle.
      Citation: Aerospace
      PubDate: 2022-05-12
      DOI: 10.3390/aerospace9050262
      Issue No: Vol. 9, No. 5 (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 176: Parametric Investigation of a Distributed
           Propulsion System on a Regional Aircraft

    • Authors: Donato de Rosa, Elisa Morales Tirado, Giuseppe Mingione
      First page: 176
      Abstract: With the mandatory requirement for more efficient aircraft due to both economic and environmental purposes, academy and industry are exploring new aircraft design opportunities including the concepts of hybrid-electric and fully electric vehicles. Within this framework, distributed electric propulsion is a key technology for future aviation, as it allows the installation of a theoretically indefinite number of small motors. The blowing effect induced by the propeller can be used to improve aerodynamic performance, hence, thanks to their reduced size, these small motors could be installed along the whole span covering the whole wing. This paper presents a study devoted to the investigation of the aerodynamic effects of distributed electric propulsion installation on a regional aircraft, computing the aerodynamic coefficients using high-fidelity CFD simulations via the RANS approach. Different propeller diameters and trust levels were analysed in climb and landing conditions, applying periodic boundary conditions on a finite span section of the wing, simulating an infinite rectangular wing. The goal of the current study is to quantify the increase of aerodynamic coefficients with reference to power off condition and report data as a function of the propeller’s characteristics. The objective is to identify and propose a simplified analytical formulation to be used in the phase of preliminary design. The implementation of such a formula in lower-fidelity tools will allow fast and reliable procedures for preliminary conceptual design.
      Citation: Aerospace
      PubDate: 2022-03-23
      DOI: 10.3390/aerospace9040176
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 177: A Beam Search-Based Channel Allocation
           Method for Interference Mitigation of NGSO Satellites with Multi-Beam
           Antennas

    • Authors: Haojie Zhang, Di Ren, Fanghua Jiang
      First page: 177
      Abstract: In the past few years, non-geostationary orbit (NGSO) satellite communication constellations have regained popularity due to their conspicuous advantages. Nevertheless, with more NGSO satellites getting involved in communications, the spectrum resources should become much more scarce. Multi-beam high throughput satellite and spectrum sharing are two major techniques in communication design. The two techniques can significantly mitigate interference and highly augment the capacity of the communication system. Thus, they are commonly used in satellite communication systems nowadays. With a massive number of NGSO satellites comprising the communication system and moving in their orbits, interference scenarios are pretty complex. In this article, the relationship between the level of interference and the beam distance is deduced. Moreover, for beams with different tilting angles, the different off-axis angles may correspond to the same beam distance, which is directly related to the interference level. Through the interference analysis, we propose a channel allocation method that uses a beam search algorithm to optimize the channel allocation problem and achieves outstanding time efficiency. The performance of the proposed method is validated by a coexisting scenario of the geostationary orbit and NGSO satellite communication systems. The results show that the level of interference can be largely mitigated, and the capacity of communication systems is significantly augmented.
      Citation: Aerospace
      PubDate: 2022-03-23
      DOI: 10.3390/aerospace9040177
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 178: An Analysis of Fixed-Wing Stall-Type
           Accidents in the United States

    • Authors: Nicoletta Fala
      First page: 178
      Abstract: Spin training has not been required for students working towards their private or commercial certificates for the past 70 years. Switching to a stall-prevention mindset within training aimed to make spin recovery unnecessary; however, stall-type accidents, consisting of stalls, spins, and spirals, still occur and are highly fatal. Although past studies have analyzed accidents, interviewed pilots at different levels, and made recommendations for changes in the industry, stall-type accidents are no less fatal now, at a fatality ratio of approximately 40–50% yearly. The research discussed in this paper aims to summarize and present accident stall-type statistics in aggregate over the past five decades and motivate future pilot- and training-centered research to address the high presence of stall-type accidents in aviation. Specifically, this article uses NTSB accident reports to answer the research question of whether there have been changes in the prevalence of spins among both fatal and non-datal fixed-wing accidents in the United States over the past sixty years. The methodology breaks down the accident analysis in three groups, based on the time period in which they occurred, due to differences in the reporting methods used. This paper finds that the prevalence and fatality ratio of stall-type accidents has remained high over the past six decades and that stall-type accidents are more than twice as fatal as an average accident. To remedy the high accident count, we recommend experimental ground and simulator-based training to improve pilot knowledge, skill, and performance.
      Citation: Aerospace
      PubDate: 2022-03-24
      DOI: 10.3390/aerospace9040178
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 179: An Investigation into the Flow of Rotating
           Orifices with Euler Angle and the Calculation Model of Discharge
           Coefficient Considering the Effect of Comprehensive Incidence Angle

    • Authors: Jie Wang, Peng Liu, Tian Qiu, Shuiting Ding
      First page: 179
      Abstract: As a typical flow element in an aero-engines, orifices play a vital role in the distribution and control of the mass flow rate within the secondary air system. In particular, rotating orifices with complex geometry (Euler angles) may significantly vary the discharge coefficients. Understanding the discharge coefficients of these orifices may guarantee a more reasonable distribution of the internal flow within the air system. This contributes to the safety, reliability, and structural integrity of the aero-engine under the all-inclusive line. In this paper, the flow state within the orifice and the discharge coefficient have been studied under the condition of different Euler angles (α0=0–30° and β0=0–30°) and rotational speeds (0–10,000 r/min). The comprehensive incidence angle is proposed to describe the combined effect of Euler angles and rotation. The correlation between the discharge coefficient and the comprehensive incidence angle is also given. At the same time, a general calculation model of the orifices is established considering the effect of the comprehensive incidence angle. The results indicate that the effects of the circumferential inclination angle, radial inclination angle, and rotation may be more clearly expressed by the comprehensive incidence angle. The larger discharge coefficient is obtained when the comprehensive incidence angle is close to 0, and under the fixed rotational speed and flow condition, the maximum discharge coefficient can be obtained by arranging the appropriate Euler angle for the orifice. Compared with the experimental results in the published literature, the calculation results of the model have an overall error of less than 6%. The calculation accuracy is high enough for the one-dimensional simulation of the secondary air system.
      Citation: Aerospace
      PubDate: 2022-03-24
      DOI: 10.3390/aerospace9040179
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 180: An Accelerated Dual Fast Marching Tree
           Applied to Emergency Geometric Trajectory Generation

    • Authors: Andréas Guitart, Daniel Delahaye, Eric Feron
      First page: 180
      Abstract: This paper addresses the generation of aircraft emergency trajectories with obstacle avoidance. After presenting in detail the fast marching tree algorithm, in this paper we propose an improvement of its performance. First, the free space checking function is sped up. Then, the algorithm is used twice, firstly with the sampling of a few points to generate an approximate trajectory, and secondly with a sampling of points close to the first computed trajectory to refine it. The proposed method significantly reduces the computing time of the emergency geometric trajectory generation.
      Citation: Aerospace
      PubDate: 2022-03-25
      DOI: 10.3390/aerospace9040180
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 181: Icon Design for Representing Safety-Critical
           Aircraft Functions to Support Supervisory Control of Remotely Piloted
           Aircraft Systems

    • Authors: Max Friedrich, Dale Richards, Mark Vollrath
      First page: 181
      Abstract: (1) Background: The transition from conventional to remote aircraft control will necessitate the development of novel human machine interfaces. When we consider the pilot interface, icons are traditionally used to associate meanings with functions on the flight deck, allowing the pilot to assimilate information effectively. Using established icon design principles, 18 icons, representing key safety-critical functions related to the operation of an aircraft, were designed for integration into a ground station. Pilots were then asked to evaluate these icons based on established icon characteristics. (2) Method: In an online questionnaire study, 29 pilots rated the icons on the icon characteristics of concreteness, complexity, familiarity, meaningfulness, and semantic distance. Alongside these metrics, concept and name agreement were captured for the icon set. (3) Results: Analysis indicated good icon-function fit overall. The findings show that emphasizing concreteness and familiarity improves icon-function fit, as long as the familiarity is directed at aviation-related artifacts. Further, concept agreement appears to be a better measure of icon-function fit in comparison to name agreement. (4) Conclusion: Most of the designed icons were well suited to represent their intended meaning. However, this study emphasizes the need for dedicated standardized icon characteristic norms for aviation systems.
      Citation: Aerospace
      PubDate: 2022-03-25
      DOI: 10.3390/aerospace9040181
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 182: Geostationary Station-Keeping of
           Electric-Propulsion Satellite Equipped with Robotic Arms

    • Authors: Chengzhang Li, Bo Xu, Wanmeng Zhou, Qibo Peng
      First page: 182
      Abstract: We propose two approaches based on feedforward control and model-predictive control, respectively, to solve the station-keeping problem of an electric-propulsion geostationary Earth orbit (GEO) satellite, whose thrusters are mounted on two robotic arms on its anti-nadir face. This novel configuration enables a wider range of thrust direction, making it possible to regard the thrust direction as control variables. To solve this control problem, we present the quick feedforward controller (QFFC) and the fuel-optimal model predictive controller (FOMPC). The QFFC is developed based on the analysis of GEO dynamics and the thruster configuration. The FOMPC applies an optimization algorithm to solve the nonlinear model predictive control (NLMPC) problem with the initial value given by the QFFC. Numerical simulations suggest that both controllers could achieve stable station-keeping over multiple objective elements with fewer thrusters and fewer maneuvers. The QFFC has higher control accuracy and lower computational requirements than the FOMPC, whereas the FOMPC could significantly save fuel consumption. The robustness assessment and other discussions of the controllers are also presented.
      Citation: Aerospace
      PubDate: 2022-03-28
      DOI: 10.3390/aerospace9040182
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 183: The Need for Multi-Sensor Data Fusion in
           Structural Health Monitoring of Composite Aircraft Structures

    • Authors: Agnes A. R. Broer, Rinze Benedictus, Dimitrios Zarouchas
      First page: 183
      Abstract: With the increased use of composites in aircraft, many new successful contributions to the advancement of the structural health monitoring (SHM) field for composite aerospace structures have been achieved. Yet its application is still not often seen in operational conditions in the aircraft industry, mostly due to a gap between research focus and application, which constraints the shift towards improved aircraft maintenance strategies such as condition-based maintenance (CBM). In this work, we identify and highlight two key facets involved in the maturing of the SHM field for composite aircraft structures: (1) the aircraft maintenance engineer who requires a holistic damage assessment for the aircraft’s structural health management, and (2) the upscaling of the SHM application to realistic composite aircraft structures under in-service conditions. Multi-sensor data fusion concepts can aid in addressing these aspects and we formulate its benefits, opportunities, and challenges. Additionally, for demonstration purposes, we show a conceptual design study for a fusion-based SHM system for multi-level damage monitoring of a representative composite aircraft wing structure. In this manner, we present how multi-sensor data fusion concepts can be of benefit to the community in advancing the field of SHM for composite aircraft structures towards an operational CBM application in the aircraft industry.
      Citation: Aerospace
      PubDate: 2022-03-30
      DOI: 10.3390/aerospace9040183
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 184: 2D Numerical Study on the Flow Mechanisms of
           Boundary Layer Ingestion through Power-Based Analysis

    • Authors: Peijian Lv, Mengmeng Zhang, Fei Cao, Defu Lin, Li Mo
      First page: 184
      Abstract: This paper aims to establish an approach of power bookkeeping in a numerical study. To study the process of power conversion coursed in the flow field, the methodology employs a power-based analysis to quantify power terms. This approach is examined in a simulation of jet flow and then applied to the cases of an isolated actuator disc and an isolated flat plate. Eventually, a numerical simulation is carried out for the boundary layer ingestion (BLI) case that integrates the flat plate and a wake-filling actuator disc. This study quantitatively discusses the mechanisms of BLI under the conditions of laminar and turbulent flow. The proposed power-based analysis might offer insights for the aircraft aerodynamic design using favorable airframe propulsion integration.
      Citation: Aerospace
      PubDate: 2022-03-30
      DOI: 10.3390/aerospace9040184
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 185: Flight Speed Evaluation Using a Special
           Multi-Element High-Speed Temperature Probe

    • Authors: Michal Schmirler
      First page: 185
      Abstract: In the context of aircraft aerodynamics, the compressibility of air flowing around the aircraft must always be considered. This fact brings with it one inconvenience: to evaluate the velocity of the flowing air (airspeed), it is necessary to know its temperature as well. Unfortunately, direct measurement of the temperature of air flowing at high speed (usually at Ma > 0.3) is practically impossible without knowledge of its velocity. Thus, there are two unknown quantities in the problem that depend on each other. The solution is achieved by a method that uses temperature probes composed of multiple sensors with different properties (different recovery factors). The comparison of rendered temperatures subsequently allows the elimination of the necessary knowledge of static temperature and the evaluation of velocity. In this paper, one of such probes is described together with its thermodynamic properties and possible applications.
      Citation: Aerospace
      PubDate: 2022-03-31
      DOI: 10.3390/aerospace9040185
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 186: Optimal Escape from Sun-Earth and Earth-Moon
           L2 with Electric Propulsion

    • Authors: Luigi Mascolo, Lorenzo Casalino
      First page: 186
      Abstract: Optimal low-thrust trajectories for the direct escape from the Earth’s sphere of influence, starting from Sun-Earth or Earth-Moon L2, are analyzed with an indirect optimization method. The dynamic model considers four-body gravitation and JPL ephemeris; solar radiation pressure is also considered. Specific techniques and improvements to the method are introduced to tackle the highly chaotic and nonlinear dynamics of motion close to Lagrangian points, which challenges the remarkable precision of the indirect method. The results show that escape trajectories have optimal performance when the solar perturbation acts favorably in both thrust and coast phases. The effects of the solar and Moon perturbations are more evident in the Earth-Moon L2 escapes compared with those from the Sun-Earth L2. EML2 escapes have single- or two-burn solutions depending on the trajectory deflection, which is needed to have a favorable solar perturbation. The SEL2 escapes, on the contrary, mainly have a single initial burn and a long coast arc, but need an additional final thrust arc if the required C3 is high. As applications of such Lagrangian Point trajectories, results include considerations about escape maneuvers from different SEL2 high-fidelity Lyapunov orbits and escape for interplanetary trajectories towards near-earth asteroids.
      Citation: Aerospace
      PubDate: 2022-04-01
      DOI: 10.3390/aerospace9040186
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 187: On the Fundamental Possibility of a
           Supersonic Civil Aircraft to Comply with ICAO Noise Requirements Using
           Existing Technologies

    • Authors: Victor F. Kopiev, Ivan V. Belyaev, Andrey I. Dunaevsky, Andrey A. Poukhov, Igor L. Trofimovsky
      First page: 187
      Abstract: Compliance with environmental protection regulations, in particular, community noise requirements, constitutes one of the major obstacles for designing future supersonic civil aircraft. Although there are several noise sources that contribute to the total noise level of supersonic aircraft, it is the turbulent jet that appears most problematic; jet noise is a dominant noise source for low-to moderate- bypass-ratio engines, and at present there are no effective methods of jet noise reduction other than decreasing jet speed by increasing bypass ratio, which, in turn, is constrained by aerodynamic requirements for supersonic flight. The present study considers a concept of supersonic civil aircraft under the assumption that its total noise is determined by turbulent jets; it is shown that compliance of the supersonic aircraft with the current regulations for subsonic aircraft noise (Chapter 14 Volume I Annex 16 ICAO) would require the decreased jet speed that corresponds to a prohibitively high bypass ratio of aircraft engines. To enable jet noise reduction without necessarily increasing bypass ratio, a novel configuration of supersonic aircraft is proposed that meets the requirements of Chapter 14, thereby demonstrating that the norms of Chapter 14 are achievable for future supersonic civil aircraft with the use of existing technologies.
      Citation: Aerospace
      PubDate: 2022-04-01
      DOI: 10.3390/aerospace9040187
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 188: A Real-Time Trajectory Optimization Method
           for Hypersonic Vehicles Based on a Deep Neural Network

    • Authors: Jianying Wang, Yuanpei Wu, Ming Liu, Ming Yang, Haizhao Liang
      First page: 188
      Abstract: Considering the high-efficient trajectory planning requirements for hypersonic vehicles, this paper proposes a real-time trajectory optimization method based on a deep neural network. First, the trajectory optimization model of the hypersonic vehicle reentry phase is developed. The pseudo-spectral method is used to perform the trajectory optimization offline, and multiple optimal trajectory data are obtained. In addition, based on the inherent relationship between the state and control variables of a trajectory, a neural network is established to predict the current control outputs. The sample library of optimal trajectory data is used to train the parameters of the deep neural network to obtain an optimal neural network model. Finally, the simulation verification of the hypersonic vehicle reentry phase is performed. The simulation results show that under the condition of the initial value deviation and environmental interference, the proposed deep learning-based method can achieve a fast generation of hypersonic vehicle optimal trajectories, while achieving the advantages of high computational efficiency and reliability. Compared to traditional trajectory optimization algorithms, the proposed method has the generalization capability that satisfies the accuracy requirements and meets the demands of online real-time trajectory optimization.
      Citation: Aerospace
      PubDate: 2022-04-01
      DOI: 10.3390/aerospace9040188
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 189: Prediction of Arrival Flight Operation
           Strategies under Convective Weather Based on Trajectory Clustering

    • Authors: Shijin Wang, Jiewen Chu, Jiahao Li, Rongrong Duan
      First page: 189
      Abstract: An airport’s terminal area is the bottleneck of the air transport system. Convective weather can seriously affect the normal flight status of arrival and departure flights. At present, pilots take different flight operation strategies to avoid convective weather based on onboard radar, visual information, adverse weather experience, etc. This paper studies trajectory clustering based on the OPTICS algorithm to obtain the arrival of typical flight routes in the terminal area. Based on weather information of the planned typical flight route and flight plan information, Random Forest (RF), K-nearest Neighbor KNN (KNN), and Support Vector Machines (SVM) algorithms were used for training and establishing the Arrival Flight Operation Strategy Prediction Model (AFOSPM). In this paper, case studies of historical arrival flights in the Guangzhou (ZGGG) and Wuhan (ZHHH) terminal area were carried out. The results show that trajectory clustering results based on the OPTICS algorithm can more accurately reflect the regular flight routes of arrival flights in a terminal area. Compared to KNN and SVM, the prediction accuracy of AFOSPM based on RF is better, reaching more than 88%. On this basis, six features—including 90% VIL, weather coverage, weather duration, planned route, max VIL, and planned Arrival Gate (AF)—were used as the input features for AFOSPM, which can effectively predict various arrival flight operation strategies. For the most frequently used arrival flight operation strategies under convective weather conditions—radar guidance, AF changing, and diversion strategy—the prediction accuracy of the ZGGG and ZHHH terminal areas can exceed 95%, 85%, and 80%, respectively.
      Citation: Aerospace
      PubDate: 2022-04-01
      DOI: 10.3390/aerospace9040189
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 190: Unmanned Aircraft Collision Detection and
           Avoidance for Dealing with Multiple Hazards

    • Authors: Federico Corraro, Gianluca Corraro, Giovanni Cuciniello, Luca Garbarino
      First page: 190
      Abstract: Collision Detection and Avoidance is one of the critical technologies for fully allowing Unmanned Aerial Systems to fly in civil airspaces. Current methods evaluate only potential conflicts with other aircraft using specific parameters (e.g., time or distance to closest point of approach) that can only be used for pair-wise encounters, not considering the surrounding environment. The present work proposes a new collision detection and avoidance concept to solve short-term conflicts in scenarios characterized by the simultaneous presence of aircraft and other path constraints (i.e., no-fly zones, bad weather areas and terrain) including geo-fencing limitations. Differently from other open literature methods, the proposed algorithm computes two parameters that synthetically describe the conflict hazard level of a given scenario and its possible evolution, independently from the type and the number of surrounding potential threats. Using such indices, a risk evaluation strategy is proposed that detects hazardous situations and generates an optimal maneuver avoiding potential collisions while not causing secondary conflicts. The effectiveness of the proposed algorithm is demonstrated by means of fast-time and real time simulations in some challenging conflict scenarios that cannot be solved by state of the art Detect and Avoid systems.
      Citation: Aerospace
      PubDate: 2022-04-01
      DOI: 10.3390/aerospace9040190
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 191: Effect of Streamwise Perturbation Frequency
           on Formation Mechanism of Ligament and Droplet in Liquid Circular Jet

    • Authors: Chenglin Zhou, Jianfeng Zou, Yang Zhang
      First page: 191
      Abstract: In order to study the influence of streamwise forcing on the formation mechanism of liquid ligaments and droplets in the primary breakup process of liquid circular jet, the VOF interface capturing method-based direct numerical simulation was adopted, and a range of sinusoidal velocity disturbances with different frequencies were considered. The selected disturbance frequency range is 0–3000 kHz. This work analyzes the evolution process of the jet surface waves at different disturbance frequencies, and the coupling effect of the jet tip and liquid core on the overall spray field from overall structure, liquid ligament, and droplet formation. The results show that different disturbance frequencies affect the droplet shape distribution and size distribution in spray field. Current work provides guidance for the control of the thermoacoustic instability of the engine and design of the nozzle.
      Citation: Aerospace
      PubDate: 2022-04-01
      DOI: 10.3390/aerospace9040191
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 192: Estimation of Transport-Category Jet
           Airplane Maximum Range and Airspeed in the Presence of Transonic Wave Drag
           

    • Authors: Jan Wislicenus, Nihad E. Daidzic
      First page: 192
      Abstract: One of the most difficult steps in estimating the cruise performance characteristics of high-subsonic transport-category turbofan-powered airplanes is the estimation of the transonic wave drag. Modern jet airplanes cruise most efficiently in the vicinity of the drag-divergence or drag-rise Mach numbers. In the initial design phase and later when the preliminary wind-tunnel and/or CFD computations and drag polars are known with increased accuracy, a method of estimating cruise performance is needed. In this study, a new semi-empirical transonic wave drag model using modified Lock’s equation was developed. For maximum range cruise estimations, an optimization criterion based on maximizing specific air range was used. The resulting nonlinear equations are of 12th- and 13th-order. Numerical Newton–Raphson nonlinear solvers were used to find real positive roots of such polynomials. The NR method was first tested for accuracy and convergence using known analytical solutions. A methodology for an initial guess was developed starting with the maximum-range cruise Mach without the wave-drag included. This guess resulted in fast quadratic convergence in all computations. Other novel features of this article include a new semi-empirical fuel-flow law, which was also extensively tested. Additionally, a semi-empirical turbofan thrust model usable for a wide range of bypass ratios and the entire flight envelope was developed. Such physics-based semi-empirical model can be used for a wide range of turbofans. The algorithm can be utilized to identify most beneficial input parameter values and combinations for the cruise flight phase. The model represents a powerful tool to estimate important cruise performance airspeeds located in the transonic regime. An intended application is in the conceptual development stages for early design optimizations of future airplanes. It is possible with additional effort to extend existing model capabilities to deal with supersonic transports optimal cruise parameters.
      Citation: Aerospace
      PubDate: 2022-04-02
      DOI: 10.3390/aerospace9040192
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 193: Terminal Impact Angle Control Guidance Law
           Considering Target Observability

    • Authors: Bin Li, Pan Tang, Haotian Xu, Duo Zheng
      First page: 193
      Abstract: The problem of the terminal impact angle control guidance law, considering the target observability for passive guidance with bearing-only measurement, is investigated in this paper. Modified line-of-sight (LOS) angle error dynamics and their closed-loop analytical solution are developed to enhance the target observability, and then their characteristics are studied, which makes the LOS angular rate oscillate in the early stage. The terminal impact angle control guidance law with the global sliding mode is designed to eliminate the approaching stage of sliding mode control, which makes the system robust throughout the entire process of control. Finally, numerical simulations are presented to demonstrate the performance of the proposed guidance law under various conditions, which achieves the desired results.
      Citation: Aerospace
      PubDate: 2022-04-03
      DOI: 10.3390/aerospace9040193
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 194: Propagation Characteristics of Modulated EHF
           Signal in the Wake Region of Plasma Sheath

    • Authors: Xiaocui Yang, Kai Yuan, Yuhao Wang, Yiwen Liu, Jiawei Xiong
      First page: 194
      Abstract: A large number of studies have confirmed that the wake region may be a more ideal antenna installation area for the reentry vehicle communication problem, but many practical issues such as how to choose the modulation mode, carrier frequency, and antenna orientation are still pending. Based on numerical simulations, the characteristics of tail channels and the bit error rate (BER) of extremely high-frequency (EHF) communication in the wake region of the plasma sheath of hypersonic vehicle are studied. It is found that, with an increase in the angle between the tail channel and the tail of the vehicle, the attenuation of the EHF signals decreases and the phase shift fluctuates more severely. In order to obtain better communication performance, 2PSK with a carrier frequency of 140 GHz or 225 GHz, or 4QAM (QPSK) modulation with a carrier frequency of 140 GHz, and the tail channel with an angle between 50°and 60°to the tail of the vehicle can be selected. This study reveals the propagation characteristics and BER performance of EHF signals in the wake region of plasma sheath, which can provide a valuable reference for the design of the hypersonic vehicle communication system.
      Citation: Aerospace
      PubDate: 2022-04-04
      DOI: 10.3390/aerospace9040194
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 195: Multi-Mode Shape Control of Active Compliant
           Aerospace Structures Using Anisotropic Piezocomposite Materials in
           Antisymmetric Bimorph Configuration

    • Authors: Xiaoming Wang, Xinhan Hu, Chengbin Huang, Wenya Zhou
      First page: 195
      Abstract: The mission performance of future advanced aerospace structures can be synthetically improved via active shape control utilizing piezoelectric materials. Multiple work modes are required. Bending/twisting mode control receives special attention for many classic aerospace structures, such as active reflector systems, active blades, and compliant morphing wings. Piezoelectric fiber composite (Piezocomposite) material features in-plane anisotropic actuation, which is very suitable for multiple work modes. In this study, two identical macro-fiber composite (MFC) actuators of the F1 type were bonded to the base plate structure in an “antisymmetric angle-ply bimorph configuration” in order to achieve independent bending/twisting shape control. In terms of the finite element model and homogenization strategy, the locations of bimorph MFCs were determined by considering the effect of trade-off control capabilities on the bending and twisting shapes. The modal characteristics were investigated via both experimental and theoretical approaches. The experimental tests implied that the shape control accuracy was heavily reduced due to various uncertainties and nonlinearities, including hysteresis and the creep effect of the actuators, model errors, and external disturbances. A multi-mode feedback control law was designed and the experimental tests indicated that synthetic (independent and coupled) bending/twisting deformations were achieved with improved shape accuracy. This study provides a feasible multi-mode shape control approach with high surface accuracy, especially by employing piezocomposite materials.
      Citation: Aerospace
      PubDate: 2022-04-06
      DOI: 10.3390/aerospace9040195
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 196: Application of High-Order WENO Scheme in the
           CFD/FW–H Method to Predict Helicopter Rotor Blade–Vortex
           Interaction Tonal Noise

    • Authors: Yan Sun, Yongjie Shi, Guohua Xu
      First page: 196
      Abstract: The accurate prediction of helicopter rotor blade–vortex interaction (BVI) noise is challenging. This paper presents an implementation of the seventh-order improved weighted essentially non-oscillatory (WENO-Z) scheme for predicting rotor BVI noise using a high-resolution numerical method based on the Reynolds-averaged Navier–Stokes and the Ffowcs Williams–Hawkings equations. The seventh-order improved WENO-Z scheme is utilized to minimize the inherent numerical dissipation of the reconstruction method in the monotone upstream-centered scheme for conservation laws (MUSCL), thereby improving the rotor wake resolution and the BVI noise-prediction accuracy. The three-layer dummy cell method is used to ensure that the flux at the boundary maintains seventh-order accuracy. The effectiveness of the flow solver and the acoustic solver is validated using the Helishape-7A rotor and the UH-1H rotor, respectively. The flow field and BVI noise characteristics of the OLS rotor obtained from the fifth- and seventh-order WENO-Z schemes are compared with that of the third-order MUSCL for coarse and fine background grids. The wake resolution, noise-prediction accuracy, and computational cost of the three schemes are compared. The results show that the high-order WENO scheme provides higher accuracy for flow field simulation and BVI noise prediction than the MUSCL, but the computational cost of the WENO scheme increases substantially as the grid resolution increases. However, the WENO scheme can predict BVI using a coarser grid than the MUSCL. The computational cost of the WENO scheme is relatively low under the same flow field simulation resolution.
      Citation: Aerospace
      PubDate: 2022-04-06
      DOI: 10.3390/aerospace9040196
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 197: Effect of Stagger on Low-Speed Performance
           of Busemann Biplane Airfoil

    • Authors: Thai Duong Nguyen, Masashi Kashitani, Masato Taguchi, Kazuhiro Kusunose
      First page: 197
      Abstract: In this study, the low-speed performances of the Busemann biplane were clarified, focusing on the relative contributions of the upper and lower elements to the total aerodynamic characteristics of the biplane. Also, the effects of the staggered biplane, which changes the horizontal distance between two wings in a biplane configuration, were investigated by balance measurements and numerical simulations. The flow velocity was 15 m/s, and the Reynolds number based on the airfoil chord length was 2.1 × 105. In the tests of the integrated biplane wing, the attack angles of the wing elements were varied by a balance system and turntable, which were set in the wind tunnel sidewall. The results show that the lower element generated most of the lift and drag of the Busemann biplane (or the baseline biplane model with no stagger) at high angles of attack. At angles above 20 deg, the contribution of the lower element to total aerodynamic characteristics is almost constant, with 95% of the total lift and 88% of the total drag. The total lift and drag of the baseline model were smaller than the sum of the individual elements that were treated as a single configuration. The increments of lift and drag due to the stagger effects were confirmed, especially at high angles of attack. When the stagger value increases, the high-pressure area near the leading edge of the lower surface of the upper element also increases, which increases the lift and drag of the up-per element. This is the main reason for the increments of total lift and drag of the biplane model. The stagger effects also prevented the leading-edge separation of the lower element in the biplane configuration and increased the lift slopes of the biplane model.
      Citation: Aerospace
      PubDate: 2022-04-06
      DOI: 10.3390/aerospace9040197
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 198: UAV Imagery for Automatic Multi-Element
           Recognition and Detection of Road Traffic Elements

    • Authors: Liang Huang, Mulan Qiu, Anze Xu, Yu Sun, Juanjuan Zhu
      First page: 198
      Abstract: Road traffic elements comprise an important part of roads and represent the main content involved in the construction of a basic traffic geographic information database, which is particularly important for the development of basic traffic geographic information. However, the following problems still exist for the extraction of traffic elements: insufficient data, complex scenarios, small targets, and incomplete element information. Therefore, a set of road traffic multielement remote sensing image datasets obtained by unmanned aerial vehicles (UAVs) is produced, and an improved YOLOv4 network algorithm combined with an attention mechanism is proposed to automatically recognize and detect multiple elements of road traffic in UAV imagery. First, the scale range of different objects in the datasets is counted, and then the size of the candidate box is obtained by the k-means clustering method. Second, mosaic data augmentation technology is used to increase the number of trained road traffic multielement datasets. Then, by integrating the efficient channel attention (ECA) mechanism into the two effective feature layers extracted from the YOLOv4 backbone network and the upsampling results, the network focuses on the feature information and then trains the datasets. At the same time, the complete intersection over union (CIoU) loss function is used to consider the geometric relationship between the object and the test object, to solve the overlapping problem of the juxtaposed dense test element anchor boxes, and to reduce the rate of missed detection. Finally, the mean average precision (mAP) is calculated to evaluate the experimental effect. The experimental results show that the mAP value of the proposed method is 90.45%, which is 15.80% better than the average accuracy of the original YOLOv4 network. The average detection accuracy of zebra crossings, bus stations, and roadside parking spaces is improved by 12.52%, 22.82%, and 12.09%, respectively. The comparison experiments and ablation experiments proved that the proposed method can realize the automatic recognition and detection of multiple elements of road traffic, and provide a new solution for constructing a basic traffic geographic information database.
      Citation: Aerospace
      PubDate: 2022-04-06
      DOI: 10.3390/aerospace9040198
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 199: Orbit-Injection Strategy and
           Trajectory-Planning Method of the Launch Vehicle under Power Failure
           Conditions

    • Authors: Yin Diao, Jialun Pu, Hechuan Xu, Rongjun Mu
      First page: 199
      Abstract: Aiming at the problem of autonomous decision making and trajectory planning (ADMTP) for launch vehicles under power failure conditions, the target degradation order strategy (TDOS) and the trajectory online planning method were studied in this paper. Firstly, the influence of power failure on the orbit-injection process was analyzed. Secondly, the TDOS was proposed according to the mission attribute, failure mode, and multi-payload combination. Then, an online planning method based on the adaptive target update iterative guidance method (ATU-IGM) and radial basis neural network (RBFNN) was proposed, where the ATU-IGM adopted the basic TDOS criterion for generating optimal orbit-injection samples and online guidance instructions, and the RBFNN was used for orbit-injection samples training and online generation of orbital missions. Finally, the comparative simulation analysis was performed under multi-failure conditions. The results showed that the TDOS proposed in this paper could meet the requirements of the mission decision making under different failures, target orbit types, orbit-injection methods, and payload compositions. The online trajectory-planning capability deviation was less than 5%, and the mission decision-making and trajectory-planning time were less than 10 ms. This study provides theoretical support for autonomous decision making and planning of space launch missions.
      Citation: Aerospace
      PubDate: 2022-04-07
      DOI: 10.3390/aerospace9040199
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 200: Optimization of Geostationary Orbit
           Transfers via Combined Chemical–Electric Propulsion

    • Authors: Shihai Yang, Bo Xu, Xin Li
      First page: 200
      Abstract: For geostationary orbit transfers, a long duration is required using electric propulsion and a large propellant mass is needed with chemical propulsion. Hybrid transfers can achieve a balance between the fuel consumption and transfer time. In this paper, a trajectory optimization method is proposed for time-fixed minimum-fuel orbital transfer with combined chemical–electric propulsion. The necessary conditions and transversality conditions related to impulsive burns are derived theoretically with Pontryagin’s maximum principle. The long-duration geostationary orbit transfer is a many-revolution transfer, and is solved with the homotopic approach from the short-duration transfer problem. The variation in fuel consumption with transfer time is nearly linear, and the variation in the magnitude of impulsive burn is exponential. A simple model is presented for the estimation of fuel consumption and magnitude of impulsive burn with given transfer time, specific impulse of propulsion system and low-thrust magnitude.
      Citation: Aerospace
      PubDate: 2022-04-07
      DOI: 10.3390/aerospace9040200
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 201: Performance Assessment of an Integrated
           Environmental Control System of Civil Hypersonic Vehicles

    • Authors: Nicole Viola, Davide Ferretto, Roberta Fusaro, Roberto Scigliano
      First page: 201
      Abstract: This paper discloses the architecture and related performance of an environment control system designed to be integrated within a complex multi-functional thermal and energy management system that manages the heat loads and generation of electric power in a hypersonic vehicle by benefitting from the presence of cryogenic liquid hydrogen onboard. A bleed-less architecture implementing an open-loop cycle with a boot-strap sub-freezing air cycle machine is suggested. Hydrogen boil-off reveals to be a viable cold source for the heat exchangers of the system as well as for the convective insulation layer designed around the cabin walls. Including a 2 mm boil-off convective layer into the cabin cross-section proves to be far more effective than a more traditional air convective layer of approximately 60 mm. The application to STRATOFLY MR3, a Mach 8 waverider cruiser using liquid hydrogen as propellant, confirmed that presence of cryogenic tanks provides up to a 70% reduction in heat fluxes entering the cabin generated outside of it but inside the vehicle, by the propulsive system and other onboard systems. The effectiveness of the architecture was confirmed for all Mach numbers (from 0.3 to 8) and all flight altitudes (from sea level to 35 km).
      Citation: Aerospace
      PubDate: 2022-04-07
      DOI: 10.3390/aerospace9040201
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 202: Three-Dimensional Impact Time Control
           Guidance Considering Field-of-View Constraint and Velocity Variation

    • Authors: Shuai Ma, Zhongyuan Wang, Xugang Wang, Qi Chen
      First page: 202
      Abstract: The problem of three-dimensional impact time control guidance considering field-of-view constraints and time-varying velocity is investigated in this study. First, considering the effect of gravity and aerodynamic forces on velocity, a simplified numerical estimation algorithm of flight time with a three-dimensional proportional navigation guidance law is derived. Then, based on the structure of the biased proportional navigation guidance law, the effect of the biased term on flight time is analyzed. The biased term is then designed to achieve impact time and field-of-view constraints considering time-varying velocity. Finally, numerical simulations are performed to demonstrate the effectiveness and superiority of the proposed guidance law.
      Citation: Aerospace
      PubDate: 2022-04-09
      DOI: 10.3390/aerospace9040202
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 203: Design of a DSP-Based Motion-Cueing
           Algorithm Using the Kinematic Solution for the 6-DoF Motion Platform

    • Authors: Ming-Yen Wei
      First page: 203
      Abstract: A motion-cueing algorithm is a motion simulation system that makes the pilot feel the flight motion by calculating the attitude of the platform. This paper presents the design a kinematics model and two motion-cueing algorithms for a multi-axis motion platform. Firstly, the relationship between each axis is derived from the kinematics theory and motion platform transformation. Next, two motion-cueing algorithms are designed providing the pilot with the bodily sensations of the 6-DoF motion platform. By using a hardware-in-the-loop (HIL) approach simulated in a real-time digital simulator, the control operations are performed in a digital signal processor (DSP). All of the motion-cueing algorithms, including the classical washout algorithm and the optimal control algorithm, are realized through a DSP, TMS-320F-28377D. The simulation results verify the theoretical analysis and illustrate the correctness and practicability of the proposed method.
      Citation: Aerospace
      PubDate: 2022-04-09
      DOI: 10.3390/aerospace9040203
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 204: Clean Sky 2 Technology
           Evaluator—Results of the First Air Transport System Level
           Assessments

    • Authors: Marc Christopher Gelhausen, Wolfgang Grimme, Alf Junior, Christos Lois, Peter Berster
      First page: 204
      Abstract: The authors have adjusted the DLR forecast model to evaluate the environmental benefits in terms of CO2 and NOx emissions of Clean Sky 2 technology innovations. The paper briefly describes the model employed: it consists of a passenger/flight volume forecast, a fleet model, and emission modelling. The novelty of the forecast approach compared to previous studies is that it is based on airport pairs instead of larger aggregates like countries or regions. Therefore, a separate breakdown on airports is unnecessary in the case of a more detailed analysis is needed, and it enables us to include airport capacity constraints which affect demand and flight volume, as well as the fleet development at constrained and unconstrained airports. We eventually present the forecast results in terms of passenger and flight volume, fleet development, and CO2 and NOx emissions. The results show that emissions can be reduced substantially by the use of Clean Sky 2 technology compared to a reference case which represents the status quo.
      Citation: Aerospace
      PubDate: 2022-04-09
      DOI: 10.3390/aerospace9040204
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 205: A Polymorphing Wing Capable of Span
           Extension and Variable Pitch

    • Authors: Muhammed S. Parancheerivilakkathil, Zawar Haider, Rafic M. Ajaj, Mohammadreza Amoozgar
      First page: 205
      Abstract: This paper presents the development of a novel polymorphing wing capable of Active Span morphing And Passive Pitching (ASAPP) for small UAVs. The span of an ASAPP wing can be actively extended by up to 25% to enhance aerodynamic efficiency, whilst its pitch near the wingtip can be passively adjusted to alleviate gust loads. To integrate these two morphing mechanisms into one single wing design, each side of the wing is split into two segments (e.g., inboard and outboard segments). The inboard segment is used for span extension whilst the outboard segment is used for passive pitch. The inboard segment consists of a main spar that can translate in the spanwise direction. Flexible skin is used to cover the inboard segment and maintain its aerodynamic shape. The skin transfers the aerodynamic loads to the main spar through a number of ribs that can slide on the main spar through linear plain bearings. A linear actuator located within the fuselage is used for span morphing. The inboard and outboard segments are connected by an overlapping spar surrounded by a torsional spring. The overlapping spar is located ahead of the aerodynamic center of the outboard segment to facilitate passive pitch. The aero-structural design, analysis, and sizing of the ASAPP wing are detailed here. The study shows that the ASAPP wing can be superior to the baseline wing (without morphing) in terms of aerodynamic efficiency, especially when the deformation of the flexible skin is minimal. Moreover, the passive pitching near the wingtip can reduce the root loads significantly, minimizing the weight penalty usually associated with morphing.
      Citation: Aerospace
      PubDate: 2022-04-09
      DOI: 10.3390/aerospace9040205
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 206: Angular-Accelerometer-Based Flexible-State
           Estimation and Tracking Controller Design for Hypersonic Flight Vehicle

    • Authors: Daqiao Zhang, Xiaolong Zheng, Yangguang Xie, Xiaoxiang Hu
      First page: 206
      Abstract: The controller design of hypersonic flight vehicles is a challenging task, especially when its flexible states are immeasurable. Unfortunately, the flexible states are difficult to measure directly. In this paper, an angular-accelerometer-based method for the estimation of flexible states is proposed. By adding a pitch angel angular accelerometer and designing an Extended Kalman Filter-based online estimation method, the flexible states could be obtained in real time. Then, based on the estimated flexible states, a stable inversion-based controller-design method was utilized, and a robust tracking controller was designed for hypersonic flight vehicles. The proposed method provides an effective means of estimating flexible states and conducting the observer-based controller design of hypersonic flight vehicles. Finally, a numeral simulation is given to show the effectiveness of the proposed control method.
      Citation: Aerospace
      PubDate: 2022-04-10
      DOI: 10.3390/aerospace9040206
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 207: Intelligent Discrete Sliding Mode Predictive
           Fault-Tolerant Control Method for Multi-Delay Quad-Rotor UAV System Based
           on DIECOA

    • Authors: Pu Yang, Zhiqing Zhang, Huiling Geng, Bin Jiang, Xukai Hu
      First page: 207
      Abstract: This paper introduces a novel intelligent sliding mode predictive fault-tolerant control method based on the Dynamic Information Exchange Coyote Optimization Algorithm (DIECOA), which is applied to a quad-rotor UAV system with multi-delay and sensor fault. First, the system nonlinearity and sensor fault are dealt with by means of interpolation transformation and system state expansion, and an equivalent system is obtained. Second, the quasi-integral sliding mode surface is used to construct the prediction model so that the initial state of the system is located on the sliding mode surface, and the global robustness is guaranteed. Third, this paper introduces an improved fault and disturbance compensation term, which effectively weakens the adverse effect of time delays and enhances the FTC performance of the system. Fourth, the Dynamic Information Exchange (DIE) strategy is designed to further improve the coyote individual replacement mechanism and speeds up the solution and convergence speed of the method in this paper. Finally, the simulation is carried out on the fault-tolerant simulation platform of the quad-rotor Unmanned Aerial Vehicle (UAV), and the results show the rationality of the method.
      Citation: Aerospace
      PubDate: 2022-04-11
      DOI: 10.3390/aerospace9040207
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 208: Performance Analysis of Empennage
           Configurations on a Surveillance and Monitoring Mission of a VTOL-Plane
           UAV Using a Computational Fluid Dynamics Simulation

    • Authors: Gesang Nugroho, Galih Zuliardiansyah, Azhar Aulia Rasyiddin
      First page: 208
      Abstract: A Vertical Take-Off and Landing-Plane (VTOL-Plane) is an Unmanned Aerial Vehicle (UAV) that combines multirotor and fixed-wing configurations. It has a good cruise range compared to a VTOL vehicle. Furthermore, it can take-off and land vertically. This technology is ideal for surveillance/monitoring missions and transmitting data in real-time. This study discusses the design of a VTOL-Plane with a preset Design Requirement Objectives (DRO), namely a Maximum Take-Off Weight (MTOW) of 14 kg, a cruise speed of 23 m/s, and a cruising range of 6 h. To maximize the performance, the empennage configurations on the VTOL-Plane varied, and then a Computational Fluid Dynamics (CFD) simulation was carried out. The empennage configurations analyzed were a U-shaped boom, an inverted U-shaped boom, an inverted V-tail boom, and a semi-inverted V-tail boom. The interpreted performance related to the stalling angle, flight efficiency, stability, stall speed, and maneuverability. The relative wind directions toward the longitudinal axis of the UAV, also called the sideslip angle, were varied. The CFD simulation results showed that the empennage configuration of the inverted U-shaped boom is suitable for a surveillance mission. This article also optimized the final empennage design by adding a vertical fin to improve stability.
      Citation: Aerospace
      PubDate: 2022-04-11
      DOI: 10.3390/aerospace9040208
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 209: Adaptive Backstepping Nonsingular Terminal
           Sliding-Mode Attitude Control of Flexible Airships with Actuator Faults

    • Authors: Shiqian Liu, James F. Whidborne, Sipeng Song, Weizhi Lyu
      First page: 209
      Abstract: This paper studies the attitude tracking control of a flexible airship subjected to wind disturbances, actuator saturation and control surface faults. Efficient flexible airship models, including elastic deformation, rigid body motions, and their coupling, are established via Lagrange theory. A fast-nonsingular terminal sliding-mode (NTSM) combined with a backstepping control is proposed for the problem. The benefits of this approach are NTSM merits of high robustness, fast transient response, and finite time convergence, as well as the backstepping control in terms of globally asymptotic stability. However, the major limitation of the backstepping NTSM is that its design procedure is dependent on the prior knowledge of the bound values of the disturbance and faults. To overcome this limitation, a wind observer is designed to compensate for the effect of the wind disturbances, an anti-windup compensator is designed to compensate for actuator saturation, and an adaptive fault estimator is designed to estimate the faults of the control surfaces. Globally exponential stability of the closed-loop control system is guaranteed by using the Lyapunov stability theory. Finally, simulation results demonstrate effectiveness and advantages of the proposed control for the Skyship-500 flexible airship, even in the presence of unknown wind disturbances, control surface faults, and different stiffness variants.
      Citation: Aerospace
      PubDate: 2022-04-11
      DOI: 10.3390/aerospace9040209
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 210: On the Feasibility of a Launcher-Deployable
           High-Altitude Airship: Effects of Design Constraints in an Optimal Sizing
           Framework

    • Authors: Carlo E.D. Riboldi, Alberto Rolando, Gregory Regazzoni
      First page: 210
      Abstract: When ground observation or signal relaying in the vicinity of an unfriendly operative scenario are of interest, such as for military actions or disaster relief, high-altitude airships (HAA) offer some technical benefits. Featuring a milder cost and higher deployment flexibility with respect to lower-Earth orbit satellites, these platforms, often baptized as high-altitude pseudo-satellites (HAPS), operate sufficiently far from the ground to provide better imaging coverage and farther-reaching signal relaying than standard low-flying systems, such as aircraft or helicopters. Despite the atmospheric conditions in the higher atmosphere, they offer stable airstreams and highly-predictable solar energy density, thus ideally giving the chance of smooth operation for a prolonged period of time. The design of airships for the task is often conditioned by the need to go through the lower layers of the atmosphere, featuring less predictable and often unstable aerodynamics, during the climb to the target altitude. With the aim of simultaneously largely increasing the ease and quickness of platform deployment, removing most of the design constraints for the HAPS induced by the crossing of the lower atmosphere, and thus allowing for the design of a machine best suited to matching optimal performance at altitude, the deployment of the HAA by means of a missile is an interesting concept. However, since the HAA platform should take the role of a launcher payload, the feasibility of the mission is subject to a careful negotiation of specification, such that the ensuing overall weight of the airship is as low as possible. A preliminary design technique for high-altitude airships is therefore introduced initially, customized to some features typical to missile-assisted deployment, but with the potential for broader applications. The proposed procedure bends itself to the inclusion in an optimal framework, with the aim of seeking a design solution automatically. A validation of the adopted models and assumptions on existing HAPS is proposed first. The design of the airship is then carried out in a parameterized fashion, highlighting the impact of operative and technological constraints on the resulting sizing solutions. This allows for the marking of the boundaries of the space of design solutions for a launcher-deployable airship.
      Citation: Aerospace
      PubDate: 2022-04-11
      DOI: 10.3390/aerospace9040210
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 211: Simulation of Unsteady Flows of Oil/Gas in
           the Ventless Bearing Chamber of an Aero-Engine

    • Authors: Shaobai Li, Caixia Li, Wei Wang
      First page: 211
      Abstract: The unsteady motion behavior of oil/gas two-phase flow in a novel ventless bearing chamber has significant impacts on the lubrication and heat transfer efficiency of bearings due to the various advantages of lower pressure levels and weaker rotating airflow effects. In this paper, the unsteady motion behavior of oil/gas two-phase flow in a ventless aero-engine bearing chamber is investigated by three-dimensional numerical simulation through the volume of fluid (VOF) method, and the numerical method is verified using published experimental data. The flow characteristics of oil/gas two-phase in the secondary flow and three-dimensional flow are investigated. The results show the evolution of vortices and the transition of the driving mode in the unsteady motion of oil/gas two-phase flow, and a criterion for the shift of the driving mode at different rotor speeds is proposed. As the rotation speed increases, the variation trend of the velocity field and pressure field of oil/gas two-phase flow is consistent, and the accumulation region of oil becomes inconspicuous. The results indicate a reference for enhancing the performance of lubrication systems for aero-engines.
      Citation: Aerospace
      PubDate: 2022-04-12
      DOI: 10.3390/aerospace9040211
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 212: System Noise Assessment and Uncertainty
           Analysis of a Conceptual Supersonic Aircraft

    • Authors: Junichi Akatsuka, Tatsuya Ishii
      First page: 212
      Abstract: This paper describes a system noise assessment of a conceptual supersonic aircraft called the NASA 55t Supersonic Technology Concept Aeroplane (STCA), its prediction uncertainty, and related validation tests. A landing and takeoff noise (LTO) standard for supersonic aircraft is needed to realize future supersonic aircraft, and the noise impact due to the introduction of future supersonic aircraft should be analyzed to develop the standard. System noise assessments and uncertainty analyses using Monte Carlo simulation (MCS) were performed. The predicted noise levels showed good agreement with the prior study for both the benchmark case and statistics of the predictions. The predicted cumulative noise level satisfied the ICAO Chapter 4 noise standard, and its standard deviation was approximately 2 EPNdB. Moreover, sensitivity analysis using the obtained datasets revealed strong correlations with the takeoff noise for jet noise, fan exhaust noise at the flyover measurement point, and airframe trailing edge noise. Further understanding of these extracted factors, which were estimated to have a significant impact on the LTO noise, will be beneficial for the development of LTO noise standards and the design of supersonic aircraft.
      Citation: Aerospace
      PubDate: 2022-04-12
      DOI: 10.3390/aerospace9040212
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 213: Design and Performance of X-Band SAR Payload
           for 80 kg Class Flat-Panel-Type Microsatellite Based on Active Phased
           Array Antenna

    • Authors: Seok Kim, Chan-Mi Song, Seung-Hun Lee, Sung-Chan Song, Hyun-Ung Oh
      First page: 213
      Abstract: The small synthetic aperture radar (SAR) technology experimental project (S-STEP) mission aims to develop an innovative spaceborne SAR microsatellite as a constellation of 32 microsatellites featuring a high-resolution stripmap mode of 1 m. The S-STEP is a spaceborne SAR microsatellite technology demonstration program in which innovative approaches have been proposed and investigated for SAR payload system designs for improving the development speed, affordability, size and weight parameters, and quality of SAR satellite systems. In this study, the major design approach includes a bus–payload integrated flat-panel-type SAR payload based on an active phased-array antenna. This study conducted an SAR image performance analysis considering the mission requirements to validate the feasibility of the innovative SAR payload design of the S-STEP. These performance analysis results are presented to demonstrate the effectiveness of the proposed SAR payload design approach under the new space paradigm.
      Citation: Aerospace
      PubDate: 2022-04-13
      DOI: 10.3390/aerospace9040213
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 214: Combustion Characteristics of a Supersonic
           Combustor with a Large Cavity Length-to-Depth Ratio

    • Authors: Xiang Li, Qingchun Lei, Xiaocun Zhao, Wei Fan, Shuang Chen, Li Chen, Ye Tian, Quan Zhou
      First page: 214
      Abstract: The combustion characteristics of a hydrogen-fueled supersonic combustor featuring a large cavity length-to-depth ratio (i.e., 11) were examined by performing experimental trials while varying the fuel injector positions and equivalence ratios. During these trials, flame chemiluminescence images were acquired simultaneously from the side and bottom of the combustor under Mach 2.0 inflow conditions. The flame was observed to stabilize inside the cavity under all conditions. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) analyses of sequential flame chemiluminescence images demonstrated the important effects of oblique shocks induced by fuel injection and heat release on flame stabilization. Because fluctuations in the locations of the flame and of the intense heat release zone were not observed and no dominant frequency was identified in POD and DMD analyses, the present configuration was evidently able to suppress combustion instability. The present research provides preliminary guidance for exploring the feasibility of using cavity combustors with large length-to-depth ratios in scramjet engines.
      Citation: Aerospace
      PubDate: 2022-04-14
      DOI: 10.3390/aerospace9040214
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 215: Probability Analysis of Widespread Fatigue
           Damage in LY12-CZ Aluminum Alloy Single-Row Seven-Hole Plate

    • Authors: Kai Liu, Fangli Wang, Wei Pan, Le Yang, Shuwei Bai, Qiang Zhu, Mingbo Tong
      First page: 215
      Abstract: In order to determine the average behavior time of widespread fatigue damage (WFD) in an aircraft multi-site damage (MSD) structure and complete the fatigue analysis of WFD sensitive parts, this paper adopts a probabilistic method to analyze the crack initiation and crack propagation of a single row of collinear seven-hole plates. The simulation analysis of the whole process from crack initiation to structural failure is realized. First, through statistical analysis of the test data of the LY12-CZ alloy single-detail plate with hole, the probability distribution of crack initiation life and growth rate is obtained, and this probability distribution is expressed by the randomization of variables. Then, using the related theories of fracture mechanics and fatigue statistics, the whole process of initiation, propagation, and connection of multiple cracks in the MSD structure to the occurrence of WFD was realized through the Monte Carlo method. Finally, a group of single-row seven-hole plate examples are used to verify the accuracy of the calculation results. The results show that the calculated results in this paper are in good agreement with the experimental data, and can accurately predict the life of MSD structures under a certain reliability.
      Citation: Aerospace
      PubDate: 2022-04-14
      DOI: 10.3390/aerospace9040215
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 216: Preliminary Analysis of Compression System
           Integrated Heat Management Concepts Using LH2-Based Parametric Gas Turbine
           Model

    • Authors: Hamidreza Abedi, Carlos Xisto, Isak Jonsson, Tomas Grönstedt, Andrew Rolt
      First page: 216
      Abstract: The investigation of the various heat management concepts using LH2 requires the development of a modeling environment coupling the cryogenic hydrogen fuel system with turbofan performance. This paper presents a numerical framework to model hydrogen-fueled gas turbine engines with a dedicated heat-management system, complemented by an introductory analysis of the impact of using LH2 to precool and intercool in the compression system. The propulsion installations comprise Brayton cycle-based turbofans and first assessments are made on how to use the hydrogen as a heat sink integrated into the compression system. Conceptual tubular compact heat exchanger designs are explored to either precool or intercool the compression system and preheat the fuel to improve the installed performance of the propulsion cycles. The precooler and the intercooler show up to 0.3% improved specific fuel consumption for heat exchanger effectiveness in the range 0.5–0.6, but higher effectiveness designs incur disproportionately higher pressure losses that cancel-out the benefits.
      Citation: Aerospace
      PubDate: 2022-04-14
      DOI: 10.3390/aerospace9040216
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 217: Joint State and Parameter Estimation for
           Hypersonic Glide Vehicles Based on Moving Horizon Estimation via Carleman
           Linearization

    • Authors: Yudong Hu, Changsheng Gao, Wuxing Jing
      First page: 217
      Abstract: Aimed at joint state and parameter estimation problems in hypersonic glide vehicle defense, a novel moving horizon estimation algorithm via Carleman linearization is developed in this paper. First, the maneuver characteristic parameters that reflect the target maneuver law are extended into the state vector, and a dynamic tracking model applicable to various hypersonic glide vehicles is constructed. To improve the estimation accuracy, constraints such as path and parameter change amplitude constraints in flight are taken into account, and the estimation problem is transformed into a nonlinear constrained optimal estimation problem. Then, to solve the problem of high time cost for solving a nonlinear constrained optimal estimation problem, in the framework of moving horizon estimation, nonlinear constrained optimization problems are transformed into bilinear constrained optimization problems by linearizing the nonlinear system via Carleman linearization. For ensuring the consistency of the linearized system with the original nonlinear system, the linearized model is continuously updated as the window slides forward. Moreover, a CKF-based arrival cost update algorithm is also provided to improve the estimation accuracy. Simulation results demonstrate that the proposed joint state and parameter estimation algorithm greatly improves the estimation accuracy while reducing the time cost significantly.
      Citation: Aerospace
      PubDate: 2022-04-14
      DOI: 10.3390/aerospace9040217
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 218: Numerical Evaluation of Riblet Drag
           Reduction on a MALE UAV

    • Authors: Chris Bliamis, Zinon Vlahostergios, Dimitrios Misirlis, Kyros Yakinthos
      First page: 218
      Abstract: Flow control methods for aerodynamic drag reduction have been a field of interest to aircraft designers, who seek to minimize fuel consumption and increase the aircraft’s aerodynamic performance. Various flow control techniques, applied to aeronautical applications ranging from large airliners to small hand-launched unmanned aerial vehicles (UAVs), have been conceptualized, designed and tested in the past. Among others, the concept of riblets, inspired by the shark’s skin morphology, has been proposed and evaluated for airliners. In this work, the implementation of riblets on a medium-altitude long-endurance UAV (MALE) is investigated. The riblets can offer drag reduction due to the decrease in total skin friction, by altering the boundary layer characteristics in the near-wall region. The riblets are implemented on specific locations on the UAV (main wing, fuselage and empennage) and appropriately selected, on which the boundary layer becomes transitional from the laminar to the turbulent flow regime. For this reason, computational fluid dynamics modelling is performed by solving the Reynolds-averaged Navier–Stokes equations, incorporating the k-ω SST eddy viscosity turbulence model. The effect of the riblets in the near-wall region is modelled with the use of an appropriate wall boundary condition for the specific turbulence dissipation rate transport equation. It is shown that a drag reduction benefit, for both the loiter and the cruise flight segments of the UAV mission, can be obtained, and this is clearly presented by the drag polar diagrams of the air vehicle. Finally, the potential benefit to flight performance in terms of endurance and payload weight increase is also evaluated.
      Citation: Aerospace
      PubDate: 2022-04-14
      DOI: 10.3390/aerospace9040218
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 219: Assessment of Radiative Heating for
           Hypersonic Earth Reentry Using Nongray Step Models

    • Authors: Xinglian Yang, Jingying Wang, Yue Zhou, Ke Sun
      First page: 219
      Abstract: Accurate prediction of the aerothermal environment is of great significance to space exploration and return missions. The canonical Fire II trajectory points are simulated to investigate the radiative transfer in the shock layer for Earth reentry at hypervelocity above 10 km/s using a developed radiation–flowfield uncoupling method. The thermochemical nonequilibrium flow is solved by an in-house PHAROS Navier–Stokes code, while the nongray radiation is integrated by the tangent slab approximation, respectively, combined with the two-, five-, and eight-step models. For the convective heating, the present results agree well with the data of Anderson’s relation. For the radiative heating, the two-step model predicts the closest values with the results of Tauber and Sutton’s relationship, while the five- and eight-step models predict far greater. The three-step models all present the same order of magnitude of radiative heating of 1 MW/m2 and show a consistent tendency with the engineering estimation. The Planck-mean absorption coefficient is calculated to show the radiative transfer significantly occurs in the shock layer. By performing the steady simulation at each flight trajectory point, the present algorithm using a nongray step model with moderate efficiency and reasonable accuracy is promising to solve the real-time problem in engineering for predicting both convective and radiative heating to the atmospheric reentry vehicle in the future.
      Citation: Aerospace
      PubDate: 2022-04-15
      DOI: 10.3390/aerospace9040219
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 220: Bionic Design Method of a Non-Uniform
           Lattice Structure for a Landing Footpad

    • Authors: Haoyu Deng, Junpeng Zhao, Chunjie Wang
      First page: 220
      Abstract: Due to its excellent performance and high design freedom, the lattice structure has shown excellent capabilities and considerable potential in aerospace and other fields. Inspired by the bamboo structure, a lattice cell configuration namely BCC4IZ is designed and a lattice alternative layout is obtained. Then, a design and modeling method for non-uniform lattice structures is proposed. Four designs of the landing footpad with different kinds of lattice cells are developed. A series of dynamic explicit finite element simulations were conducted to evaluate and compare the energy absorption and capacity of resisting impact deformation performance of different designs. The results show that the combination of the bionic design and the lattice structure can effectively improve the performance of the lattice-filled footpad. This study proves the feasibility and potential of application for bionic design in lattice structure.
      Citation: Aerospace
      PubDate: 2022-04-15
      DOI: 10.3390/aerospace9040220
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 221: Cooperative Smooth Nonsingular Terminal
           Sliding Mode Guidance with Tracking Differentiator for Active Aircraft
           Defense

    • Authors: Quancheng Li, Yonghua Fan, Tian Yan, Xuechao Liang, Jie Yan
      First page: 221
      Abstract: Aimed at the poor performance of guidance algorithms designed based on a linearized model in active defense under large leading angle deviation, both-way and one-way cooperative sliding mode guidance algorithms based on the smooth nonsingular terminal sliding mode for the defense missile are proposed. The relative kinematics and linearized models of the target, the active defense missile, and the attacking missile are established. In the design process, two smooth nonsingular terminal sliding mode surfaces are constructed based on zero-effort miss distance and zero-effort velocity, as well as their integral values. A tracking differentiator is introduced for excessive initial command deviation to meet the overload constraints of the active missile and the target. The sensitivity of guidance law to the estimated time-to-go error is reduced, and the target is allowed to perform an independent evasive maneuver. The effectiveness of the proposed guidance strategy is verified by numerical simulation and compared to the existing guidance strategies, the high accuracy, anti-chattering, and strong robustness of the proposed guidance algorithm are verified.
      Citation: Aerospace
      PubDate: 2022-04-15
      DOI: 10.3390/aerospace9040221
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 222: High-Performance Properties of an Aerospace
           Epoxy Resin Loaded with Carbon Nanofibers and Glycidyl Polyhedral
           Oligomeric Silsesquioxane

    • Authors: Liberata Guadagno, Spiros Pantelakis, Andreas Strohmayer, Marialuigia Raimondo
      First page: 222
      Abstract: This paper proposes a new multifunctional flame retardant carbon nanofiber/glycidyl polyhedral oligomeric silsesquioxane (GPOSS) epoxy formulation specially designed for lightweight composite materials capable of fulfilling the ever-changing demands of the future aerospace industry. The multifunctional resin was designed to satisfy structural and functional requirements. In particular, this paper explores the advantages deriving from the combined use of GPOSS and CNFs (short carbon nanofibers) to obtain multifunctional resins. The multifunctional material was prepared by incorporating in the epoxy matrix heat-treated carbon nanofibers (CNFs) at the percentage of 0.5 wt% and GPOSS compound at 5 wt% in order to increase the mechanical performance, electrical conductivity, thermal stability and flame resistance property of the resulting nanocomposite. Dynamic mechanical analysis (DMA) shows that the values of the Storage Modulus (S.M.) of the resin alone and the resin containing solubilized GPOSS nanocages are almost similar in a wide range of temperatures (from 30 °C to 165 °C). The presence of CNFs, in the percentage of 0.5 wt%, determines an enhancement in the S.M. of 700 MPa from −30 °C to 180 °C with respect to the resin matrix and the resin/GPOSS systems. Hence, a value higher than 2700 MPa is detected from 30 °C to 110 °C. Furthermore, the electrical conductivity of the sample containing both GPOSS and CNFs reaches the value of 1.35 × 10−1 S/m, which is a very satisfying value to contrast the electrical insulating property of the epoxy systems. For the first time, TUNA tests have been performed on the formulation where the advantages of GPOSS and CNFs are combined. TUNA investigation highlights an electrically conductive network well distributed in the sample. The ignition time of the multifunctional nanocomposite is higher than that of the sample containing GPOSS alone of about 35%.
      Citation: Aerospace
      PubDate: 2022-04-16
      DOI: 10.3390/aerospace9040222
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 223: Automatic Balancing for Satellite Simulators
           with Mixed Mechanical and Magnetic Actuation

    • Authors: Andrea Curatolo, Anton Bahu, Dario Modenini
      First page: 223
      Abstract: Dynamic spacecraft simulators are becoming a widespread tool to enable effective on-ground verification of the attitude determination and control subsystem (ADCS). In such facilities, the on-orbit rotational dynamics shall be simulated, thereby requiring minimization of the external torques acting on the satellite mock-up. Gravity torque is often the largest among the disturbances, and an automatic procedure for balancing is usually foreseen in such facilities as it is significantly faster and more accurate than manual methods. In this note, we present an automatic balancing technique which combines mechanical and magnetic actuation by the joint use of sliding masses and magnetorquers. A feedback control is employed for in-plane balancing in which the proportional and integral actions are provided by moving the masses, while the derivative action is provided by the magnetorquers. Compared to an earlier implementation by the authors relying on shifting masses only, the novel approach is shown to reduce the in-plane unbalance by an additional 45% on average.
      Citation: Aerospace
      PubDate: 2022-04-16
      DOI: 10.3390/aerospace9040223
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 224: Feasibility Study of Electrified Light-Sport
           Aircraft Powertrains

    • Authors: Madeline McQueen, Ahmet E. Karataş, Götz Bramesfeld, Eda Demir, Osvaldo Arenas
      First page: 224
      Abstract: A theory-based aerodynamic model developed and applied to electrified powertrain configurations was intended to analyze the feasibility of implementing fully electric and serial hybrid electric propulsion in light-sport aircraft. The range was selected as the primary indicator of feasibility. A MATLAB/Simulink environment was utilized to create the models, involving the combination of proportional-integral-derivative controllers, aerodynamic properties of a reference aircraft, and powertrain limitations taken from off-the-shelf components. Simulations conducted by varying missions, batteries, fuel mass, and energy distribution methods provided results showcasing the feasibility of electrified propulsion with current technology. Results showed that the fully electric aircraft range was only 5% of a traditionally powered aircraft with current battery technology. Hybrid electric aircraft could achieve 44% of the range of a traditionally powered aircraft, but this result was found to be almost wholly related to fuel mass. Hybrid electric powertrains utilizing an energy distribution with their optimal degree of hybridization can achieve ranges up to 3% more than the same powertrain utilizing a different energy distribution. Results suggest that improvements in the power-to-weight ratio of the existing battery technology are required before electrified propulsion becomes a contender in the light-sport aircraft segment.
      Citation: Aerospace
      PubDate: 2022-04-17
      DOI: 10.3390/aerospace9040224
      Issue No: Vol. 9, No. 4 (2022)
       
  • Aerospace, Vol. 9, Pages 225: Gust Alleviation and Wind Tunnel Test by
           Using Combined Feedforward Control and Feedback Control

    • Authors: Yitao Zhou, Zhigang Wu, Chao Yang
      First page: 225
      Abstract: Gust alleviation is of great significance for improving aircraft ride quality and reducing gust load. Using aircraft response (feedback control) and gust disturbance information (feedforward control) to improve the gust alleviation effect is worthy of attention. In this paper, a combined control system (CCS) composed of feedforward control system (FFCS) and feedback control system (FBCS) is designed and analyzed. At the same time, the gust alleviation effect of the CCS, the single FFCS and the single FBCS are analyzed and compared by means of numerical simulation and wind tunnel test, respectively. Taking a flexible wing as the research object, the gust alleviation effects of three control systems under different forms of gust excitation (1-cos discrete gust, sine gust and Dryden turbulence) are analyzed by numerical simulation. In the wind tunnel test, the sine gust generated by a gust generator was used, and the gust alleviation test was carried out under different wind speeds and gust frequencies. The simulation and experimental results show that the CCS has better gust alleviation performance for various gust excitations. When comparing FFCS and FBCS, the FFCS has better robustness and control effect than the FBCS. When comparing FFCS and CCS, the better the alleviation effect of FFCS, the more difficult it is to achieve significant effect improvement by using CCS, which is obtained by adding FBCS on the FFCS.
      Citation: Aerospace
      PubDate: 2022-04-18
      DOI: 10.3390/aerospace9040225
      Issue No: Vol. 9, No. 4 (2022)
       
 
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