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Aerospace, Volume 11, Issue 4 (April 2024) – 83 articles

Cover Story (view full-size image): In the field of aeronautical engineering, analyzing wing-box structures is crucial for ensuring flight safety and efficiency. Addressing the complexities inherent in this domain, this research investigates the dynamic behaviour of such structures, aiming to refine existing models and enhance design methodologies. This study focuses on understanding the intricate dynamics of wing structures, particularly in relation to vibration analysis and aeroelastic effects. Acknowledging the limitations of traditional linear models, this work examines nonlinear couplings and bending–torsion effects to develop more comprehensive solutions. The research culminates in the development of two distinct models tailored to capture different facets of structural behaviour. View this paper
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23 pages, 9597 KiB  
Article
Research on the Flow Mechanism of a High-Loading Biomimetic Low-Pressure Turbine Cascade
by Hanliu Deng, Zhijun Lei, Xiaoqing Ouyang, Yuxiang He, Hang Yuan, Gang Li, Yanfeng Zhang, Xingen Lu and Gang Xu
Aerospace 2024, 11(4), 328; https://doi.org/10.3390/aerospace11040328 - 22 Apr 2024
Viewed by 602
Abstract
The biomimetic turbine has an excellent flow drag reduction ability and wide incidence adaptability, so it has the potential to achieve high efficiency within a wide working range of high-performance variable cycle engines. A biomimetic cascade that can broaden the effective working incidence [...] Read more.
The biomimetic turbine has an excellent flow drag reduction ability and wide incidence adaptability, so it has the potential to achieve high efficiency within a wide working range of high-performance variable cycle engines. A biomimetic cascade that can broaden the effective working incidence angles was designed based on a high-loading low-pressure turbine cascade, and its flow mechanism and aerodynamic performance were studied using experimental and numerical methods under the incidences angle (i) of 0° to 15° and Reynolds number of 1.0 × 105. A series of counter rotating vortex pairs induced by the biomimetic cascade bring additional dissipation losses, but it accelerates the energy exchange between the boundary layer and mainstream, enhancing the dissipation of the pressure side leg of horseshoe vortex, and thus suppressing the flow separation and passage vortices. The undulating surface of biomimetic cascades can suppress the expansion of secondary flow in a spanwise direction in the end region, especially for large-scale separation under high incidence conditions. When i < 5°, the loss of biomimetic cascades is slightly higher than that of the original cascades, but the increase is only 0.5%; when i > 5°, the losses of biomimetic cascades are significantly reduced, with a maximum reduction of 70% at i = 15°. Full article
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13 pages, 5328 KiB  
Communication
Observation of Oblique Laser-Supported Detonation Wave Propagating in Atmospheric Air
by Kohei Matsui, Kimiya Komurasaki, Keisuke Kanda and Hiroyuki Koizumi
Aerospace 2024, 11(4), 327; https://doi.org/10.3390/aerospace11040327 - 22 Apr 2024
Viewed by 577
Abstract
Elucidation of the propagation velocity of a laser-supported detonation (LSD) wave and its propagation mechanism is necessary for various engineering applications. This study was conducted to observe an oblique laser-supported detonation wave off the laser axis. The relation between the local laser intensity [...] Read more.
Elucidation of the propagation velocity of a laser-supported detonation (LSD) wave and its propagation mechanism is necessary for various engineering applications. This study was conducted to observe an oblique laser-supported detonation wave off the laser axis. The relation between the local laser intensity and detonation-wave propagation velocity was investigated. For this purpose, the time-space distribution of the laser intensity was measured precisely. The change of the LSD wavefront shape was visualized using an ultrahigh-speed camera. The relation between the local laser intensity and the propagation velocity of the oblique LSD wave measured off the laser axis was found to be identical to the relation between the local laser intensity and the detonation propagation velocity at the laser axis. Full article
(This article belongs to the Special Issue Laser Propulsion Science and Technology)
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17 pages, 4947 KiB  
Article
Research on Solving the Structural Instability of Composite Propellants by Using Non-Ablative Cladding Layers
by Gang Zhang, Mingming Zhan, Wen Feng, Youwen Tan, Yang Liu and Weihua Hui
Aerospace 2024, 11(4), 326; https://doi.org/10.3390/aerospace11040326 - 22 Apr 2024
Viewed by 540
Abstract
In a high-temperature test of the gas generator with a free-loading composite propellant, an abnormal jitter appeared in the latter part of the internal ballistic curve, whereas no such abnormality was observed in the low-temperature and normal-temperature tests. To investigate the cause, quasi-steady-state [...] Read more.
In a high-temperature test of the gas generator with a free-loading composite propellant, an abnormal jitter appeared in the latter part of the internal ballistic curve, whereas no such abnormality was observed in the low-temperature and normal-temperature tests. To investigate the cause, quasi-steady-state simulations of the internal flow field, as well as strength and buckling simulations of the grain, were conducted. The strength simulation revealed that the maximum stress experienced by the composite propellant during operation at 323 K is 0.7 MPa, which is lower than the ultimate stress of the grain (1.01 MPa), indicating no stress failure. The buckling simulation demonstrated that the instability arises from an imbalance of pressure on the inner and outer surfaces of the grain. In the original structure, the ventilation effect on each surface of the grain varied with the regression of the burning surface, leading to a pressure imbalance on the inner and outer surfaces of the composite propellant. Consequently, a non-ablative cladding layer was applied to ensure that the ventilation effect of each channel remains constant. The simulation demonstrated that the pressure on the surfaces of the composite propellant gradually balanced with the operation of the gas generator. Upon retesting at high temperatures, no abnormal jitter was observed in the internal ballistic curve. This indicates that maintaining a constant ventilation area for the combustion chamber and preventing changes in the ventilation effect can ensure the structural integrity of the composite propellant during operation. The working state of the composite propellant with this non-ablative cladding layer is not affected by variations in the design of the solid rocket motor. This approach enhances the adaptability and reliability of the free-loading composite propellant under different motor structures. Full article
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26 pages, 11482 KiB  
Article
Analysis and Design of Bat-Like Flapping-Wing Aircraft
by Fan Wang, Xinbiao Pei, Guangxin Wu and Yue Bai
Aerospace 2024, 11(4), 325; https://doi.org/10.3390/aerospace11040325 - 22 Apr 2024
Viewed by 659
Abstract
As the only flying mammal in nature, bats have superb flight skills and aerodynamic characteristics that have been the subject of research by scholars from all over the world. In recent years, the research on bionic flapping-wing aircraft has made good progress. However, [...] Read more.
As the only flying mammal in nature, bats have superb flight skills and aerodynamic characteristics that have been the subject of research by scholars from all over the world. In recent years, the research on bionic flapping-wing aircraft has made good progress. However, such research mostly uses birds or insects as the research objects, and there are few studies on bat-imitating flapping-wing aircraft. This paper combines the characteristics of bats’ flexible wings to model and analyze the aerodynamic theory and parameters of the flexible wings of bat-like flapping aircraft. The longitudinal dynamic and kinematic model design of bat-like flapping aircraft is based on the pitch angle of LQR. In terms of height control, the controller uses energy control methods to complete the closed-loop longitudinal channel control of the bat-like flapping aircraft. Finally, this study performed the simulation and flight experimentation of the designed bat-like flapping aircraft, demonstrating the correctness of this system. Full article
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23 pages, 7367 KiB  
Article
Agile Stage-Gate Approach for Design, Integration, and Testing of a 1U CubeSat
by Enrique Rafael García-Sánchez, Héctor Simón Vargas-Martínez, Filiberto Candia-García and Joel Contreras-Lima
Aerospace 2024, 11(4), 324; https://doi.org/10.3390/aerospace11040324 - 22 Apr 2024
Viewed by 614
Abstract
Life cycle stages are very important for the aerospace industry. Many models have emerged for handling the processes within and across the development of new products. Developing CubeSat-based missions has shortened the required time and has reduced expenses. However, the lack of strategic [...] Read more.
Life cycle stages are very important for the aerospace industry. Many models have emerged for handling the processes within and across the development of new products. Developing CubeSat-based missions has shortened the required time and has reduced expenses. However, the lack of strategic planning in the design, integration, and testing of product development models has been highlighted as one of the key issues contributing to failures. The objective of this study is to propose a new hybrid model for the physical development of a product using an Agile Stage-Gate methodology focused on a 1U CubeSat (AztechSat-1). This study aims to explain the full process throughout the project timeline from conceptualization to execution. The benefits of such a model include ensuring adaptive responses to not only improve technical integration but also allow the successful validation and verification of a nanosatellite. Our theoretical approach articulates an in-depth understanding of Agile Stage-Gate methodology through experience obtained from experts and team members. Our analysis supports the expected benefits of the iterative process at every stage. Through this approach, product development could benefit from reduced times and better innovations. Nevertheless, there are also drawbacks to this method. The requirements of greater human effort, more frequent demonstrations, and a constant review process have negative impacts. Additionally, particular modifications must be made for each area of research. For educational purposes, the initial results seem to be encouraging. Full article
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19 pages, 18083 KiB  
Article
A Resilient Approach to a Test Rig Setup in the Qualification of a Tilt Rotor Carbon Fiber-Reinforced Polymer (CFRP) Wing
by Pasquale Vitale, Gianluca Diodati, Salvatore Orlando, Francesco Timbrato, Mario Miano, Antonio Chiariello and Marika Belardo
Aerospace 2024, 11(4), 323; https://doi.org/10.3390/aerospace11040323 - 21 Apr 2024
Viewed by 676
Abstract
The evolution of aircraft wing development has seen significant progress since the early days of aviation, with static testing emerging as a crucial aspect for ensuring safety and reliability. This study focused specifically on the engineering phase of static testing for the Clean [...] Read more.
The evolution of aircraft wing development has seen significant progress since the early days of aviation, with static testing emerging as a crucial aspect for ensuring safety and reliability. This study focused specifically on the engineering phase of static testing for the Clean Sky 2 T-WING project, which is dedicated to testing the innovative composite wing of the Next-Generation Civil Tiltrotor Technology Demonstrator. During the design phase, critical load cases were identified through shear force/bending moment (SFBM) and failure mode analyses. To qualify the wing, an engineering team designed a dedicated test rig equipped with hydraulic jacks to mirror the SFBM diagrams. Adhering to specifications and geometric constraints due to several factors, the jacks aimed to minimize the errors (within 5%) in replicating the diagrams. An effective algorithm, spanning five phases, was employed to pinpoint the optimal configuration. This involved analyzing significant components, conducting least square linear optimizations, selecting solutions that met the directional constraints, analyzing the Pareto front solutions, and evaluating the external jack forces. The outcome was a test rig setup with a viable set of hydraulic jack forces, achieving precise SFBM replication on the wing with minimal jacks and overall applied forces. Full article
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15 pages, 4039 KiB  
Article
Sensitivity Analysis for Design Parameters of Electric Tilt-Rotor Aircraft
by Yu Wang, Wenyuan Ma and Zhaolin Chen
Aerospace 2024, 11(4), 322; https://doi.org/10.3390/aerospace11040322 - 20 Apr 2024
Viewed by 563
Abstract
In recent years, there has been rapid development in electric aircraft, particularly electric vertical takeoff and landing (eVTOL) aircraft, as part of efforts to promote green aviation. During the conceptual design stage, it is crucial to select appropriate values for key parameters and [...] Read more.
In recent years, there has been rapid development in electric aircraft, particularly electric vertical takeoff and landing (eVTOL) aircraft, as part of efforts to promote green aviation. During the conceptual design stage, it is crucial to select appropriate values for key parameters and conduct sensitivity analysis on these parameters. This study focuses on an electric tilt-rotor aircraft and proposes a performance analysis method for electric aircraft while developing a general design tool specifically for this type of aircraft. Subsequently, the impact of wing incidence angle, sweep angle, span, propeller solidity, battery-specific energy, and battery mass on range, maximum takeoff weight, and hover power are analyzed. The results show that the battery mass, wingspan, and wingtip chord length have great effects on the maximum takeoff weight; among these, battery mass had the greatest influence. In terms of range, the battery energy density has a great positive effect on range, while the increase in wing angle of incidence, wingtip chord length and battery mass have some negative effects on range. Full article
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16 pages, 4142 KiB  
Article
Seasonal Variations in Lunar-Assisted GEO Transfer Capability for Southward Launch
by Su-Jin Choi and Hoonhee Lee
Aerospace 2024, 11(4), 321; https://doi.org/10.3390/aerospace11040321 - 19 Apr 2024
Viewed by 584
Abstract
The launch azimuth of the Naro Space Center is limited toward the south of the Korean peninsula, at 170 ± 10 degrees, suitable for the polar orbit, sun-synchronous orbit, and safety range issues. In this circumstance, one option to send a satellite into [...] Read more.
The launch azimuth of the Naro Space Center is limited toward the south of the Korean peninsula, at 170 ± 10 degrees, suitable for the polar orbit, sun-synchronous orbit, and safety range issues. In this circumstance, one option to send a satellite into GEO is to perform a dog-leg maneuver during ascent, thus forming a medium-inclination orbit under such a restrictive condition. However, this option requires an immense amount of energy for the dog-leg maneuver, as well as a plane change maneuver. The only remaining option is to raise the apogee to the Moon, utilizing lunar gravity to lower the inclination to near zero and then returning to the vicinity of the Earth at an altitude of 35,786 km without maneuver. In order to design lunar-assisted GEO transfer, all feasible paths are defined, but questions remain about how seasonal variations affect all these potential paths. Therefore, this study aims to design and analyze all available trajectories for the year 2031 using a high-fidelity dynamic model, root-finding algorithm, and well-arranged initial conditions, focusing on the impact of seasonal trends. The simulation results indicate that cislunar free-return trajectories generally require less ΔV compared to circumlunar free-return trajectories, and circumlunar trajectories are minimally affected by lunisolar effects due to their relatively short return time of flight. Conversely, cislunar trajectories show seasonal variations, so spring and fall seasons require up to 20 m/s less ΔV than summer and winter seasons due to the relatively long time of return duration. Full article
(This article belongs to the Special Issue Spacecraft Orbit Transfers)
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20 pages, 3975 KiB  
Article
Wing Efficiency Enhancement at Low Reynolds Number
by Lance W. Traub
Aerospace 2024, 11(4), 320; https://doi.org/10.3390/aerospace11040320 - 19 Apr 2024
Viewed by 690
Abstract
The aerodynamic performance of wings degrades severely at low Reynolds number; lift often becomes non-linear, while drag increases significantly, caused by large extents of separation. Consequently, a non-conventional wing design approach is implemented to assess its ability to enhance performance. The design methodology [...] Read more.
The aerodynamic performance of wings degrades severely at low Reynolds number; lift often becomes non-linear, while drag increases significantly, caused by large extents of separation. Consequently, a non-conventional wing design approach is implemented to assess its ability to enhance performance. The design methodology is that of wing segmentation, where the wing is divided into spanwise panels that can be separated, thereby yielding small gaps between the panels. A moderate aspect ratio wing comprised of four separate wing panels was manufactured and wind tunnel tested through a Re range from 40,000 to 80,000. Force balance data and surface flow visualization were used to characterize performance. The results indicate that segmentation is effective in significantly augmenting efficiency at Reynolds numbers at which the fused wing (i.e., no gaps) shows large extents of open separation. Drag is greatly reduced, while lift is increased, and stall is delayed. The benefit of segmentation was noted to diminish at higher Re where the fused wing’s performance improves markedly. Wing segmentation could find application in micro-unmanned-aerial-vehicle and drone design. Further study would entail the effects of AR and the number of spanwise panels on performance. Full article
(This article belongs to the Section Aeronautics)
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25 pages, 14119 KiB  
Article
Dynamic Analysis of Three-Rotor System with Hollow Shaft under Clutch Misalignment
by Guofang Nan, Haoyu Wang and Dengliang Yu
Aerospace 2024, 11(4), 319; https://doi.org/10.3390/aerospace11040319 - 19 Apr 2024
Viewed by 678
Abstract
Rotor system of aviation engines is often made of multiple rotors connected by the clutch. Due to manufacturing and assembly errors, there is a clutch misalignment, including the parallel misalignment and the angle misalignment. This misalignment produces additional torque in the operation of [...] Read more.
Rotor system of aviation engines is often made of multiple rotors connected by the clutch. Due to manufacturing and assembly errors, there is a clutch misalignment, including the parallel misalignment and the angle misalignment. This misalignment produces additional torque in the operation of the system, leading to an abnormal increase in its oscillation, which causes the rubbing between the stator and the rotor. The rub-collision poses great harm to the safety and stability of the aero-engine. The analytical model of the rotor system with misalignment and rubbing faults is established, and the influence of the rotational speed, the misalignment, and the rubbing on the nonlinear characteristics of the rotor is investigated. Considering the nonlinear Hertz contact force and bearing gap, the model of the inter-shaft bearing is built; the parallel and angle misalignments of clutch are taken into account to analyze the characteristic frequency of the faults. For raising the thrust-to-weight ratio of aviation engines, the hollow shaft is often adopted, and the effect of the wall thickness for the shaft on the nonlinear vibration of the system is also investigated. It is innovative to study the transfer mechanism from wall thickness to the nonlinear vibrational responses of the overall structure. The result indicates that, with the increase in the wall thickness of the shaft, the second critical rotating speed increases, while the first critical rotating speed is almost unchanged. The characteristic frequencies for the three-rotor system with coupling faults are obtained. Despite intuition, the parallel misalignment can inhibit rub-collision vibration to a certain extent. The research has important reference values for the fault recognition and structural optimization of the three-rotor system. Full article
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25 pages, 18506 KiB  
Article
Long-Duration Dynamic Numerical Simulation of Combustion and Flow in Hybrid Rocket Motors Considering Nozzle Erosion
by Xiangyu Meng, Hui Tian, Xiaoting Niu, Hao Zhu, Jingfei Gao and Guobiao Cai
Aerospace 2024, 11(4), 318; https://doi.org/10.3390/aerospace11040318 - 18 Apr 2024
Viewed by 649
Abstract
Hybrid rocket motors have great development potential due to their outstanding thrust adjustment flexibility and long-term operation ability. However, nozzle erosion during the motor operation can cause an increase in the throat area of the nozzle, which leads to a decrease in combustion [...] Read more.
Hybrid rocket motors have great development potential due to their outstanding thrust adjustment flexibility and long-term operation ability. However, nozzle erosion during the motor operation can cause an increase in the throat area of the nozzle, which leads to a decrease in combustion chamber pressure and nozzle efficiency. Therefore, a performance prediction model for hybrid rocket motors considering nozzle erosion has become a key technology that must be addressed when developing hybrid rocket motors. This study uses dynamic grid technology to simulate the regression of the combustion surface and nozzle erosion, which fits well with experimental values. The behavior of high-energy particles in the combustion chamber is simulated through a discrete phase model. Notably, distinctive behavior is observed in Al and Mg droplets, with Al droplets exhibiting incomplete vaporization in the combustion chamber while Mg droplets completely vaporize. A ground firing test using the Φ336 mm hybrid rocket motor lasting 200 s is conducted. The results show that the dynamic numerical simulation, accounting for nozzle erosion, substantially enhances performance prediction accuracy. The average deviation in motor thrust remains below 1.8%, and the combustion chamber pressure deviation stays under 2.6%, confirming the precision of the model. Ultimately, both simulation and experimental outcomes indicate a gradual decrease in specific impulse and characteristic velocity over the long-term operation, attributed to the gradual deviation of the oxygen-fuel ratio. This research provides valuable insights for guiding hybrid rocket motor design and optimizing design parameters to improve overall performance. This model can achieve long-duration and high-precision performance predictions for hybrid rocket motors. Full article
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10 pages, 582 KiB  
Article
Cooling of Superconducting Motors on Aircraft
by Alan Caughley, Grant Lumsden, Hubertus Weijers, Sangkwon Jeong and Rodney A. Badcock
Aerospace 2024, 11(4), 317; https://doi.org/10.3390/aerospace11040317 - 18 Apr 2024
Viewed by 728
Abstract
Superconducting electric motors are required in order to deliver lower-carbon aviation. Critical to the success and viability of operating superconducting electric motors in aviation is keeping the superconducting coils at their operating temperature. This paper examines the challenges of keeping a superconducting motor [...] Read more.
Superconducting electric motors are required in order to deliver lower-carbon aviation. Critical to the success and viability of operating superconducting electric motors in aviation is keeping the superconducting coils at their operating temperature. This paper examines the challenges of keeping a superconducting motor cold if it were used on a single aisle passenger aircraft such as an Airbus A320. The cooling problem is defined and different cooling scenarios are investigated to determine viability. The investigation has shown that for a motor with a superconducting rotor only (copper stator), a Stirling-type cryocooler would be sufficient. However, if the motor is to be fully superconducting, then the cooling loads of the stator, which are much higher, make mechanical refrigeration impractical and the only option is to cool the motor with the heat sink of a liquid hydrogen fuel. Full article
(This article belongs to the Special Issue Electric Machines for Electrified Aircraft Propulsion)
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20 pages, 1013 KiB  
Article
Period-Multiplying Bifurcations in the Gravitational Field of Asteroids
by P. Rishi Krishna and Joel George Manathara
Aerospace 2024, 11(4), 316; https://doi.org/10.3390/aerospace11040316 - 18 Apr 2024
Viewed by 652
Abstract
Periodic orbit families around asteroids serve as potential trajectories for space probes, mining facilities, and deep space stations. Bifurcations of these families provide additional candidate orbits for efficient trajectory design around asteroids. While various bifurcations of periodic orbit families around asteroids have been [...] Read more.
Periodic orbit families around asteroids serve as potential trajectories for space probes, mining facilities, and deep space stations. Bifurcations of these families provide additional candidate orbits for efficient trajectory design around asteroids. While various bifurcations of periodic orbit families around asteroids have been extensively studied, period-multiplying bifurcations have received less attention. This paper focuses on studying period-multiplying bifurcations of periodic orbit families around asteroids. In particular, orbits with periods of approximately 7 and 17 times that of the rotational period of asteroid 216 Kleopatra were computed. The computation of high-period orbits provides insights into the numerical aspects of simulating long-duration trajectories around asteroids. The previous literature uses single-shooting and multiple-shooting methods to compute bifurcations of periodic orbit families around asteroids. Computational difficulties were encountered while using the shooting methods to obtain period-multiplying bifurcations of periodic orbit families around asteroids. This work used the Legendre–Gauss collocation method to compute period-multiplying bifurcations around asteroids. This study recommends the use of collocation methods to obtain long-duration orbits around asteroids when computational difficulties are encountered while using shooting methods. Full article
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14 pages, 7738 KiB  
Article
Aerodynamic Analysis of Deorbit Drag Sail for CubeSat Using DSMC Method
by Jiaheng Chen, Song Chen, Yuhang Qin, Zeyu Zhu and Jun Zhang
Aerospace 2024, 11(4), 315; https://doi.org/10.3390/aerospace11040315 - 18 Apr 2024
Viewed by 704
Abstract
Reducing space debris is a critical challenge in current space exploration. This study focuses on designing a drag sail for CubeSat models and examining their aerodynamic properties using the direct simulation Monte Carlo (DSMC) method. The analysis encompasses the aerodynamic performance of intricate [...] Read more.
Reducing space debris is a critical challenge in current space exploration. This study focuses on designing a drag sail for CubeSat models and examining their aerodynamic properties using the direct simulation Monte Carlo (DSMC) method. The analysis encompasses the aerodynamic performance of intricate three-dimensional shapes with varying sail dimensions at orbital altitudes of 125 km, 185 km, 300 km, and 450 km. Additionally, free molecular flow (FMF) theory is applied and compared with the DSMC findings for both a flat-plate model and the CubeSat. The results reveal that FMF accurately predicts the drag coefficient at altitudes of 185 km and above, while significant discrepancies occur at lower altitudes due to increased inter-molecular collisions. This study also suggests that the drag sail substantially enhances the CubeSat’s drag force, which effectively reduces its deorbiting time. Full article
(This article belongs to the Section Astronautics & Space Science)
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21 pages, 2618 KiB  
Article
DDPG-Based Convex Programming Algorithm for the Midcourse Guidance Trajectory of Interceptor
by Wan-Li Li, Jiong Li, Ji-Kun Ye, Lei Shao and Chi-Jun Zhou
Aerospace 2024, 11(4), 314; https://doi.org/10.3390/aerospace11040314 - 17 Apr 2024
Viewed by 698
Abstract
To address the problem of low accuracy and efficiency in trajectory planning algorithms for interceptors facing multiple constraints during the midcourse guidance phase, an improved trajectory convex programming method based on the lateral distance domain is proposed. This algorithm can achieve fast trajectory [...] Read more.
To address the problem of low accuracy and efficiency in trajectory planning algorithms for interceptors facing multiple constraints during the midcourse guidance phase, an improved trajectory convex programming method based on the lateral distance domain is proposed. This algorithm can achieve fast trajectory planning, reduce the approximation error of the planned trajectory, and improve the accuracy of trajectory guidance. First, the concept of lateral distance domain is proposed, and the motion model of the midcourse guidance segment in the interceptor is converted from the time domain to the lateral distance domain. Second, the motion model and multiple constraints are convexly and discretely transformed, and the discrete trajectory convex model is established in the lateral distance domain. Third, the deep reinforcement learning algorithm is used to learn and train the initial solution of trajectory convex programming, and a high-quality initial solution trajectory is obtained. Finally, a dynamic adjustment method based on the distribution of approximate solution errors is designed to achieve efficient dynamic adjustment of grid points in iterative solving. The simulation experiments show that the improved trajectory convex programming algorithm proposed in this paper not only improves the accuracy and efficiency of the algorithm but also has good optimization performance. Full article
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21 pages, 4615 KiB  
Article
Data-Driven 4D Trajectory Prediction Model Using Attention-TCN-GRU
by Lan Ma, Xianran Meng and Zhijun Wu
Aerospace 2024, 11(4), 313; https://doi.org/10.3390/aerospace11040313 - 17 Apr 2024
Viewed by 759
Abstract
With reference to the trajectory-based operation (TBO) requirements proposed by the International Civil Aviation Organization (ICAO), this paper concentrates on the study of four-dimensional trajectory (4D Trajectory) prediction technology in busy terminal airspace, proposing a data-driven 4D trajectory prediction model. Initially, we propose [...] Read more.
With reference to the trajectory-based operation (TBO) requirements proposed by the International Civil Aviation Organization (ICAO), this paper concentrates on the study of four-dimensional trajectory (4D Trajectory) prediction technology in busy terminal airspace, proposing a data-driven 4D trajectory prediction model. Initially, we propose a Spatial Gap Fill (Spat Fill) method to reconstruct each aircraft’s trajectory, resulting in a consistent time interval, noise-free, high-quality trajectory dataset. Subsequently, we design a hybrid neural network based on the seq2seq model, named Attention-TCN-GRU. This consists of an encoding section for extracting features from the data of historical trajectories, an attention module for obtaining the multilevel periodicity in the flight history trajectories, and a decoding section for recursively generating the predicted trajectory sequences, using the output of the coding part as the initial input. The proposed model can effectively capture long-term and short-term dependencies and repetitiveness between trajectories, enhancing the accuracy of 4D trajectory predictions. We utilize a real ADS-B trajectory dataset from the airspace of a busy terminal for validation. The experimental results indicate that the data-driven 4D trajectory prediction model introduced in this study achieves higher predictive accuracy, outperforming some of the current data-driven trajectory prediction methods. Full article
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21 pages, 7280 KiB  
Article
Determining the Location of the UAV When Flying in a Group
by Milan Džunda, Peter Dzurovčin, Sebastián Čikovský and Lucia Melníková
Aerospace 2024, 11(4), 312; https://doi.org/10.3390/aerospace11040312 - 17 Apr 2024
Viewed by 597
Abstract
This paper created a flight trajectory model of five uncrewed aerial vehicles (UAVs) in the geocentric coordinate system, provided the UAVs fly in the specified formation. Based on this model, equations for determining the position of a selected member of a group of [...] Read more.
This paper created a flight trajectory model of five uncrewed aerial vehicles (UAVs) in the geocentric coordinate system, provided the UAVs fly in the specified formation. Based on this model, equations for determining the position of a selected member of a group of UAVs were created, provided that the group communicates with each other in its telecommunications network. The simulation confirmed that if we know the exact coordinates of the four member UAVs of the group and their distances from the leader of the group, then the mean value of the error in determining its position in flight is equal to 0.044 m, and the variance is equal to 2.9 m2. We consider these errors to be methodological errors of the proposed method. Next, we checked how the error of determining the position of the group leader depends on the distance measurement errors between the individual UAVs and the group leader. The simulation confirmed that if errors in measuring the distance between individual UAVs and the group leader are from 0.01 m to 12.0 m, the mean values of group commander position determination errors range from 0.11 m to 34.6 m. The simulation result showed that to accurately determine the group commander’s position, the distance measurement errors between individual UAVs and the group commander must be less than 1.9 m. The research results showed that the telemetry method can be used to determine the position of individual members of the UAV group. The advantage of this method is that it does not require the reception of signals from satellite navigation systems, which can be interfered with under certain conditions. The disadvantage of the method is the need to synchronize the time bases of individual UAVs that communicate in the telecommunications network. Full article
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14 pages, 4873 KiB  
Article
Driving Force and Blossoming Analysis of a Composite Triangular Rollable and Collapsible (TRAC) Boom Used in Aerospace Technologies
by Sicong Wang, Shuhong Xu, Lei Lu and Lining Sun
Aerospace 2024, 11(4), 311; https://doi.org/10.3390/aerospace11040311 - 17 Apr 2024
Viewed by 546
Abstract
Deployable and foldable tape-spring booms are widely used in aerospace technologies, especially for large-scale membrane structures. Semi-circular (STEM) and lenticular (CTM) boom cross-sections were invented for specific applications since these configurations have either a concise structure or a high twisting stiffness. Moreover, a [...] Read more.
Deployable and foldable tape-spring booms are widely used in aerospace technologies, especially for large-scale membrane structures. Semi-circular (STEM) and lenticular (CTM) boom cross-sections were invented for specific applications since these configurations have either a concise structure or a high twisting stiffness. Moreover, a triangular cross-section (TRAC) boom was proposed years ago, as its more scattered configuration could afford a higher bending stiffness after deployment. Meanwhile, blossoming is one of the most serious failure modes during boom deployment, and is commonly caused by a relatively high load acting on the boom tip. For the sake of avoiding blossoming failure, the highest load a boom can withstand should be found theoretically for a better design. This paper aims at acquiring the highest tip load (i.e., driving force) a TRAC boom can withstand through establishing an analytical model. Furthermore, a numerical analysis is carried out to provide some verification, whose modeling and analysis method has been verified by a comparison with the experimental data from previous investigations. The research in this paper gives more guidance for the design of deployable TRAC tape-spring booms. Full article
(This article belongs to the Special Issue Deployable Space Structures and Mechanisms)
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14 pages, 3523 KiB  
Article
Study on the Penetration Performance of a Double-Angle Linear Shaped Charge: Performance Improvement and Miniaturization
by Jongmin Park and Sejin Kwon
Aerospace 2024, 11(4), 310; https://doi.org/10.3390/aerospace11040310 - 16 Apr 2024
Viewed by 624
Abstract
This study was conducted on a linear shaped charge with a double-angle liner. The double-angle liner has a large inner apex angle and a small outer liner angle. Experiments and numerical analysis were performed in a penetration performance study, and it was confirmed [...] Read more.
This study was conducted on a linear shaped charge with a double-angle liner. The double-angle liner has a large inner apex angle and a small outer liner angle. Experiments and numerical analysis were performed in a penetration performance study, and it was confirmed that the experimental results and numerical analysis results matched well. As a result of the numerical analysis, at the standoff distance of 1.5 CD, the penetration performance of the double-angle linear shaped charge was improved by 14.5% compared to the conventional linear shaped charge, and at the standoff distance of 2.5 CD, the penetration performance was improved by 12.5%. For miniaturization, numerical analysis was performed by reducing the height of the explosive and the standoff distance. As a result of the numerical analysis, the penetration performance of the double-angle linear shaped charge was improved by 14.6% compared to the conventional linear shaped charge. Double-angle liners are effective in improving the penetration performance of linear shaped charges. Full article
(This article belongs to the Special Issue Space Propulsion: Advances and Challenges (2nd Edition))
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21 pages, 40654 KiB  
Article
Monoethanolamine-Based Fuels Hypergolic with Rocket-Grade Hydrogen Peroxide
by Luca Caffiero, Stefania Carlotti and Filippo Maggi
Aerospace 2024, 11(4), 309; https://doi.org/10.3390/aerospace11040309 - 16 Apr 2024
Viewed by 802
Abstract
The object of this work is to study the ignition performances of promising catalytically promoted amino-based green fuels to be used in combination with rocket-grade hydrogen peroxide. The main hypergolic parameter, the ignition delay time, was experimentally determined with an automated drop test [...] Read more.
The object of this work is to study the ignition performances of promising catalytically promoted amino-based green fuels to be used in combination with rocket-grade hydrogen peroxide. The main hypergolic parameter, the ignition delay time, was experimentally determined with an automated drop test setup. Additionally, the kinematic viscosity was experimentally measured, while the CEA2 software was used to determine the ideal rocket performances of the propellants. Three inorganic copper salts were selected as catalysts to be used in combination with monoethanolamine in concentrations ranging from 0.5 wt% to 20 wt%. Then, N,N-dimethylethylenediamine was introduced as part of a blend with monoethanolamine to target the high viscosity and low gravimetric specific impulse of the fuel for the pure monoethanolamine case. Due to the reduced monoethanolamine and low additive content, some formulations were observed to be characterized by gravimetric specific impulse higher than 320 s, and kinematic viscosity lower than 5 cSt while retaining ignition delay times shorter than 30 ms with 98 wt% HTP. Finally, the addition of ethanol to the blend was preliminarily investigated to improve the additive solubility. The effects on the ignition delay time were found to depend on the concentration ratio of the two amines. Full article
(This article belongs to the Special Issue Aerospace Combustion Engineering (2nd Edition))
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15 pages, 3645 KiB  
Article
Tuning the Ballistic Performance of a Single-Burning-Rate Grain Solid Rocket Motor via New Discontinuous Embedded Metal Wires
by Qiu Wu and Quanbin Ren
Aerospace 2024, 11(4), 308; https://doi.org/10.3390/aerospace11040308 - 15 Apr 2024
Viewed by 674
Abstract
This work proposes a new effective method to realize variable thrust through discontinuous embedded metal wires in the solid rocket motor (SRM). We aimed to study the influence of discontinuous embedded metal wires on the performance of an SRM with a single-burning-rate grain. [...] Read more.
This work proposes a new effective method to realize variable thrust through discontinuous embedded metal wires in the solid rocket motor (SRM). We aimed to study the influence of discontinuous embedded metal wires on the performance of an SRM with a single-burning-rate grain. A model based on convection heat transfer, heat conduction, and heat radiation was established to calculate the heat transfer in the discontinuous embedded metal wires in the grain, to then obtain the burning rate ratio. Most importantly, a solid rocket motor was designed to verify the feasibility of variable thrust and of the present model prediction, with the embedded silver–nickel alloy wire divided into two segments in the grain. According to the SRM ignition experiment, the silver–nickel alloy wires raised the burning rate of the grain. The pressure varied regularly with changes in the discontinuous embedded metal wires. The theoretical burning rate ratio matched the experimental result well. Based on the verified model, the effects of the burning rate, pressure exponent, burning rate ratio, and number of wires on thrust were investigated. Burning rate, burning rate ratio, and pressure exponent were found to be positively correlated with thrust ratio. The thrust ratio could reach 12.5 when the burning rate ratio was 5. The ability to adjust thrust tended to increase with an increase in the number of wires. This study also provided a method to assess whether the consecutive embedded metal wires had been broken or not. The method using discontinuous embedded metal wires in the grain was proven to be feasible to realize multi-thrusts of single-burning-rate grain, which is a new idea for the design of a multi-thrust SRM. Full article
(This article belongs to the Special Issue Combustion Evaluation and Control of Solid Rocket Motors)
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26 pages, 8415 KiB  
Article
An Autonomous Tow Truck Algorithm for Engineless Aircraft Taxiing
by Stefano Zaninotto, Jason Gauci and Brian Zammit
Aerospace 2024, 11(4), 307; https://doi.org/10.3390/aerospace11040307 - 14 Apr 2024
Viewed by 790
Abstract
The aviation industry has proposed multiple solutions to reduce fuel consumption, air pollution, and noise at airports, one of which involves deploying electric trucks for aircraft towing between the stand and the runway. However, the introduction of tow trucks results in increased surface [...] Read more.
The aviation industry has proposed multiple solutions to reduce fuel consumption, air pollution, and noise at airports, one of which involves deploying electric trucks for aircraft towing between the stand and the runway. However, the introduction of tow trucks results in increased surface traffic, posing challenges from the perspective of air traffic controllers (ATCOs). Various solutions involving automated planning and execution have been proposed, but many are constrained by their inability to manage multiple active runways simultaneously, and their failure to account for the tow truck battery state of charge during assignments. This paper presents a novel system for taxi operations that employs autonomous tow trucks to enhance ground operations and address deficiencies in existing approaches. The system focuses on identifying conflict-free solutions that minimise taxi-related delays and route length while maximising the efficient use of the tow trucks. The algorithm operates at a strategic level and uses a centralised approach. It has the capacity to cater for multiple active runways and considers factors such as the tow truck battery state of charge and availability of charging stations. Furthermore, the proposed algorithm is capable of scheduling and routing tow trucks for aircraft taxiing without generating traffic conflicts. Full article
(This article belongs to the Collection Air Transportation—Operations and Management)
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15 pages, 668 KiB  
Article
Secrecy Performance of a Non-Orthogonal Multiple Access-Based Space–Air–Ground Integrated Network System with Stochastic Geometry Distribution of Terrestrial Terminals and Fog Absorption in Optical Link
by Xuhui Wang, Jinyu He, Guanjun Xu, Jiajia Chen and Yuhan Gao
Aerospace 2024, 11(4), 306; https://doi.org/10.3390/aerospace11040306 - 12 Apr 2024
Viewed by 567
Abstract
Recently, non-orthogonal multiple access (NOMA)-based space–air–ground integrated networks (SAGINs) have gained increasing attention due to their robust communication, broader coverage, and resource-saving advantages. However, it is imperative to consider physical layer security as a crucial performance metric in NOMA-based SAGINs. This study addresses [...] Read more.
Recently, non-orthogonal multiple access (NOMA)-based space–air–ground integrated networks (SAGINs) have gained increasing attention due to their robust communication, broader coverage, and resource-saving advantages. However, it is imperative to consider physical layer security as a crucial performance metric in NOMA-based SAGINs. This study addresses this concern by constructing a NOMA-based free space optical (FSO)/radio frequency (RF) dual-hop SAGIN system with eavesdroppers on both links. The two new fading channel models were proposed, considering the FSO link’s fog absorption and the RF link’s stochastic distribution based on Málaga and shadowed Rician distributions. The closed-form expressions for the secrecy outage probability are derived for the SAGIN system. Monte Carlo simulations were conducted to validate the theoretical findings. The results revealed the influence of fog absorption and the stochastic geometry distribution on the SAGIN system. Full article
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19 pages, 16327 KiB  
Article
Experimental Investigation of the Mechanical Behavior of the Strain Isolation Pad in Thermal Protection Systems under Tension
by Maoxu Lu, Zhenqiang Wu, Ziqing Hao and Liu Liu
Aerospace 2024, 11(4), 305; https://doi.org/10.3390/aerospace11040305 - 12 Apr 2024
Viewed by 617
Abstract
A strain isolation pad is a critical connection mechanism that enables deformation coordination between the rigid thermal insulation tile and the primary structure in the thermal protection system of a reusable hypersonic vehicle. An experimental investigation has been conducted to determine the static, [...] Read more.
A strain isolation pad is a critical connection mechanism that enables deformation coordination between the rigid thermal insulation tile and the primary structure in the thermal protection system of a reusable hypersonic vehicle. An experimental investigation has been conducted to determine the static, loading–unloading, and high-cycle fatigue (HCF) responses of the SIP with 0.2 mm adhesive under through-thickness tension at room temperature. The contributions of the rigid thermal insulation tile and metallic substructure have not been considered so far. The results indicate that the tensile behavior of the SIP joint is highly nonlinear. The static and fatigue tensile failures both initiate from the corner close to the adhesive/SIP interface due to the stress concentration and the edge effect. The uniform breakage of the aramid fiber can be seen on the cross-section. A novel method is proposed to quantify the residual strain due to the short-time ratcheting effect of the SIP joint in the initial loading–unloading tensile response. As the number of fatigue cycles increases, the thickness of the SIP joint continues to increase until failure. An explicit expression associated with the growth of SIP joint thickness, fatigue cycle number, and peak cyclic stress is established. The turning point of the thickness growth rate with the fatigue cycle number is proposed as a new fatigue failure index for the SIP joint under tensile fatigue, and a fatigue life prediction model is developed. Full article
(This article belongs to the Special Issue Advanced Aerospace Composite Materials and Smart Structures)
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18 pages, 6290 KiB  
Article
Collaborative Localization Method Based on Hybrid Network for Aerial Swarm
by Rong Wang, Huiyuan Zhang, Chen Gu, Zhi Xiong and Jianye Liu
Aerospace 2024, 11(4), 304; https://doi.org/10.3390/aerospace11040304 - 12 Apr 2024
Viewed by 572
Abstract
In light of the satellite rejection environment and how aircraft can obtain high-precision positioning, this paper proposes a collaborative correction algorithm for aircraft based on the rank-defect network. Aiming at the problem of insufficient anchor points, which result in insufficient observations and the [...] Read more.
In light of the satellite rejection environment and how aircraft can obtain high-precision positioning, this paper proposes a collaborative correction algorithm for aircraft based on the rank-defect network. Aiming at the problem of insufficient anchor points, which result in insufficient observations and the divergence of aircraft inertial navigation errors, this algorithm can effectively improve the navigation performance of cluster aircraft. On the basis of the observation information provided by the anchor aircraft, the observation information between aircraft is fully utilized to improve the observability of the aircraft cluster positioning method. At the same time, the pseudo-observation equation of heterogeneous aircraft cluster positioning is introduced, and the divergence of inertial navigation positioning errors caused by insufficient observations is suppressed by the pseudo-observation solution. On the basis of introducing the pseudo-observation equation, the inertial navigation error is solved and corrected by the Newton iterative method and the divergence of the inertial navigation position error is restrained. Compared with an aircraft cluster positioning method that does not use the inertial navigation error co-correction based on the pseudo-observation solution, this paper can achieve better overall cluster positioning accuracy when the available observations are insufficient, which is suitable for practical applications. Full article
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13 pages, 2662 KiB  
Review
A Mini-Review of Recent Developments in Plenoptic Background-Oriented Schlieren Technology for Flow Dynamics Measurement
by Yulan Liu, Feng Xing, Liwei Su, Huijun Tan and Depeng Wang
Aerospace 2024, 11(4), 303; https://doi.org/10.3390/aerospace11040303 - 12 Apr 2024
Viewed by 661
Abstract
To uncover the underlying fluid mechanisms, it is crucial to explore imaging techniques for high-resolution and large-scale three-dimensional (3D) measurements of the flow field. Plenoptic background-oriented schlieren (Plenoptic BOS), an emerging volumetric method in recent years, has demonstrated being able to resolve volumetric [...] Read more.
To uncover the underlying fluid mechanisms, it is crucial to explore imaging techniques for high-resolution and large-scale three-dimensional (3D) measurements of the flow field. Plenoptic background-oriented schlieren (Plenoptic BOS), an emerging volumetric method in recent years, has demonstrated being able to resolve volumetric flow dynamics with a single plenoptic camera. The focus-stack-based plenoptic BOS system can qualitatively infer the position of the density gradient in 3D space based on the relative sharpness of the refocused BOS image. Plenoptic BOS systems based on tomography or specular enhancement techniques are realized for use in high-fidelity 3D flow measurements due to the increased number of acquisition views. Here, we first review the fundamentals of plenoptic BOS, and then discuss the system configuration and typical application of single-view and multi-view plenoptic BOS. We also discuss the related challenges and outlook on the potential development of plenoptic BOS in the future. Full article
(This article belongs to the Special Issue Gust Influences on Aerospace)
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32 pages, 20655 KiB  
Article
UAV Control Based on Pattern Recognition in Aquaculture Application
by Sheng-I Chang and Jih-Gau Juang
Aerospace 2024, 11(4), 302; https://doi.org/10.3390/aerospace11040302 - 11 Apr 2024
Viewed by 877
Abstract
This study proposes a drone application for the net cage aquaculture industry. A visual control structure is applied to the drone to obtain water-quality information surrounding the net cages. This study integrates a hexacopter, camera, onboard computer, flight control board, servo motor, and [...] Read more.
This study proposes a drone application for the net cage aquaculture industry. A visual control structure is applied to the drone to obtain water-quality information surrounding the net cages. This study integrates a hexacopter, camera, onboard computer, flight control board, servo motor, and global positioning system’s auto-cruise function to adjust the drone position and control the servo motor retractable sensor to reach the desired target at an accurate location. In object identification, a deep learning neural network is used to identify the net cages. An onboard computer calculates the horizontal distance between the drone and the net cage. A “You only look once” (YOLO) neural network is used to detect the net cage images. Considering the hardware calculation speed and ability, an onboard computer is applied to process the flight control board and control the drone. In the mission, an aerial camera detects targets (net cage) and provides visual information to the drone for the target approaching control process. After executing the water-quality measurement, the drone will end the mission and return to the base. This study modifies the architecture of YOLO, compares it with the original model, and then finds a proper architecture for this mission. This study aims to assist cage aquaculture operators by using drones to measure water quality, which can reduce aquaculture’s labor costs. Full article
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20 pages, 3099 KiB  
Article
Dynamic Event-Triggered Prescribed Performance Robust Control for Aggressive Quadrotor Flight
by Zeliang Wu, Jianchuan Ye and Tao Song
Aerospace 2024, 11(4), 301; https://doi.org/10.3390/aerospace11040301 - 11 Apr 2024
Viewed by 714
Abstract
Aggressive flight has become increasingly important for expanding the applications of quadrotors. The typical characteristic of large and rapid changes in commands poses stringent demands on the maneuverability of quadrotors. Ensuring flight stability alone is not enough; dynamic responses must also be selectively [...] Read more.
Aggressive flight has become increasingly important for expanding the applications of quadrotors. The typical characteristic of large and rapid changes in commands poses stringent demands on the maneuverability of quadrotors. Ensuring flight stability alone is not enough; dynamic responses must also be selectively constrained, presenting quadcopter flight control with daunting challenges. The prescribed performance control (PPC) method is seen as having the potential to solve this problem by allowing for the constrained control of specified performance, leading to extensive research. However, its practical application still faces challenges, such as the system divergence caused by errors exceeding boundaries due to sudden command mutations. This paper presents a robust dynamic event-triggered PPC (DETPPC) method for an aggressive quadrotor flight. By assessing the direction and proximity of tracking errors approaching constraint boundaries, a dynamic event-triggered compensation mechanism for performance function boundaries is established to mitigate the divergence caused by error surpassing and to preserve preset control over the targeted metrics. Controllers were designed for both the translational and rotational subsystems of the quadrotor, and stability analysis was conducted based on Lyapunov functions. Simulation tests on agile trajectory tracking and abrupt attitude control were carried out, demonstrating the effectiveness of the proposed method. Full article
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21 pages, 4521 KiB  
Article
Artificial Intelligence Approach in Aerospace for Error Mitigation
by Jorge Bautista-Hernández and María Ángeles Martín-Prats
Aerospace 2024, 11(4), 300; https://doi.org/10.3390/aerospace11040300 - 11 Apr 2024
Viewed by 788
Abstract
Many of the reports created at assembly lines, where all components of an aircraft are installed, frequently indicate that errors threaten safety. The proposed methodology in this study evaluates error prediction and risk mitigation to prevent failures and their consequences. The results linked [...] Read more.
Many of the reports created at assembly lines, where all components of an aircraft are installed, frequently indicate that errors threaten safety. The proposed methodology in this study evaluates error prediction and risk mitigation to prevent failures and their consequences. The results linked to a typical electrical harness manufacture of a military aircraft estimated reductions of 93% in time and 90% in error during the creation of engineering manufacturing processes using AI techniques. However, traditional risk assessments methods struggle to identify and mitigate errors effectively. Thus, developing an advanced methodology to ensure systems safety is needed. This paper addresses how innovative AI technology solutions can overcome these challenges, mitigate error risks, and enhance safety in aerospace. Technologies, such as artificial intelligence, predictive algorithms, machine learning, and automation, can play a key role in enhancing safety. The aim of this study is to develop a model that considers the factors that can potentially contribute to error creation, through an artificial intelligence (AI) approach. The specific AI techniques used such as support vector machine, random forest, logistic regression, K-nearest neighbor, and XGBoost (Python 3.8.5) show good performance for use in error mitigation. We have compared the modeled values obtained in this study with the experimental ones. The results confirm that the best metrics are obtained by using support vector machine and logistic regression. The smallest deviation between the measured and modeled values for these AI methods do not exceed 5%. Furthermore, using advancements in machine learning methods can enhance error mitigation in aerospace. The use of AutoML can play a key role in automatically finding an appropriate model which provides the best performance metrics and therefore the most reliable forecast for data prediction and error mitigation. Full article
(This article belongs to the Special Issue Machine Learning for Aeronautics)
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24 pages, 18418 KiB  
Article
Investigation on Phase Transition and Collection Characteristics of Non-Spherical Ice Crystals with Eulerian and Lagrangian Methods
by Shengfang Lu, Weijian Chen, Dalin Zhang, Zihao Zhang and Guangya Zhu
Aerospace 2024, 11(4), 299; https://doi.org/10.3390/aerospace11040299 - 11 Apr 2024
Viewed by 690
Abstract
Ice crystal icing occurs in jet engine compressors, which can severely degrade jet engine performance. In this paper, two different numerical calculation methods, the Eulerian method and the Lagrangian method, were used to evaluate the dynamics, mass transfer, heat transfer, phase transition and [...] Read more.
Ice crystal icing occurs in jet engine compressors, which can severely degrade jet engine performance. In this paper, two different numerical calculation methods, the Eulerian method and the Lagrangian method, were used to evaluate the dynamics, mass transfer, heat transfer, phase transition and trajectory of ice crystals. Then, we studied the effects of initial diameter, initial sphericity, initial temperature of ice crystal, and relative humidity of airflow on the phase transition and collection characteristics of ice crystal particles. Results indicate that the non-spherical characteristics of ice crystals have a significant impact on their impingement limits and collection characteristics. The collection coefficient of unmelted ice crystals is positively correlated with the initial particle diameter and sphericity, and negatively correlated with the initial particle temperature and the relative humidity of airflow. The melting rate of ice crystal particles on the impact surface increases exponentially with the initial diameter of the particles, linearly increases with the relative humidity of the airflow and initial temperature of the particles, and exponentially decreases with the sphericity of the particles. Full article
(This article belongs to the Special Issue Deicing and Anti-Icing of Aircraft (Volume III))
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