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Aerospace, Volume 10, Issue 10 (October 2023) – 81 articles

Cover Story (view full-size image): This research provides an insight into the flight stability of an unconventional configuration such as the box-wing. This article, starting with a discussion of the available literature on this topic, represents a broad and comprehensive conceptual study showing how the static stability of the both the longitudinal and directional box-wing configuration does not introduce critical issues in its design development. Detailed performance analysis also describes the impact that the stability and controllability constraints have on the definition of this lifting system architecture and identifies the typical aeromechanical features of a box-wing aircraft, both in high- and low-speed flight conditions. View this paper
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26 pages, 18535 KiB  
Article
Computational Investigation of the Water Droplet Effects on Shapes of Ice on Airfoils
by Andrey Kozelkov, Nikolay Galanov, Ilya Semenov, Roman Zhuchkov and Dmitry Strelets
Aerospace 2023, 10(10), 906; https://doi.org/10.3390/aerospace10100906 - 23 Oct 2023
Viewed by 998
Abstract
The paper presents the results of studying the effects of droplet diameters on the NACA0012 airfoil ice accretion, which have been obtained in the 3D numerical simulation of icing. To simulate the motion of water droplets as a multiphase medium, the Eulerian approach [...] Read more.
The paper presents the results of studying the effects of droplet diameters on the NACA0012 airfoil ice accretion, which have been obtained in the 3D numerical simulation of icing. To simulate the motion of water droplets as a multiphase medium, the Eulerian approach is used, which assumes that water droplets have spherical shapes, do not undergo deformation and breakup, do not interact with each other, and that coalescence/fragmentation of droplets does not take place. Both monodisperse (of the same size) and polydisperse (of various sizes) droplets are considered; they are represented by the spectral Langmuir distributions. These spectral distributions take into account the polydisperse nature of droplets and provide a higher efficiency in predicting ice shapes. The obtained ice shapes on an airfoil are compared with the available experimental and calculated data. It should be noted according to the simulation results that the use of the standard size of droplet diameter equal to 20 μm does not allow for obtaining correct shapes of ice on the leading edge of the wing profile not at all temperature regimes. For temperatures from −20 °C to −10 °C, there is a noticeable difference compared to the experimental data. At the same time, for this temperature range, the use of the Langmuir spectral distribution of droplet diameters relative to 15 μm provides a better agreement of the formed ice forms with the experiment. Full article
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23 pages, 12213 KiB  
Article
Modeling and Application of Out-of-Cabin and Extra-Vehicular Dynamics of Airdrop System Based on Kane Equation
by Yi Wang and Chunxin Yang
Aerospace 2023, 10(10), 905; https://doi.org/10.3390/aerospace10100905 - 23 Oct 2023
Viewed by 1030
Abstract
The application of the Kane equation in analyzing airdrop dynamics problems is rare. The main objective of this paper is to apply the Kane equation dynamics model to the analysis of the status continuity problem during the out-of-cabin process and the line sail [...] Read more.
The application of the Kane equation in analyzing airdrop dynamics problems is rare. The main objective of this paper is to apply the Kane equation dynamics model to the analysis of the status continuity problem during the out-of-cabin process and the line sail phenomenon during the extra-vehicular process. In the out-of-cabin process, an analysis of off-aircraft security and traction ratio impact was conducted. Furthermore, the BP neural network model was trained to predict the status transition of the payload for a multiple airdrop mission. In the extra-vehicular process, the spring network method was used together with the Kane equation to analyze the form and overload of the parachute line. The modeling avoids complex equations and derivations. The results suggest significant potential applications of the Kane equation in precision airdrop missions during out-of-cabin and extra-vehicular processes without heavy reliance on experimental data. Full article
(This article belongs to the Special Issue Flight Dynamics, Control & Simulation)
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60 pages, 15901 KiB  
Article
Simulating Flight Crew Workload Settings to Mitigate Fatigue Risk in Flight Operations
by Dajana Bartulović, Sanja Steiner, Dario Fakleš and Martina Mavrin Jeličić
Aerospace 2023, 10(10), 904; https://doi.org/10.3390/aerospace10100904 - 23 Oct 2023
Viewed by 1088
Abstract
In flight operations, the workload settings refer to the shift work, duty time, flight time, number of sectors, rest periods, time of day, duty patterns, number of time-zone transitions, number of consecutive duty days, and changes in the schedule. Workload factors, together with [...] Read more.
In flight operations, the workload settings refer to the shift work, duty time, flight time, number of sectors, rest periods, time of day, duty patterns, number of time-zone transitions, number of consecutive duty days, and changes in the schedule. Workload factors, together with the biological mechanisms (the circadian rhythm, homeostatic sleep pressure, sleep inertia), can lead to the appearance of fatigue. Fatigue affects numerous tasks, such as performing inaccurate flight procedures, missing radio calls, missing or being too slow to pick up system warnings, forgetting or performing routine tasks inaccurately, and others. The focus of this paper is to determine which flight crew workload settings elements impact the appearance of fatigue. The process of collecting data regarding flight crew workload settings and fatigue is conducted on a sample of four airline pilots using an electronic CRD system of standardized chronometric cognitive tests and subjective self-assessment scales. Causal modeling tools of the IBM SPSS Statistics were used to detect correlations among flight crew workload settings, indicators of the subjective perception of fatigue, and measured fatigue indicators. In the final step, a set of simulations was created using simulation tools of the IBM SPSS Statistics to show how modifications of flight crew workload settings, such as modified duty time, number of days off, and others, can impact the level of fatigue. The obtained results can help improve the future planning of flight crew workload set-up and mitigate or prevent the appearance of fatigue in flight operations. Full article
(This article belongs to the Special Issue Human Factors during Flight Operations)
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14 pages, 4324 KiB  
Article
Receptivity and Stability Theory Analysis of a Transonic Swept Wing Experiment
by Yuanqiang Liu, Yan Liu, Zubi Ji, Yutian Wang and Jiakuan Xu
Aerospace 2023, 10(10), 903; https://doi.org/10.3390/aerospace10100903 - 23 Oct 2023
Viewed by 1049
Abstract
Surface suction provides an efficient way to delay boundary layer transitions. In order to verify the suction effects and determine the mechanism of suction control in transonic swept wing boundary layers, wind tunnel transition measurements in a hybrid laminar flow control (HLFC) wind [...] Read more.
Surface suction provides an efficient way to delay boundary layer transitions. In order to verify the suction effects and determine the mechanism of suction control in transonic swept wing boundary layers, wind tunnel transition measurements in a hybrid laminar flow control (HLFC) wind tunnel model uses an infrared thermography technique in the Aircraft Research Association (ARA) 2.74 m × 2.44 m low turbulence level transonic wind tunnel. Based on the experimental data of stationary crossflow dominant transitions without and with surface suction in transonic swept wing boundary layers, in this paper, the effects on the receptivity and linear and nonlinear evolution of stationary crossflow vortices have been analyzed with the consideration of curvature. Theoretical analysis agreed with the experimental observations in regard to the transition delay caused by boundary layer suction near the leading-edge region. Full article
(This article belongs to the Special Issue Intelligent Design, Control and Perception for Unmanned Aerial System)
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17 pages, 4381 KiB  
Article
The Aerodynamic Performance of a Novel Overlapping Octocopter Considering Horizontal Wind
by Yao Lei, Jie Wang and Yazhou Li
Aerospace 2023, 10(10), 902; https://doi.org/10.3390/aerospace10100902 - 22 Oct 2023
Cited by 1 | Viewed by 1080
Abstract
This paper investigates the aerodynamic performance of an overlapping octocopter with the effect of horizontal wind ranging from 0 to 4 m/s using both low-speed wind tunnel tests and numerical simulations. The hovering efficiency and the potential control strategies of the octocopter under [...] Read more.
This paper investigates the aerodynamic performance of an overlapping octocopter with the effect of horizontal wind ranging from 0 to 4 m/s using both low-speed wind tunnel tests and numerical simulations. The hovering efficiency and the potential control strategies of the octocopter under the effect of horizontal wind are also validated using blade element momentum theory. The velocity distribution, rotor pressure and vortex of the downwash flow with the horizontal wind are presented using the Computational Fluid Dynamics (CFD) method. Finally, wind tunnel tests were performed to obtain the thrust and power consumption with the rotor speed ranging from 1500 to 2200 rpm for horizontal winds at 0 m/s, 2.5 m/s and 4 m/s. The results showed that horizontal wind decreased the flight efficiency of the planar octocopter and had little effect on the coaxial octocopter. It is also interesting to note that horizontal wind is beneficial for thrust increments at a higher rotor speed and power decrements at a lower rotor speed for the overlapping octocopter. Specifically, the horizontal wind of 2.5 m/s for a lower rpm is presented with a power decrement with proper aerodynamic interference between the rotor blades. Additionally, the overlapping octocopter obtains a higher hover efficiency at 4 m/s compared to traditional octocopters, which is more suitable for flying in a cross wind with a more compact structure. Full article
(This article belongs to the Special Issue Aerodynamic Numerical Optimization in UAV Design)
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27 pages, 1273 KiB  
Review
Bridging the Technology Gap: Strategies for Hybrid Rocket Engines
by Christopher Glaser, Jouke Hijlkema and Jérôme Anthoine
Aerospace 2023, 10(10), 901; https://doi.org/10.3390/aerospace10100901 - 22 Oct 2023
Cited by 2 | Viewed by 2906
Abstract
Hybrid rocket propulsion, first demonstrated by the Russian GIRD-09 rocket in 1933, combines liquid oxidizer and solid fuel for thrust generation. Despite numerous advantages, such as enhanced safety, controllability, and potential environmental benefits, hybrid propulsion has yet to achieve its full potential in [...] Read more.
Hybrid rocket propulsion, first demonstrated by the Russian GIRD-09 rocket in 1933, combines liquid oxidizer and solid fuel for thrust generation. Despite numerous advantages, such as enhanced safety, controllability, and potential environmental benefits, hybrid propulsion has yet to achieve its full potential in space applications. In recent years, the research on hybrid propulsion has gained enormous momentum in both academia and industry. Recent accomplishments such as the altitude record for student rockets (64 km), the launch of the first electric pump-fed hybrid rocket, and a successful 25 s hovering test highlight the potential of hybrid rockets. However, although the hybrid community is growing constantly, industrial utilizations and in-space validations do not yet exist. In this work, we reassess the possibilities of hybrid rocket engines by presenting potential fields of applications from the literature. Most importantly, we identify the technical challenges that hinder the breakthrough of hybrid propulsion in the space sector and evaluate the technologies and approaches necessary to bridge the gaps in hybrid rocket development. Full article
(This article belongs to the Special Issue Hybrid Rocket Engines)
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14 pages, 3522 KiB  
Article
An Analysis of the Vibration Characteristics of an Aviation Hydraulic Pipeline with a Clamp
by Yong Liu, Jinting Wei, Hao Du, Zhenpeng He and Fangchao Yan
Aerospace 2023, 10(10), 900; https://doi.org/10.3390/aerospace10100900 - 22 Oct 2023
Cited by 1 | Viewed by 1136
Abstract
Taking an aviation hydraulic pipeline as the research object, a fluid–solid coupling vibration model of the pipeline system, considering the influence of the clamp, is established. The clamp is equivalent to the combined form of the constraint point and the pipeline. The equivalent [...] Read more.
Taking an aviation hydraulic pipeline as the research object, a fluid–solid coupling vibration model of the pipeline system, considering the influence of the clamp, is established. The clamp is equivalent to the combined form of the constraint point and the pipeline. The equivalent stiffness of the clamp in each direction is obtained via the finite element method and substituted into the vibration model. The vibration response of the hydraulic pipeline system is obtained by changing the boundary conditions. The validity and accuracy of the vibration model were verified via the finite element method. The results show that the maximum error of the natural frequency of the pipeline system is within the acceptable range, which can prove that the model can better simulate the dynamic characteristics of the pipeline system and has a certain engineering reference value for the vibration analysis of hydraulic pipelines in aviation. Full article
(This article belongs to the Special Issue State Monitoring and Health Management of Complex Equipment)
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15 pages, 25779 KiB  
Article
Elliptical Orbit Design Based on Air-Breathing Electric Propulsion Technology in Very-Low Earth Orbit Space
by Yuxian Yue, Jinyue Geng, Guanhua Feng and Wenhao Li
Aerospace 2023, 10(10), 899; https://doi.org/10.3390/aerospace10100899 - 20 Oct 2023
Viewed by 1108
Abstract
Very-low Earth orbit (VLEO) space below 200 km is essential for high-quality communications and near-Earth space environment detection. Due to the significant atmospheric drag, orbital maintenance is required for spacecraft staying here. Based on air-breathing electric propulsion (ABEP) technology, this paper analyzed the [...] Read more.
Very-low Earth orbit (VLEO) space below 200 km is essential for high-quality communications and near-Earth space environment detection. Due to the significant atmospheric drag, orbital maintenance is required for spacecraft staying here. Based on air-breathing electric propulsion (ABEP) technology, this paper analyzed the orbital boundary conditions of the spacecraft under the constraints of parameters including slenderness ratio, thrust-to-power ratio, drag coefficient, and effective specific impulse. The energy balance is the key constraint for low VLEO orbits, which is determined by the drag coefficient, slenderness ratio, and thrust-to-power ratio. Under the existing technical conditions, the lowest circular orbit (along the terminator) is about 170 km. An elliptical orbital flight scheme is also analyzed to reach a 150 km perigee. A half-period control method was proposed based on the on–off control method for the elliptical orbit, which could enable the spacecraft to maintain a stable 150–250 km elliptical orbit. Full article
(This article belongs to the Special Issue Numerical Simulations in Electric Propulsion)
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33 pages, 2312 KiB  
Article
Lessons Learned in Transcribing 5000 h of Air Traffic Control Communications for Robust Automatic Speech Understanding
by Juan Zuluaga-Gomez, Iuliia Nigmatulina, Amrutha Prasad, Petr Motlicek, Driss Khalil, Srikanth Madikeri, Allan Tart, Igor Szoke, Vincent Lenders, Mickael Rigault and Khalid Choukri
Aerospace 2023, 10(10), 898; https://doi.org/10.3390/aerospace10100898 - 20 Oct 2023
Cited by 1 | Viewed by 2278
Abstract
Voice communication between air traffic controllers (ATCos) and pilots is critical for ensuring safe and efficient air traffic control (ATC). The handling of these voice communications requires high levels of awareness from ATCos and can be tedious and error-prone. Recent attempts aim at [...] Read more.
Voice communication between air traffic controllers (ATCos) and pilots is critical for ensuring safe and efficient air traffic control (ATC). The handling of these voice communications requires high levels of awareness from ATCos and can be tedious and error-prone. Recent attempts aim at integrating artificial intelligence (AI) into ATC communications in order to lessen ATCos’s workload. However, the development of data-driven AI systems for understanding of spoken ATC communications demands large-scale annotated datasets, which are currently lacking in the field. This paper explores the lessons learned from the ATCO2 project, which aimed to develop an unique platform to collect, preprocess, and transcribe large amounts of ATC audio data from airspace in real time. This paper reviews (i) robust automatic speech recognition (ASR), (ii) natural language processing, (iii) English language identification, and (iv) contextual ASR biasing with surveillance data. The pipeline developed during the ATCO2 project, along with the open-sourcing of its data, encourages research in the ATC field, while the full corpus can be purchased through ELDA. ATCO2 corpora is suitable for developing ASR systems when little or near to no ATC audio transcribed data are available. For instance, the proposed ASR system trained with ATCO2 reaches as low as 17.9% WER on public ATC datasets which is 6.6% absolute WER better than with “out-of-domain” but gold transcriptions. Finally, the release of 5000 h of ASR transcribed speech—covering more than 10 airports worldwide—is a step forward towards more robust automatic speech understanding systems for ATC communications. Full article
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18 pages, 8947 KiB  
Article
Numerical Study on the Aerodynamic Heating Characteristics of the Cantilevered Injection System for Oblique Detonation Engine Inlets
by Fan Yang, Mingyue Lin, Zongmin Hu and Guilai Han
Aerospace 2023, 10(10), 897; https://doi.org/10.3390/aerospace10100897 - 20 Oct 2023
Viewed by 954
Abstract
This paper investigates the flowfield patterns and distributions of surface heat flux of the cantilevered injection system for oblique detonation engine inlets. Three-dimensional complex shock wave/boundary layer interaction and shock wave/shock wave interaction between injectors are studied by solving Navier–Stokes equations under laminar [...] Read more.
This paper investigates the flowfield patterns and distributions of surface heat flux of the cantilevered injection system for oblique detonation engine inlets. Three-dimensional complex shock wave/boundary layer interaction and shock wave/shock wave interaction between injectors are studied by solving Navier–Stokes equations under laminar flow conditions. The results indicate that there are three possible positions of localized peak heat flux, i.e., the leading edge of the injector near the bottom, the inlet wall surface below the injector, and the downstream of the injector sidewall. All the regions of high heat flux are related to flow reattachment or stagnation. Three types of flow patterns are observed along the inlet surface, i.e., partial separation, completely regular separation, and completely nonregular separation, resulting in increasingly complex distributions of heat flux. The localized peak heat flux which appears at the leading edge and the sidewalls of the injectors can reach values dozens of times higher than the undisturbed region within the interaction region. Full article
(This article belongs to the Special Issue Recent Advances in Ramjets)
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14 pages, 889 KiB  
Article
Studies on the Relationship between Occupational Stress and Mental Health, Performance, and Job Satisfaction of Chinese Civil Aviation Pilots
by Yanzeng Zhao, Yanlong Wang, Wei Guo, Lin Cheng, Jialu Tong, Ruipeng Ji, Yizhi Zhou, Ziyu Liu and Lijing Wang
Aerospace 2023, 10(10), 896; https://doi.org/10.3390/aerospace10100896 - 20 Oct 2023
Viewed by 1447
Abstract
This research work delves into the potential impact of occupational stress on the mental health, performance, and job satisfaction of civil aviation pilots. To explore this triadic relationship, a battery of six distinct scales was employed, including the Chinese Civil Aviation Pilot Occupational [...] Read more.
This research work delves into the potential impact of occupational stress on the mental health, performance, and job satisfaction of civil aviation pilots. To explore this triadic relationship, a battery of six distinct scales was employed, including the Chinese Civil Aviation Pilot Occupational Stress Scale, the Symptom Check List-90 (SCL-90), the Flight Performance Scale, the Job Satisfaction Scale, the Minnesota Satisfaction Questionnaire (MSQ), and the Simplified Coping Style Questionnaire (SCSQ). A total of 131 valid questionnaires were collected for analysis, yielding a valid response rate of 65.5%. The findings demonstrate a negative correlation between occupational stress experienced by Chinese civil aviation pilots and their mental health, performance, and job satisfaction. Notably, a positive coping style was identified as a moderator in the relationship between occupational stress and flight performance, effectively mitigating the negative impact of stress on flight performance. Similarly, a negative coping style was found to moderate the relationship between occupational stress and job satisfaction, attenuating the adverse effects of occupational stress on job satisfaction. This study underscores the predictive utility of investigating the occupational stress experienced by pilots for understanding their mental health, performance, and job satisfaction. Furthermore, it highlights the potential for adjusting the negative impact of occupational stress on flight performance and job satisfaction through interventions that target pilots’ coping styles. Full article
(This article belongs to the Special Issue Human Factors during Flight Operations)
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19 pages, 7530 KiB  
Article
Energy-Harvesting Strategy Investigation for Glider Autonomous Soaring Using Reinforcement Learning
by Jiachi Zhao, Jun Li and Lifang Zeng
Aerospace 2023, 10(10), 895; https://doi.org/10.3390/aerospace10100895 - 19 Oct 2023
Viewed by 1175
Abstract
Birds and experienced glider pilots frequently use atmospheric updrafts for long-distance flight and energy conservation, with harvested energy from updrafts serving as the foundation. Inspired by their common characteristics in autonomous soaring, a reinforcement learning algorithm, the Twin Delayed Deep Deterministic policy gradient, [...] Read more.
Birds and experienced glider pilots frequently use atmospheric updrafts for long-distance flight and energy conservation, with harvested energy from updrafts serving as the foundation. Inspired by their common characteristics in autonomous soaring, a reinforcement learning algorithm, the Twin Delayed Deep Deterministic policy gradient, is used to investigate the optimal strategy for an unpowered glider to harvest energy from thermal updrafts. A round updraft model is utilized to characterize updrafts with varied strengths. A high-fidelity six-degree-of-glider model is used in the dynamic modeling of a glider. The results for various flight initial positions and updraft strengths demonstrate the effectiveness of the strategy learned via reinforcement learning. To enhance the updraft perception ability and expand the applicability of the trained glider agent, an extra wind velocity differential correction module is introduced to the algorithm, and a strategy symmetry method is applied. Comparison experiments regarding round updraft, the Gedeon thermal model, and Dryden continuous turbulence indicate the crucial role of the further optimized methods in improving the updraft-sensing ability of the reinforcement learning glider agent. With optimized methods, a glider trained in a simplified thermal updraft with a simple training method can have more effective flight strategies. Full article
(This article belongs to the Special Issue UAV Path Planning and Navigation)
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16 pages, 471 KiB  
Article
A Methodology for Assessing Capacity of the Terminal Maneuvering Area Based on Service Resource Equilibrium
by Qifeng Mou, Ze Yang and Liming Zhang
Aerospace 2023, 10(10), 894; https://doi.org/10.3390/aerospace10100894 - 19 Oct 2023
Viewed by 1058
Abstract
To effectively estimate and optimize the airport terminal maneuvering area throughput based on the equilibrium of air traffic service resource supply and demand, this research proposes an approach to assess terminal maneuvering area capacity from the perspective of air traffic service resource availability. [...] Read more.
To effectively estimate and optimize the airport terminal maneuvering area throughput based on the equilibrium of air traffic service resource supply and demand, this research proposes an approach to assess terminal maneuvering area capacity from the perspective of air traffic service resource availability. Terminal maneuvering area capacity is optimized based on the equilibrium of air traffic service resource supply and demand. The supply–demand nexus is examined in consideration of terminal maneuvering area route structure, traffic flow characteristics, and safety regulations. A flight service probability matrix and a terminal maneuvering area demand and supply service time model are constructed to quantify resource expenditure at varied capacity levels. An optimization model is then developed to allocate the airport resources effectively, fully utilizing the capacity to provide maximal outputs under resource limitations. Model computation and simulation results demonstrate the deviation between estimated and amended capacities is under 0.3 flight sorties per hour. The outcomes are congruent with historical statistics, thereby validating the accuracy and reliability of the model proposed in this study. Given capacity parameters, the model can deduce the maximal aircraft quantity served concurrently in terminal maneuvering areas during peak periods. These revelations indicate that the submitted model furnishes theoretical foundation and reference for terminal maneuvering area sector partition and traffic alerting. Full article
(This article belongs to the Special Issue Advances in Air Traffic and Airspace Control and Management)
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33 pages, 14464 KiB  
Article
An Extension Algorithm of Regional Eigenvalue Assignment Controller Design for Nonlinear Systems
by Ahmet Çağrı Arıcan, Engin Hasan Çopur, Gokhan Inalhan and Metin Uymaz Salamci
Aerospace 2023, 10(10), 893; https://doi.org/10.3390/aerospace10100893 - 19 Oct 2023
Viewed by 1169
Abstract
This paper provides a new method to nonlinear control theory, which is developed from the eigenvalue assignment method. The main purpose of this method is to locate the pointwise eigenvalues of the linear-like structure built by freezing the nonlinear systems at a given [...] Read more.
This paper provides a new method to nonlinear control theory, which is developed from the eigenvalue assignment method. The main purpose of this method is to locate the pointwise eigenvalues of the linear-like structure built by freezing the nonlinear systems at a given time instant in a desired disk region. Since the control requirements for the transient response characteristics are the major constraints on the selection of the disk centre and radius, two different update algorithms are also developed to reshape the disk region by changing the disk centre and radius at each time step. The effectiveness of the proposed methods is tested in both simulations and experiments. A validated three-DOF laboratory helicopter is used for experiments. Full article
(This article belongs to the Special Issue Flight Control)
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15 pages, 7934 KiB  
Communication
Simulations of Compression Ramp Shock Wave/Turbulent Boundary Layer Interaction Controlled via Steady Jets at High Reynolds Number
by Tingkai Dai and Bo Zhang
Aerospace 2023, 10(10), 892; https://doi.org/10.3390/aerospace10100892 - 19 Oct 2023
Viewed by 967
Abstract
Shock wave/turbulent boundary layer interaction (SBLI) is one of the most common physical phenomena in transonic wing and supersonic aircraft. In this study, the compression ramp SBLI (CR-SBLI) was simulated at a 24° corner at Mach 2.84 using the open-source OpenFOAM improved delayed [...] Read more.
Shock wave/turbulent boundary layer interaction (SBLI) is one of the most common physical phenomena in transonic wing and supersonic aircraft. In this study, the compression ramp SBLI (CR-SBLI) was simulated at a 24° corner at Mach 2.84 using the open-source OpenFOAM improved delayed detached eddy simulation (IDDES) turbulence model and the “Rescaling and Recycling” method at high Reynolds number 1.57×106. The results of the control effect of the jet vortex generator on CR-SBLI showed that the jet array can effectively reduce the length of the separation zone. The simulation results of different jet parameters are obtained. With the increasing jet angle, the reduction in the length of the separation zone first increased and then decreased. In this work, when the jet angle was 60°, the location of the separation point was x/δ=1.48, which was smaller than other jet angles. The different distances of the jet array also had a great influence. When the distance between the jet and the corner djet=70 mm, the location of the separation point x/δ=1.48 was smaller than that when djet=65/60 mm. A closer distance between the jet hole and the corner caused the vortex structures to squeeze each other, preventing the formation of a complete vortex structure. On the other hand, when the jet was farther away, the vortex structures could separate effectively before reaching the shock wave, resulting in a better inhibition of SBLI. The simulation primarily focused on exploring the effects of the jet angle and distance, and we obtained the jet parameters that provided the best control effect, effectively reducing the length of the CR-SBLI separation zone. Full article
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30 pages, 10731 KiB  
Article
Adaptive Neural Network-Based Sliding Mode Backstepping Control for Near-Space Morphing Vehicle
by Shutong Huang, Ju Jiang and Ouxun Li
Aerospace 2023, 10(10), 891; https://doi.org/10.3390/aerospace10100891 - 18 Oct 2023
Viewed by 934
Abstract
In order to obtain good flight performance in the near-space morphing vehicle (NMV) cruise phase, this paper proposes an adaptive sliding mode backstepping control scheme based on a neural network, aiming at the reduction of elevator control efficiency and issues of uncertainties. Firstly, [...] Read more.
In order to obtain good flight performance in the near-space morphing vehicle (NMV) cruise phase, this paper proposes an adaptive sliding mode backstepping control scheme based on a neural network, aiming at the reduction of elevator control efficiency and issues of uncertainties. Firstly, this paper analyzes the aerodynamic parameters of NMV in the states of winglet stretching and retracting during the cruise phase. Based on the above, the flight efficiency of NMV can be improved by retracting winglets in the level flight mode and stretching winglets in the altitude climbing mode. Secondly, an enhanced triple power reaching law (ETPRL) is proposed to ensure that the sliding mode control system can converge quickly and reduce chattering. Then, the sliding mode control based on ETPRL and backstepping control are combined to ensure the stability of the system, and adaptive control laws are developed to estimate and compensate for uncertainties. In addition, in face of the problem of reduced elevator control efficiency, the adaptive neural network is used to estimate and compensate for interference on the control channel to improve tracking accuracy and robustness of NMV. Finally, three sets of simulations verified the effectiveness of the proposed method. Full article
(This article belongs to the Section Astronautics & Space Science)
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22 pages, 9006 KiB  
Article
Fast-Responding Pressure-Sensitive Paint Measurements of the IC3X at Mach 7.2
by Valeria Delgado Elizondo, Abinayaa Dhanagopal and Christopher S. Combs
Aerospace 2023, 10(10), 890; https://doi.org/10.3390/aerospace10100890 - 18 Oct 2023
Viewed by 1004
Abstract
Global surface pressure measurements of a 5.7% scale AFRL Initial Concept 3.X vehicle (IC3X) were obtained using a fast-responding ruthenium-based pressure-sensitive paint (PSP) at the UTSA Mach 7 Ludwieg Tube Wind Tunnel at two different angles of attack, 0° and 2.5°. Static calibration [...] Read more.
Global surface pressure measurements of a 5.7% scale AFRL Initial Concept 3.X vehicle (IC3X) were obtained using a fast-responding ruthenium-based pressure-sensitive paint (PSP) at the UTSA Mach 7 Ludwieg Tube Wind Tunnel at two different angles of attack, 0° and 2.5°. Static calibration of the paint was performed over a range of 0.386 kPa to 82.7 kPa to relate luminescent intensity to pressure. Details on the facility, paint preparation, application, calibration, and image processing techniques are provided in the manuscript. The results from statistical, spectral, and proper orthogonal decomposition (POD) analyses are presented to characterize the pressure field observed on the model. The experimental results qualitatively follow the expected trends and correspond to the occurrence of shock waves and expansion fans, which were visualized via Schlieren imaging. The theoretical pressure range obtained from conical shock analysis for 0° agrees with the experimentally derived pressure range for the model, and the outliers are attributed to errors in image registration. This study presents preliminary pressure measurements that pave the way for obtaining time-resolved global PSP measurements to train and validate aerothermodynamic machine learning models. Full article
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18 pages, 8366 KiB  
Article
Medium-Energy Proton Detector Onboard the FY-4B Satellite
by Huanxin Zhang, Shenyi Zhang, Guohong Shen, Xin Zhang, Weiguo Zong, Jianguang Guo, Anqin Chen, Liguo Zhang and Ruyi Zhang
Aerospace 2023, 10(10), 889; https://doi.org/10.3390/aerospace10100889 - 18 Oct 2023
Viewed by 886
Abstract
This work introduces the instrument design of the medium-energy proton detector (MEPD, detection range: 30 keV–5 MeV) mounted on the Chinese Fengyun-4B (FY-4B) satellite. Compared to a similar detector on the Fengyun-3E (FY-3E) satellite, this instrument has undergone significant changes due to the [...] Read more.
This work introduces the instrument design of the medium-energy proton detector (MEPD, detection range: 30 keV–5 MeV) mounted on the Chinese Fengyun-4B (FY-4B) satellite. Compared to a similar detector on the Fengyun-3E (FY-3E) satellite, this instrument has undergone significant changes due to the different orbital radiation environment and solar lighting conditions. Based on the calculation of the radiation model AP8, the geometrical factor is reduced to 0.002 cm2sr, while that of the MEPD on the FY-3E satellite is 0.005 cm2sr. Another difference is that the sensors in some directions are exposed to direct sunlight for 80 min every day on this orbit, depending on the attitude angle of the satellite, which is much worse than that on the FY-3E satellite. According to the calculation results of transmittance of photons through different materials, a 100 nm thickness nickel film is added in front of the sensors to eliminate light pollution completely. The test using a solar simulator shows that the measure is effective and the detector has no error count when the solar irradiance coefficient is 1.0. In addition, the Geant4 software is applied to simulate the particle transportation process under complete machine condition to check the contamination of electrons in the sensors in all directions after magnetic deflection. The data obtained in orbit show that the instrument works properly, and the data are in good agreement with the AP8 model. The observations of the MEPD on board the FY-4B satellite can provide important support for the safety of spacecraft and theoretical research related to space weather. Full article
(This article belongs to the Special Issue Meteorological Satellites Data Analysis)
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11 pages, 3587 KiB  
Article
Closed-Loop Cavity Shear Layer Control Using Plasma Dielectric Barrier Discharge Actuators
by Pavel N. Kazanskii
Aerospace 2023, 10(10), 888; https://doi.org/10.3390/aerospace10100888 - 18 Oct 2023
Cited by 1 | Viewed by 986
Abstract
The complex unsteady flow in cavities leads to the formation of large-scale disturbances in the shear layer. Natural closed-loop mechanisms provoke a dramatic increase in pressure pulsations and aerodynamic noise. This paper presents the experimental study of pressure fluctuations in closed-loop control in [...] Read more.
The complex unsteady flow in cavities leads to the formation of large-scale disturbances in the shear layer. Natural closed-loop mechanisms provoke a dramatic increase in pressure pulsations and aerodynamic noise. This paper presents the experimental study of pressure fluctuations in closed-loop control in rectangular cavities using plasma dielectric barrier discharge. The flow velocity was 37 m/s, and the Reynolds number based on a cavity depth was approximately 120,000. The discharge ignition near the leading edge of the cavity provoked the shear layer restructuring. It was found that pressure fluctuations with an amplitude of 120 dB occur at frequencies 480 and 820 Hz. Frequency modulation of the discharge at resonant peaks was carried out by changing the phase shift of the power supply. The peak amplitude was reduced or increased by phase shifts from natural disturbances to forced ones. The optimum energy input was 50 W/m. This was three times less than the power consumption of the open-loop mode. The PIV visualization was organized in the phase-locked mode. The pressure spectrum corresponds to the magnitude of coherent structures in the shear layer of the cavity. Full article
(This article belongs to the Special Issue Plasma Actuator)
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28 pages, 3797 KiB  
Article
Earth-Venus Mission Analysis via Weak Capture and Nonlinear Orbit Control
by Giulio De Angelis, Stefano Carletta, Mauro Pontani and Paolo Teofilatto
Aerospace 2023, 10(10), 887; https://doi.org/10.3390/aerospace10100887 - 17 Oct 2023
Viewed by 1174
Abstract
Exploration of Venus is recently driven by the interest of the scientific community in understanding the evolution of Earth-size planets, and is leading the implementation of missions that can benefit from new design techniques and technology. In this work, we investigate the possibility [...] Read more.
Exploration of Venus is recently driven by the interest of the scientific community in understanding the evolution of Earth-size planets, and is leading the implementation of missions that can benefit from new design techniques and technology. In this work, we investigate the possibility to implement a microsatellite exploration mission to Venus, taking advantage of (i) weak capture, and (ii) nonlinear orbit control. This research considers the case of a microsatellite, equipped with a high-thrust and a low-thrust propulsion system, and placed in a highly elliptical Earth orbit, not specifically designed for the Earth-Venus mission of interest. In particular, to minimize the propellant mass, phase (i) of the mission was designed to inject the microsatellite into a low-energy capture around Venus, at the end of the interplanetary arc. The low-energy capture is designed in the dynamical framework of the circular restricted 3-body problem associated with the Sun-Venus system. Modeling the problem with the use of the Hamiltonian formalism, capture trajectories can be characterized based on their state while transiting in the equilibrium region about the collinear libration point L1. Low-energy capture orbits are identified that require the minimum velocity change to be established. These results are obtained using the General Mission Analysis Tool, which implements planetary ephemeris. After completing the ballistic capture, phase (ii) of the mission starts, and it is aimed at driving the microsatellite toward the operational orbit about Venus. The transfer maneuver is based on the use of low-thrust propulsion and nonlinear orbit control. Convergence toward the desired operational orbit is investigated and is proven analytically using the Lyapunov stability theory, in conjunction with the LaSalle invariance principle, under certain conditions related to the orbit perturbing accelerations and the low-thrust magnitude. The numerical results prove that the mission profile at hand, combining low-energy capture and low-thrust nonlinear orbit control, represents a viable and effective strategy for microsatellite missions to Venus. Full article
(This article belongs to the Collection Space Systems Dynamics)
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18 pages, 4767 KiB  
Article
Model Predictive Control Based Washout Algorithm Design for Flight Simulator Upset Prevention and Recovery Training
by Yu Tong, Haoyun Zhou, Zhao Wu, Qifu Li and Bei Lu
Aerospace 2023, 10(10), 886; https://doi.org/10.3390/aerospace10100886 - 16 Oct 2023
Viewed by 1076
Abstract
To migrate Loss of Control In-flight, the number one cause of aviation fatalities, pilots need to undergo upset prevention and recovery training with flight simulators. The fidelity of a moving base flight simulator is greatly dependent on the washout algorithm of the Stewart [...] Read more.
To migrate Loss of Control In-flight, the number one cause of aviation fatalities, pilots need to undergo upset prevention and recovery training with flight simulators. The fidelity of a moving base flight simulator is greatly dependent on the washout algorithm of the Stewart platform, which may reach the workspace limits when simulating the aircraft recovery from upset conditions. In this paper, a washout algorithm optimal design method based on the model predictive control technique is proposed for flight simulator upset prevention and recovery training. The parameters of the washout algorithm are calculated directly based on the platform model, and the system limits are explicitly taken into account. The human perception model is incorporated into the optimization problem, for which the objective is to minimize the pilot’s perceived motion mismatch between the real flight and the simulator training. Simulations are conducted and compared with the classical filter-based washout algorithm. Responses of the flight simulator model show that the proposed method can improve the motion cueing effect when the aircraft is in upset conditions. Full article
(This article belongs to the Section Aeronautics)
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17 pages, 3531 KiB  
Article
Efficient BEM Modeling of the Heat Transfer in the Turbine Blades of Aero-Parts
by Yue-Fang Hsiao and Yui-Chuin Shiah
Aerospace 2023, 10(10), 885; https://doi.org/10.3390/aerospace10100885 - 13 Oct 2023
Viewed by 789
Abstract
The modeling of the turbine blades in aero-parts presents difficulties in conventional domain solution techniques, especially when internal cooling air passages and a thermal barrier coating (TBC) are applied. This paper presents a very efficient 3D modeling of the anisotropic heat conduction in [...] Read more.
The modeling of the turbine blades in aero-parts presents difficulties in conventional domain solution techniques, especially when internal cooling air passages and a thermal barrier coating (TBC) are applied. This paper presents a very efficient 3D modeling of the anisotropic heat conduction in turbine blades with the boundary element method (BEM), where both the TBC and cooling air passages are considered. The BEM is very ideal for this modeling, since only boundary meshes are required for it; however, a serious problem of nearly singular integration will arise in modeling with coarse meshes. In this article, an efficient modeling and computational algorithm using the BEM is applied for the simulation of heat conduction in the turbine blades of aero-parts. The present work proposes a simplified BEM model to replace multiple thin coating layers on the top of the blade. In the end, the veracity of the implemented BEM code as well as its computational efficiency are illustrated with a few examples, showing that the settled temperature on the substrate can be reduced by 20% by employing a TBC. As compared to the analyses with ANSYS, the percentages of difference were within 2%, while the CPU time spent by the BEM algorithm was about 1/8 of that of ANSYS, not to mention the meshing efforts saved by adopting by a treatment of equivalent convection. Full article
(This article belongs to the Section Aeronautics)
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36 pages, 6949 KiB  
Article
AI-Enabled Interference Mitigation for Autonomous Aerial Vehicles in Urban 5G Networks
by Anirudh Warrier, Saba Al-Rubaye, Gokhan Inalhan and Antonios Tsourdos
Aerospace 2023, 10(10), 884; https://doi.org/10.3390/aerospace10100884 - 13 Oct 2023
Viewed by 1440
Abstract
Integrating autonomous unmanned aerial vehicles (UAVs) with fifth-generation (5G) networks presents a significant challenge due to network interference. UAVs’ high altitude and propagation conditions increase vulnerability to interference from neighbouring 5G base stations (gNBs) in the downlink direction. This paper proposes a novel [...] Read more.
Integrating autonomous unmanned aerial vehicles (UAVs) with fifth-generation (5G) networks presents a significant challenge due to network interference. UAVs’ high altitude and propagation conditions increase vulnerability to interference from neighbouring 5G base stations (gNBs) in the downlink direction. This paper proposes a novel deep reinforcement learning algorithm, powered by AI, to address interference through power control. By formulating and solving a signal-to-interference-and-noise ratio (SINR) optimization problem using the deep Q-learning (DQL) algorithm, interference is effectively mitigated, and link performance is improved. Performance comparison with existing interference mitigation schemes, such as fixed power allocation (FPA), tabular Q-learning, particle swarm optimization, and game theory demonstrates the superiority of the DQL algorithm, where it outperforms the next best method by 41.66% and converges to an optimal solution faster. It is also observed that, at higher speeds, the UAV sees only a 10.52% decrease in performance, which means the algorithm is able to perform effectively at high speeds. The proposed solution effectively integrates UAVs with 5G networks, mitigates interference, and enhances link performance, offering a significant advancement in this field. Full article
(This article belongs to the Special Issue Global Navigation Satellite System for Unmanned Aerial Vehicle)
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17 pages, 2568 KiB  
Article
Sentimental Approach to Airline Service Quality Evaluation
by Benedikt Badanik, Rebeka Remenysegova and Antonin Kazda
Aerospace 2023, 10(10), 883; https://doi.org/10.3390/aerospace10100883 - 13 Oct 2023
Cited by 1 | Viewed by 1354
Abstract
This paper focuses on the analysis of traditional methods of service quality evaluation and represents a new sentimental approach to airline service quality evaluation employing user-generated content. It identifies aspects of airline service that passengers react to positively or negatively using the word [...] Read more.
This paper focuses on the analysis of traditional methods of service quality evaluation and represents a new sentimental approach to airline service quality evaluation employing user-generated content. It identifies aspects of airline service that passengers react to positively or negatively using the word cloud method—a basic straightforward exploratory analysis tool. The aim is to introduce an approach that can be implemented using freely available analytical software tools and freely available data. As a case study, authors evaluated selected airlines’ service quality using sentimental analysis of user-generated content. The research relied on sentiment analysis of Twitter posts related to selected airlines’ service quality. The paper describes how Twitter can be used for data mining, sentimental analysis, and airline service quality evaluation. The authors analysed over 30,000 posts related to the service quality of Ryanair, Southwest Airlines, American Airlines and KLM and proposed two types of word clouds (for each individual airline) which allow more informed decisions about enhancing the service quality of selected airlines. Compared to rather expensive traditional methods of airline service quality evaluation, such as onboard surveys of airline passengers or on-site surveys of passengers at airport departure gates, the key advantages of this new approach are the availability of free data and free analytical software tools. Moreover, this approach allows analysis of the service quality of competing airlines and, thus, provides internal opportunities for comparison. The results contribute to the literature by clarifying how both positive and negative passenger feedback impacts airline service quality and airline product planning. Full article
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27 pages, 11028 KiB  
Article
A Hybrid Gate-to-Gate Simulation Environment for the Air Traffic System
by Bekir Yildiz, Peter Förster, Jonas Langner, Thomas Feuerle and Peter Hecker
Aerospace 2023, 10(10), 882; https://doi.org/10.3390/aerospace10100882 - 12 Oct 2023
Viewed by 1003
Abstract
This paper presents a concept of a fast-time gate-to-gate simulation environment. The implementation is divided into an air traffic part that uses BADA performance parameters and a simulation of ground processes. The main objective of the flow-based hybrid simulation environment is to cover [...] Read more.
This paper presents a concept of a fast-time gate-to-gate simulation environment. The implementation is divided into an air traffic part that uses BADA performance parameters and a simulation of ground processes. The main objective of the flow-based hybrid simulation environment is to cover commercial European air traffic, in order to investigate network-related effects when exposed to disturbances. Based on historic traffic scenarios, the hybrid simulation platform enables the investigation of the local and global effects of a variety of disruptions. With respect to current flow-based models, it is intended to gain better insights into the underlying interdependencies by modelling higher levels of detail for selected parts, whilst covering the whole European air traffic network. After a validation and first calibration of the approach, Monte Carlo simulations, based on flight plans, are performed as proof of concept. This aims to illustrate the local effects of network-wide disturbances and is applied by means of stochastic influences of ground processes, gained from real operational data. Full article
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16 pages, 2772 KiB  
Article
Optimal Sequencing of Arrival Flights at Metroplex Airports: A Study on Shared Waypoints Based on Path Selection and Rolling Horizon Control
by Furong Jiang and Zhaoning Zhang
Aerospace 2023, 10(10), 881; https://doi.org/10.3390/aerospace10100881 - 12 Oct 2023
Cited by 2 | Viewed by 1192
Abstract
The civil aviation industry is experiencing significant growth in air traffic density within terminal areas, necessitating improved air traffic efficiency. In China’s pursuit of world-class airport clusters, operational complexities arise due to the co-location of these airports in the same terminal area airspace, [...] Read more.
The civil aviation industry is experiencing significant growth in air traffic density within terminal areas, necessitating improved air traffic efficiency. In China’s pursuit of world-class airport clusters, operational complexities arise due to the co-location of these airports in the same terminal area airspace, resulting in lower operational efficiency. To mitigate congestion and flight delays, this study proposes an integrated model that considers multiple runways and route selections, accounting for actual route point restrictions. Utilizing actual operational data from Shanghai metroplex, the proposed model is validated. The study focuses on the airport metroplex system and presents a comprehensive mixed-integer programming (MIP) model for arrival sequencing, considering multiple airports, runways, and routes. The maximum landing efficiency is adopted as the objective function, optimizing arrival scheduling while considering time intervals, route selection, and landing constraints. The Multi-waypoint Rolling Horizon Control (MWRHC) algorithm is employed to tackle time-efficiency challenges, ensuring flight safety by continuous monitoring of flights in the terminal area. Comparative analysis reveals the algorithm’s superior optimization performance for single-runway airports compared to dual-runway airports. Overall, the proposed model and algorithm effectively improve the efficiency of multi-airport arrival scheduling in airport metroplex systems. Full article
(This article belongs to the Section Air Traffic and Transportation)
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14 pages, 4184 KiB  
Article
Deep Learning-Based Semantic Segmentation of Urban Areas Using Heterogeneous Unmanned Aerial Vehicle Datasets
by Ahram Song
Aerospace 2023, 10(10), 880; https://doi.org/10.3390/aerospace10100880 - 12 Oct 2023
Cited by 1 | Viewed by 1167
Abstract
Deep learning techniques have recently shown remarkable efficacy in the semantic segmentation of natural and remote sensing (RS) images. However, these techniques heavily rely on the size of the training data, and obtaining large RS imagery datasets is difficult (compared to RGB images), [...] Read more.
Deep learning techniques have recently shown remarkable efficacy in the semantic segmentation of natural and remote sensing (RS) images. However, these techniques heavily rely on the size of the training data, and obtaining large RS imagery datasets is difficult (compared to RGB images), primarily due to environmental factors such as atmospheric conditions and relief displacement. Unmanned aerial vehicle (UAV) imagery presents unique challenges, such as variations in object appearance due to UAV flight altitude and shadows in urban areas. This study analyzed the combined segmentation network (CSN) designed to train heterogeneous UAV datasets effectively for their segmentation performance across different data types. Results confirmed that CSN yielded high segmentation accuracy on specific classes and can be used on diverse data sources for UAV image segmentation. The main contributions of this study include analyzing the impact of CSN on segmentation accuracy, experimenting with structures with shared encoding layers to enhance segmentation accuracy, and investigating the influence of data types on segmentation accuracy. Full article
(This article belongs to the Special Issue Collaborative UAVs Intelligent Decision Optimization)
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22 pages, 7581 KiB  
Article
Numerical Study of the Effects of Injection Conditions on Rotating Detonation Engine Propulsive Performance
by Lisong Shi, E Fan, Hua Shen, Chih-Yung Wen, Shuai Shang and Hongbo Hu
Aerospace 2023, 10(10), 879; https://doi.org/10.3390/aerospace10100879 - 12 Oct 2023
Cited by 4 | Viewed by 1200
Abstract
A three-dimensional upwind conservation element and solution element method (CESE) in cylindrical coordinates is first developed to effectively solve the unsteady reactive Euler equations governing a hydrogen–air rotating detonation engine (RDE) with coaxial structures. The effects of the annular width on the structure [...] Read more.
A three-dimensional upwind conservation element and solution element method (CESE) in cylindrical coordinates is first developed to effectively solve the unsteady reactive Euler equations governing a hydrogen–air rotating detonation engine (RDE) with coaxial structures. The effects of the annular width on the structure of the detonation front and the relationship between the thrust and mass flow rate are then investigated. Additionally, RDEs with various injection conditions are systematically analyzed regarding flow patterns and propulsion performance. The results reveal a positive correlation between the specific impulse and the area ratio of the injection slot to the head-end wall. Nevertheless, the specific impulse shows minimal dependence on the injector slot’s location when the area ratio is constant. Ultimately, it is concluded that the area ratio between the injector and the head-end wall is critical in determining the loss of specific impulse. Full article
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12 pages, 3863 KiB  
Article
Study on the Combustion Characteristics of Ethanol Nanofuel
by Kwanyoung Noh, Hyemin Kim, Siwook Nam and Soonho Song
Aerospace 2023, 10(10), 878; https://doi.org/10.3390/aerospace10100878 - 11 Oct 2023
Viewed by 913
Abstract
This study investigates the thermophysical and combustion characteristics of ethanol-based nanofuels incorporating aluminum (Al) and nickel-coated aluminum (Ni-Al). The nanofuels are prepared with varying concentrations of Al and Ni-Al nanoparticles. The results reveal that, despite the non-uniform deposition of nickel on Al particles, [...] Read more.
This study investigates the thermophysical and combustion characteristics of ethanol-based nanofuels incorporating aluminum (Al) and nickel-coated aluminum (Ni-Al). The nanofuels are prepared with varying concentrations of Al and Ni-Al nanoparticles. The results reveal that, despite the non-uniform deposition of nickel on Al particles, a sintering reaction occurs between the two materials. Nanofuels containing Al exhibit unburned Al residues after combustion, while nanofuels containing Ni-Al show intense AlO radical emission during combustion termination, indicating enhanced combustion. However, nanofuels containing Ni-Al demonstrate a lower burning rate compared to Al nanofuels, attributed to the lower thermal conductivity of nickel. Overall, the findings suggest that nanofuels containing Ni-Al possess higher energy potential but extended combustion duration. Full article
(This article belongs to the Section Aeronautics)
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15 pages, 10511 KiB  
Article
SFSNet: An Inherent Feature Segmentation Method for Ground Testing of Spacecraft
by Yingxiao Li, Ping Ma and Ju Huo
Aerospace 2023, 10(10), 877; https://doi.org/10.3390/aerospace10100877 - 11 Oct 2023
Viewed by 922
Abstract
In the final approach stage of rendezvous and docking of a spacecraft, the pose parameters of the target spacecraft need to meet docking or berthing capture conditions. Visible light visual measurement systems are increasingly employed in spacecraft ground tests to extract the geometric [...] Read more.
In the final approach stage of rendezvous and docking of a spacecraft, the pose parameters of the target spacecraft need to meet docking or berthing capture conditions. Visible light visual measurement systems are increasingly employed in spacecraft ground tests to extract the geometric features of spacecraft to calculate and verify the accuracy of pose parameters. Most current feature-segmentation algorithms are unable to break through the scale transformation problem of spacecraft movement and the noise interference of multi-layer insulation materials in imaging. To overcome these challenges, we propose a novel feature segmentation algorithm based on the framework of deep convolutional neural networks. Firstly, a full convolution model of the encoding-decoding structure is constructed based on data for the ground test. A feature concatenation module is applied and combined with a network backbone to improve the segmentation performance. Then, a comprehensive loss function is presented and optimized by the pose characteristics of the spacecraft in the approach phase. Furthermore, a specific spacecraft simulation dataset to train and test our segmentation model is built through data augmentation. The experimental results verify that the proposed method achieves accurate segmentation of spacecraft of different scales, suppresses the interference caused by multilayer insulation material, and has strong robustness against motion ambiguity. The pixel accuracy of our proposed method reaches 96.5%, and the mean intersection over union is 93.0%. Full article
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