Authors:Dmitry Roldugin, Anna Okhitina, Uliana Monakhova, Mikhail Ovchinnikov First page: 975 Abstract: In this article, five feedback magnetic attitude control algorithms are compared in terms of stabilization accuracy and implementation problems. The control strategies are classic Lyapunov control with scalar gain; the same control strategy with matrix gain and a specific gain-tuning procedure; sliding control with a variable surface; a linear quadratic regulator constructed for a special time-invariant system of a higher degree than the initial time-varying system; and a special controllable trajectory developed using particle swarm optimization. A new sliding surface construction method is proposed in this paper. Surface parameters were changed in every control iteration to ensure that the required control torque component along the geomagnetic induction vector was small. The advantages and drawbacks of the considered methods and their applicability for different target attitudes are discussed. Citation: Aerospace PubDate: 2023-11-21 DOI: 10.3390/aerospace10120975 Issue No:Vol. 10, No. 12 (2023)
Authors:Bowen Huang, Jinglei Xu, Kaikai Yu First page: 976 Abstract: Compared to conventional aircraft, hypersonic aircraft place a greater emphasis on the integration of aircraft and engines to meet their high-performance requirements. The design challenges of the nozzle are evident in the requirement of a significant area ratio between the inlet and outlet, as well as the need for the aircraft to have a compact overall size. In this study, the height constraint is directly incorporated into the maximum-thrust nozzle design method. A new method is proposed for designing nozzles under height constraints, taking into consideration the maximum thrust theory. Initially, a mathematical deduction of the condition in which the nozzle achieves the maximum thrust under the height constraint is performed. The method of characteristics is then used to develop a nozzle design that satisfies the height constraint. Subsequently, the influence of the design parameters on the design method is studied in a parametric manner. The results show that the Mach number scale and asymmetrical factors can affect the length of the nozzle’s ramp and flap, respectively. These factors greatly influence the performance of axial thrust and lift within a specific height constraint. Compared to the traditional truncation design method, the proposed method increases the thrust coefficient by 11.93% and the lift by 138.45%. Citation: Aerospace PubDate: 2023-11-21 DOI: 10.3390/aerospace10120976 Issue No:Vol. 10, No. 12 (2023)
Authors:Jixin Man, Beirao Xue, Xiangde Bian, Wengao Yan, Da Qiao, Wu Zeng First page: 977 Abstract: Friction dampers are widely employed to reduce blade resonance vibration amplitude in turbomachinery. In this paper, a study was performed on the forced response of two blades with dual friction dampers. Numerical simulation and experimental testing were conducted. Firstly, the dynamics of the blade and dual friction damper system assembly are modeled. A nonlinear code based on the multi-harmonic balance method was developed to calculate the resonance response. In this analysis, both the blade and the damper are modeled with the finite element and the matrices reduced with the component mode synthesis method, while the contact forces are modeled with a one-dimensional variable normal load array element. Secondly, a test rig made of two blades and dual friction dampers, the material of which was steel, was established to measure the nonlinear frequency response function curves of the blade system. The results indicate that when a dual friction damper is applied, superior vibration reduction characteristics are demonstrated, with the system exhibiting an average 21% reduction in the response amplitude levels and an increase of 3% in the frequency shifting range compared to a single damper. Dampers positioned at relatively higher locations contribute significantly to the vibration reduction process. In the end, the numerical predictions match very well with the experimental ones. Citation: Aerospace PubDate: 2023-11-22 DOI: 10.3390/aerospace10120977 Issue No:Vol. 10, No. 12 (2023)
Authors:Nanxing Shi, Yunsong Gu, Tingting Wu, Yuhang Zhou, Yi Wang, Shuai Deng First page: 978 Abstract: This research developed a pressure-based thrust vectoring angle estimation method for fluidic thrust vectoring nozzles. This method can accurately estimate the real-time in-flight thrust vectoring angle using only wall pressure information on the inner surface of the nozzle. We proposed an algorithm to calculate the thrust vectoring angle from the wall pressure inside the nozzle. Non-dominated sorting genetic algorithm II was applied to find the optimal sensor arrays and reduce the wall pressure sensor quantity. Synchronous force and wall pressure measurement experiments were carried out to verify the accuracy and real-time response of the pressure-based thrust vectoring angle estimation method. The results showed that accurate estimation of the thrust vectoring angle can be achieved with a minimum of three pressure sensors. The pressure-based thrust vectoring angle estimation method proposed in this study has a good prospect for engineering applications; it is capable of accurate real-time in-flight monitoring of the thrust vectoring angle. This method is important and indispensable for the closed-loop feedback control and aircraft attitude control of fluidic thrust vectoring control technology. Citation: Aerospace PubDate: 2023-11-22 DOI: 10.3390/aerospace10120978 Issue No:Vol. 10, No. 12 (2023)
Authors:Seok-Hwan Oh, Tae-Seong Roh, Hyoung Jin Lee First page: 979 Abstract: This study was focused on the configuration design of a star grain by using machine learning in the optimal design process. The key to optimizing the grain design is aimed at obtaining a set of configuration variables that satisfy the requirements. The optimization problem consists of an objective area profile subject to certain constraints and an objective function that quantitatively calculates the design level. Designers must formulate suitable optimization problems to achieve an optimal design. However, because a method to alleviate the influence of the sliver section is not yet available, the optimization problem is typically solved based on experience, which is time- and effort-intensive. Consequently, a more practical and objective grain design method must be developed. In this study, an optimal design method using machine learning was developed to increase the convenience and success rate. A support vector machine was used to train a classification model that predicts a class. The classification model was used to alleviate the influence of the sliver zone and correct the search problem to ensure that an optimal solution existed in the region satisfying the requirements. The proposed method was validated through star grain optimal design using the genetic algorithm. The optimization was performed considering the area profiles, and the effectiveness of the proposed method was demonstrated by the enhanced accuracy. Citation: Aerospace PubDate: 2023-11-22 DOI: 10.3390/aerospace10120979 Issue No:Vol. 10, No. 12 (2023)
Authors:Shao Xuan Seah, Sutthiphong Srigrarom First page: 980 Abstract: This paper explores the use of deep reinforcement learning in solving the multi-agent aircraft traffic planning (individual paths) and collision avoidance problem for a multiple UAS, such as that for a cargo drone network. Specifically, the Deep Q-Network (DQN) with Hindsight Experience Replay framework is adopted and trained on a three-dimensional state space that represents a congested urban environment with dynamic obstacles. Through formalising a Markov decision process (MDP), various flight and control parameters are varied between training simulations to study their effects on agent performance. Both fully observable MDPs (FOMDPs) and partially observable MDPs (POMDPs) are formulated to understand the role of shaping reward signals on training performance. While conventional traffic planning and optimisation techniques are evaluated based on path length or time, this paper aims to incorporate economic analysis by considering tangible and intangible sources of cost, such as the cost of energy, the value of time (VOT) and the value of reliability (VOR). By comparing outcomes from an integration of multiple cost sources, this paper is better able to gauge the impact of various parameters on efficiency. To further explore the feasibility of multiple UAS traffic planning, such as cargo drone networks, the trained agents are also subjected to multi-agent point-to-point and hub-and-spoke network environments. In these simulations, delivery orders are generated using a discrete event simulator with an arrival rate, which is varied to investigate the effect of travel demand on economic costs. Simulation results point to the importance of signal engineering, as reward signals play a crucial role in shaping reinforcements. The results also reflect an increase in costs for environments where congestion and arrival time uncertainty arise because of the presence of other agents in the network. Citation: Aerospace PubDate: 2023-11-22 DOI: 10.3390/aerospace10120980 Issue No:Vol. 10, No. 12 (2023)
Authors:Liqi Zhang, Yonghui Zhao First page: 981 Abstract: Based on measured gust information, a multi-input multi-output (MIMO) adaptive feed-forward control scheme for gust load alleviation (GLA) on a semi-span flying-wing aircraft using multiple control surfaces is proposed. In order to remedy weight drift and biased estimation problems that are commonly encountered in adaptive control, the circular leaky LMS (CLLMS) algorithm is employed, which utilizes gust measurement information, filtered reference signals, and error signals to update controller parameters online. The results demonstrate that good load reductions are achieved in both continuous and discrete gust environments. For instance, the designed GLA control system leads to an 80.72% reduction in the root-mean-square (RMS) values of wing-root bending moment in the Dryden gust environment and a 77.59% reduction of its maximum value in the 1-cos discrete gust condition. Based on the limited power of the actuator and the limited authority for control surface deflections when integrating GLA into the flight control system, a weight-updating algorithm with deflection angle and rate constraints on control surfaces is proposed. The simulation results show that the strict constraints on control surface deflections will degrade the GLA performance. Finally, the influence of the partial jamming fault of actuators on GLA performance is studied. It is found that good GLA performance can be preserved despite the degraded performance during the initial stage of the actuator jamming fault. This is due to the robustness brought about by multiple control surfaces and the adaptability of the control algorithm. Citation: Aerospace PubDate: 2023-11-22 DOI: 10.3390/aerospace10120981 Issue No:Vol. 10, No. 12 (2023)
Authors:Zhiqian Zhang, Lei Liu, Lin Quan, Guohong Shen, Rui Zhang, Yuqi Jiang, Yuxiong Xue, Xianghua Zeng First page: 982 Abstract: Accurately predicting proton flux in the space radiation environment is crucial for satellite in-orbit management and space science research. This paper proposes a proton flux prediction method based on a hybrid neural network. This method is a predictive approach for measuring proton flux profiles via a satellite during its operation, including crossings through the SAA region. In the data preprocessing stage, a moving average wavelet transform was employed to retain the trend information of the original data and perform noise reduction. For the model design, the TPA-LSTM model was introduced, which combines the Temporal Pattern Attention mechanism with a Long Short-Term Memory network (LSTM). The model was trained and validated using 4,174,202 proton flux data points over a span of 12 months. The experimental results indicate that the prediction accuracy of the TPA-LSTM model is higher than that of the AP-8 model, with a logarithmic root mean square error (logRMSE) of 3.71 between predicted and actual values. In particular, an improved accuracy was observed when predicting values within the South Atlantic Anomaly (SAA) region, with a logRMSE of 3.09. Citation: Aerospace PubDate: 2023-11-22 DOI: 10.3390/aerospace10120982 Issue No:Vol. 10, No. 12 (2023)
Authors:Wooseok Jeong, Seungeon Jang, Hong-Jip Kim First page: 983 Abstract: Since a heat exchanger used in a gas generator of an open-cycle liquid rocket engine was operated in a high-temperature environment, the coupled analysis for heat transfer characteristics and structural integrity should be performed simultaneously. For these reasons, a numerical analysis of the heat exchanger in a liquid rocket engine was performed to elucidate the effects of heat transfer and structural deformation simultaneously using conjugate heat transfer (CHT) analysis and open-source tools. For the baseline heat exchanger, which had an inner helically coiled tube with nine turns (Nc=9), the heat transfer characteristics were investigated and findings showed that the heat transfer performance was reduced from the sixth turn. Further analysis was performed to examine the effect of the number of turns in terms of heat flux and the corresponding pressure drop and the weight of the structure. The results indicated that the heat exchanger with Nc=3 had a significantly reduced outlet temperature due to an excessively shortened flow residence time. The heat exchanger with Nc=6 showed an outlet temperature similar to that of the baseline; it also presented advantages in terms of the pressure drop and structure weight. In addition, the thermal deformation and stress caused by temperature changes were numerically investigated to consider the structural integrity of the heat exchanger with Nc=3,6,9. Further numerical analyses were performed at various flow rates. As the flow rate of helium increased, the amount of heat received from the high-temperature exhaust gas from the gas generator increased but the outlet temperature of helium decreased gradually. Finally, the temperature difference between the outer and inner walls increased due to the high heat flux in the region around the inlet, resulting in an increase in thermal stress. Based on these results, the optimal shape and flow rate of the system were identified. Furthermore, the heat transfer performance was found to correlate with the flow characteristics of the coiled tube. Citation: Aerospace PubDate: 2023-11-22 DOI: 10.3390/aerospace10120983 Issue No:Vol. 10, No. 12 (2023)
Authors:Jorge Bautista-Hernández, María Ángeles Martín-Prats First page: 984 Abstract: Cybersecurity plays a relevant role in the new digital age within the aerospace industry. Predictive algorithms are necessary to interconnect complex systems within the cyberspace. In this context, where security protocols do not apply, challenges to maintain data privacy and security arise for the organizations. Thus, the need for cybersecurity is required. The four main categories to classify threats are interruption, fabrication, modification, and interception. They all share a common thing, which is to soften the three pillars that cybersecurity needs to guarantee. These pillars are confidentiality, availability, and integrity of data (CIA). Data injection can contribute to this event by the creation of false indicators, which can lead to error creation during the manufacturing engineering processes. In this paper, the impact of data injection on the existing dataset used in manufacturing processes is described. The design model synchronizes the following mechanisms developed within machine learning techniques, which are the risk matrix indicator to assess the probability of producing an error, the dendrogram to cluster the dataset in groups with similarities, the logistic regression to predict the potential outcomes, and the confusion matrix to analyze the performance of the algorithm. The results presented in this study, which were carried out using a real dataset related to the electrical harnesses installed in a C295 military aircraft, estimate that injection of false data indicators increases the probability of creating an error by 24.22% based on the predicted outcomes required for the generation of the manufacturing processes. Overall, implementing cybersecurity measures and advanced methodologies to detect and prevent cyberattacks is necessary. Citation: Aerospace PubDate: 2023-11-23 DOI: 10.3390/aerospace10120984 Issue No:Vol. 10, No. 12 (2023)
Authors:Daniel F. Ryan, Sophie Musset, Hamish A. S. Reid, Säm Krucker, Andrea F. Battaglia, Eric Bréelle, Claude Chapron, Hannah Collier, Joel Dahlin, Carsten Denker, Ewan Dickson, Peter T. Gallagher, Iain Hannah, Natasha L. S. Jeffrey, Jana Kašparová, Eduard Kontar, Philippe Laurent, Shane A. Maloney, Paolo Massa, Anna Maria Massone, Tomasz Mrozek, Damien Pailot, Melody Pallu, Melissa Pesce-Rollins, Michele Piana, Illya Plotnikov, Alexis Rouillard, Albert Y. Shih, David Smith, Marek Steslicki, Muriel Z. Stiefel, Alexander Warmuth, Meetu Verma, Astrid Veronig, Nicole Vilmer, Christian Vocks, Anna Volpara First page: 985 Abstract: Models of particle acceleration in solar eruptive events suggest that roughly equal energy may go into accelerating electrons and ions. However, while previous solar X-ray spectroscopic imagers have transformed our understanding of electron acceleration, only one resolved image of γ-ray emission from solar accelerated ions has ever been produced. This paper outlines a new satellite instrument concept—the large imaging spectrometer for solar accelerated nuclei (LISSAN)—with the capability not only to observe hundreds of events over its lifetime, but also to capture multiple images per event, thereby imaging the dynamics of solar accelerated ions for the first time. LISSAN provides spectroscopic imaging at photon energies of 40 keV–100 MeV on timescales of ≲10 s with greater sensitivity and imaging capability than its predecessors. This is achieved by deploying high-resolution scintillator detectors and indirect Fourier imaging techniques. LISSAN is suitable for inclusion in a multi-instrument platform such as an ESA M-class mission or as a smaller standalone mission. Without the observations that LISSAN can provide, our understanding of solar particle acceleration, and hence the space weather events with which it is often associated, cannot be complete. Citation: Aerospace PubDate: 2023-11-23 DOI: 10.3390/aerospace10120985 Issue No:Vol. 10, No. 12 (2023)
Authors:Ruifan Hu, Yongliang Chen, Jifei Wu, Shuling Tian First page: 986 Abstract: At cryogenic temperatures, gases exhibit significant deviations from ideal behaviour, and the commonly employed gas model may inadequately represent the thermodynamic properties of cryogenic gases, subsequently impacting numerical simulations using various thermodynamic and transport models at cryogenic temperatures. The findings of this study reveal that the relative errors in aerodynamic characteristics obtained through different isentropic relations are noteworthy, with the maximum relative error in the drag coefficient reaching 16%. The impact of the equation of state, viscosity model, and thermal conductivity model is relatively minor, with relative errors in the pressure drag coefficient and viscous drag coefficient remaining well below 1%. Nevertheless, the relative error in the skin friction coefficient cannot be ignored due to transonic shock wave/boundary layer interactions. Consequently, when conducting numerical simulations of cryogenic flow, it is imperative to select appropriate gas models to attain precise results. Citation: Aerospace PubDate: 2023-11-23 DOI: 10.3390/aerospace10120986 Issue No:Vol. 10, No. 12 (2023)
Authors:David Orozco Suárez, Jose Carlos del Toro Iniesta, Francisco Javier Bailén Martínez, María Balaguer Jiménez, Daniel Álvarez García, Daniel Serrano, Luis F. Peñin, Alicia Vázquez-Ramos, Luis Ramón Bellot Rubio, Julia Atienzar, Isabel Pérez Grande, Ignacio Torralbo Gimeno, Esteban Sanchis Kilders, José Luis Gasent Blesa, David Hernández Expósito, Basilio Ruiz Cobo, Javier Trujillo Bueno, Robertus Erdélyi, Jackie A. Davies, Lucie M. Green, Sarah A. Matthews, David M. Long, Michail Mathioudakis, Christian Kintziger, Jorrit Leenaarts, Silvano Fineschi, Eamon Scullion First page: 987 Abstract: Measuring magnetic fields in the inner corona, the interface between the solar chromosphere and outer corona, is of paramount importance if we aim to understand the energetic transformations taking place there, and because it is at the origin of processes that lead to coronal heating, solar wind acceleration, and of most of the phenomena relevant to space weather. However, these measurements are more difficult than mere imaging because polarimetry requires differential photometry. The coronal magnetograph mission (CMAG) has been designed to map the vector magnetic field, line-of-sight velocities, and plane-of-the-sky velocities of the inner corona with unprecedented spatial and temporal resolutions from space. This will be achieved through full vector spectropolarimetric observations using a coronal magnetograph as the sole instrument on board a spacecraft, combined with an external occulter installed on another spacecraft. The two spacecraft will maintain a formation flight distance of 430 m for coronagraphic observations, which requires a 2.5 m occulter disk radius. The mission will be preferentially located at the Lagrangian L5 point, offering a significant advantage for solar physics and space weather research. Existing ground-based instruments face limitations such as atmospheric turbulence, solar scattered light, and long integration times when performing coronal magnetic field measurements. CMAG overcomes these limitations by performing spectropolarimetric measurements from space with an external occulter and high-image stability maintained over time. It achieves the necessary sensitivity and offers a spatial resolution of 2.5″ and a temporal resolution of approximately one minute, in its nominal mode, covering the range from 1.02 solar radii to 2.5 radii. CMAG relies on proven European technologies and can be adapted to enhance any other solar mission, offering potential significant advancements in coronal physics and space weather modeling and monitoring. Citation: Aerospace PubDate: 2023-11-23 DOI: 10.3390/aerospace10120987 Issue No:Vol. 10, No. 12 (2023)
Authors:Igor O. Shamshin, Vladislav S. Ivanov, Viktor S. Aksenov, Pavel A. Gusev, Konstantin A. Avdeev, Sergey M. Frolov First page: 988 Abstract: Rotating detonation engines (RDEs) are considered to be promising thrusters for aerospace propulsion. Detonation initiation in RDEs can be accompanied by a destructive explosion of an excess volume of the fuel mixture in the combustor. To exclude this phenomenon, a “mild” rather than “strong” initiation of detonation is required. For the mild initiation of detonation in RDEs, it is necessary to ignite a mixture of a certain minimum volume sufficient for deflagration-to-detonation transition (DDT). In this study, the critical conditions for detonation initiation through DDT in a semiconfined slit combustor simulating the RDE combustor with a separate supply of ethylene and oxygen diluted with nitrogen (from 0 to 40%) were obtained experimentally. It turned out that for the mild initiation of detonation, it is necessary to ignite the mixture upon reaching the critical (minimum) height of the combustible mixture layer. Thus, for the mild initiation of detonation in the undiluted C2H4 + 3O2 mixture filling such a slit combustor, the height of the mixture layer must exceed the slit width by approximately a factor of 12. In terms of the transverse size of the detonation cell λ the minimum layer height of such mixtures in experiments is ~150λ. Compared to the experiments with the premixed composition, the critical height of the layer is 20% larger, which is explained by the finite rate of mixing. As the degree of oxygen dilution with nitrogen increases, the critical height of the layer increases, and the role of finite rate mixing decreases: the results no longer depend on the method of combustible mixture formation. Citation: Aerospace PubDate: 2023-11-23 DOI: 10.3390/aerospace10120988 Issue No:Vol. 10, No. 12 (2023)
Authors:Lei Liu, Guozhan Li, Ban Wang, Shaofeng Wu First page: 989 Abstract: This study presents a numerical investigation of suction control in an aggressive S-shaped air intake with large boundary ingestion. The results show that the variation of suction control parameters such as suction location, suction pipe diameter, and suction angle all have an impact on the effectiveness of the flow control. In general, further upstream suction, such as near the throat, is favorable for the decrease of the second flow intensity and the area of the low-energy fluid region at the exit of the S-shaped inlet. However, it is bad for the total pressure recovery and the circumferential total pressure uniform distribution. From the perspective of the uniformity of the total pressure distribution at the air intake exit, there is an optimal location for suction between the throat and the separation start point. A bigger suction pipe diameter brings better effects as the suction location and suction angle keep constant, due to more low-energy fluid being sucked out. But this doesn’t mean the largest mass flow suction results in the biggest improvement. Overall, sucking at the 1st bend, with suction angle and suction pipe diameter equaling 15 degrees and 12 mm, respectively, is the optimal suction scheme here. Since the change rule of the cross-section area along the centerline has not changed during suction control, the second flow and complex surface streamline at the air intake exit cannot be eliminated, though they can be decreased a lot with reasonable suction control. Similarly, owing to large boundary ingestion, the remarkable low-energy fluid region always exists despite the significant reduction of the separation and second flow, which is very different from the results of this kind of micro-suction executed in the non-BLI S-duct. To pursue a higher improvement, suction combined with vortex generator vanes has been further studied. Corresponding results analysis shows that the hybrid flow control method has great potential and should be investigated in detail in the future. Citation: Aerospace PubDate: 2023-11-24 DOI: 10.3390/aerospace10120989 Issue No:Vol. 10, No. 12 (2023)
Authors:Haohao Wang, Limin Gao, Baohai Wu First page: 990 Abstract: Many probability-based uncertainty quantification (UQ) schemes require a large amount of sampled data to build credible probability density function (PDF) models for uncertain parameters. Unfortunately, the amounts of data collected as to compressor blades of aero-engines are mostly limited due to the expensive and time-consuming tests. In this paper, we develop a preconditioner-based data-driven polynomial chaos (PDDPC) method that can efficiently deal with uncertainty propagation of limited amounts of sampled data. The calculation accuracy of a PDDPC method is closely related to the sample size of collected data. Therefore, the influence of sample size on this PDDPC method is investigated using a nonlinear test function. Subsequently, we consider the real manufacturing errors in stagger angles for compressor blades. Under three different operating conditions, the PDDPC method is applied to investigate the effect of stagger-angle error on UQ results of multiple aerodynamic parameters of a two-dimensional compressor blade. The results show that as the sample-size of measured data increases, UQ results regarding aerodynamic performance obtained by the PDDPC method gradually converge. There exists a critical sample size that ensures accurate UQ analysis of compressor blades. The probability information contained in the machining error data is analyzed through Kullback–Leibler divergence, and the critical sample size is determined. The research results can serve as a valuable reference for the fast and cheap UQ analysis of compressor blades in practical engineering. Citation: Aerospace PubDate: 2023-11-25 DOI: 10.3390/aerospace10120990 Issue No:Vol. 10, No. 12 (2023)
Authors:Tao Zhang, Xinyu Song, Xingping Kai, Yeguang He, Rundong Li First page: 991 Abstract: In order to understand the breakup characteristics of a transverse liquid jet flow in an actual combustion chamber, a numerical study was conducted using the Volume of Fluid (VOF) method combined with grid adaptation technology. The study focused on the primary breakup characteristics of liquid jets under the conditions of a steady and oscillating air crossflow. The simulated mediums were set to water and air. The research findings revealed that fluctuations in the incoming gas velocity can influence the development speed of surface waves and the mode of jet breakup during the initial stage of jet development as compared to the steady condition. In both conditions, the surface waves were initially observed to appear within 1/4 T–2/4 T. The surface wave of the jet develops faster under steady conditions because the average velocity of the steady flow is higher than that of the oscillation flow during this stage. As a result, the fragmentation of the jet is primarily influenced by the surface wave. Under an oscillating flow, the rear of the jet begins to break up earlier due to the slower development of surface waves. The velocity of the oscillating air inflow increases over time, and the speed of surface wave development also increases, gradually leading to the dominance of surface-wave-induced jet breakup. In the second stage of air inflow oscillation, an “up and down slapping” phenomenon occurs at the tail of the jet. Additionally, increasing the air inflow velocity leads to a longer jet breakup length and a higher number of droplets near the jet column. Surface waves are observed on both the windward and leeward sides of the jet. The penetration depth of the jet fluctuates with changes in the crossflow velocity, and the response of the jet penetration depth to the velocity fluctuations in the transverse air is delayed by half a period. Citation: Aerospace PubDate: 2023-11-25 DOI: 10.3390/aerospace10120991 Issue No:Vol. 10, No. 12 (2023)
Authors:Weijun Wang, Yuxin Cui, Chenkun Qi, Yanyan Cao, Yuhua Zhang, Chongfeng Zhang, Shigang Wang First page: 992 Abstract: In this paper, a pawl composite linkage transfer mechanism is designed for the automatic in-orbit sample transfer mission of Chang’E-5 lunar sample return mission, which can realize the sample container in-orbit transfer under various critical constraints such as lightweight, miniaturization, and narrow working space. Resistance during the whole process as well as the sensitive factors that affect the resistance during the sample container transfer process are investigated and designed. The sample container transfer process has been verified by the test system on the ground, indicating that the design can satisfy the requirements of the sample transfer mission. The developed transfer mechanism completed the Chang’E-5 sample return mission successfully with good consistency between space and ground, verifying the correctness and effectiveness of the design. Citation: Aerospace PubDate: 2023-11-25 DOI: 10.3390/aerospace10120992 Issue No:Vol. 10, No. 12 (2023)
Authors:Alice De Oliveira, Michèle Lavagna First page: 993 Abstract: This paper introduces a Reusable Launch Vehicle (RLV) descent dynamics simulator coupled with closed-loop guidance and control (G&C) integration. The studied vehicle’s first-stage booster, evolving in the terrestrial atmosphere, is steered by a Thrust Vector Control (TVC) system and planar fins through gain-scheduled Proportional–Integral–Derivative controllers, correcting the trajectory deviations until precise landing from the reference profile computed in real time by a successive convex optimisation algorithm. Environmental and aerodynamic models that reproduce realistic atmospheric conditions are integrated into the simulator for enhanced assessment. Comparative performance results were achieved in terms of control configuration (TVC-only, fins-only, and both) for nominal conditions as well as with external disturbances such as wind gusts or multiple uncertainties through a Monte Carlo analysis to assess the G&C system. These studies demonstrated that the configuration combining TVC and steerable planar fins has sufficient control authority to provide stable flight and adequate uncertainties and disturbance rejection. The developed simulator provides a preliminary assessment of G&C techniques for the RLV descent and landing phase, along with examining the interactions that occur. In particular, it paves the way towards the development and assessment of more advanced and robust algorithms. Citation: Aerospace PubDate: 2023-11-26 DOI: 10.3390/aerospace10120993 Issue No:Vol. 10, No. 12 (2023)
Authors:Zhifei Xi, Yingxin Kou, You Li, Zhanwu Li, Yue Lv First page: 994 Abstract: Air combat situation assessment is the basis of target assignment and maneuver decisions. The current air combat situation assessment models, whether nonparametric or parametric, ignore the continuity and timing of situation changes, making the situation assessment results lose tactical significance. Aimed at the shortcomings of current air combat situation assessment, a dynamic air combat situation assessment model based on situation knowledge extraction and weight optimization was proposed by combining a multiple regression model of hidden logic process, a weight optimization model based on grey prospect theory, a weight mapping model based on autoencoder and extreme learning machine (AE-ELM) and an air combat situation characteristic parameter prediction model based on dynamic weight online extreme learning machine (DWOSELM). Firstly, considering the timing and continuity of air combat situation change, a hidden logic process multiple regression model was introduced to realize the segmentation of air combat situation time series data and the extraction of air combat situation primitives. Secondly, the weight optimization method based on grey prospect theory was used to obtain the weight of the evaluation index under different air combat situations. On this basis, the dynamic mapping model between air combat situation characteristic parameters and the weight of index was constructed by using AE-ELM. Then, the dynamic weighted extreme learning machine was used to build the target maneuver trajectory prediction model, and the future position information of the target was predicted. On this basis, the future situation information between the enemy and us was obtained. Finally, the time weight calculation model based on normal cumulative distribution was used to determine the importance of the situation at each time. The situation information at multiple times in the air combat process was fused to obtain the comprehensive air combat situation assessment results at the current time. The simulation results show that the model can fully exploit the influence of historical information, effectively integrate the air combat situation information at multiple moments, and generate the air combat situation assessment results with practical tactical significance according to the individual differences of different pilots. Citation: Aerospace PubDate: 2023-11-27 DOI: 10.3390/aerospace10120994 Issue No:Vol. 10, No. 12 (2023)
Authors:Donglong Zhou, Jianlong Chang, Huawei Shan First page: 995 Abstract: In the combustion chamber of scramjets, fuel jets interact with supersonic airflow in the form of a liquid jet in crossflow (LJIC). It is difficult to achieve adequate jet–crossflow mixing and the efficient combustion of fuel in an instant. Large eddy simulation (LES), the coupled level-set and volume of fluid (CLSVOF) method, and an adaptive mesh refinement (AMR) framework are used to simulate supersonic LJICs in this article. This way, LJIC atomization characteristics and mechanisms can be further explored and analyzed in detail. It is found that the surface waves of the liquid column exist in a two-dimensional form, including vertical and spanwise directions. Column breakup occurs when all the spanwise surface waves between adjacent vertical surface waves break up. Bow shock waves, composed of multiple connected arcuate shock waves, are dynamic and will change with the evolution of the liquid column. The vortex ring movement of supersonic LJICs, whose trends in the vertical and spanwise directions are different, is relatively complex, which is due to the complex and time-dependent shape of liquid columns. Citation: Aerospace PubDate: 2023-11-27 DOI: 10.3390/aerospace10120995 Issue No:Vol. 10, No. 12 (2023)
Authors:Lingzhi Wang, Taoyong Su First page: 996 Abstract: An electrically controlled rotor (ECR) is a kind of swashplateless rotor that implements the primary control via the trailing-edge flap system instead of a swashplate and demonstrates great potential in vibration reduction and noise alleviation. In this paper, the mesoscopic numerical simulation method known as the lattice Boltzmann method (LBM) is employed to investigate the aerodynamic characteristics of an ECR. In the LBM, the discretized Boltzmann transport equation is solved to simulate the macroscopic motion of the fluid, and the D3Q27 model is applied for this study. The effects of the flap deflection on the ECR aerodynamic characteristics can be accurately included with the appropriate refined wall lattice resolution. On this basis, the adaptive wake-refinement strategy is applied to track the evolution of the wake and adequately capture details of the wake structure in the wake flow field. Based on this method, an aerodynamic analysis model for the ECR can be established on the XFlow simulation platform. The aerodynamic analysis model is validated, and the results indicate that the LBM can accurately capture the details of the rotor flow field and calculate blade aerodynamic load, as well as predict the downwash of the rotor. Therefore, based on this model, the ECR aerodynamic characteristics under hovering and forward flight conditions are analyzed, and the effects of the flap deflection on the wake structure, induced inflow, and disc load can be captured. The results indicate that a relatively large flap deflection required to trim the rotor will cause the additional intense flap wake vortex in the ECR wake flow field, apart from the concentrated vorticity at the blade tip and root demonstrated in the conventional rotor wake flow field, and thus significantly change the distributions of the disc-induced inflow and aerodynamic load. Citation: Aerospace PubDate: 2023-11-28 DOI: 10.3390/aerospace10120996 Issue No:Vol. 10, No. 12 (2023)
Authors:Quan Sun, Xuhui Pan, Xiao Ling, Bo Wang, Qinghong Sheng, Jun Li, Zhijun Yan, Ke Yu, Jiasong Wang First page: 997 Abstract: In the realm of non-cooperative space security and on-orbit service, a significant challenge is accurately determining the pose of abandoned satellites using imaging sensors. Traditional methods for estimating the position of the target encounter problems with stray light interference in space, leading to inaccurate results. Conversely, deep learning techniques require a substantial amount of training data, which is especially difficult to obtain for on-orbit satellites. To address these issues, this paper introduces an innovative binocular pose estimation model based on a Self-supervised Transformer Network (STN) to achieve precise pose estimation for targets even under poor imaging conditions. The proposed method generated simulated training samples considering various imaging conditions. Then, by combining the concepts of convolutional neural networks (CNN) and SIFT features for each sample, the proposed method minimized the disruptive effects of stray light. Furthermore, the feedforward network in the Transformer employed in the proposed method was replaced with a global average pooling layer. This integration of CNN’s bias capabilities compensates for the limitations of the Transformer in scenarios with limited data. Comparative analysis against existing pose estimation methods highlights the superior robustness of the proposed method against variations caused by noisy sample sets. The effectiveness of the algorithm is demonstrated through simulated data, enhancing the current landscape of binocular pose estimation technology for non-cooperative targets in space. Citation: Aerospace PubDate: 2023-11-28 DOI: 10.3390/aerospace10120997 Issue No:Vol. 10, No. 12 (2023)
Authors:Agata Kuśmierek, Rafał Grzeszczyk, Andreas Strohmayer, Cezary Galiński First page: 998 Abstract: Given the increase in air traffic, the main challenges in aircraft design are in-flight emissions and noise heard by the community. These problems have thus far been solved by incremental improvements in aerodynamics, engine technology and operation. To dramatically reduce aviation’s carbon footprint towards an environmentally friendly air transport system, alternative propulsion concepts are one of the promising areas of research and first applications. In this context, the goal of integrating a hybrid-electric powertrain with a suitable airframe is to increase efficiency while reducing in-flight emissions, reduce noise for the community, drive down direct operating costs and increase reliability. This article presents an inexpensive approach to testing small, manned aircraft with a hybrid fuel–electric propulsion system. First, the design assumptions of the research flying platform are presented. Next, modifications of the existing two-seater glider are analyzed. These modifications are necessary to fit the fuel–electric hybrid propulsion system. The analysis allows us to select the elements of an appropriate hybrid electric system. It also shows that this type of small experimental propulsion system can be mounted on a two-seater aerobatic glider without significant structural modifications and still comply with the most important points of the Certification Standard-22. Finally, the design of the ground test stand for the propulsion system is described. It is believed that a thorough examination of the propulsion system on the ground will reveal both the advantages and disadvantages of the system. This should facilitate the successful installation of the system under study on a flying aircraft. Citation: Aerospace PubDate: 2023-11-28 DOI: 10.3390/aerospace10120998 Issue No:Vol. 10, No. 12 (2023)
Authors:Huixue Dang, Jiang Xu, Wei Wang, Xiaochen Wang, Bin Li, Ruizhi Cao, Liuhong Kang, Zhichun Yang First page: 999 Abstract: Civilian aircraft can experience noticeable vibrations in the cockpit and cabin due to mechanical faults during flight. To address this issue, a hybrid approach was utilized to investigate fluid-induced vibration load characteristics in the front landing gear compartment under different hatch opening angles. The results reveal that the root mean square (RMS) of cumulative pressure loads on both small and large hatches under different opening angles is largest at a 15°. For all the simulated cases (0°, 5°, 10°, 15°, 20°), the power spectral density (PSD) results of the chosen monitoring points on the inner wall of the large hatch exhibit broadband frequency characteristics, and the peak PSD values for the chosen monitoring points on the outer wall of the small hatch exhibit a significant concentration of energy at approximately 75 Hz. The peak PSD values for the selected monitoring points on the inner wall of the small hatch demonstrate a more uniform distribution of energy. Utilizing the iso-surface of Q-criterion, spatial streamlines, and streamlines at different cross-sections to analyze flow characteristics, the study investigates the fluctuating load mechanisms of the compartments. The results indicate that unsteady loads stem from the blunt edges of the hatches, which induce unsteady flow and spanwise flow. Geometric gaps between different locations cause flow separation, and the flows inside the compartment exhibit characteristics similar to those of a clean cavity. Furthermore, the mutual interference can be described using circulating flow and spanwise flow, resulting in flow unsteadiness. The flow separation zones enlarge and vortex intensity increases with the increase of the hatch opening angle from 0° to 15°; then, their values decrease as the hatch opening angle increases from 15° to 20°. These variations explain the maximum RMS of cumulative pressure loads at 15°. Citation: Aerospace PubDate: 2023-11-28 DOI: 10.3390/aerospace10120999 Issue No:Vol. 10, No. 12 (2023)
Authors:Constantin Sandu, Andrei-George Totu, Andrei-Tudor Trifu, Marius Deaconu First page: 1000 Abstract: This paper presents the technological advancement of using friction powders to increase the absorption of acoustic liners used in the reduction of tonal noise generated by aero-engines or for other applications related to Helmholtz resonators used in noise absorption of low frequencies. The experimental research was conducted during the European project ARTEM (2017–2022), and after. This concept was inspired by the discovery made by several historians of narrow neck bottles filled with ash in the old Christian churches. These artifacts were made with the purpose of absorbing low frequency noises. Based on this creative idea, the present authors proposed a new method of noise absorption capabilities of acoustic liners filled with various types and quantities of natural and artificial powders. Considering the positive results the ARTEM project offered, COMOTI continued testing this concept by using even finer cork powders manufactured with a new technology. Measurements in Kundt tubes showed that noise absorption increased significantly in broadband for low frequencies (over 0.9 at high frequencies and 0.6 at low frequencies, 500 Hz). Some of the researched powders can be used in the field of bladed machines to reduce the aerodynamic noise of an aircraft or in the automotive industry where the reduction of low frequency noises is necessary. Citation: Aerospace PubDate: 2023-11-28 DOI: 10.3390/aerospace10121000 Issue No:Vol. 10, No. 12 (2023)
Authors:Jiayu Wen, Yanguo Song, Huanjin Wang, Dong Han, Changfa Yang First page: 1001 Abstract: Tiltrotor aircrafts have both fixed-wing control surfaces and helicopter rotors for attitude control. The redundancy of control surfaces provides the possibility for the control system to reconfigure the control law when actuator faults occur during flight. Possible actuator faults have been classified into two categories: predictable and unpredictable faults, and a different strategy has been adopted to deal with each kind of fault. Firstly, the predictable faults are handled by a multiple-model switching adaptive scheme. These kinds of faults are modeled, and their corresponding controllers are derived offline. Secondly, since the degree of drop in aerodynamic effectiveness cannot be predicted a priori, unpredictable faults are handled by a simple adaptive control scheme, to force the plant with faults to track the prescribed reference model. The presented methodology has been verified by nonlinear full-envelope flight simulation for both categories of actuator faults. The predictable fault is represented by the elevator floating. Elevator damage causing an aerodynamic effectiveness drop by 80% is chosen as the example of unpredictable fault. Both faults are simulated at the late stage of the tiltrotor conversion mode. Results show that the presented strategy of reconfiguration is able to detect the fault rapidly and stabilize the aircraft when a fault occurs, while the aircraft motion diverges without the reconfiguration scheme. The aircraft also presents a relatively good performance under controller reconfiguration with a well-tracked conversion path. Citation: Aerospace PubDate: 2023-11-28 DOI: 10.3390/aerospace10121001 Issue No:Vol. 10, No. 12 (2023)
Authors:Kirill Suslov, Maksim Shirobokov, Anastasia Tselousova First page: 1002 Abstract: This paper explores the use of the averaging method in the optimal control problem related to the multirevolution orbital transfer of a spacecraft with low-thrust capabilities. The regularized equations of motion are expressed using modified equinoctial elements with the eccentric longitude as a fast variable. The control function is represented as a Fourier series relative to the eccentric longitude. The classical averaging technique’s usage results in the averaged trajectory depending only on a limited number of optimization parameters. Moreover, when transferring between near-circular orbits, the averaged motion can be estimated using analytical formulas. As such, the optimal multiorbit flight problem is simplified to nonlinear programming with fewer parameters, thereby accelerating the optimal solution’s derivation. Two practical examples illustrate the technique’s application: orbital transfer near the geostationary orbit and circular orbit raising maneuver. The solutions derived are compared with Pontryagin extremals. Citation: Aerospace PubDate: 2023-11-29 DOI: 10.3390/aerospace10121002 Issue No:Vol. 10, No. 12 (2023)
Authors:Ariadna Calcines Calcines Rosario First page: 1003 Abstract: This paper presents the conceptual design of an on-axis 6 metre aperture space telescope designed to cover a field of view of ±0.2 degrees with an optical quality at the diffraction limit within a spectral range between 0.5 μm and 2.5 μm. The plate scale is 3 arcsec/mm, and the overall length is less than 12 m. A Korsch layout has been selected based on the superb aberration compensation offered by Three-Mirror Anastigmat systems. The proposed design presents some characteristics: an almost flat response in RMS wavefront error across the field and for the entire spectral range; a flat mirror has been included to reduce the overall volume, and this has been adjusted to be placed at an intermediate pupil position, acting as a baffle for stray light and as a Lyott to restrict background radiation. This mirror presents a central hole, defined to the aperture of the pupil, allowing the transmission of the beam towards the image focal plane, where it can be split for multiple payloads. It also allows the transmission of the central field, at 90 degrees with respect to the science beam, to be used for Active Optics monitoring and correction of the primary mirror in order to ensure optimum optical performance. This on-axis solution significantly reduces the technical complexity for manufacturing, metrology, integration, and tests and has an important impact in the cost of the telescope. Citation: Aerospace PubDate: 2023-11-29 DOI: 10.3390/aerospace10121003 Issue No:Vol. 10, No. 12 (2023)
Authors:Harjot Singh Saluja, Feijia Yin, Arvind Gangoli Rao, Volker Grewe First page: 1004 Abstract: The climate impact of aviation is considerably different from that of other transport modes. The turbofan engine’s efficiency can be increased by increasing the Operating Pressure Ratio (OPR), bypass ratio (BPR) and Turbine Inlet Temperature (TIT), thereby reducing CO2 and H2O emissions. However, this may have an adverse effect on the secondary emissions, such as NOx, soot, etc. Taking a holistic view in evaluating the climate impact of engine development trends considering all the climate forcers is imperative for design trends in the future. This research investigates the impact of some key engine design parameters on climate. The emission changes due to design variations in the CFM56-5B are estimated using in-house engine performance and emission prediction tools. Accordingly, the changes in the species’ Average Temperature Response for 100 years (ATR100) are analyzed using a climate assessment tool, AirClim. The results show that the overall climate impact increases by 40% when increasing OPR from 25 to 40. Meanwhile, the Twin Annular Premixed Swirler (TAPS-II) combustor reduces the total ATR100 drastically, in the range of 52–58%, due to lean combustion. Citation: Aerospace PubDate: 2023-11-29 DOI: 10.3390/aerospace10121004 Issue No:Vol. 10, No. 12 (2023)
Authors:Haoyuan Shao, Daochun Li, Zi Kan, Shiwei Zhao, Jinwu Xiang, Chunsheng Wang First page: 1005 Abstract: Catapult-assisted takeoff is the initiation of flight missions for carrier-based aircrafts. Ensuring the safety of aircrafts during catapult-assisted takeoff requires a thorough analysis of their motion characteristics. In this paper, a rigid–flexible coupling model using the Finite Element Method and Multibody Dynamics (FEM-MBD) approach is developed to simulate the aircraft catapult process. This model encompasses the aircraft frame, landing gear, carrier deck, and catapult launch system. Firstly, reasonable assumptions were made for the dynamic modeling of catapult-assisted takeoff. An enhanced plasticity algorithm that includes transverse shear effects was employed to simulate the tensioning and release processes of the holdback system. Additionally, the forces applied by the launch bar and holdback bar, nonlinear aerodynamics loads, shock absorbers, and tires were introduced. Finally, a comparative analysis was conducted to assess the influence of different launch bar angles and holdback bar fracture stain on the aircraft’s attitude and landing gear dynamics during the catapult process. The proposed rigid–flexible coupling dynamics model enables an effective analysis of the dynamic behavior throughout the entire catapult process, including both the holdback bar tensioning and release, takeoff taxing, and extension of the nose landing gear phases. The results show that higher launch bar angle increase the load and extension of the nose landing gear and cause pronounced fluctuations in the aircraft’s pitch attitude. Additionally, the holdback bar fracture strain has a significant impact on the pitch angle during the first second of the aircraft catapult process, with greater holdback bar fracture strain resulting in larger pitch angle variations. Citation: Aerospace PubDate: 2023-11-29 DOI: 10.3390/aerospace10121005 Issue No:Vol. 10, No. 12 (2023)
Authors:Jiayu Wen, Yanguo Song, Huanjin Wang, Dong Han, Changfa Yang First page: 1006 Abstract: Neural networks have been widely used as compensational models for aircraft control designs and as surrogate models for other optimizations. In the case of tiltrotor aircraft, the total number of aircraft states and controls is much greater than that of both traditional fixed-wings and helicopters. This requires, in general, a huge amount of training data for the network to reach a satisfactory approximation precision and makes the network size rise considerably. To solve the practical problem of reducing the size of the approximating network, efforts have to be made in the efficient utilization of the limited amount of training data. This work presents the methodology of optimizing the sample pattern of the training data set by adopting the metaheuristic algorithm of the particle swarm optimizer improved by the fourth-order Runge–Kutta algorithm. A 6-degree-of-freedom nonlinear flight dynamics model of the tiltrotor aircraft is derived, along with its approximation radial basis function neural network. An example case of approximating a highly nonlinear function is studied to illustrate the principle and main parameters of the optimizer, and the approximation performance of the time-domain response of the unstable nonlinear system is revealed by the study of a Van der Pol oscillator. Then, the presented method is applied to the modeled tiltrotor aircraft for its early and late conversion modes. The optimization scheme shows great improvement in both cases, as the function approximation error is reduced significantly. Citation: Aerospace PubDate: 2023-11-29 DOI: 10.3390/aerospace10121006 Issue No:Vol. 10, No. 12 (2023)
Authors:Tao Liu, Jinqiu Duan, Yan Zheng, Yingjing Qian First page: 1007 Abstract: The novel concept of a functionally graded three-phase composite structure is derived from the urgent need to improve the mechanical properties of traditional two-phase composite structures in aviation. In this paper, we study the free vibrations of a new functionally graded three-phase composite cylindrical shell reinforced synergistically with graphene platelets and carbon fibers. We calculate the equivalent elastic properties of the new three-phase composite cylindrical shell using the Halpin-Tsai and Mori-Tanaka models. The governing equations of this three-phase composite cylindrical shell are derived by using first-order shear deformation theory and Hamilton’s principle. We obtain the natural frequencies and mode shapes of the new functionally graded three-phase composite cylindrical shell under artificial boundary conditions. By comparing the results of this paper with the numerical results of finite element software, the calculation method is verified. The effects of the boundary spring stiffness, GPL mass fraction, GPL functionally graded distributions, carbon fiber content, and the carbon fiber layup angle on the free vibrations of the functionally graded three-phase composite cylindrical shell are analyzed in depth. The conclusions provide a certain guiding significance for the future application of this new three-phase composite structure in the aerospace and engineering fields. Citation: Aerospace PubDate: 2023-11-29 DOI: 10.3390/aerospace10121007 Issue No:Vol. 10, No. 12 (2023)
Authors:Zijie Li, Hao Wang First page: 908 Abstract: A recently developed launching device called the gun–track launch system is affected by its constrained track, such that the form of the muzzle jet changes from the state of free development in the entire space to a constrained state, where this lends unique characteristics of development to its flow field. In this study, the authors establish the corresponding model for numerical simulations based on the dynamic mesh method. We also considered a model of simulation of the muzzle jet with an “infinitely” constrained track to analyze its performance under real launch conditions to explore the mechanism of development and the disturbance-induced propagation of the shock wave when the muzzle jet impinges on moving bodies. The results showed that the muzzle jet exhibited a circumferential asymmetric shape that tilted toward the area above the muzzle and generated transverse air flow that led to the generation of a vortex on it. Because the muzzle was close to the ground, the jet was reflected by it to enhance the development and evolution of the shock waves and vortices and to aggravate the rate of distortion and asymmetry of the jet. The wave reflected from the ground was emitted once again when it encountered the infinitely constrained track. No local low-pressure area or a prominent vortex was observed after multiple reflections. Because the track in the test model was short, the waves reflected by the ground were not blocked, and vortices were formed in the area above the ground. Significant differences in the changes in pressure were also observed at key points in the domain. The results of a comparative analysis showed that the infinitely constrained track increased the Mach number of the moving body from 1.4 to 1.6. The work provides a theoretical basis and the requisite technical support for applications of the gun–track launch system. Citation: Aerospace PubDate: 2023-10-25 DOI: 10.3390/aerospace10110908 Issue No:Vol. 10, No. 11 (2023)
Authors:Nicole Viola, Roberta Fusaro, Guido Saccone, Valeria Borio First page: 909 Abstract: According to the latest report of the Intergovernmental Panel on climate change, aviation contributes to only about 2% to anthropogenic global greenhouse gas (GHG) emissions. However, in view of the growing market demand and the dramatic reductions in other transport sectors, including maritime and automotive, the aviation sector’s percentage impact on global GHG emissions is expected to reach 50% of the transport share by 2040. High-speed aviation exploiting liquid hydrogen as the propellant can represent a valuable solution toward the decarbonization of the sector. However, to avoid jeopardizing the dream of a new generation of high-speed aircraft, it will be necessary to introduce non-CO2 emissions estimations beginning with the design process. To unlock the possibility of anticipating the nitrogen oxides emissions estimation, the authors developed the hydrogen and high-speed P3-T3 methodology (H2-P3T3), an evolution of the widely used P3-T3 method, properly conceived to support (i) innovative air-breathing propulsive systems for supersonic and hypersonic flights and (ii) greener fuels, such as hydrogen. This paper presents a step-by-step approach to developing novel analytical formulations customized for an Air Turbo-Rocket engine and discusses the discovered correlation of nitrogen oxides production with the fuel-to-air ratio (FAR), the Mach number, and the Damköhler number (Da), the last being a nondimensional variable directly related to hydrogen/air combustion, considering the matching between the residence time and the ignition delay times. The most complete formulation allows for reduction in the prediction errors below 5%. Citation: Aerospace PubDate: 2023-10-25 DOI: 10.3390/aerospace10110909 Issue No:Vol. 10, No. 11 (2023)
Authors:Shengjie Xiao, Yuhong Sun, Dapeng Ren, Kai Hu, Huichao Deng, Yun Wang, Xilun Ding First page: 910 Abstract: A key challenge in flapping-wing micro air vehicle (FWMAV) design is to generate high aerodynamic force/torque for improving the vehicle’s maneuverability. This paper presents a bio-inspired hover-capable flapping-wing micro air vehicle, named RoboFly.S, using a cross-tail wing to adjust attitude. We propose a novel flapping mechanism composed of a two-stage linkage mechanism, which has a large flapping angle and high reliability. Combined with the experimentally optimized wings, this flapping mechanism can generate more than 34 g of lift with a total wingspan of 16.5 cm, which is obviously superior to other FWMAVs of the same size. Aerodynamic force/torque measurement systems are used to observe and measure the flapping wing and aerodynamic data of the vehicle. RoboFly.S realizes attitude control utilizing the deflection of the cross-tail wing. Through the design and experiments with tail wing parameters, it is proved that this control method can generate a pitch torque of 2.2 N·mm and a roll torque of 3.55 N·mm with no loss of lift. Flight tests show that the endurance of RoboFly.S can reach more than 2.5 min without interferences. Moreover, the vehicle can carry a load of 3.4 g for flight, which demonstrates its ability to carry sensors for carrying out tasks. Citation: Aerospace PubDate: 2023-10-25 DOI: 10.3390/aerospace10110910 Issue No:Vol. 10, No. 11 (2023)
Authors:Guang Feng, Bingyan Jiang, Yiyao Jiang First page: 911 Abstract: The existence of joint clearances in the nose landing gear (NLG) is inevitable and significantly affects shimmy. It was found that the interaction of each joint clearance is closely related to the analysis of shimmy stability. In this study, the shimmy model of NLG with three-dimensional joint clearance was established by using LMS VirtualLab Motion. Based on the method of multibody dynamics (MBD), the load transfer mechanism at the joints of the NLG was analyzed, and the oscillation characteristics with multiple joint clearances were investigated. The results indicate that the radial and axial contact force of the joint decreases from bottom to top, and the radial contact forces are relatively high at the end positions of the connection shafts, resulting in uneven wear. When the joint clearance reaches a certain value, periodic shimmy of the NLG will occur, and an increase in torsional damping can reduce the amplitude of the shimmy. Therefore, this study reveals the influence of multi-position joint clearance coupling on shimmy, and provides a valuable insight for the maintenance and design of landing gear joints. Citation: Aerospace PubDate: 2023-10-25 DOI: 10.3390/aerospace10110911 Issue No:Vol. 10, No. 11 (2023)
Authors:Octavian Thor Pleter, Cristian Emil Constantinescu First page: 912 Abstract: The paper is an introductory study on the possible transition from Magnetic North reference to True North reference in air navigation, as envisaged by the International Association of Institutes of Navigation’s AHRTAG Group. The use of the Magnetic Field of the Earth as a direction reference in aviation is explained briefly. Magnetic North is an unstable and irregular directional reference that aviation manages well, but with significant costs. The unpredictability and uncertainties of the Magnetic Field of the Earth might be critical in the future, especially in the case of reversal of the magnetic poles, or incipient reversal. The paper puts forward the case for calculating the probability of such a catastrophic event, with a view to engaging further expert research in the geomagnetic phenomena. The purpose of such a probability estimate would be for the aviation decision makers to determine whether contingency planning might be required or not. Furthermore, the paper analyses the adoption of True North in maritime navigation as a possible model. Citation: Aerospace PubDate: 2023-10-25 DOI: 10.3390/aerospace10110912 Issue No:Vol. 10, No. 11 (2023)
Authors:Xinyu Chen, Yunsheng Fan, Guofeng Wang, Dongdong Mu First page: 913 Abstract: This paper designs a cooperative control method for the multi-quadrotor suspension system based on consistency theory and realizes the cooperative formation trajectory tracking control of the multi-quadrotor suspension system by designing a consistent formation cooperative algorithm of virtual piloting and a nonlinear controller. First, a new quadrotor suspension system model is established based on the traditional quadrotor model using the Newton–Euler method. This model can accurately reflect the influence of the load on the quadrotor while obtaining the swing of the load. Then, the vertical and horizontal positions are designed separately based on the quadrotor motion characteristics, and the formation algorithm based on the virtual pilot consistency theory ensures that the final convergence of each position is consistent. An integral backstepping controller and an integral backstepping sliding mode controller are designed for quadrotor position, attitude, and load swing control to achieve accurate and fast quadrotor trajectory tracking control while reducing load swing. The stability of all the controllers is demonstrated using Lyapunov functions. Finally, a multi-quadrotor suspension system formation cooperative simulation experiment is designed to verify the designed control method. Citation: Aerospace PubDate: 2023-10-26 DOI: 10.3390/aerospace10110913 Issue No:Vol. 10, No. 11 (2023)
Authors:Dong Sui, Hanping Chen, Tingting Zhou First page: 914 Abstract: With the escalating complexity of surface operations at large airports, the conflict risk for aircraft taxiing has correspondingly increased. Usually, the Air Traffic Controllers (ATCOs) generate route, speed and holding instructions to resolve conflicts. In this paper, we introduce a conflict resolution framework that incorporates prior knowledge by integrating a Multi-Layer Perceptron (MLP) neural network into the Monte Carlo Tree Search (MCTS) approach. The neural network is trained to learn the allocation strategy for waiting time extracted from actual aircraft taxiing trajectory data. Subsequently, the action probability distribution generated with the neural network is embedded into the MCTS algorithm as a heuristic evaluation function to guide the search process in finding the optimal conflict resolution strategy. Experimental results show that the average conflict resolution rate is 96.8% in different conflict scenarios, and the taxiing time required to resolve conflicts is reduced by an average of 42.77% compared to the taxiing time in actual airport surface operations. Citation: Aerospace PubDate: 2023-10-26 DOI: 10.3390/aerospace10110914 Issue No:Vol. 10, No. 11 (2023)
Authors:Carmen García-López, Germán Álvarez-Tey First page: 915 Abstract: Thermal processing equipment used in the aerospace industry must meet the requirements of the processes for which they are intended. The periodic tests performed by calibration laboratories, according to the AMS2750 specification, are intended to ensure compliance with these equipment requirements. While this specification does not explicitly state the need for uncertainty calculation, it does specify that pyrometry laboratories must have an ISO/IEC 17025 Quality System accredited by a recognized regional body which is a member of the International Laboratory Accreditation Cooperation (ILAC). Therefore, the calculation of uncertainties is necessary. This work presents a methodology for conducting temperature uniformity surveys and uncertainty assessment in these tests. This methodology has been applied to four different types of equipment to analyse, in each case, the contributions of uncertainties and to assess their potential for improvement. The objectives that laboratories should aim for include improving measurement accuracy and reducing uncertainty components in order to meet the criteria of both AMS2750 and ISO/IEC 17025. Citation: Aerospace PubDate: 2023-10-26 DOI: 10.3390/aerospace10110915 Issue No:Vol. 10, No. 11 (2023)
Authors:Kyungwon Oh, Seonghee Kho First page: 916 Abstract: The purpose of this paper is to analyze the structural stability of an underwater high-speed vehicle. The drag characteristics of a moving body moving at high speed in water were analyzed, and a stability analysis of the structure was performed by applying the non-conservative property according to the driven force in a rocket propulsion environment. To this end, the fluid characteristics that enable high-speed maneuvering in an underwater environment were described, and the structural stability was analyzed by simplifying modeling by increasing the resulting drag. In addition, for high-speed underwater movement, an analysis of the following force according to drag and axial load and the effect on structural stability was conducted by simplifying the structure attached to a specific location when a supercavitation occurs. Citation: Aerospace PubDate: 2023-10-26 DOI: 10.3390/aerospace10110916 Issue No:Vol. 10, No. 11 (2023)
Authors:Giordana Bonavolontà, Craig Lawson, Atif Riaz First page: 917 Abstract: The reduction of sonic boom levels is the main challenge but also the key factor to start a new era of supersonic commercial flights. Since 1970, a FAA regulation has banned supersonic flights overland for unacceptable sonic booms at the ground, and many research studies have been carried out from that date to understand sonic boom generation, propagation and effects, both on the environment and communities. Minimization techniques have also been developed with the attempt to reduce sonic boom annoyance to acceptable levels. In the last 20 years, the advances in both knowledge and technologies, and companies and institutions’ significant investments have again raised the interest in the development of new methods and tools for the design of low boom supersonic aircraft. The exploration of unconventional configurations and exotic solutions and systems seems to be needed to effectively reduce sonic boom and allow supersonic flight everywhere. This review provides a description of all aspects of the sonic boom phenomenon related to the design of the next generation of supersonic aircraft. In particular, a critical review of the prediction and minimization methods found in the literature, aimed at identifying their strengths, limitations and gaps, is made, along with a complete overview of disruptive unconventional aircraft configurations and exotic active/passive solutions to boom level reduction. The aim of the work is to give a clear statement of state-of-the-art sonic boom prediction methods and possible reduction solutions to be explored for the design of next low-boom supersonic aircraft. Citation: Aerospace PubDate: 2023-10-27 DOI: 10.3390/aerospace10110917 Issue No:Vol. 10, No. 11 (2023)
Authors:Yu Gu, Guoxin Zhang, Ying Bi, Wenyue Meng, Xiaoping Ma, Wenjun Ni First page: 918 Abstract: Moving mass control (MMC) is considered a promising approach to regulating the attitude of an aircraft via the motion of internal moving masses. The present investigation proposes a moving mass control scheme for a high-altitude long-endurance (HALE) unmanned aerial vehicle (UAV) with a single slider moving longitudinally. To that end, a longitudinal nonlinear motion model is established, and pitch dynamics are analyzed. Furthermore, the influence of the slider parameters on the dynamic characteristics of the UAV and the change in control efficiency with speed are analyzed. Finally, a detailed root-locus-based stability and sensitivity analysis of the proposed control scheme is formulated. At an altitude of 20,000 m, the MMC scheme’s efficiency coefficient was 200% of that of elevator scheme at the cruise speed. The simulation results show that the control efficiency of the moving mass control scheme was significantly higher than that of the traditional elevator control scheme under the conditions of high altitude and low speed. Citation: Aerospace PubDate: 2023-10-28 DOI: 10.3390/aerospace10110918 Issue No:Vol. 10, No. 11 (2023)
Authors:Francesco Lopez, Anna Mauro, Stefano Mauro, Giuseppe Monteleone, Domenico Edoardo Sfasciamuro, Andrea Villa First page: 919 Abstract: The goal of this research is to define a lunar-orbiting system that provides power to the lunar surface through wireless power transmission. To meet the power demand of a lunar base, a constellation of satellites placed in stable orbits is used. Each satellite of this constellation consists of solar arrays and batteries that supply a power transmission system. This system is composed of a laser that transmits power to receivers on the lunar surface. The receivers are photonic power converters, photovoltaic cells optimized for the laser’s monochromatic light. The outputs of this work will cover the architecture of the system by studying different orbits, specifically analyzing some subsystems such as the laser, the battery pack and the receiver placed on the lunar ground. The study is conducted considering two different energy demands and thus two different receivers location: first, at the strategic location of the Artemis missions’ landing site, the Shackleton Crater near the lunar south pole; second, on the lunar equator, in anticipation of future and new explorations. The goal is to evaluate the possible configurations to satisfy the power required for a lunar base, estimated at approximately 100 kW. To do this, several cases were analyzed: three different orbits, one polar, one frozen and one equatorial (Earth–Moon distant retrograde orbit) with different numbers of satellites and different angles of the receiver’s cone of transmission. The main objective of this paper is to perform a comprehensive feasibility study of the aforementioned system, with specific emphasis placed on selected subsystems. While thermal control, laser targeting, and attitude control subsystems are briefly introduced and discussed, further investigation is required to delve deeper into these areas and gain a more comprehensive understanding of their implementation and performance within the system. Citation: Aerospace PubDate: 2023-10-28 DOI: 10.3390/aerospace10110919 Issue No:Vol. 10, No. 11 (2023)
Authors:Daniel Izquierdo, Gabriel Casas, Ana G. Garriga, Ignacio Castro, Aleksandra Zieminska-Stolarska, Mariia Sobulska, Ireneusz Zbicinski First page: 920 Abstract: The Hybrid Electric Regional Aircraft Distribution Technologies (HECATE) Clean Aviation project will mature and develop breakthrough technologies and perform scalability and impact analysis to ensure safe and power-dense technologies that will enable Entry Into Service (EIS) of hybrid-electric regional aircraft by 2035. Along the project, a circular economy approach in future aircraft will be ensured through the use of Life Cycle Assessment (LCA), performing this type of assessment on the overall electrical system and primary/secondary distribution and conversion technologies, helping to be in line with long-term environmental roadmaps such as Flightpath 2050. This communication includes a description of the HECATE activities and how LCA will be applied to the future Regional Aircraft Electrical Distribution System. Citation: Aerospace PubDate: 2023-10-28 DOI: 10.3390/aerospace10110920 Issue No:Vol. 10, No. 11 (2023)
Authors:Justice J. Mason, Christine Allen-Blanchette, Nicholas Zolman, Elizabeth Davison, Naomi Ehrich Leonard First page: 921 Abstract: In many real-world settings, image observations of freely rotating 3D rigid bodies may be available when low-dimensional measurements are not. However, the high-dimensionality of image data precludes the use of classical estimation techniques to learn the dynamics. The usefulness of standard deep learning methods is also limited, because an image of a rigid body reveals nothing about the distribution of mass inside the body, which, together with initial angular velocity, is what determines how the body will rotate. We present a physics-based neural network model to estimate and predict 3D rotational dynamics from image sequences. We achieve this using a multi-stage prediction pipeline that maps individual images to a latent representation homeomorphic to SO(3), computes angular velocities from latent pairs, and predicts future latent states using the Hamiltonian equations of motion. We demonstrate the efficacy of our approach on new rotating rigid-body datasets of sequences of synthetic images of rotating objects, including cubes, prisms and satellites, with unknown uniform and non-uniform mass distributions. Our model outperforms competing baselines on our datasets, producing better qualitative predictions and reducing the error observed for the state-of-the-art Hamiltonian Generative Network by a factor of 2. Citation: Aerospace PubDate: 2023-10-29 DOI: 10.3390/aerospace10110921 Issue No:Vol. 10, No. 11 (2023)
Authors:Hongming Cai, Zhuoran Zhang, Ziqi Li, Hongda Li First page: 922 Abstract: Cavity flows are a prevalent phenomenon in aerospace engineering, known for their intricate structures and substantial pressure fluctuations arising from interactions among vortices. The primary objective of this research is to predict noise levels in high-speed cavity flows at Mach 4 for a rectangular cavity characterized by an aspect ratio of L/D = 7. Moreover, this study delves into the influence of the plasma actuator on noise control within the cavity flow regime. To comprehensively analyze acoustic characteristics and explore effective noise reduction strategies, a computational fluid dynamics technique with the combination of a delayed detached eddy simulation (DDES) and plasma phenomenological model is established. Remarkably, the calculated overall sound pressure level (OASPL) and plasma-induced velocity closely align with the experimental data, validating the reliability of the proposed approach. The results show that the dielectric barrier discharge (DBD) plasma actuator changes the movement range of a dominating vortex in the cavity to affect the OASPL at the point with the maximum noise level. The control of excitation voltage can reduce the cavity noise by 2.27 dB at most, while control of the excitation frequency can only reduce the cavity noise by 0.336 dB at most. Additionally, the increase in excitation frequency may result in high-frequency sound pressure, but the influence is weakened with the increase in the excitation frequency. The findings highlight the potential of the plasma actuator in reducing high-Mach-number cavity noise. Citation: Aerospace PubDate: 2023-10-29 DOI: 10.3390/aerospace10110922 Issue No:Vol. 10, No. 11 (2023)
Authors:Tarafder Elmi Tabassum, Zhengjia Xu, Ivan Petrunin, Zeeshan A. Rana First page: 923 Abstract: To enhance system reliability and mitigate the vulnerabilities of the Global Navigation Satellite Systems (GNSS), it is common to fuse the Inertial Measurement Unit (IMU) and visual sensors with the GNSS receiver in the navigation system design, effectively enabling compensations with absolute positions and reducing data gaps. To address the shortcomings of a traditional Kalman Filter (KF), such as sensor errors, an imperfect non-linear system model, and KF estimation errors, a GRU-aided ESKF architecture is proposed to enhance the positioning performance. This study conducts Failure Mode and Effect Analysis (FMEA) to prioritize and identify the potential faults in the urban environment, facilitating the design of improved fault-tolerant system architecture. The identified primary fault events are data association errors and navigation environment errors during fault conditions of feature mismatch, especially in the presence of multiple failure modes. A hybrid federated navigation system architecture is employed using a Gated Recurrent Unit (GRU) to predict state increments for updating the state vector in the Error Estate Kalman Filter (ESKF) measurement step. The proposed algorithm’s performance is evaluated in a simulation environment in MATLAB under multiple visually degraded conditions. Comparative results provide evidence that the GRU-aided ESKF outperforms standard ESKF and state-of-the-art solutions like VINS-Mono, End-to-End VIO, and Self-Supervised VIO, exhibiting accuracy improvement in complex environments in terms of root mean square errors (RMSEs) and maximum errors. Citation: Aerospace PubDate: 2023-10-29 DOI: 10.3390/aerospace10110923 Issue No:Vol. 10, No. 11 (2023)
Authors:Haojun Luo, Chih-Yung Wen First page: 924 Abstract: Unmanned Ground Vehicles (UGVs) and Unmanned Aerial Vehicles (UAVs) are commonly used for various purposes, and their cooperative systems have been developed to enhance their capabilities. However, tracking and interacting with dynamic UAVs poses several challenges, including limitations of traditional radar and visual systems, and the need for the real-time monitoring of UAV positions. To address these challenges, a low-cost method that uses LiDAR (Light Detection and Ranging) and RGB-D cameras to detect and track UAVs in real time has been proposed. This method relies on a learning model and a linear Kalman filter, and has demonstrated satisfactory estimation accuracy using only CPU (Central Processing Unit)- in GPS (Global Positioning System)-denied environments without any prior information. Citation: Aerospace PubDate: 2023-10-29 DOI: 10.3390/aerospace10110924 Issue No:Vol. 10, No. 11 (2023)
Authors:Jiawei Zhu, Kenlun Chen, Xuehe Yang, Qijie Zhou, Zhipeng Ye, Yaqiu Li First page: 925 Abstract: Propeller-crossing probability analysis is crucial for evaluating the impact resistance and foreign object exclusion capability of turboprop engines. However, due to the complex structure of the propeller and the uncertainties associated with the impact location as well as the flight attitude of the foreign object, developing a comprehensive model for analyzing the propeller-crossing process remains a significant challenge. This paper presents a novel simulation method that can obtain the probability of a foreign object successfully crossing the propeller using a high-fidelity structure model of the propeller and a comprehensive substituted model of the foreign object. To validate the performance of the proposed method, an analytical model is developed that takes into account the spatial structure constraints of the propeller and the foreign object. The proposed method is applied to calculating the probability of bird ingestion, and the results reveal that the increments in flight speed and aspect ratio of the bird have opposite effects on the propeller-crossing probability, and the values eventually converge to a constant value. Citation: Aerospace PubDate: 2023-10-30 DOI: 10.3390/aerospace10110925 Issue No:Vol. 10, No. 11 (2023)
Authors:Liang Ding, Xian Yi, Zhanwei Hu, Xiangdong Guo First page: 926 Abstract: Icing detection is the premise and basis for the operation of aircraft icing protection system, and is the primary issue in flight safety assurance. At present, there is a lack of research methods and design reference for the layout optimization of ice detectors. Therefore, in order to simulate the real icing environment encountered by the aircraft more accurately, a large-scale icing wind tunnel was used to carry out experimental research on the icing characteristics of the sensor probes. A closed-loop experimental method including the typical condition selection, sensor array interference examination and ice shape repeatability verification was initially proposed. A stepwise optimization process and a sensitivity analysis on ambient conditions were combined to determine the optimal distribution for sensor installation. It is found that the water collection coefficient on the cylinder surface of the probe first increases and then decreases along the axial direction, reaching the extreme value at a certain position. The height of this extreme point will gradually increase with the development of the wall boundary layer, showing a variation range of 2~30 mm. Improper design may cause the sensor probe to fail to capture the point with the maximum icing thickness, affecting the sensitivity of icing detection. In addition, each probe position has different sensitivity to changes in flow parameters; the points with larger icing mass and lower sensitivity to changes in attack angle will have better detection effect. The measured data and analysis in the present work can provide a basis for the accurate design of icing sensor probes. Citation: Aerospace PubDate: 2023-10-30 DOI: 10.3390/aerospace10110926 Issue No:Vol. 10, No. 11 (2023)
Authors:Yihua Dan, Jian Yang First page: 927 Abstract: The radome is an important component of the aircraft seeker. The radome of high-speed aircraft usually has ablation, which affects the electromagnetic performance of the radome. Therefore, it is important to study the electromagnetic performance of the radome wall during high-temperature ablation. However, most existing studies mainly consider the influence of temperature and ignore structural changes caused by ablation. To solve the above problems, this paper studies the influence of ablation on the electromagnetic performance of inhomogeneous radome walls (IRW) by considering the structure parameters, thermal expansion characteristics, and dielectric parameters during the ablation. The two typical types of IRW design methods are analyzed, the parameters calculation method in the ablation process is proposed, and the influence of ablation on the two types of IRW is studied. The results give the electromagnetic changing characteristics of the IRW under different ablation conditions. The contribution of this work is to lay a solid theoretical foundation for improving the performance of the radome in the ablation process, which is of great significance. Citation: Aerospace PubDate: 2023-10-30 DOI: 10.3390/aerospace10110927 Issue No:Vol. 10, No. 11 (2023)
Authors:Razvan Nicoara, Daniel Crunteanu, Valeriu Vilag First page: 928 Abstract: As a main component of most gas-turbine engines, the axial flow turbines have been in a process of continuous improvement, reaching high efficiencies and reliability. A well-known drawback of these systems is the rapid decrease in performance when operating at lower than nominal conditions. Thus, a novel performance-enhancement method for axial turbines operating at partial loads has been previously proposed and numerically characterized. In this paper, one applies the aforementioned method for a smaller size axial flow turbine, part of a gas-generator assembly for a microjet engine, to determine, by the use of CFD analysis, the influence of the system at different partial regimes across the working line. A logical scheme based on iterative steps and multiple numerical simulations is also used to determine the engine response to the injection of compressor bleed air into the turbine passages. The results show, as determined in the previous study, that the generated power can be increased for all partial regimes, with the influence being more noticeable at higher regimes, leading to a reduction in fuel consumption in order to achieve the same regimes. Citation: Aerospace PubDate: 2023-10-30 DOI: 10.3390/aerospace10110928 Issue No:Vol. 10, No. 11 (2023)
Authors:Yuji Takubo, Masahiro Kanazaki First page: 929 Abstract: Landing of supersonic transport (SST) suffers from a large uncertainty due to its highly sensitive aerodynamic properties in the subsonic domain, as well as the wind gusts around runways. At the vehicle design stage, a landing trajectory optimization under wind uncertainty in a multi-objective solution space is desired to explore the possible trade-off in its key flight performance metrics. The proposed algorithm solves this robust constrained multi-objective optimal control problem by integrating non-intrusive polynomial chaos expansion into a constrained evolutionary algorithm. The computationally tractable optimization is made possible through the conversion of a probabilistic problem into an equivalent deterministic representation while maintaining a form of the multi-objective problem. The generated guidance trajectories achieve a significant reduction of the uncertainty in their terminal states with a marginal modification in the control history of the deterministic solutions, validating the importance of the consideration of robustness in trajectory optimization. Citation: Aerospace PubDate: 2023-10-30 DOI: 10.3390/aerospace10110929 Issue No:Vol. 10, No. 11 (2023)
Authors:Julio Ronceros, Carlos Raymundo, Eduardo Ayala, Diego Rivera, Leonardo Vinces, Gustavo Ronceros, Gianpierre Zapata First page: 930 Abstract: This study delves into the examination of internal flow characteristics within closed (with nozzles) and open-end pressure-swirl atomizers (lacking nozzles). The number of inlet channels “n” and the opening parameter “C” were manipulated in this study, as they play a pivotal role in understanding various atomizer attributes, such as uniformity of the air-core diameter, the discharge coefficient, spray angle, and more, all of which hold significance in the design of bipropellant atomizers for liquid rocket engines (LREs). To validate our findings, six distinct hexahedral meshes were generated using Ansys ICEM software 2023. Subsequently, we employed Ansys Fluent, considering the RNG k-ε turbulence model and the VOF (volume-of-fluid) multiphase model to identify the liquid–gas interface, to aid in analyzing the uniformity of the air core, which is directly linked to the even distribution of mass, the mixing ratio of propellants, combustion efficiency, and stability. The results indicate that the uniformity of the air core is not solely contingent on an increase in parameter “n” but is also influenced by an increase in the parameter “C”. It is worth noting that the key dimensions of these six atomizers were determined using a mathematical model based on Abramovich and Kliachko theories. Citation: Aerospace PubDate: 2023-10-31 DOI: 10.3390/aerospace10110930 Issue No:Vol. 10, No. 11 (2023)
Authors:Haochen Li, Haibing Chen, Chengpeng Tan, Zaiming Jiang, Xinyi Xu First page: 931 Abstract: Optimal entry flight of hypersonic vehicles requires achieving specific mission objectives under complex nonlinear flight dynamics constraints. The challenge lies in rapid generation of optimal or near-optimal flight trajectories with significant changes in the initial flight conditions during entry. Deep Neural Networks (DNNs) have shown the capability to capture the inherent nonlinear mapping between states and optimal actions in complex control problems. This paper focused on comprehensive investigation and evaluation of a DNN-based method for three-dimensional hypersonic entry flight trajectory generation. The network is designed using cross-validation to ensure its performance, enabling it to learn the mapping between flight states and optimal actions. Since the time-consuming training process is conducted offline, the trained neural network can generate a single optimal control command in about 0.5 milliseconds on a PC, facilitating onboard applications. With the advantages in mapping capability and calculating speed of DNNs, this method can rapidly generate control action commands based on real-time flight state information from the DNN model. Simulation results demonstrate that the proposed method maintains a high level of accuracy even in scenarios where the initial flight conditions (including altitude, velocity, and flight path angle) deviate from their nominal values, and it has certain generalization ability. Citation: Aerospace PubDate: 2023-10-31 DOI: 10.3390/aerospace10110931 Issue No:Vol. 10, No. 11 (2023)
Authors:Seung-Min Jeong, Hyung-Seok Han, Bu-Kyeng Sung, Wiedae Kim, Jeong-Yeol Choi First page: 932 Abstract: This study numerically investigated the combustion instability and characteristics of a laboratory-scale gaseous hydrogen-fueled scramjet combustor. For this purpose, a numerical simulation with an improved detached eddy simulation and a detailed hydrogen/oxygen reaction mechanism was performed. The numerical framework used high-resolution schemes with high-order accuracy to ensure high resolution and fidelity. A total of five fuel injection pressures were considered to characterize the combustion instability as a function of the equivalence ratio. A sampling time of up to 100 ms was considered to sufficiently accumulate several cycles of low-frequency combustion instability dynamics with a period in the order of 100 Hz. Numerical results revealed the repetitive formation/dissipation dynamics of the upstream-traveling shock wave, and it acts as a key factor of combustion instability. The period and derived principal frequency of these upstream-traveling shock waves is several ms. The frequency analysis showed that the instability frequency increased in the low-frequency range as the combustion mode transitioned from the cavity shear-layer to the jet-wake type. This characteristic was derived from the transition in combustion mode at the same equivalence ratio. Therefore, it suggests that the instability frequency shifting is governed by the combustion mode rather than the equivalence ratio. These comprehensive numerical results demonstrated not only the effect of the equivalence ratio but also the important role of the combustion mode on the low-frequency combustion instability. Citation: Aerospace PubDate: 2023-10-31 DOI: 10.3390/aerospace10110932 Issue No:Vol. 10, No. 11 (2023)
Authors:Yan Li, Jibo He, Shi Cao, Jiajie Zheng, Yazhou Dou, Chenxi Liu, Xufeng Liu First page: 933 Abstract: During the COVID-19 pandemic, the question of how to reduce the risk of viral infection for international airline pilots without increasing the risk of fatigue was a novel and urgent theoretical and practical problem, which had never been encountered in the world civil aviation industry. A new scheduling method implemented by the Civil Aviation Administration of China (CAAC) is the extra augmented crew (EAC) schedule, which avoids crew layover in another country on international flights by extending the maximum duty time and adding two additional crew members to such long-haul flights. In this study, a multi-day flight crew fatigue assessment was conducted to evaluate the impact of EAC flight. We recruited 71 pilots as participants, and their fatigue during EAC flights was measured using a multimodality approach integrating a subjective fatigue report, a psychomotor vigilance task, sleep monitoring, and biomathematical model predictions. The results showed that the subjective fatigue level increased during duty time compared to off-duty time, but still with acceptable levels of under 7, as measured by the Karolinska Sleepiness Scale; objective secondary task performance, as measured by the classic psychomotor vigilance task, showed no differences; pilots were able to get around 6 h of sleep, although they slept less during duty time compared to off-duty time. Model fitting using the FAID biomathematical model of fatigue confirmed that the EAC scheduling was compliant with the FAID tolerance level 91.3% of the time. The results suggest that the EAC flight created some moderate level of increased fatigue but no severe fatigue to cross-continent long-haul flight crews. This research can inform current and future scheduling and fatigue risk control during the pandemic or for future time-sensitive periods. Citation: Aerospace PubDate: 2023-10-31 DOI: 10.3390/aerospace10110933 Issue No:Vol. 10, No. 11 (2023)
Authors:Xiaojun Yang, Hongming Cai, Jinhui Kang, Wenbo Liu, Peiran Li First page: 934 Abstract: In modern civil aeroengines, the hot streak and swirl at the exit of the combustor have a significant impact on the aerothermal performance of the high-pressure turbine (HPT). Due to the different design purposes of the combustor and the turbine, hot streak (HS) and swirl (SW) have different spatial distributions at the turbine inlet. This paper conducts a transient simulation of the GE E3 first-stage HPT, considering the swirl and hot streak facing the middle of the passage and the leading edge of the nozzle guide vane, respectively, and also explores the impact of positive and negative swirl. The results show that different clocking positions and swirl directions will change the incident angle and streamline distribution of the vane, thereby affecting the migration of the hot streak, the temperature and the Nusselt number distribution on the stator surface. In positive cases, the hot streak gathers in the upper part of the passage, and in negative cases, it is in the lower part. In middle cases, high-temperature areas appear in both vanes, and the distributions are opposite. Affected by the swirl, when facing the passage center, the pressure side stagnation lines of the two vanes are also different, so the Nusselt number distribution is opposite. When facing the leading edge, only one vane appears. Due to the insensitive interference of the rotor–stator, the transient migration of the hot streak in the rotor is mainly affected by the inherent secondary flow and the temperature at the inlet of the rotor (especially the conditions facing the leading edge), while the upstream residual swirl is less affected. Unlike the middle case, in leading edge cases, the hot streak is separated and needs to be re-mixed before entering the blade passage, so the temperature change in the blade cascade is relatively gentle. Based on this, the Nusselt number distribution on the surface of the blade is similar. In order to obtain the most favorable operating conditions for the engine, the turbine efficiency is used to compare the aerothermal performance under different conditions. Ultimately, it was found that the turbine with the hot streak and positive swirl directly facing the leading edge was the most efficient. Citation: Aerospace PubDate: 2023-10-31 DOI: 10.3390/aerospace10110934 Issue No:Vol. 10, No. 11 (2023)
Authors:Hadar Ben-Gida First page: 935 Abstract: Weapons bays have gained much attraction in the last decade, mainly in the context of next-generation aircraft. Although internal store carriage provides numerous advantages, aero-mechanical challenges still exist, particularly for safe store separation. Therefore, it is essential to gain fundamental knowledge of the flow field within weapons bays, which can be achieved by studying the flow within a more simplified geometry of a cavity. In this study, detached eddy simulations are performed using the Elastic-Zonal-Navier–Stokes-Solver (EZNSS) to characterize the unsteady turbulent flow within NASA’s benchmark rectangular cavity with a store model located at various positions. Simulations are performed at a Mach number of 0.4 and a Reynolds number of 7 million to form a transitional cavity flow, which is common in jet-fighter weapons bays. The numerical results are validated with experimental data for the empty cavity and cavity-with-store configurations. The effect of the store’s position on the cavity flow characteristics is analyzed and verified, as well as the aerodynamic loads exerted on the store. Results show a complex interaction between the store model and the cavity flow field, manifested by distortion of the wall pressure fluctuations and mean flow structures and large amplitude fluctuations of the loads exerted on the store. The insights reported herein can serve future development efforts of more accurate numerical frameworks for cavity-with-store configurations towards improving their applicability for weapons bays store separation in certification procedures. Citation: Aerospace PubDate: 2023-10-31 DOI: 10.3390/aerospace10110935 Issue No:Vol. 10, No. 11 (2023)
Authors:Haoxuan Sun, Kenan Yong, Yaohua Shen First page: 936 Abstract: In this paper, to make an interceptor intercept a maneuvering target, a parallel approaching guidance law is developed. In order to estimate the target maneuver more accurately and reduce its influence on the guidance accuracy, a distance-scalar disturbance observer is employed. Specifically, the estimation accuracy of the designed observer is not affected by the relative distance. Finite-time prescribed performance is employed to ensure that the line-of-sight angular rate is capable of converging to a predetermined small region within the specified finite time. All signals of the interception system can guarantee an ultimately uniformly boundedness, as proven by Lyapunov stability theory. Finally, the function of the parallel approaching guidance law is demonstrated using numerical simulation. Citation: Aerospace PubDate: 2023-11-01 DOI: 10.3390/aerospace10110936 Issue No:Vol. 10, No. 11 (2023)
Authors:Miroslav Spodniak, Michal Hovanec, Peter Korba First page: 937 Abstract: The propulsion system for an aircraft is one of its most crucial systems; therefore, its reliable work must be ensured during all operational conditions and regimes. Modern materials, techniques and methods are used to ensure this goal; however, there is still room for improvement of this complex system. The proposed manuscript describes a progressive approach for the mechanical properties prediction of the turbine section during jet engine operation using an artificial neural network, and it illustrates its application on a small experimental jet engine. The mechanical properties are predicted based on the measured temperature, pressure and rpm during the jet engine operation, and targets for the artificial neural network are finite element analyses results. The artificial neural network (ANN) is trained using training data from the experimental measurements (temperatures, pressure and rpm) and the results from finite element analyses of the small experimental engine turbine section proposed in the paper. The predicted mechanical stress by ANN achieved high accuracy in comparison to the finite element analyses results, with an error of 1.38% for predicted mechanical stress and correlation coefficients higher than 0.99. Mechanical stress and deformation prediction of the turbine section is a time-consuming process when the finite element method is employed; however, the method with artificial neural network application presented in this paper decreased the solving time significantly. Mechanical structural analyses performed in ANSYS software using finite element modeling take around 30–40 min for one load step. In contrast, the artificial neural network presented in this paper predicts the stress and deformation for one load step in less than 0.00000044 s. Citation: Aerospace PubDate: 2023-11-01 DOI: 10.3390/aerospace10110937 Issue No:Vol. 10, No. 11 (2023)
Authors:Lennart Lobitz, Hendrik Traub, Mats Overbeck, Maximilian Bień, Sebastian Heimbs, Christian Hühne, Jens Friedrichs, Peter Horst First page: 938 Abstract: Laminar flow offers significant potential for increasing the energy-efficiency of future transport aircraft. The German Cluster of Excellence SE2A is developing a new approach for hybrid laminar flow control. The concept aims to maintain laminar flow up to 80% of the chord length by integrating suction panels at the rear part of the wing, which consist of a thin suction skin and a supporting core structure. This study examines effects of various suction panel configurations on wing mass and load transfer for an all-electric short-range aircraft. Suction panel material, as well as thickness and relative density of the suction panel core are modified in meaningful boundaries. Suction panels made from Ti6Al4V offer the most robust design resulting in a significant increase in wing mass. For the studied configurations, they represent up to 33.8% of the mass of the wingbox. In contrast, panels made from Nylon11CF or PU1000 do not significantly increase the wing mass. However, the use of these materials raises questions about their robustness under operational conditions. The results demonstrate that the choice of material strongly influences the load path within the wing structure. Ti6Al4V suction panels provide sufficient mechanical properties to significantly contribute to load transfer and buckling stiffness. Locally, the share of load transfer attributed to the suction panel exceeds 50%. In contrast, compliant materials such as Nylon11CF or PU1000 are inherently decoupled from load transfer. Unlike the thickness of the suction skin, the relative density of the core structure strongly affects the wrinkling stiffness. However, wrinkling failure did not appear critical for the examined suction panel configurations. In the present study, the mechanical properties of Ti6Al4V cannot fully be exploited. Therefore, compliant suction panels made from Nylon11CF are preferred in order to achieve a lightweight solution, provided that they meet operational requirements. Citation: Aerospace PubDate: 2023-11-02 DOI: 10.3390/aerospace10110938 Issue No:Vol. 10, No. 11 (2023)
Authors:Sejeong Kim, Jongho Park First page: 939 Abstract: Recently, an Unmanned Aerial Vehicle (UAV)-based Wireless Sensor Network (WSN) for data collection was proposed. Multiple UAVs are more effective than a single UAV in wide WSNs. However, in this scenario, many factors must be considered, such as collision avoidance, the appropriate flight path, and the task time. Therefore, it is important to effectively divide the mission areas of the UAVs. In this paper, we propose an improved k-means clustering algorithm that effectively distributes sensors with various densities and fairly assigns mission areas to UAVs with comparable performance. The proposed algorithm distributes mission areas more effectively than conventional methods using cluster head selection and improved k-means clustering. In addition, a postprocessing procedure for reducing the path length during UAV path planning for each mission area is important. Thus, a waypoint refinement algorithm that considers the sensing ranges of the sensor node and the UAV is proposed to effectively improve the flight path of the UAV. The task completion time is determined by evaluating how the UAV collects data through communication with the cluster head node. The simulation results show that the mission area distribution by the improved k-means clustering algorithm and postprocessing by the waypoint refinement algorithm improve the performance and the UAV flight path during data collection. Citation: Aerospace PubDate: 2023-11-02 DOI: 10.3390/aerospace10110939 Issue No:Vol. 10, No. 11 (2023)
Authors:Bowen Xiao, Tianyu Lu, Zeyuan Ma, Qunli Xia First page: 940 Abstract: The disturbance rejection rate (DRR) is an inherent problem of the seeker. The additional line-of-sight (LOS) angular velocity information of the seeker caused by the DRR will affect the attitude of the aircraft through the guidance system, thus forming a parasitic loop in the guidance and control system of the aircraft, which has a great influence on the guidance accuracy. In this study, the influence of the DRR of the roll–pitch seeker on the stable tracking of a maneuvering target is explored. First, the tracking principle of the roll–pitch seeker is analyzed and the conditions for completely isolating the disturbance of the aircraft attitude are deduced. Then, the expression of the frame error angle is derived, a semi-strap-down stable control closed-loop scheme is established, and the DRR transfer function is derived by adding different disturbance torque models. Finally, the simulation of stability tracking characteristics is carried out. The results show that when the aircraft attitude is disturbed at a low frequency or the target is maneuvering at a low frequency, the DRR caused by the spring torque has a great influence on the tracking angle of the two frames, the line of-sight rate accuracy of the optical axis output and the detector error angle. On the contrary, the damping torque DRR plays a leading role in tracking accuracy. Citation: Aerospace PubDate: 2023-11-03 DOI: 10.3390/aerospace10110940 Issue No:Vol. 10, No. 11 (2023)
Authors:Ella Pinska-Chauvin, Hartmut Helmke, Jelena Dokic, Petri Hartikainen, Oliver Ohneiser, Raquel García Lasheras First page: 941 Abstract: This paper describes the safety assessment conducted in SESAR2020 project PJ.10-W2-96 ASR on automatic speech recognition (ASR) technology implemented for air traffic control (ATC) centers. ASR already now enables the automatic recognition of aircraft callsigns and various ATC commands including command types based on controller–pilot voice communications for presentation at the controller working position. The presented safety assessment process consists of defining design requirements for ASR technology application in normal, abnormal, and degraded modes of ATC operations. A total of eight functional hazards were identified based on the analysis of four use cases. The safety assessment was supported by top-down and bottom-up modelling and analysis of the causes of hazards to derive system design requirements for the purposes of mitigating the hazards. Assessment of achieving the specified design requirements was supported by evidence generated from two real-time simulations with pre-industrial ASR prototypes in approach and en-route operational environments. The simulations, focusing especially on the safety aspects of ASR application, also validated the hypotheses that ASR reduces controllers’ workload and increases situational awareness. The missing validation element, i.e., an analysis of the safety effects of ASR in ATC, is the focus of this paper. As a result of the safety assessment activities, mitigations were derived for each hazard, demonstrating that the use of ASR does not increase safety risks and is, therefore, ready for industrialization. Citation: Aerospace PubDate: 2023-11-03 DOI: 10.3390/aerospace10110941 Issue No:Vol. 10, No. 11 (2023)
Authors:Qi Liu, Yong Li, Yanlin Hu, Wei Mao First page: 942 Abstract: The objective of this study is to investigate the effects of a magnetic field gradient on the performance of a magnetically shielded Hall thruster. The Particle-in-cell with Monte Carlo collision method (PIC-MCC) is used to simulate the discharge process of the thruster. The performance and plasma characteristics are obtained in conditions with different magnetic field gradients by numerical simulations. As the maximum of the gradient is increased from 1.2 to 3.33 T/m, the electron number density near the channel exit decreases, which leads to less ionization and a weaker radial electric field. As a result, the thrust and specific impulse are decreased, while the plume divergence angle is reduced. Citation: Aerospace PubDate: 2023-11-05 DOI: 10.3390/aerospace10110942 Issue No:Vol. 10, No. 11 (2023)
Authors:Minglei Du, Haodong Zou, Tinghui Wang, Ke Zhu First page: 943 Abstract: A passive localization algorithm based on UAV aerial images and Angle of Arrival (AOA) is proposed to solve the target passive localization problem. In this paper, the images are captured using fixed-focus shooting. A target localization factor is defined to eliminate the effect of focal length and simplify calculations. To synchronize the positions of multiple UAVs, a dynamic navigation coordinate system is defined with the leader at its center. The target positioning factor is calculated based on image information and azimuth elements within the UAV photoelectric reconnaissance device. The covariance equation is used to derive AOA, which is then used to obtain the target coordinate value by solving the joint UAV swarm positional information. The accuracy of the positioning algorithm is verified by actual aerial images. Based on this, an error model is established, the calculation method of the co-localization PDOP is given, and the correctness of the error model is verified through the simulation of the Monte Carlo statistical method. At the end of the article, the trackless Kalman filter algorithm is designed to improve positioning accuracy, and the simulation analysis is performed on the stationary and moving states of the target. The experimental results show that the algorithm can significantly improve the target positioning accuracy and ensure stable tracking of the target. Citation: Aerospace PubDate: 2023-11-06 DOI: 10.3390/aerospace10110943 Issue No:Vol. 10, No. 11 (2023)
Authors:Juyu Wang, Shenyi Zhang, Guohong Shen, Ying Sun, Binquan Zhang, Zheng Chang, Chunqin Wang, Donghui Hou, Zhe Yang First page: 944 Abstract: Based on orbit detection data acquired by a positive channel Metal Oxide Semiconductor (PMOS) dose detectors on FY4-A (GEO), BD3-M15 (MEO), and YH1-01A (LEO) between November 2018 and November 2022, investigations reveal variations in total dose and the mechanism of radiation dose increase within the geostationary earth orbit (GEO), medium earth orbit (MEO), and low earth orbit (LEO) during the transition from the 24th to the 25th solar cycles. It provides the radiation dose parameters for the study of the space environment from different altitude orbits, and also provides an important basis for studying the solar minimum activity and dose generation The data indicate directional disparities in radiation doses among the orbital regions, with the hierarchy being FY4-A > YH1-01A > BD3-M15. Furthermore, the results show that the total doses of FY4-A and BD3-M15 were higher than that of YH1-01A by two orders of magnitude, with BD3-M15 > FY4-A > YH1-01A. The monthly radiation dose rates of FY4-A in GEO and BD3-M15 in MEO exhibited positive correlation with their corresponding APs during the solar minimum. Notably, for FY4-A, the monthly radiation dose rate during geomagnetic disturbed periods exceeded that of the dose rate during geomagnetic quiet periods by one order of magnitude. This analysis revealed the substantial impact of geomagnetic storms and space environment disturbances on radiation doses detected by MEO and GEO orbital satellites. These perturbations, attributable to medium- and small-scale high-energy electron storms induced by reproducible coronal holes, emerged as key driving factors of the increase in radiation doses in MEO and GEO environments. Citation: Aerospace PubDate: 2023-11-06 DOI: 10.3390/aerospace10110944 Issue No:Vol. 10, No. 11 (2023)
Authors:Tianming Feng, Jin Lei, Yujie Zeng, Xinyan Qin, Yanqi Wang, Dexin Wang, Wenxing Jia First page: 945 Abstract: The Flying–Walking Power Line Inspection Robot (FPLIR) faces challenges in maintaining stability and reliability when operating in harsh transmission line environments with complex conditions. The robot often switches modes frequently to land accurately on the line, resulting in increasing following errors and premature or delayed switching caused by reference path switching. To address these issues, a path-following control method based on improved line of sight (LOS) is proposed. The method features an adaptive acceptance circle strategy that adjusts the radius of the acceptance circle of the path point based on the angle of the path segment and the flight speed at the time of switching, improving path-following accuracy during reference trajectory switching. Also, an adaptive heading control with vertical distance feedback is designed to prioritize different path-following methods in real time based on variations in vertical distance, achieving rapid convergence along the following path. The state feedback following control law, based on the improved LOS, achieves the stable following of the reference path, which was validated by simulations. The simulation results show that the improved LOS reduces the convergence time by 0.8 s under controllable error conditions for path angles of θ ∈ (0, π⁄2). For path angles of θ ∈ (π⁄2, π), the following error is reduced by 0.3 m, and the convergence time is reduced by 0.4 s. These results validate the feasibility and effectiveness of the proposed method. This method demonstrates advantages over the traditional LOS in terms of following accuracy and convergence speed, providing theoretical references for future 3D path following for path-following robots and aerial vehicles. Citation: Aerospace PubDate: 2023-11-06 DOI: 10.3390/aerospace10110945 Issue No:Vol. 10, No. 11 (2023)
Authors:Rhys Jones, Ramesh Chandwani, Chris Timbrell, Anthony J. Kinloch, Daren Peng First page: 946 Abstract: Adhesively bonded doublers and adhesively bonded repairs are extensively used to extend the operational life of metallic aircraft structures. Consequently, this paper focuses on the tools needed to address sustainment issues associated with both adhesively bonded doublers and adhesively bonded repairs to (metallic) aircraft structures, in a fashion that is consistent with the building-block approach mandated in the United States Air Force (USAF) airworthiness certification standard MIL-STD-1530D and also in the United States (US) Joint Services Structural Guidelines JSSG-2006. In this context, it is shown that the effect of biaxial loads on cohesive crack growth in a bonded doubler under both constant amplitude fatigue loads and operational flight loads can be significant. It is also suggested that as a result, for uniaxial tests to replicate the cohesive crack growth seen in adhesively bonded doublers and adhesively bonded repairs under operational flight loads, the magnitude of the applied load spectrum may need to be continuously modified so as to ensure that the crack tip similitude parameter in the laboratory tests reflects that seen in the full-scale aircraft. Citation: Aerospace PubDate: 2023-11-07 DOI: 10.3390/aerospace10110946 Issue No:Vol. 10, No. 11 (2023)
Authors:Denise Keil, Stefan Scharring, Erik Klein, Raoul-Amadeus Lorbeer, Dennis Schumacher, Frederic Seiz, Kush Kumar Sharma, Michael Zwilich, Lukas Schnörer, Markus Roth, Mohamed Khalil Ben-Larbi, Carsten Wiedemann, Wolfgang Riede, Thomas Dekorsy First page: 947 Abstract: Environmental pollution exists not only within our atmosphere but also in space. Space debris is a critical problem of modern and future space infrastructure. Congested orbits raise the question of spacecraft disposal. Therefore, state-of-the-art satellites come with a deorbit system in cases of low Earth orbit (LEO) and with thrusters for transferring into the graveyard orbit for geostationary and geosynchronous orbits. No practical solution is available for debris objects that stem from fragmentation events. The present study focuses on objects in LEO orbits with dimensions in the dangerous class of 1 to 10 cm. Our assumed method for the change of trajectories of space debris is laser ablation for collision avoidance or complete removal by ground-based laser systems. Thus, we executed an experimental feasibility study with focus on thermal and impulse coupling between laser and sample. Free-fall experiments with a 10 ns laser pulse at nominally 60 J and 1064 nm were conducted with GSI Darmstadt’s nhelix laser on various sample materials with different surfaces. Ablated mass, heating, and trajectory were recorded. Furthermore, we investigated the influence of the sample surface roughness on the laser-object interaction. We measured impulse coupling coefficients between 7 and 40 µNs/J and thermal coupling coefficients between 2% and 12.5% both depending on target fluence, surface roughness, and material. Ablated mass and changes in surface roughness were considered via simulation to discriminate their relevance for a multiple shot concept. Citation: Aerospace PubDate: 2023-11-07 DOI: 10.3390/aerospace10110947 Issue No:Vol. 10, No. 11 (2023)
Authors:Linfeng Su, Jinbo Wang, Hongbo Chen First page: 948 Abstract: The mission of hypersonic vehicles faces the problem of highly nonlinear dynamics and complex environments, which presents challenges to the intelligent level and real-time performance of onboard guidance algorithms. In this paper, inverse reinforcement learning is used to address the hypersonic entry guidance problem. The state-control sample pairs and state-rewards sample pairs obtained by interacting with hypersonic entry dynamics are used to train the neural network by applying the distributed proximal policy optimization method. To overcome the sparse reward problem in the hypersonic entry problem, a novel reward function combined with a sophisticated discriminator network is designed to generate dense optimal rewards continuously, which is the main contribution of this paper. The optimized guidance methodology can achieve good terminal accuracy and high success rates with a small number of trajectories as datasets while satisfying heating rate, overload, and dynamic pressure constraints. The proposed guidance method is employed for two typical hypersonic entry vehicles (Common Aero Vehicle-Hypersonic and Reusable Launch Vehicle) to demonstrate the feasibility and potential. Numerical simulation results validate the real-time performance and optimality of the proposed method and indicate its suitability for onboard applications in the hypersonic entry flight. Citation: Aerospace PubDate: 2023-11-07 DOI: 10.3390/aerospace10110948 Issue No:Vol. 10, No. 11 (2023)
Authors:In-Hoi Koo, Keon-Hyeong Lee, Min-Su Kim, Hyung-Seok Han, Holak Kim, Jeong-Yeol Choi First page: 949 Abstract: Fuel injection and mixing affect the characteristics of detonation initiation and propagation, as well as the propulsion performance of rotating detonation engine (RDE). A study on the injector is carried out in the present investigation. A rectangular-shaped hole-type fuel injector (RHFI) and slit-type fuel injector (SFI) were designed and compared experimentally at equivalent conditions. The investigation of the detonation propagation modes and the analysis of propulsion performance were carried out using fast Fourier transform (FFT), short-time Fourier transform (STFT), and unwrapped image post-processing. Under 50, 75, and 100 g/s flow rate conditions at an equivalence ratio of 1.0 ± 0.05, the RHFI has relatively stable detonation propagation characteristics, higher thrust, and specific impulse performance. Additionally, the results of the experiment indicate that the number of detonation waves affects performance. Citation: Aerospace PubDate: 2023-11-08 DOI: 10.3390/aerospace10110949 Issue No:Vol. 10, No. 11 (2023)
Authors:Tong Lin, Mingying Huo, Naiming Qi, Jianfeng Wang, Tianchen Wang, Haopeng Gu, Yiming Zhang First page: 950 Abstract: Electroaerodynamic unmanned aerial vehicles (EAD-UAVs) are innovative UAVs that use high-voltage asymmetric electrodes to ionize air molecules and Coulomb force to push these ions to produce thrust. Unlike fixed-wing and rotor UAVs, EAD-UAVs contain no moving surfaces and have the advantages of very low noise, low mechanical fatigue, and no carbon emissions. This paper proposes an EAD-UAV configuration with an orthogonal arrangement of multiple EAD thrusters to adjust the EAD-UAV attitude and flight trajectory through voltage distribution control alone. Based on a one-dimensional dynamic model of an EAD thruster, the attitude–path coupling dynamics of the EAD-UAV were derived. To achieve EAD-UAV flight control for a specified target, the Bezier shaping approach (BSA) was implemented to realize rapid trajectory optimization considering the coupling dynamic constraints. The numerical simulation results indicate that the BSA can quickly procure an optimized flight trajectory that satisfies the dynamic and boundary constraints. Compared with the Gaussian pseudospectral method (GPM), the BSA changes the optimization index of the objective function by nearly 1.14% but demands only nearly 1.95% of the computational time on average. Hence, the improved integrative Bezier shaping approach (IBSA) can overcome the poor convergence issue of the BSA under the continuous acceleration constraint of multi-target flight trajectories. Citation: Aerospace PubDate: 2023-11-10 DOI: 10.3390/aerospace10110950 Issue No:Vol. 10, No. 11 (2023)
Authors:Quang-Ngoc Le, Hyeong-Mo Park, Yeongjin Kim, Huy-Hoang Pham, Jai-Hyuk Hwang, Quoc-Viet Luong First page: 951 Abstract: Aircraft landing gear equipped with a magnetorheological (MR) damper is a semi-active system that contains nonlinear behavior, disturbances, uncertainties, and delay times that can have a huge impact on the landing’s performance. To solve this problem, this paper adopts two types of controllers, which are an intelligent controller and a model predictive controller, for a landing gear equipped with an MR damper to improve the landing gear performance considering response time in different landing cases. A model predictive controller is built based on the mathematical model of the landing gear system. An intelligent controller based on a neural network is designed and trained using a greedy bandit algorithm to improve the shock absorber efficiency at different aircraft masses and sink speeds. In this MR damper, the response time is assumed to be constant at 20 ms, which is similar to the response time of the commercial MR damper. To verify the efficiency of the proposed controllers, numerical simulations compared with a passive damper and a skyhook controller in different landing cases are executed. The major finding indicates that the suggested controller performs better in various landing scenarios than other controllers in terms of shock absorber effectiveness and adaptability. Citation: Aerospace PubDate: 2023-11-11 DOI: 10.3390/aerospace10110951 Issue No:Vol. 10, No. 11 (2023)
Authors:Sybert Stroeve First page: 952 Abstract: TCAS II is a rule-based airborne collision avoidance system (ACAS) that is used in current commercial air transport operations, and ACAS Xa is a new optimization-based system. Operational validation studies have mainly used deterministic simulations of ACAS performance using various sets of encounters. Recently a new approach was developed, which employs Monte Carlo (MC) simulation of agent-based models to evaluate the impact of sensor errors and pilot response variability. This paper contrasts the results of both approaches in a comparison of TCAS II and ACAS Xa for various types of synthetic encounters. It was found that conventional estimates of near mid-air collision (NMAC) probabilities are often lower than the estimates achieved using MC simulation, and that the biases in the P(NMAC) estimates are consistently larger for ACAS Xa than for TCAS II. Contributions to unresolved risk are largest for pilot performance, then for encounter types, and finally for sensor errors. The contribution of non-responding pilots is much larger than the differences between TCAS II and ACAS Xa. It is concluded that the agent-based MC simulation overcomes the limitations in traditional evaluation of altimetry errors and pilot response, providing an independent means to effectively analyze the robustness of ACASs. Citation: Aerospace PubDate: 2023-11-11 DOI: 10.3390/aerospace10110952 Issue No:Vol. 10, No. 11 (2023)
Authors:Wenbin Liu, Youshan Wang, Yuchen Ji First page: 953 Abstract: Landing impact load design is essential, but the process has rarely been fully described, and some designers have even neglected the differences between wheel-axle and ground-contact loads, as well as loads in the longitudinal direction, especially in experimental validations. In this paper, the entire design process of a nose landing gear is addressed, including a theoretical analysis of the unit and its experimental validation. In the theoretical analysis, a mathematical model of a two-mass system with four degrees of freedom was adopted, a computer simulation model was built accordingly, and a preliminary analysis was subsequently conducted to analyze the landing impact loads, verify the landing gear performance, and gauge the difference between the wheel-axle and ground-contact loads. For the experimental validation of the gear, a landing gear drop test was conducted in an optimized manner that emphasized pre-test preparation and during-test wheel-axle load measurement. The test results showed that both the vertical and less studied longitudinal loads, as well as the wheel-axle and ground-contact loads, had good agreement with the analysis; thus, the model, the tool, and the preliminary design were considered to be experimentally validated. Citation: Aerospace PubDate: 2023-11-12 DOI: 10.3390/aerospace10110953 Issue No:Vol. 10, No. 11 (2023)
Authors:Junfang Fan, Denghui Dou, Yi Ji First page: 954 Abstract: In this study, two different impact-angle-constrained guidance and control strategies using deep reinforcement learning (DRL) are proposed. The proposed strategies are based on the dual-loop and integrated guidance and control types. To address comprehensive flying object dynamics and the control mechanism, a Markov decision process is used to solve the guidance and control problem, and a real-time impact-angle error in the state vector is used to improve the model applicability. In addition, a reasonable reward mechanism is designed based on the state component which reduces both the miss distance and the impact-angle error and solves the problem of sparse rewards in DRL. Further, to overcome the negative effects of unbounded distributions on bounded action spaces, a Beta distribution is used instead of a Gaussian distribution in the proximal policy optimization algorithm for policy sampling. The state initialization is then realized using a sampling method adjusted to engineering backgrounds, and the control strategy is adapted to a wide range of operational scenarios with different impact angles. Simulation and Monte Carlo experiments in various scenarios show that, compared with other methods mentioned in the experiment in this paper, the proposed DRL strategy has smaller impact-angle errors and miss distance, which demonstrates the method’s effectiveness, applicability, and robustness. Citation: Aerospace PubDate: 2023-11-13 DOI: 10.3390/aerospace10110954 Issue No:Vol. 10, No. 11 (2023)
Authors:Enrico Cestino, Davide Pisu, Vito Sapienza, Lorenzo Chesta, Valentina Martilla First page: 955 Abstract: A new Range Equation for a hybrid-electric propeller-driven aircraft was formulated by an original derivation based on the comparison of Virtual Electrical Aircraft (VEA) and Virtual Thermal Aircraft (VTA) range equations. The new formulation makes it possible to study the range of a hybrid aircraft with pre-established values of electric motor usage rate. The fuel and battery mass are defined "a priori", and do not depend on the power split, so even the aircraft’s total mass is constant. The comparison with the typical range formulas available for hybrid aircraft was made on the basis of a reference composite VLA category aircraft manufactured by the CFM Air company. The analysis carried out shows that there is an optimum hybridization level as a function of the pre-set specific energy of the batteries system. Citation: Aerospace PubDate: 2023-11-13 DOI: 10.3390/aerospace10110955 Issue No:Vol. 10, No. 11 (2023)
Authors:Chenghua Cong, Honggang Qin, Xingyou Yi First page: 956 Abstract: The unsteady characteristics of the second throat of a transonic wind tunnel have an important influence on the design and test of the wind tunnel. Therefore, the forced oscillation characteristics were studied by a numerical simulation method. The governing equation was the viscous compressible unsteady Navier–Stokes equation. Under the sinusoidal pressure disturbance of the computational domain exit, the shock wave presents a clear forced oscillation state, and the shock wave periodically changes its position. Under a pressure disturbance of 1%, the shock wave displacement reaches 150 mm. Additionally, overshoot occurs when the shock moves upstream or downstream. The shock-boundary layer interference is very sensitive to the motion characteristics of the shock wave, resulting in a transformation of the flow field symmetry. The flow field downstream of the shock wave exhibits periodic structural changes. Compared with the pressure change at the outlet, the pressure change near the shock wave has a phase delay. The increasing disturbance near the shock wave shows a clear amplification effect. The pressure disturbance near the shock wave had an obvious amplification effect, and its fluctuation amount reached 16% under the pressure disturbance of 1%. The variation trend of the second throat wall force, wavefront Mach number, and Mach number in the test section with time is similar to that of the downstream disturbance, but it does not have a complete follow-up effect, which indicates that the pressure disturbance can propagate into the test section through the boundary layer or the shock gap. Nevertheless, the second throat choking can still control the Mach number stability of the test section. The dynamic characteristics of shock oscillation are related to the amplitude and frequency of the applied pressure disturbance. The shock displacement decreases with the increase in the excitation frequency. When the excitation frequency is higher than 125 Hz, the flow field basically does not change. Citation: Aerospace PubDate: 2023-11-13 DOI: 10.3390/aerospace10110956 Issue No:Vol. 10, No. 11 (2023)
Authors:Jiachen Wang, Zhou Zhou First page: 957 Abstract: This paper introduces the novel application of the mass and force lumping technique to enhance the finite element discretization of the fully intrinsic beam formulation. In our aeroelastic system model, 2-D unsteady aerodynamics were incorporated alongside simple calculations for thrust and gravity. Through the central difference discretization method, the discretized system was thoroughly examined, shedding light on the advantages of the mass and force lumping approach. With the use of a first-order lumping method, we successfully reconstructed the inertia matrices, external forces, and moments. The resulting equations are more systematically structured, facilitating the extraction of a regular state-space linear system using the direct index reduction method post-linearization. Numerical results further confirm that the proposed techniques can effectively capture the nonlinear dynamics of aeroelastic systems, enabling equation reconstruction and leading to significant benefits in system order reduction and flight dynamical analysis. Citation: Aerospace PubDate: 2023-11-13 DOI: 10.3390/aerospace10110957 Issue No:Vol. 10, No. 11 (2023)
Authors:Yang Yu, Yuepeng Mao, Tao Yu, Yalin Yang, Shulin Xu, Sijia Liang First page: 958 Abstract: Flow separation and transitions of separation patterns are common phenomena of nozzles working with a wide Mach range. The maximum thrust method is applied to design the single-expansion ramp nozzle (SERN) for specific operating conditions. The nozzle is used to numerically simulate the transition processes of separation patterns under the linear change in the external flow Mach number and the actual trajectory take-off condition of a rocket-based combined cycle (RBCC), to investigate the mechanism through which the external flow field influences the separation pattern transition during acceleration. The computational fluid dynamics (CFD) method is briefly introduced, followed by experimental validation. Then, the design procedure of SERN is described in detail. The simulation results indicate that as the external Mach number increases, the flow field in the nozzle undergoes transitions from RSS (ramp) to FSS, and finally exhibits a no-flow separation pattern. The rate at which the external Mach number varies has little effect on the transition principle of the nozzle flow separation patterns, but it has a significant effect on the critical Mach number of the transition points. The external flow field of the nozzle has an airflow accumulation effect during acceleration, which can delay the transition of the flow separation pattern. Citation: Aerospace PubDate: 2023-11-13 DOI: 10.3390/aerospace10110958 Issue No:Vol. 10, No. 11 (2023)
Authors:Ahmed Mahfouz, Gabriella Gaias, D. M. K. K. Venkateswara Rao, Holger Voos First page: 959 Abstract: In this paper, the problem of autonomous optimal absolute orbit keeping for a satellite mission in Low Earth Orbit using electric propulsion is considered. The main peculiarity of the approach is to support small satellite missions in which the platform is equipped with a single thruster nozzle that provides acceleration on a single direction at a time. This constraint implies that an attitude maneuver is necessary before or during each thrusting arc to direct the nozzle into the desired direction. In this context, an attitude guidance algorithm specific for the orbit maneuver has been developed. A Model Predictive Control scheme is proposed, where the attitude kinematics are coupled with the orbital dynamics in order to obtain the optimal guidance profiles in terms of satellite state, reference attitude, and thrust magnitude. The proposed control scheme is developed exploiting formation flying techniques where the reference orbit is that of a virtual spacecraft that the main satellite is required to rendezvous with. In addition to the controller design, the closed-loop configuration is presented supported by numerical simulations. The efficacy of the proposed autonomous orbit-keeping approach is shown in several application scenarios. Citation: Aerospace PubDate: 2023-11-13 DOI: 10.3390/aerospace10110959 Issue No:Vol. 10, No. 11 (2023)
Authors:Ellen L. Sirks, Richard Massey, Ajay S. Gill, Jason Anderson, Steven J. Benton, Anthony M. Brown, Paul Clark, Joshua English, Spencer W. Everett, Aurelien A. Fraisse, Hugo Franco, John W. Hartley, David Harvey, Bradley Holder, Andrew Hunter, Eric M. Huff, Andrew Hynous, Mathilde Jauzac, William C. Jones, Nikky Joyce, Duncan Kennedy, David Lagattuta, Jason S.-Y. Leung, Lun Li, Stephen Lishman, Thuy Vy T. Luu, Jacqueline E. McCleary, Johanna M. Nagy, C. Barth Netterfield, Emaad Paracha, Robert Purcaru, Susan F. Redmond, Jason D. Rhodes, Andrew Robertson, L. Javier Romualdez, Sarah Roth, Robert Salter, Jürgen Schmoll, Mohamed M. Shaaban, Roger Smith, Russell Smith, Sut Ieng Tam, Georgios N. Vassilakis First page: 960 Abstract: In April 2023, the superBIT telescope was lifted to the Earth’s stratosphere by a helium-filled super-pressure balloon to acquire astronomical imaging from above (99.5% of) the Earth’s atmosphere. It was launched from New Zealand and then, for 40 days, circumnavigated the globe five times at a latitude 40 to 50 degrees south. Attached to the telescope were four “drs” (Data Recovery System) capsules containing 5 TB solid state data storage, plus a gnss receiver, Iridium transmitter, and parachute. Data from the telescope were copied to these, and two were dropped over Argentina. They drifted 61 km horizontally while they descended 32 km, but we predicted their descent vectors within 2.4 km: in this location, the discrepancy appears irreducible below ∼2 km because of high speed, gusty winds and local topography. The capsules then reported their own locations within a few metres. We recovered the capsules and successfully retrieved all of superBIT’s data despite the telescope itself being later destroyed on landing. Citation: Aerospace PubDate: 2023-11-14 DOI: 10.3390/aerospace10110960 Issue No:Vol. 10, No. 11 (2023)
Authors:Mengchuang Zhang, Shasha Xia, Yongsheng Huang, Jiawei Tian, Zhiping Yin First page: 961 Abstract: Flight maneuver recognition (FMR) is a critical tool for capturing essential information about the state of an aircraft, which is necessary to improve pilot training, flight safety, and autonomous air combat. However, due to the alignment of multidimensional, multimodal time series and insufficient data, challenges exist that limit the accuracy of FMR. In this paper, two FMR methods, including an improved dynamic time-warping distance-based algorithm (D-DTW) and a perceptually important point-based method, are proposed based on time series mining techniques. The differential dynamics equations of the aircraft’s center of gravity in the trajectory coordinate system are established. Subsequently, based on the obtained flight data, the engine thrust is derived by employing criteria based on flight mechanics and coordinate system transformation methods. Finally, the flight profile is clustered and divided based on the preprocessed data. The engine load factor is obtained through centroid transformation and coordinate system translation based on flight dynamics calculations. The results indicate that the two methods exhibit varying applicability with respect to FMR. However, the second method is more suitable regarding the recognition or prediction of engine thrust and load factor. Citation: Aerospace PubDate: 2023-11-15 DOI: 10.3390/aerospace10110961 Issue No:Vol. 10, No. 11 (2023)
Authors:Hao Li, Yuping Li, Zhongliang Zhao, Xiaobing Wang, Haiyong Yang, Shang Ma First page: 962 Abstract: To research serious nonlinear coupling problems among aerodynamics, flight mechanics, and flight control during high maneuvers, a virtual flight testing platform has been developed for a large-scale, high-speed wind tunnel, based on the real physical environment, and it can significantly mitigate risks and reduce the costs of subsequent flight tests. The platform of virtual flight testing is composed of three-degrees-of-freedom model support, measuring devices for aerodynamic and motion parameters, a virtual flight control system, and a test model. It provides the ability to realistically simulate real maneuvers, investigate the coupling characteristics of unsteady aerodynamics and nonlinear flight dynamics, evaluate flight performance, and verify the flight control law. The typical test results of a pitch maneuver with open-loop and closed-loop control are presented, including a one-degree-of-freedom pitch motion and a two-degrees-of-freedom pitch and roll motion. The serious pitch and roll-coupled motion during a pitch maneuver at a high angle of attack is revealed, and the flight control law for decoupled control is successfully verified. The comparison of the test results and the flight data of a real pitch maneuver proves the reliability and capability of virtual flight testing. Citation: Aerospace PubDate: 2023-11-15 DOI: 10.3390/aerospace10110962 Issue No:Vol. 10, No. 11 (2023)
Authors:Yuan-Jen Chang, He-Kai Hsu, Tzu-Hsuan Hsu, Tsung-Ti Chen, Po-Wen Hwang First page: 963 Abstract: With the development of next-generation airplanes, the complexity of equipment has increased rapidly, and traditional maintenance solutions have become cost-intensive and time-consuming. Therefore, the main objective of this study is to adopt predictive maintenance techniques in daily maintenance in order to reduce manpower, time, and the cost of maintenance, as well as increase aircraft availability. The landing gear system is an important component of an aircraft. Wear and tear on the parts of the landing gear may result in oscillations during take-off and landing rolling and even affect the safety of the fuselage in severe cases. This study acquires vibration signals from the flight data recorder and uses prognostic and health management technology to evaluate the health indicators (HI) of the landing gear. The HI is used to monitor the health status and predict the remaining useful life (RUL). The RUL prediction model is optimized through hyperparameter optimization and using the random search algorithm. Using the RUL prediction model, the health status of the landing gear can be monitored, and adaptive maintenance can be carried out. After the optimization of the RUL prediction model, the root-mean-square errors of the three RUL prediction models, that is, the autoregressive model, Gaussian process regression, and the autoregressive integrated moving average, decreased by 45.69%, 55.18%, and 1.34%, respectively. In addition, the XGBoost algorithm is applied to simultaneously output multiple fault types. This model provides a more realistic representation of the actual conditions under which an aircraft might exhibit multiple faults. With an optimal fault diagnosis model, when an anomaly is detected in the landing gear, the faulty part can be quickly diagnosed, thus enabling faster and more adaptive maintenance. The optimized multi-fault diagnosis model proposed in this study achieves average accuracy, a precision rate, a recall rate, and an F1 score of more than 96.8% for twenty types of faults. Citation: Aerospace PubDate: 2023-11-15 DOI: 10.3390/aerospace10110963 Issue No:Vol. 10, No. 11 (2023)
Authors:Chen Xu, Yang Wang, Zhiqi Niu, Sheng Luo, Fenghuai Du First page: 964 Abstract: In this paper, by accounting for the angle constraint (AC) and autopilot lag compensation (ALC), a novel fixed-time convergent guidance law is developed based on a fixed-time state observer and bi-limit homogeneous technique. The newly proposed guidance law exhibits three attractive features: (1) unlike existing guidance laws with AC and ALC which can only guarantee asymptotic stability or finite-time stability, the newly proposed guidance scheme can achieve fixed-time stability. Thus, the newly proposed scheme can drive the guidance error to zero within bounded time which is independent of the initial system conditions. (2) To compensate for autopilot lag, existing guidance schemes need the unmeasurable second derivative of the range along line-of-sight (LOS) and second derivative of LOS angle or the derivative of missile’s acceleration. Without using these unmeasurable states, the newly proposed guidance law still can guarantee the fixed-time stability. (3) By using the bi-limit homogeneous technique to construct an integral sliding-mode surface, the proposed scheme eliminates the singular problem without using the commonly-used approximate method in recent fixed-time convergent guidance schemes. Finally, the simulation results demonstrate the effectiveness of the proposed scheme. Citation: Aerospace PubDate: 2023-11-16 DOI: 10.3390/aerospace10110964 Issue No:Vol. 10, No. 11 (2023)
Authors:Elena Karpovich, Timur Kombaev, Djahid Gueraiche, Daria Evdokimova, Kirill Alexandrov First page: 965 Abstract: The paper presents specifications for the Long-Endurance Mars Exploration Flying Vehicle (LEMFEV), which will be used as future design input data. The specifications are based on the analysis of previous Mars missions and scientific data collected by the operating Martian probes. The design specifications include the requirements related to the airplane’s delivery to the Martian surface; the requirements related to the Martian conditions (atmosphere and climate); and the requirements related to the scientific payload parameters and the mission flight profile. Citation: Aerospace PubDate: 2023-11-16 DOI: 10.3390/aerospace10110965 Issue No:Vol. 10, No. 11 (2023)
Authors:Hongxin Zhu, Yimin Zhu, Xiaoyi Zhang, Jian Chen, Mingyu Luo, Weiguang Huang First page: 966 Abstract: Performing online damage evaluation of blades subjected to complex cyclic loads based on the operating state of a gas turbine enables real-time reflection of a blade’s damage condition. This, in turn, facilitates the achievement of predictive maintenance objectives, enhancing the economic and operational stability of gas turbine operations. This study establishes a hybrid model for online damage evaluation of gas turbine blades based on their operational state. The model comprises a gas turbine performance model based on thermodynamic simulation, a component load calculation model based on a surrogate model, an updated cycle counting method based on four-point rainflow, and an improved damage mechanism evaluation model. In the new model, the use of a surrogate model for the estimation of blade loading information based on gas turbine operating parameters replaces the conventional physical modeling methods. This substitution enhances the accuracy of blade loading calculations while ensuring real-time performance. Additionally, the new model introduces an updated cycle counting method based on four-point rainflow and an improved damage mechanism evaluation model. In the temperature counting part, a characteristic stress that represents the stress information during the cyclic process is proposed. This inclusion allows for the consideration of the impact of stress fluctuations on creep damage, thereby enhancing the accuracy of the fatigue damage assessment. In the stress counting part, the model incorporates time information associated with each cycle. This concept is subsequently applied in determining the identified cyclic strain information, thereby improving the accuracy of the fatigue damage evaluation. Finally, this study applies the new model to an online damage evaluation of a turbine stationary blade using actual operating data from a micro gas turbine. The results obtained from the new model are compared with the EOH recommended by the OEM, validating the accuracy and applicability of the new model. Citation: Aerospace PubDate: 2023-11-16 DOI: 10.3390/aerospace10110966 Issue No:Vol. 10, No. 11 (2023)
Authors:David Gerhardinger, Anita Domitrović, Karolina Krajček Nikolić, Darko Ivančević First page: 967 Abstract: This paper introduces an expert system approach for predicting the remaining useful life (RUL) of light aircraft structural components by analyzing operational and maintenance records. The expert system consists of four modules: knowledge acquisition, knowledge base, inference, and explanation. The knowledge acquisition module retrieves data from mandatory records, such as aircraft logbooks and mass and balance sheets. The knowledge base stores specific remaining useful lives (SRULs) for different load profiles that are determined using numerical strength analysis. The inference module utilizes the Palmgren-Miner rule to estimate the accumulated fatigue damage of the structural component based on the input data and the knowledge base. Lastly, the explanation module links the accumulated damage to the maintenance program and suggests the appropriate maintenance action. The Cessna 172R main landing gear leg is utilized as a case study, demonstrating the variance of RUL depending on the operating conditions. The objective of this approach is to enhance light aircraft maintenance decision making and advance operational safety. Citation: Aerospace PubDate: 2023-11-17 DOI: 10.3390/aerospace10110967 Issue No:Vol. 10, No. 11 (2023)
Authors:Seon-Chil Kim, Sung-Hwan Kim First page: 968 Abstract: Aircraft are exposed to cosmic radiation depending on their flight altitude and latitude. Therefore, flight attendants are exposed to radiation for long periods. In this study, a 0.3 mm thick fabric was designed with which to manufacture crew clothes to shield them against external exposure to space radiation, and the shielding performance was analyzed based on empirical experiments in a real environment. Gadolinium oxide, which has a high neutron reaction cross-section, and tungsten, which is useful for gamma-ray shielding, were proposed as the main raw materials for the shielding fabric, and the shielding performance was evaluated using detectors on Arctic flight routes. Composite (KG-01) and single (KG-02) shielding materials were used. In the case of KG-01, the transmission dose rate was 90.7 ± 5.6% compared with the unshielded case, showing an average space-radiation dose reduction of 9.3%. With KG-02, the transmission dose rate was 103.1 ± 2.0% compared with the unshielded case, and the average dose rate increased by 3.1%; therefore, there was no shielding effect against space radiation. Considering the statistical error of the environmental radiation at aircraft flight altitudes, KG-01 had a shielding effect of at least 5%; however, KG-02 yielded no significant shielding effects. Citation: Aerospace PubDate: 2023-11-17 DOI: 10.3390/aerospace10110968 Issue No:Vol. 10, No. 11 (2023)
Authors:Rejish Jesudasan, Ardeshir Hanifi, Raffaello Mariani First page: 969 Abstract: Wing-in-Ground (WIG) effect aircraft are gaining attention for their potential in reducing environmental impact. However, optimising wing planforms based solely on aerodynamics might improve performance while compromising static height stability of WIG aircraft. This study investigates the effects of planar and nonplanar wing planform optimisation for regional transport ground effect aircraft. Three distinct multiobjective wing planform optimisations are explored: planar wing optimisation, nonplanar wing optimisation, and nonplanar wingtip optimisation. These optimisations assess the impact on both aerodynamic efficiency and static height stability characteristics of a wing planform in ground effect, at three different flying altitudes. In extreme ground effect, the Pareto set includes wings with negative spanwise camber, enhancing both cushion sensation and aerodynamic efficiency by effectively utilizing ground effect, thus proving advantageous over planar wing configurations. Citation: Aerospace PubDate: 2023-11-17 DOI: 10.3390/aerospace10110969 Issue No:Vol. 10, No. 11 (2023)
Authors:Naser T. Burahmah, Lawrence H. Heilbronn First page: 970 Abstract: As humanity prepares for extended lunar exploration, understanding the radiation environment on the Moon is important for astronaut safety. This study utilized the Particle and Heavy-Ion Transport code System (PHITS), a stochastic Monte Carlo-based radiation transport code, to simulate the radiation environment inside a habitat, focusing on the impact of galactic cosmic rays (GCRs) interacting with local lunar and habitat material, and to calculate the effective dose equivalent. Placing a lunar base in a crater can provide additional shielding by reducing the GCR flux incident on the base. Furthermore, the secondary radiation field created by GCR interactions may be altered by the local topological features. GCR transport calculations were performed for a hypothetical base on a flat surface and in shallow and deep craters to determine the overall efficacy in dose reduction gained by placing a base in a 100 m diameter crater. Our findings indicate that the depth of lunar habitats significantly influences the effective dose equivalent, with deeper locations offering substantial protection. Specifically, alongside a crater wall at a deep depth (15 m), in solar minimum conditions, the total dose was reduced by approximately 44.9% compared to the dose at the surface. Similarly, at a shallow depth (5 m), a reduction of approximately 10.7% was observed. As the depth of the crater increased, the neutron contribution to the total dose also increased. Comparing the simulated doses to NASA’s lifetime exposure limits provides insights into mission planning and astronaut safety, emphasizing the importance of strategic habitat placement and design. Citation: Aerospace PubDate: 2023-11-18 DOI: 10.3390/aerospace10110970 Issue No:Vol. 10, No. 11 (2023)
Authors:Yuting Shang, Yifan Deng, Yuanli Cai, Yu Chen, Sirui He, Xuanchong Liao, Haonan Jiang First page: 971 Abstract: The escalating proliferation of space debris poses an increasing risk to spinning satellites, elevating the probability of hazardous collisions that can result in severe damage or total loss of functionality. To address this concern, a pioneering inflatable protective structure is employed to ensure the optimal functionality of spinning satellites. Additionally, a multi-body dynamic modeling method based on spring hinge unfolding/spring expansion is proposed to tackle the complex dynamics of spinning satellites with inflatable protective structures during flight. This method enables analysis of the motion parameters of spinning satellites. First, the structural composition of a spinning satellite with inflatable protective structures is introduced and its flight process is analyzed. Then, an articulated spring hinge unfolding model or a spring expansion model using the Newton–Euler method is established to describe the unfolding or expansion of the spinning satellite with inflatable protective structures during flight. Finally, the effects on the motion parameters of a spinning satellite are analyzed through simulation under various working conditions. Citation: Aerospace PubDate: 2023-11-18 DOI: 10.3390/aerospace10110971 Issue No:Vol. 10, No. 11 (2023)
Authors:Mohammed Baz First page: 972 Abstract: The aviation industry is one of the fastest-growing sectors and is crucial for both passenger transport and logistics. However, the high costs associated with maintenance, refurbishment, and overhaul (MRO) constitute one of the biggest challenges facing this industry. Motivated by the significant role that remaining useful life (RUL) prognostics can play in optimising MRO operations and saving lives, this paper proposes a novel data-driven RUL prognosis model based on counter propagation network principles. The proposed model introduces the recursive growing hierarchical self-organisation map (ReGHSOM) as a variant of SOM that can cluster multivariate time series with high correlations and hierarchical dependencies typically found in RUL datasets. Moreover, ReGHSOM is designed to allow this clustering to evolve dynamically at runtime without imposing constraints or prior assumptions on the hypothesis spaces of the architectures. The output of ReGHSOM is fed into the supervised learning layers of Grossberg to make the RUL prediction. The performance of the proposed model is comprehensively evaluated by measuring its learnability, evolution, and comparison with related work using standard statistical metrics. The results of this evaluation show that the model can achieve an average mean square error of 5.24 and an average score of 293 for the C-MPASS dataset, which are better results than most of the comparable works. Citation: Aerospace PubDate: 2023-11-20 DOI: 10.3390/aerospace10110972 Issue No:Vol. 10, No. 11 (2023)
Authors:Miguel Limón-González, Enrique Rafael García-Sánchez, Héctor Simón Vargas-Martínez, Nicolás Quiroz-Hernández, Selene Edith Maya-Rueda First page: 973 Abstract: Communication between a nanosatellite located in Low Earth Orbit (LEO) and a ground station is limited in regions far from the poles, occurring for only a few minutes on different days and at different times. By utilizing satellite-to-satellite communication, it is possible to transmit and receive information more efficiently, circumventing the restrictions inherent in satellite-ground station links. The objective of this study is to present a comparative report on the results of data transmission through inter-satellite and satellite-to-ground station communication, focusing on a 1U CubeSat nanosatellite (AztechSat-1). This paper discusses the use of the GlobalStar network and a nanosatellite for inter-satellite communication. This paper also discusses the use of proprietary and open-source ground stations for satellite-ground communication. We provide an overview of the GlobalStar network and the associated ground stations involved in this research, along with the results and their subsequent analysis. Citation: Aerospace PubDate: 2023-11-20 DOI: 10.3390/aerospace10110973 Issue No:Vol. 10, No. 11 (2023)
Authors:Jae-Hyeon Park, Seong-Keun Jeong, Hyun-Ung Oh First page: 974 Abstract: A critical-strain-based methodology was proposed to overcome the theoretical limitations of Steinberg’s method, and its effectiveness was experimentally verified through fatigue tests of ball grid arrays, column grid arrays, and lead-type specimens on printed circuit boards (PCBs) with various boundary conditions. These verifications were performed only on PCB units with a single electronic package mounted. However, in actual industrial fields, electronics with various types of electronic packages mounted comprehensively are mainly applied to electronics combined in a mechanical housing structure. Therefore, the verification of the corresponding methodology for the above actual conditions is essential. This study aimed to validate the theoretical feasibility of the design technique under the condition that the elastic mode vibration of a mechanical housing structure acts complexly on PCBs. The proposed methodology was validated analytically and experimentally through a vibration test on a comprehensive PCB specimen with various types of electronic packages mounted on electronic mechanical housing structures. Citation: Aerospace PubDate: 2023-11-20 DOI: 10.3390/aerospace10110974 Issue No:Vol. 10, No. 11 (2023)
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