Aerospace

Endurance is a critical factor for solar-powered unmanned aerial vehicles (SUAVs). Taking inspiration from birds, SUAVs have the ability to harvest extra energy from atmospheric thermal updrafts to extend their endurance. Though recent research has mainly focused on estimating the characteristics of thermal updrafts, there is a noticeable dearth of studies investigating the energy performance of SUAVs during soaring under different conditions. To begin with, this work establishes a thermal updraft and SUAV energy model. In addition, it introduces an integrated guidance and control process to achieve static soaring within thermal for SUAVs. Numerical simulations are implemented to analyze the electric energy performance at different solar irradiation levels, SUAV velocities and thermal strengths. Several remarkable conclusions are drawn from the simulations, which could provide significant insights for SUAVs to further exploit thermal energy. Full article

Recent efforts in on-orbit servicing, manufacturing, and debris removal have accentuated some of the challenges related to close-proximity space manipulation. Orbital debris threatens future space endeavors driving active removal missions. Additionally, refueling missions have become increasingly viable to prolong satellite life and mitigate future debris generation. The ability to capture cooperative and non-cooperative spacecraft is an essential step for refueling or removal missions. In close-proximity capture, collision avoidance remains a challenge during trajectory planning for space manipulators. In this research, a deep reinforcement learning control approach is applied to a three-degrees-of-freedom manipulator to capture space objects and avoid collisions. This approach is investigated in both free-flying and free-floating scenarios, where the target object is either cooperative or non-cooperative. A deep reinforcement learning controller is trained for each scenario to effectively reach a target capture location on a simulated spacecraft model while avoiding collisions. Collisions between the base spacecraft and the target spacecraft are avoided in the planned manipulator trajectories. The trained model is tested for each scenario and the results for the manipulator and base motion are detailed and discussed. Full article

In this paper, an adaptive neural network global fractional order fast terminal sliding mode model-free intelligent PID control strategy (termed as TDE-ANNGFOFTSMC-MFIPIDC) is proposed for the hypersonic vehicle ground thermal environment simulation test device (GTESTD). Firstly, the mathematical model of the GTESTD is transformed into an ultra-local model to ensure that the control strategy design process does not rely on the potentially inaccurate dynamic GTESTD model. Meanwhile, time delay estimation (TDE) is employed to estimate the unknown terms of the ultra-local model. Next, a global fractional-order fast terminal sliding mode surface (GFOFTSMS) is introduced to effectively reduce the estimation error generated by TDE. It also eliminates arrival time, accelerates the convergence speed of the sliding phase, guarantees finite time arrival, avoids the singularity phenomenon, and bolsters robustness. Then, as the upper bound of the disturbance error is unknown, an adaptive neural network (ANN) control is designed to approximate the upper bound of the estimation error closely and mitigate the chattering phenomenon. Furthermore, the stability of the control system and the convergence time are proven by the Lyapunov stability theorem and are calculated, respectively. Finally, simulation results are conducted to validate the efficacy of the proposed control strategy. Full article

An active rotor with trailing-edge flaps (TEFs) is an effective active vibration control method for helicopters. Blade flapping dynamic characteristics have a significant effect on the active vibration control performance of an active rotor. In this study, an aeroelastic model is developed using the Hamilton principle, and a quasi-steady Theodorsen model for the airfoil with a TEF is utilized to calculate the aerodynamic loads induced by the dynamic deflection of TEFs. The accuracy of this model is validated through a comparison with the CAMRAD calculation and flight test results of a SA349/2 helicopter. Based on the modal orthogonality and the equilibrium equation of the blade flapping motion, the method of changing the blade flapping dynamic characteristics is obtained. Blade sectional characteristics are adjusted to study the effect of blade flapping dynamics on the vibration control authority of an active rotor. The simulation results demonstrate that if the modal frequency of second-order flap is tuned to close to the rotor passage frequency, the flapping dynamic characteristics are capable of enhancing the vibration control performance of the active rotor. Full article

Advanced Air Mobility (AAM) is a concept that is expected to transform the current air transportation system and provide more flexibility, agility, and accessibility by extending the operations to urban environments. This study focuses on flight test, integration, and analysis considerations for the feasibility of the future AAM concept and showcases the outputs of the Air Mobility Urban-Large Experimental Demonstration (AMU-LED) project demonstrations at Cranfield University. The purpose of the Cranfield demonstrations is to explore the integrated decentralized architecture of the AAM concept with layered airspace structure through various use cases within a co-simulation environment consisting of real and simulated standard-performing vehicle (SPV) and high-performing vehicle (HPV) flights, manned, and general aviation flights. Throughout the real and simulated flights, advanced U-space services are demonstrated and contingency management activities, including emergency operations and landing, are tested within the developed co-simulation environment. Moreover, flight tests are verified and validated through key performance indicator analysis, along with a social acceptance study. Future recommendations on relevant industrial and regulative activities are provided. Full article

In the launch environment, satellites are subjected to severe dynamic loads. These dynamic loads in the launch environment can lead to the malfunction of the payload, or to mission failure. In order to improve the structural stability of satellites and enable the reliable execution of space missions, it is necessary to have a reinforcement structure that reduces structural vibrations. However, for active small SAR satellites, the mass requirements are very strict, and this makes it difficult to apply an additional structure for vibration reduction. Therefore, we have developed a carbon fiber-reinforced plastic (CFRP)-based laminated patch to obtain a vibration reduction structure with a lightweight design for improving the structural stability of an S-STEP satellite. To verify the vibration reduction performance of the CFRP-based patch, sine and random vibration tests were conducted at the specimen level. Finally, the structural stability of the S-STEP satellite with the proposed CFRP-based laminated patch was experimentally verified using sine and random vibration tests. The validation results indicate that the CFRP-based laminated patch is an efficient solution which can effectively reduce the vibration response without the need for major changes to the design of the satellite structure. The lightweight vibration reduction mechanism developed in this study is one of the best solutions for protecting vibration-sensitive components. Full article

Overcoming the problem of excessive engine noise at low altitudes is a formidable task on the way to developing a supersonic passenger aircraft. The focus of this paper is on the fan noise shielding during take-off, investigated as part of the DLR project ELTON SST (estimation of landing and take-off noise of supersonic transport) for an in-house aircraft design. The supersonic inlet is required to provide the proper quantity and uniformity of air to the engine over a wider range of flight conditions than the subsonic inlet. For passenger aircraft, the noise problem influences engine integration and placement, and the new generation of supersonic transport would require innovative engineering solutions in order to come up with an efficient low-noise design. Potential solutions are evaluated using DLR tools capable of accurate source generation and noise propagation to the far-field. For low-speed aircraft operation, the method of choice is a strongly coupled volume-resolving discontinuous Galerkin (DG) and fast multipole boundary element method (FM-BEM) which is applied due to a large disparity between the Mach numbers on the interior and exterior of the inlet. The method is used for obtaining the acoustic signature of the full-scale model at realistic flight points, including the application of the programmed lapse rate (PLR), which involves simulations at higher pitch angles than for the reference flight path. The results show that the proposed method is highly suitable for obtaining accurate noise footprints during the low-speed phase and could be used to assist with certification procedures of future supersonic aircraft. Full article

Air carriers shall not readily relinquish their held flight slots. In cases where the historical flight slot pool cannot be easily altered, a pressing need arises for an allocation method that can efficiently utilize the incremental resources of these time slots. This paper presents an integer planning model to address the efficient allocation of incremental airport time slot resources. The model considers the capacity of key resource nodes and flight waveforms as constraints to maximize the total incremental slots. Moreover, it considers the adaptation of strategic and tactical optimization. After conducting a case study using Beijing Capital International Airport for verification, the proposed model effectively reduces potential operational delays by 66.27% while adding 366 to 397-time slots. Notably, the model demonstrates remarkable delay reduction capabilities and can serve as a valuable decision-support tool for the incremental allocation of time slots. Full article

TOPIC: The task of the 21st century is the implementation of manned flights in Earth’s orbit with the view to building orbital and planetary bases. This requires addressing the impacts on people and small social groups in terms of psychological, psychosocial, physiological and health. The author presents her own comprehensive research and intervention approach to exploring and supporting the operation of the space crew in the four-month isolation period of “SIRIUS-18/19”, which can be used in the future for manned flights into deep space. GOAL: The main goal is to present three main areas, within the implementation of social research, designed to analyze the operation of the crew in a simulated space flight: 1. WORKING CONDITIONS, WORKING ENVIRONMENT AND SOCIAL ATMOSPHERE; 2. the STRUCTURE AND DYNAMICS OF RELATIONSHIPS and TIES; 3. a set of other specific areas. The key outputs of the comprehensive analysis of the “SIRIUS-19” crew operations concerning the level of satisfaction with the working environment and conditions, the structure and dynamics of relationships and other specific areas are presented. The suitability of the implementation of intervention activities for isolated crews is pointed out. The purpose is to contribute to the preparation of human crews for manned flights in deep space and to reduce the risks of damage to human biopsychosocial health. METHODS: For a comprehensive analysis, a set of the author’s own questionnaire methods, verified over 25 years in the normal and extremely demanding conditions of specific professions, was used. The diagnostic and intervention method sociomapping, based on fuzzy theory and the mathematical modeling of outputs, was used for the analysis of the structure and dynamics of relationships as it is a technique suitable for the analysis of nonlinear dynamical systems. The methodology enabled the author to obtain a comprehensive view of the experimental situation from a psychosocial and sociological point of view. RESULTS: The model of the author’s analytical approach confirmed the legitimacy of its implementation in the case of isolation experiments. A comprehensive analysis of the “SIRIUS-18/19” crew’s work environment yielded outputs from the 10 main and 48 sub-areas analyzed. The analysis of the six-member, gender-mixed, multicultural crew in the area of structure and dynamics of relationships focused on 35 areas; a total of 344 sociomaps were created. The files were analyzed qualitatively and quantitatively using control diagrams. CONCLUSIONS: Outputs have the potential to be used in other isolation experiments as sociotechnical measures for project organizers and as verification of the need to introduce work with the crew in the form of development workshops using the sociomapping method. Full article

This research investigates the potential application of generative language models, especially ChatGPT, in aviation safety analysis as a means to enhance the efficiency of safety analyses and accelerate the time it takes to process incident reports. In particular, ChatGPT was leveraged to generate incident synopses from narratives, which were subsequently compared with ground-truth synopses from the Aviation Safety Reporting System (ASRS) dataset. The comparison was facilitated by using embeddings from Large Language Models (LLMs), with aeroBERT demonstrating the highest similarity due to its aerospace-specific fine-tuning. A positive correlation was observed between the synopsis length and its cosine similarity. In a subsequent phase, human factors issues involved in incidents, as identified by ChatGPT, were compared to human factors issues identified by safety analysts. The precision was found to be 0.61, with ChatGPT demonstrating a cautious approach toward attributing human factors issues. Finally, the model was utilized to execute an evaluation of accountability. As no dedicated ground-truth column existed for this task, a manual evaluation was conducted to compare the quality of outputs provided by ChatGPT to the ground truths provided by safety analysts. This study discusses the advantages and pitfalls of generative language models in the context of aviation safety analysis and proposes a human-in-the-loop system to ensure responsible and effective utilization of such models, leading to continuous improvement and fostering a collaborative approach in the aviation safety domain. Full article

In order to solve the problem of full flight envelope control for aircraft engines, the design of a linear parameter-varying (LPV) controller is described in this paper. First, according to the nonlinear aerodynamic model of the aircraft engine, the LPV engine model for the controller design is obtained through the Jacobian linearization and fitting technique. Then, the flight envelope is divided into several sub-regions, and the intersection of adjacent sub-regions is not empty. The sub-region LPV controller is designed using the parameter-dependent Lyapunov function (PDLF)-based LPV synthesis method, while eliminating the dependence of the LPV controller on scheduling parameter derivatives. In order to ensure the stability and performance of the aircraft engine across the full flight envelope, a mixing LPV control method is proposed to design the LPV controller in the overall region. The effectiveness of the proposed method is verified by simulating a dual-spool turbofan engine on a nonlinear component level model and comparing the proposed method with the gain scheduling based on PI and H_∞ point design. Full article

This paper investigates the distance-based formation and cooperative path-following control problems for multiple fixed-wing unmanned aerial vehicles (UAVs). In this study, we design the distance-based formation control structure to achieve the virtual leader and followers pre-defined rigid formation pattern, ensuring simultaneously relative localization. A path-following control strategy based on adaptive dynamic surface and neural network control technology is proposed to approximate the uncertain disturbances of the environment and unmodeled dynamics. And the longitudinal and lateral subsystems’ adaptive fault-tolerant controllers are designed, respectively, to achieve the fault-tolerant control of UAVs’ formation in three-dimensional environments. Furthermore, the adaptive sliding mode controller with an auxiliary controller is designed to realize the UAVs path following with limited input saturation. Finally, simulation examples are given to clarify and verify the effectiveness of the theoretical results. Full article

Solid rocket motors are prone to combustion instabilities, which may lead to various problems for the rockets, from unexpected oscillations, precision decreasing, to explosion. The unsteady combustion dynamics of the propellants play a crucial role in most solid rocket motors experiencing combustion instabilities. A modeling framework for the unsteady combustion of the solid propellant is constructed via the Zel’dovich-Novozhilov (ZN) phenomenological perspective. The overall unsteady combustion features of a quasi-steady homogeneous one-dimensional (QSHOD) model are investigated. The phenomenological ZN parameters are then calculated. Compared with the traditional ZN-QSHOD linear equivalence relation, the new calculated system yields better results for the pressure coupling response, especially in the non-linear regime. The proposed phenomenological modeling provides a new methodology for the model reduction of the complex flame models. Full article

Transition delaying is of great importance for the drag and heat flux reduction of hypersonic flight vehicles. The first mode, with low frequency, and the second mode, with high frequency, exist simultaneously during the transition through the hypersonic boundary layer. This paper proposes a novel bi-frequency synthetic jet to suppress low- and high-frequency disturbances at the same time. Orthogonal table and variance analyses were used to compare the control effects of jets with different positions (USJ or DSJ), low frequencies (f₁), high frequencies (f₂), and amplitudes (a). Linear stability analysis results show that, in terms of the growth rate varying with the frequency of disturbance, an upstream synthetic jet (USJ) with a specific frequency and amplitude can hinder the growth of both the first and second modes, thereby delaying the transition. On the other hand, a downstream synthetic jet (DSJ), regardless of other parameters, increases flow instability and accelerates the transition, with higher frequencies and amplitudes resulting in greater growth rates for both modes. Low frequencies had a significant effect on the first mode, but a weak effect on the second mode, whereas high frequencies demonstrated a favorable impact on both the first and second modes. In terms of the growth rate varying with the spanwise wave number, the control rule of the same parameter under different spanwise wave numbers was different, resulting in a complex pattern. In order to obtain the optimal delay effect upon transition and improve the stability of the flow, the parameters of the bi-synthetic jet should be selected as follows: position it upstream, with f₁ = 3.56 kHz, f₂ = 89.9 kHz, a = 0.009, so that the maximum growth rate of the first mode is reduced by 9.06% and that of the second mode is reduced by 1.28% compared with the uncontrolled state, where flow field analysis revealed a weakening of the twin lattice structure of pressure pulsation. Full article

Focusing on the large maneuver penetration of the hypersonic glide vehicle with multiple constraints and uncertain disturbance, a robust integrated guidance and control law, which can achieve the snake-shape maneuver, is designed. A snake-shape maneuver acceleration command, in the framework of sine function, determined by the altitude, target declination of the line of sight and the missile-target distance, is discussed. The integrated guidance and control law includes the terminal guidance law with multiple constraints, attitude control law and angular velocity control law. In the terminal guidance law design, the sliding mode control is adopted while the adaptive technique is applied to estimate the disturbance. The selected sliding mode surface has variable gain determined by the estimated time-to-go. With the designed terminal guidance law, using the snake-shape maneuver acceleration command as the bias item, the angular rate of the line of sight will converge to zero and the line of sight angle will converge to the expected value, simultaneously. The attitude control law and angular velocity control law are designed to track the expected attack and bank angles. The stability of the whole system is proved with the application of the Lyapunov theorem. The effectiveness and robustness of the proposed integrated guidance and control law is verified by simulation. Full article

This paper investigates the effects of two modifications to a vaned recessed casing treatment. First, the shape of a circular curve was used in the top of the treated casing. Second, a fully curved guide vane was also applied. The goals of the modifications are to enhance the flow recirculation as well as to relieve the low-speed flow, which is normally accumulated within the corners of the vaned recessed casing treatment. The solid casing in addition to the two vaned recessed configurations with 23.2% and 53.5% rotor blade tip axial chord exposure have been studied numerically. The results indicated that two mechanisms are involved in the stall margin enhancement. First, the circumferential pressure gradient is reduced for both configurations. The reduction in pressure gradient largely reduces the development of tip leakage vortex and, thus, the generation of low-speed fluid is diminished. Second, the main flow/tip leakage interface moves toward downstream and the movement of interface toward the leading edge is delayed. The second configuration with a greater rotor blade tip exposure enables extra flow recirculation due to decreasing surface area and, therefore, could be superior to the application of the first casing treatment configuration. The major streamlines within the casing treatment are also discussed. The time-averaged results are presented in this paper, while the unsteady results including instantaneous flow fields, origins of the unsteadiness and frequency analysis are discussed in part II. Full article

In this paper, unsteady characteristics of a modified vaned-recessed casing treatment with 23.2% rotor blade tip axial chord exposure were studied numerically. The modifications to the traditional vaned-recessed casing treatments were composed of geometrical amendments to the casing treatment’s guide vanes and the top of the treated casing. The solid casing and the casing treatment configurations were simulated using the Unsteady Reynolds-Averaged Navier–Stokes equations (URANS), and the results were validated by experimental results. Firstly, standard deviation and frequency analysis were performed to find the sources of unsteadiness. Secondly, velocity components analysis, including velocity triangles, was presented instantaneously to clarify their effects on rotor tip flow fields as well as stall margin improvement. Thirdly, unsteady interactions between the rotor and casing treatment flow fields, including flow structure and pressure distributions, were discussed. In the end, flow streamline patterns, in addition to the physical mechanism of the vaned-recessed casing treatment, were also discussed. The results indicated that unsteadiness plays an important role in the flow mechanism and cannot be ignored. The unsteadiness increases as the mass flow is reduced toward the stall/surge condition. Moreover, the analysis of velocity components demonstrated that the casing treatment has distinct behavior at the last operating points before the onset of the stall for solid casing and casing treatment configurations in terms of axial velocity change. Full article

Condition-Based Maintenance (CBM) is a policy that uses information about the health condition of systems and structures to identify optimal maintenance interventions over time, increasing the efficiency of maintenance operations. Despite CBM being a well-established concept in academic research, the practical uptake in aviation needs to catch up to expectations. This research aims to identify challenges, limitations, solution directions, and policy implications related to adopting CBM in aviation. We use a generalizable and holistic assessment framework to achieve this aim, following a process-oriented view of CBM development as an aircraft lifecycle management policy. Based on various inputs from industry and academia, we identified several major sets of challenges and suggested three primary solution categories. These address data quantity and quality, CBM implementation, and the integration of CBM with future technologies, highlighting future research and practice directions. Full article

In this paper, a new method using the backpropagation (BP) neural network combined with the improved genetic algorithm (GA) is proposed for the inverse design of thin-walled reinforced structures. The BP neural network model is used to establish the mapping relationship between the input parameters (reinforcement type, rib height, rib width, skin thickness and rib number) and the output parameters (structural buckling load). A genetic algorithm is added to obtain the inversely designed result of a thin-wall stiffened structure according to the actual demand. In the end, according to the geometric parameters of inverse design, the thin-walled stiffened structure is reconstructed geometrically, and the numerical solutions of finite element calculation are compared with the target values of actual demand. The results show that the maximal inversely designed error is within 5.1%, which implies that the inverse design method of structural geometric parameters based on the machine learning and genetic algorithm is efficient and feasible. Full article