Aerospace, Volume 10, Issue 2 (February 2023) – 113 articles

Using the unsteady vortex lattice method based on the potential flow theory, a rapid modeling approach is developed for the aerodynamic computation of multi-lifting surfaces. Multiple lifting surfaces with different geometric parameters and grid divisions can be quickly integrated and meshed with the object-oriented data structure. The physical influence between different lifting surfaces was modeled, and the wake–surface interaction was also considered by using different built-in vortex core models. The trajectory data were used to replace the pre-calculated downwash superposition for boundary condition integration, and the instantaneous boundary condition was generated directly from the kinematic states and mesh messages of the model concerned. Considering the direct coupling effect between aerodynamics and rigid body dynamics, the function for free flight was built for medium-fidelity dynamic simulations and aerodynamic data identifications. The proposed high-efficiency modeling and simulation process can be easily applied to models with any number of different lifting surfaces and arbitrary motion modes. Full article

Aiming at the problem that thermocouples used in different parts of aeroengines need a lot of repeated design work in application and the high precision requirements as special test sensors, a parameterized optimization method for a thermocouple shape combined with a numerical simulation method is proposed. The performance of a dual-screen thermocouple (DST), single-screen thermocouple (SST), and no-screen thermocouple (NST) is tested by a numerical simulation method, and is represented by the velocity error ${\sigma }_V$ and the restitution coefficient r. The dual-screen thermocouple (DST) is the best one, and it is selected as the object to parametric optimization, and the parametric optimization methods based on it, geometrically modeled parametrically, adaptive mesh generation and parametric numerical simulation, are proposed. For a dual-screen thermocouple (DST), eight design structural parameters and four environment parameters are suggested for geometrically modeled parametrically and parametric numerical simulation, respectively. The dichotomy method is used to find the optimal length of the screen L, which is considered the most relevant parameter for thermocouple performance. It can be found that the length of the screen L corresponding to the optimal restitution coefficient r ranges from 56.25 to 62.5 mm. Full article

Since deep space exploration tasks, such as space gravitational wave detection, put forward increasingly higher requirements for the satellite platform, the scale and complexity of the satellite management unit (SMU) software are also increasing, and the trend of intelligentization is showing. It is difficult for the traditional SMU based on single-core system on chip (SoC) to meet the various requirements brought by the above trends. This paper presents a high-performance general-purpose SMU design. Based on rad-hard multi-core SoC, we configure and tailor Linux, and design an SMU software architecture with three modes. It has the characteristics of high performance, high reliability, general purpose and scalability, which can meet the needs of the SMU of future complex satellites. Finally, through the application experiment in the background of the space gravitational wave detection project, the performance and application prospect of our proposed SMU are demonstrated. Full article

Photodetector spectral responsivity is usually affected by photosensitive surface temperatures. The Photosensitive Surface Temperatures (PSTs) of the long wavelength-type InGaAs detector used in the Polarized Scanning Atmospheric Corrector (PSAC), which adopts an active Constant-Current Cooling (CCC) scheme, can be changed with ambient temperature. To correct this responsivity temperature characteristic, a Responsivity Temperature Dependence Correction (RTDC) model was established with parameters obtained using an instrument-level experiment. Moreover, a detector-level experiment under ambient conditions was also explored to acquire model parameters. The instrument-level and detector-level experimental results show that the responsivity of a PSAC 2250 nm channel operating on orbit (PST ≈ −65 °C) with a 35 °C PST difference is reduced by approximately 1.2% and 1.5% compared with a laboratory-based radiometric test (PST ≈ −30 °C). The 1.08% responsivity change (−61 °C < PST < −38 °C) in the temperature drift simulation experiment is reduced to approximately 0.38% and 0.34%, respectively. The consistency between the two experimental results preliminarily verifies the substitutability of this detector-level experiment for this type of detector. The RTDC experiments are applicable to other spaceborne remote sensors. The detector-level experiment explored herein provides a reference for realizing RTDC under ambient temperature conditions at low costs. Full article

One essential problem in aircraft conceptual design is initial sizing in which the aircraft primary parameters such as weight, size, and thrust are estimated for given design requirements. The airbreathing hypersonic aircraft is a type of novel aircraft and has significant differences from conventional aircraft in terms of its flight speed and propulsion system. Traditional initial sizing methods are not suitable for this type of novel aircraft. This paper presents an improved initial sizing method for the conceptual design of airbreathing hypersonic aircraft. An illustrative airbreathing hypersonic aircraft is used to describe the detailed procedure of the method. The weight and size of the aircraft are estimated through the simultaneous solution of the weight equation and the volume equation. Constraint analysis is applied to determine the solution space of the thrust-to-weight ratio and the wing loading. A thrust trade is conducted to find the minimum takeoff gross weight of the aircraft. The impacts of technology parameters on the weight, size, and thrust are investigated by sensitivity analyses. The presented method is based on rational derivation. It can be expected that the initial sizing results from the method are reasonable and satisfactory for conceptual design of the airbreathing hypersonic aircraft. Full article

This paper focuses on the triaxial augmentation ability of the active disturbance rejection control (ADRC) technique on the tailless layout with a fully moving wing tip to achieve high control performance for the supersonic tailless aircraft. Firstly, the stability characteristics and controllability of the flying wing layout are analyzed to determine the coupling characteristics of this kind of aircraft. Secondly, an attitude controller is designed based on ADRC theory, and the linear ADRC frequency domain analysis method is introduced to analyze the influence of the bandwidth of linear extended stator on the control system. In addition, the tuning process of the attitude control law is given. Carrier dropping simulations of flight missions under nominal condition, model parameter perturbation, and wind disturbance are conducted. The results show that the designed controller can achieve full-speed domain triaxial augmentation of supersonic flying wing. This work has the potential to significantly boost the engineering acceptability and robustness of supersonic aircraft control design in real-world scenarios. The presented cascaded ADRC approach can significantly improve the performance and robustness of supersonic vehicles. Full article

Advanced rotational variable-swept missile wings require the ability to rapidly deploy, retract and reach the designated position. Therefore, the establishment of an effective time-varying aeroelastic model of a rotating missile wing is the prerequisite for performing transient response analysis during the rapid morphing process. In this paper, the finite element model of the wing at the fixed configuration is combined with the floating frame method to describe the small elastic deformations and large rigid-body displacements of the wing, respectively. Combining the structural dynamic model with the supersonic piston theory, a nonlinear and time-varying aeroelastic model of a missile wing undergoing the rapid morphing process is established. A method for the real-time determination of the time-varying lifting surface during morphing is discussed. Based on the proposed aeroelastic equations of motion, the flutter characteristics of the wing at different sweep angles are obtained. The influences of the actuator spring constant, the damping ratio during the morphing and the post-lock stages, as well as the velocity quadratic term in the aeroelastic equations, on the transient responses of the system are studied. The simulation results show that the flutter characteristics of the wing are greatly influenced by the sweep angle. Moreover, the jumping phenomenon in flutter speed due to the switching of flutter modes is found with the increase of the sweep angle. The morphing simulations demonstrate that the transient aeroelastic responses mainly occur in the post-lock stage, so much more attention needs to be focused on the post-lock vibrations. In addition, under the given simulation parameters, the nonlinear quadratic velocity term has little effect on the transient responses of the system. This study provides an efficient method for predicting the transient aeroelastic responses of a rotational variable swept wing. Full article

The variable cycle engine switches working modes by way of changing variable-geometry components to achieve the dual advantages of high unit thrust and low specific fuel consumption. Due to the lack of a large amount of rig test data and the complex modeling of rotating components, the incomplete characteristics of the variable-geometry rotating components lead to the non-convergence of the component-level model of the variable cycle engine, which makes it difficult to design the follow-up control system. Aiming at this problem, a characteristics modeling method of variable-geometry rotating components for variable cycle engine based on reference characteristic curves is proposed in this paper. This method establishes a neural network estimation model for the offset coefficients of key component operating points based on the characteristic law of the maturely designed variable-geometry rotating component. Combining the neural network model and the reference characteristic curves of the variable-geometry component to be designed, the offset positions of the operating points for positive and negative guide vane angles are determined. Instead of directly connecting operating points to generate characteristic lines, this paper solves the Bezier curve optimization problem based on sequential quadratic programming (SQP) to smoothly fit characteristic lines. Thereby, component characteristics that conform to the actual variable-geometry characteristics can be quickly established in the absence of rig test data. The simulations show that the characteristics of the variable-geometry rotating components established by the proposed method have satisfactory accuracy and reliability, which further improves the operation stability of the component-level model of the variable cycle engine. Full article

The relative pose estimation of the space target is indispensable for on-orbit autonomous service missions. Line segment detection is an important step in pose estimation. The traditional line segment detectors show impressive performance under sufficient illumination, while it is easy to fail under complex illumination conditions where the illumination is too bright or too dark. We propose a robust line segment detector for space applications considering the complex illumination in space environments. An improved two-dimensional histogram construction strategy is used to optimize the Otsu method to improve the accuracy of anchor map extraction. To further improve line segment detection’s effect, we introduce an aggregation method that uses the angle difference between segments, the distance between endpoints, and the overlap degree of segments to filter the aggregation candidate segments and connect disjoint line segments that probably came from the same segment. We demonstrate the performance of the proposed line segment detector using a variety of images collected on a semiphysical simulation platform. The results show that our method has better performance than traditional line segment detectors including LSD, Linelet, etc., in terms of line detection precision. Full article

The aim of this paper is to investigate the performance of a robotic spacecraft, whose primary propulsion system is an electric solar wind sail (E-sail), in a mission to a heliostationary point (HP)—that is, a static equilibrium point in a heliocentric and inertial reference frame. A spacecraft placed at a given HP with zero inertial velocity maintains that heliocentric position provided the on-board thrust is able to counterbalance the Sun’s gravitational force. Due to the finite amount of storable propellant mass, a prolonged mission toward an HP may be considered as a typical application of a propellantless propulsion system. In this respect, previous research has been concentrated on the capability of high-performance (photonic) solar sails to reach and maintain such a static equilibrium condition. However, in the case of a solar-sail-based spacecraft, an HP mission requires a sail design with propulsive characteristics that are well beyond the capability of current or near-future technology. This paper shows that a medium-performance E-sail is able to offer a viable alternative to the use of photonic solar sails. To that end, we discuss a typical HP mission from an optimal viewpoint, by looking for the minimum time trajectory necessary for a spacecraft to reach a given HP. In particular, both two- and three-dimensional scenarios are considered, and the time-optimal mission performance is analyzed parametrically as a function of the HP heliocentric position. The paper also illustrates a potential mission application involving the observation of the Sun’s poles from such a static inertial position. Full article

Experimental and numerical studies of a linear high-loaded turbine cascade with a dual−cavity tip structure are presented in this paper. The experimental conditions contained an increase in the outlet Mach number from 0.42 to 0.92, a change in the incidence angle from −15° to 15° and an increase in the relative clearance size from 0.36% to 1.4%. The ability of the dual−cavity tip to control leakage losses and vortices is assessed using the total pressure coefficient and the Q-criterion. This research indicates that the leakage vortex interacts strongly with the passage vortex, and the change in working conditions affects the balance between the two vortices and thus the flow field structure. The experimental and numerical results prove that the dual−cavity tip can reduce losses in all operating conditions, with the best control effect reduced by 0.025 in a large clearance size condition. In addition, the leakage control effect of the blade tip structure is more influenced by the incoming flow angle and clearance size than the Mach number. Full article

With the growing popularity of small satellites, the interaction with the air in low and especially in very low Earth orbits becomes a significant resource for passive angular stabilisation. However, the possibility of spin motion remains a considerable challenge for missions involving aerodynamically stabilised satellites. The goal of this paper was to investigate the attitude motion of arbitrarily spinning satellites in LEO and VLEO under the action of aerodynamic, gravitational, and magnetic torques, taking into account the aerodynamic damping. Using an umbrella-shaped deployable satellite as an example, the study demonstrated that both regular and chaotic attitude regimes are possible in the attitude motion. The occurrence of chaos was verified by means of Poincaré sections. The results revealed that, to prevent chaotic motion, active attitude control and reliable deployment techniques for aerodynamically stabilised satellites are needed. Full article

In this paper, the effects of the geometry of a submerged nozzle on the nozzle damping characteristics are studied numerically. Firstly, the numerical method is verified by the previous experimental data. Then, the mesh sensitivity analysis and the monitor position independence analysis are carried out. Thirdly, the effects of nozzle geometry on nozzle damping are systematically studied, and focuses are placed on the cavity size, convergent angle and divergent angle. The pulse decay method is utilized to evaluate the nozzle decay coefficient. Several important results are obtained: the submerged cavity with large volume leads to low frequency acoustic oscillations in the combustion chamber and corresponds to a small nozzle decay coefficient; then, as the nozzle convergent angle is decreased, the nozzle decay coefficient is increased. In addition, the nozzle divergent angle has a trivial effect on the nozzle decay coefficient; and lastly, the effects of the temperature on the nozzle damping capability are conducted. The results show that an increase of the working temperature leads to an increase of the nozzle decay coefficient; therefore, the damping force is increased. Full article

In this work, a dynamic model is proposed to simulate the drilling and steering process of an autonomous burrowing mole to access scientific samples from the deep subsurface of the Moon. The locomotive module is idealized as a rigid rod. The characteristic parameters are considered, including the length, cross-section diameter, and centroid of a cylindrical rod. Based on classical Lagrangian mechanics, a 3-DOF dynamic model for the locomotion of this autonomous device is developed. By introducing resistive force theory, the interaction scheme between the locomotive body and the lunar regolith is described. The effects of characteristic parameters on resistive forces and torques are studied and discussed. Proportional-derivative control strategies are introduced to calculate the tracking control forces following a planned trajectory. The simulation results show that this method provides a reliable manipulation of a mole-type robot to avoid obstacles during the tracking control process in layered sediments. Overall, the proposed reduced-order model is able to simulate the operating and controlling scenarios of an autonomous burrowing robot in lunar subsurface environments. This model provides intuitive inputs to plan the space missions of a drilling robot to extract subsurface samples on an extraterrestrial planet such as the Moon or Mars. Full article

English is used in all parts of aviation, especially in aircraft maintenance, where all documentation and various manuals are written in this language. However, there are no formal requirements for aircraft mechanics to have a certain level of English. Nevertheless, aircraft mechanics must master their English language skills, since they are needed for managing their work tasks. This study deals with the issue of insufficiency of standardized English courses, and determines the English language needs of aircraft maintenance in the Slovak Republic, using a triangular approach. The gathered data from 80 respondents for this paper were subjected to descriptive and inferential statistics, which were calculated by the means of Jamovi statistical software. The results revealed that aircraft mechanics engage most often in communication situations that require their knowledge of the reading skill. The importance of all language skills (reading, writing, listening, speaking) is proven by the determination of the most-common communication activities of aircraft mechanics, which should be included in specialized English courses. The results of this study are useful in the creation of language courses which increase the level of English in aircraft maintenance, thus, increasing safety in aviation. Full article

In this paper, the transient flow simulation in an annular isolator under rotating feedback pressure perturbations simplified from the rotating denotation wave (RDW) is performed. The instantaneous flow characteristics and the self-similarity of the isolator flow-field are investigated in detail. It is found that a helical moving shock wave (MSW) and a quasi-toroidal terminal shock wave (TSW) are induced in the isolator. Hence, the flow-fields on the meridian planes could be classified into three zones, i.e., the undisturbed zone, the terminal shock wave/moving shock wave/boundary layer interaction (TSW/MSW/BLI) zone and the moving shock wave/boundary layer interaction (MSW/BLI) zone. The TSW/MSW/BLI zone is characterized by the coupling of the TSW/BLI and the MSW/BLI due to their small axial distance, which intensifies the adverse pressure gradient on the meridian planes, thus rolling up large separation bubbles developing along the MSW driven by the circular pressure gradient. In the MSW/BLI zone, the shock induces the boundary layer to separate, forming a helical vortex located at the foot of the MSW. During the upstream propagation process, the pattern of the MSWs transforms from a moving normal shock wave to a moving oblique shock wave with decreased strength. Moreover, after the collision with the MSWs, P, T_emp and S of the flow elevate with the prompt decrease of v_a, while v_θ increases to a higher level. Despite the deflection effect of the MSWs on the streamlines, the flow direction of the air still maintains an almost axial position at the exit, except in the adjacent region of the MSW. Likewise, three types of zones can be determined in the flow pattern at the exit: the rotating detonation wave/boundary layer interaction (RDW/BLI) zone, the expansion zone, and the vortices discharge zone. Comparing the transient flow patterns at different moments in one cycle and between adjacent cycles, an interesting discovery is that the self-similarity property is observed in the flow-field of the annular isolator under rotating feedback pressure perturbations. The global flow structure of the isolator at different moments shows good agreement despite its rotation with the RDW, and the surface pressure profiles of the corresponding meridian planes all match perfectly. Such a characteristic indicates that the rotation angular velocity of the TSW and the MSW are equal and hold invariant, and the isolator flow could be regarded as a quasi-steady flow. On this basis, the theoretical model of the inclination angles of the MSW by the coordinate transformation and velocity decomposition is developed and validated. The relative errors of the inclination angles between the predicted and measured results are below 3%, which offers a rapid method to predict the shape of the MSW, along with a perspective to better understand the physical meaning of the shape of the MSW. Full article

This present study investigates the effect of blade tip configurations, such as the sweepback angle and anhedral angle, on the performance and hub vibratory loads for the lift-offset coaxial rotor of a 30,000-pound-class high-speed long-range utility helicopter. The rotorcraft comprehensive analysis code, CAMRAD II, is utilized to conduct the performance and hub vibratory load analyses for the present lift-offset coaxial rotor. The total rotor thrust, torque, and individual rotor’s hub pitch moment and hub roll moment are considered the trim targets. The general properties for the lift-offset coaxial rotor are designed from the X2TD, S-97 Raider, and SB > 1 Defiant, which are lift-offset compound helicopters. The rotor performance and hub vibratory loads are studied with the various blade tip configurations including the sweepback angle and anhedral angle. The rotor power when the rotor blade tip considers only the sweepback angle (20°) is lower than the baseline rotor model by 41.25% at 170 knots. The maximum rotor effective lift-to-drag ratio (L/D_e) for the lift-offset coaxial rotor using only the sweepback angle and the rotor with both sweepback (20°) and anhedral angles (10°) at 170 knots increase by 10.82% and 5.02%, respectively, compared with the baseline rotor model without both sweepback and anhedral angles. The vibration index (VI) for the rotor with only the sweepback angle is higher than that for the baseline rotor model without both sweepback and anhedral angles by 37.14%. Furthermore, when the rotor blade tip has the anhedral angle, the magnitude of the Blade Vortex Interaction (BVI) decreases compared with the rotor without the sweepback and anhedral angles. Full article

The increasing use of on-board sensor monitoring and data-driven algorithms has stimulated the recent shift to data-driven predictive maintenance for aircraft. This paper discusses emerging challenges for data-driven predictive aircraft maintenance. We identify new hazards associated with the introduction of data-driven technologies into aircraft maintenance using a structured brainstorming conducted with a panel of maintenance experts. This brainstorming is facilitated by a prior modeling of the aircraft maintenance process as an agent-based model. As a result, we identify 20 hazards associated with data-driven predictive aircraft maintenance. We validate these hazards in the context of maintenance-related aircraft incidents that occurred between 2008 and 2013. Based on our findings, the main challenges identified for data-driven predictive maintenance are: (i) improving the reliability of the condition monitoring systems and diagnostics/prognostics algorithms, (ii) ensuring timely and accurate communication between the agents, and (iii) building the stakeholders’ trust in the new data-driven technologies. Full article

A model of a NUAA-PTRE pre-cooled air turbine engine was established. The design point parameters of the engine were optimized, including the pressure ratio, air flow rate of the compressor, efficiency, throat area, and efficiency of the turbine. The air flow rate at the engine operating point was 142.73 kg/s. High performance of the key components under a wide range of working conditions was realized after optimization. To achieve the indicators of the overall scheme, adaptability studies of key components were conducted. A three-stage variable geometry design was applied to the inlet. The pre-cooler was optimized with a power-to-weight ratio of over 100 kW/kg and a compactness of 278 m²/m³. The built-in rocket gas generator and dual-component injector were developed, and the combustion and heat transfer processes were simulated. The overall optimization design of the NUAA-PTRE and the adaptive design of the components were completed, and high performance of the engine in a wide range of flight conditions at Ma 0~5 and altitude 0~25 km was achieved. Full article

The high curvature of modern S-ducts causes a strong secondary flow, which seriously affects the uniformity of the compressor inlet flow. In this study, the flow control method of a pulsed jet was applied in the S-duct at an incoming Mach number of 0.4. The jet holes were with an angle of 45° and were symmetrically distributed on the upper wall. Three jet intensities of 0.16%, 0.24%, and 0.31% were simulated using the unsteady Reynolds-averaged Navier–Stokes equations (URANS) and were validated by experiments. The mechanism of the pulsed jet, with respect to controlling the flow separation in the S-duct, was analyzed through secondary flow behaviors and boundary layer characteristics. The results indicated that the radial and axial pressure gradients were crucial to the formation of the large-scale vortices and reversed fluids in the S-duct. The pulsed jets were found to resist the adverse pressure gradient by exciting the turbulent kinetic energy of the boundary layer fluids. In addition, the dissipation process of vorticity was accelerated due to the promotion of the mixing effect by these devices. Moreover, in the current study, the area with high total pressure loss coefficients decreased gradually along with the intensity increase. Specifically, a maximum loss reduction of 5.9% was achieved when the pulse jet intensity was set to 0.31%, which means that the pulsed jet has great potential in controlling the flow separation in the S-duct. Full article

In the process of unmanned aerial vehicle (UAV) visual-navigation-algorithm design and accuracy verification, the question of how to develop a high-precision and high-reliability semi-physical simulation platform has become a significant engineering problem. In this study, a new UAV semi-physical-simulation-platform architecture is proposed, which includes a six-degree-of-freedom mechanical structure, a real-time control system and real-time animation-simulation software. The mechanical structure can realistically simulate the flight attitude of a UAV in a three-dimensional space of 4 × 2 × 1.4 m. Based on the designed mechanical structure and its dynamics, the control system and the UAV real-time flight-animation simulation were designed. Compared with the conventional simulation system, this system enables real-time flight-attitude simulation in a real physical environment and simultaneous flight-attitude simulation in virtual-animation space. The test results show that the repeated positioning accuracy of the three-axis rotary table reaches 0.006°, the repeated positioning accuracy of the three-axis translation table reaches 0.033 mm, and the dynamic-positioning accuracy reaches 0.04° and 0.4 mm, which meets the simulation requirements of high-precision visual UAV navigation. Full article

To assist air traffic controllers (ATCOs) in resolving tactical conflicts, this paper proposes a conflict detection and resolution mechanism for handling continuous traffic flow by adopting finite discrete actions to resolve conflicts. The tactical conflict solver (TCS) was developed based on deep reinforcement learning (DRL) to train a TCS agent with the actor–critic using a Kronecker-factored trust region. The agent’s actions are determined by the ATCOs’ instructions, such as altitude, speed, and heading adjustments. The reward function is designed in accordance with air traffic control regulations. Considering the uncertainty in a real-life situation, this study characterised the deviation of the aircraft’s estimated position to improve the feasibility of conflict resolution schemes. A DRL environment was developed with the actual airspace structure and traffic density of the air traffic operation simulation system. Results show that for 1000 test samples, the trained TCS could resolve 87.1% of the samples. The conflict resolution rate decreased slightly to 81.2% when the airspace density was increased by a factor of 1.4. This research can be applied to intelligent decision-making systems for air traffic control. Full article

Carbon fiber-reinforced polymers (CFRP) are extensively used in aerospace applications. Out-of-plane wrinkles frequently occur in aerospace CFRP parts that are commonly large and complex. Wrinkles acting as failure initiators severely damage the mechanical performance of CFRP parts. Wrinkles have no significant acoustic impedance mismatch, reflecting weak echoes. The total focusing method (TFM) using weak reflection signals is vulnerable to noise, so our primary work is to design discrete-time filters to relieve the noise interference. Wrinkles in CFRP composites are geometric defects, and their direct detection requires high spatial precision. The TFM method is a time-domain delay-and-sum algorithm, and it requires that the time information of filtered signals has no change or can be corrected. A linear phase filter can avoid phase distortion, and its filtered signal can be corrected by shifting a constant time. We first propose a wrinkle detection method using linear phase FIR-filtered ultrasonic array data. Linear phase filters almost do not affect the wrinkle geometry of detection results and can relieve noise-induced dislocation. Four filters with different bandwidths have been designed and applied for wrinkle detection. The 2 MHz bandwidth filter is recommended as an optimum choice. Full article

This paper introduces the concept of a thermal management system (TMS) with integrated on-board power generation capabilities for a Mach 8 hypersonic aircraft powered by liquid hydrogen (LH2). This work, developed within the EU-funded STRATOFLY Project, aims to demonstrate an opportunity for facing the challenges of hypersonic flight for civil applications, mainly dealing with thermal and environmental control, as well as propellant distribution and on-board power generation, adopting a highly integrated plant characterized by a multi-functional architecture. The TMS concept described in this paper makes benefit of the connection between the propellant storage and distribution subsystems of the aircraft to exploit hydrogen vapors and liquid flow as the means to drive a thermodynamic cycle able, on one hand, to ensure engine feed and thermal control of the cabin environment, while providing, on the other hand, the necessary power for other on-board systems and utilities, especially during the operation of high-speed propulsion plants, which cannot host traditional generators. The system layout, inspired by concepts studied within precursor EU-funded projects, is detailed and modified in order to suggest an operable solution that can be installed on-board the reference aircraft, with focus on those interfaces impacting its performance requirements and integration features as part of the overall systems architecture of the plane. Analysis and modeling of the system is performed, and the main results in terms of performance along the reference mission profile are discussed. Full article

A MCOHP (micro-channel oscillating heat pipe) can provide lightweight and efficient temperature control capabilities for aerospace spacecraft with a high power and small size. The research about the heat flow effects on the thermal performance of MCOHPs is both necessary and essential for aerospace heat dissipation. In this paper, the heat flow effects on the thermal performance of MCOHPs are summarized and studied. The flow thermal performance enhancement changes of MCOHPs are given, which are caused by the heat flow work fluids of nano-fluids, gases, single liquids, mixed liquids, surfactants, and self-humidifying fluids. The use of graphene nano-fluids as the heat flow work medium can reduce the thermal resistance by 83.6%, which can enhance the maximum thermal conductivity by 105%. The influences of gravity and flow characteristics are also discussed. The heat flow pattern changes with the work stage, which affects the flow mode and the heat and mass transfer efficiency of OHP. The effective thermal conductivity varies from 4.8 kW/(m·K) to 70 kW/(m·K) when different gases are selected as the working fluid in OHP. The study of heat flow effects on the thermal performance of MCOHPs is conducive to exploring in-depth aerospace applications. Full article

Radiographic testing is generally used in the quality management of aeroengine turbine blades. Traditional radiographic testing is critically dependent on artificially detecting professional inspectors. Thus, it sometimes tends to be error-prone and time-consuming. In this study, we gave an automatic defect detection method by combining radiographic testing with computer vision. A defect detection algorithm named DBFF-YOLOv4 was introduced for X-ray images of aeroengine turbine blades by employing two backbones to extract hierarchical defect features. In addition, a new concatenation form containing all feature maps was developed which play an important role in the present defect detection framework. Finally, a defect detection and recognition system was established for testing and output of complete turbine blade X-ray images. Meanwhile, nine cropping cycles for one defect, flipping, brightness increasing and decreasing were applied for expansion of training samples and data augmentation. The results found that this defect detection system can obtain a recall rate of 91.87%, a precision rate of 96.7%, and a false detection rate of 7% within the score threshold of 0.5. It was proven that cropping nine times and data augmentation are extremely helpful in improving detection accuracy. This study provides a new way of automatic radiographic testing for turbine blades. Full article

The runway system is more likely to be a bottleneck area for airport operations because it serves as a link between the air routes and airport ground traffic. As a key problem of air traffic flow management, the aircraft runway scheduling problem (ARSP) is of great significance to improve the utilization of runways and reduce aircraft delays. This paper proposes a large neighborhood search algorithm combined with simulated annealing and the receding horizon control strategy (RHC-SALNS) which is used to solve the ARSP. In the framework of simulated annealing, the large neighborhood search process is embedded, including the breaking, reorganization and local search processes. The large neighborhood search process could expand the range of the neighborhood building in the solution space. A receding horizon control strategy is used to divide the original problem into several subproblems to further improve the solving efficiency. The proposed RHC-SALNS algorithm solves the ARSP instances taken from the actual operation data of Wuhan Tianhe Airport. The key parameters of the algorithm were determined by parametric sensitivity analysis. Moreover, the proposed RHC-SALNS is compared with existing algorithms with excellent performance in solving large-scale ARSP, showing that the proposed model and algorithm are correct and efficient. The algorithm achieves better optimization results in solving large-scale problems. Full article

Space-based Earth Observation (EO) systems have undergone a continuous evolution in the twenty-first century. With the help of space-based Maritime Domain Awareness (MDA), specially Automatic Identification Systems (AIS), their applicability across the world’s waterways, among others, has grown substantially. This research work explores the potential applicability of Synthetic Aperture Radar (SAR) and Distributed Satellite Systems (DSS) for the MDA operation. A robust multi-baseline Along-Track Interferometric Synthetic Aperture Radar (AT-InSAR) Formation Flying concept is proposed to combine several along-track baseline observations effectively for single-pass interferometry. Simulation results are presented to support the feasibility of implementing this acquisition mode with autonomous orbit control, using low-thrust actuation suitable for electric propulsion. To improve repeatability, a constellation of this formation concept is also proposed to combine the benefits of the DSS. An MDA application is considered as a hypothetical mission to be solved by this combined approach. Full article

The marsupial unmanned aircraft system (UAS) consists of a large parent unmanned aerial vehicle (UAV) and multiple small children UAVs that can be launched and recovered in the air. The employment of marsupial UAS can expand the mission range of small UAVs and enhance the collaborative capabilities of small UAVs. However, the serious aerodynamic interference between the parent UAV and the child UAV will affect the flight safety during the launch and recovery process. In this paper, the interference characteristics of marsupial UAS is investigated through ground tests and CFD simulation. Ground tests compared the lift and power of the child UAV with and without parent UAV interference in different areas, and the simulation extended the experimental scope. Three specific interference regions above the parent UAV are defined, including the area above the rotors, the area above body and the transition area. In the first two aeras, the variation of the disturbed lift is more than 30% of the child UAV weight. In the transition aera, the child UAV will be subjected to significant lift variations and asymmetric moments. According to the interference characteristics of different regions, the safe flight boundaries and the appropriate paths of children UAVs are proposed. Full article

The flow structures and surface pressure distributions on corrugated airfoils significantly differed from those on a conventional, smooth airfoil. An unsteady, two-dimensional computational simulation was carried out to investigate the flow behavior and associated aerodynamic performance of a group of corrugated airfoils with different levels of waviness at angles of attack from 0° to 20° with an interval of 2° at a low Reynolds number regime (Re = 1.2 × 10⁵) and were quantitatively compared with those of its smooth counterpart. Time-averaged aerodynamic coefficients demonstrated that the corrugated airfoils have a lower lift and higher drag because of trapped vortices in the corrugations. The pressure drag of the corrugated airfoils was greater than that of the smooth airfoil. In contrast, the viscous drag of the corrugated airfoils was smaller than that of the smooth airfoil because the recirculation generated in the corrugation could reduce the viscous drag. The averaged velocity gradient in the boundary layer showed that the thickness of the boundary layer increased significantly for the corrugated airfoils because of recirculating flow caused by the small-standing vortices trapped in the valley of corrugations. The smoother the corrugated surface, the closer the aerodynamic characteristics are to those of the smooth airfoil. Full article