Aerospace

A simultaneous surface pressure and displacement measurement method that integrates pressure-sensitive paint (PSP) and binocular stereophotogrammetry is proposed. The assays were completed on the Φ4 m rotor test stand at China Aerodynamic Research and Development Center (CARDC). A single-shot lifetime approach was utilized to acquire the instantaneous pressure field on a rotor blade coated with PSP. At the same time, the PSP feature points were used to obtain the 3D coordinates of stereo cameras, which yielded the blade displacement field. The experimental results showed that the displacement measuring accuracy was better than 0.2 mm, and the pressure measurement accuracy was not affected, with Standard Deviation (STD) values below 700 Pa. The advantages of the proposed system are its simple structure, low cost, high accuracy and high test efficiency, which will offer a practical solution for the exploration of fluid–structure interplay. Hence, such a system is a prospective for the wind tunnel tests of helicopter rotor blades. Full article

In order to study the aerodynamic interaction of the airfoil and jet flow, the free streamline model and the panel method are combined to develop a fast calculation method for the airfoil in two-dimensional inviscid jet flow. The vortex strength and position of the jet boundary are determined by using the free streamline model and the constant total pressure difference assumption, the circulation of the airfoil is solved by the vortex panel method, and the whole process is coupled by relaxation iteration. Firstly, the convergence and effectiveness of the present method are verified. Next, the influence of the length ratio of jet height to airfoil chord, the velocity ratio of jet velocity to freestream velocity, and the ground effect on airfoil aerodynamics are studied. The results show that the aerodynamic characteristics of the airfoil in finite width jet flow and in freestream have a large difference, and it is important to consider the jet deflection for jet/airfoil interaction. In jet flow, the velocity ratio can be regarded as an aerodynamic similarity parameter for the airfoil. When the jet flow is deflected, the airfoil will not only generate lift but also drag, and the ground effect can be used to decrease drag. The developed method in this paper can not only capture the jet deflection but also has higher calculation efficiency than Computational Fluid Dynamic (CFD), which is beneficial for the preliminary design of a powered-lift device. Full article

The use of electromechanical actuators (EMAs) for aeronautical applications promises substantial benefits regarding efficiency and operability. To advance the design of power electronics and secondary power supply, there is a need for the ability to swiftly study the effects of aircraft mission and operational aspects on the actuator energy consumption. Pursuant to this, the aim of the work presented in this paper is twofold: (i) to build a generic mission-level flight control surface EMA power consumption simulation framework and (ii) to apply this framework to a case study involving a small all-electric aircraft, in which selected factors that impact energy consumption are investigated. The core of the framework comprises physics-based EMA power estimators, linked with a six-degree-of-freedom flight dynamics and control simulation module. The case study results show that the actuator power consumption correlates positively with the proportional gains in the flight control system but is inversely proportional to the trajectory radius and linearly dependent on turbulence intensity. The developed framework could aid in the selection of the actuator, as well as in the optimisation of airborne electronics and secondary power supply. Full article

Conducting a wrinkling analysis for a membrane structure of complex boundary conditions is quite difficult. This paper develops a numerical calculation method for completing a wrinkling analysis of a square membrane structure and a trapezoidal membrane structure with static corner forces. Furthermore, an experimental system for measuring the wrinkle is designed and established to verify the correctness of the method. The difference between simulation analysis results and experimental results is quite small for small corner forces, which means the method used for the wrinkling analysis under small loads is effective. Full article

The pilot is the main person in charge of taxiing safety while moving on the airport surface. The visual separation and speed adjustment are directly related to safety and efficiency of airport surface operation. According to the actual taxiing procedures and airport control rules in China, this paper proposes a novel microscopic simulation model based on the pilots’ visual separation. This model is also built by refining the aircraft taxiing procedures at intersections. The observation range, the separation judgment, pilots’ visual distance, rate of proximity and the intention for speed governing are discussed as parameters in the model. The rules for aircraft separation judgment, pilots’ autonomous speed governing, and position updates are also set up and discussed. The proposed simulation can accurately simulate the acceleration and deceleration intentions under different motion trends while reproducing the motion process including the following acceleration, following deceleration and delayed deceleration caused by separation changes. The results demonstrate that the number of conflicts can be reduced to 50% based on visual separation adjustment of 50 s when the convergence angle is 30°. The pilot’s visual distance is inversely proportional to the fluctuation range of the speed of the rear aircraft, the proximity rate of the front and rear aircraft and the probability of conflict. The simulation results of this model conform to the actual taxiing routes and control rules, which provides technical support for improving the safety level of airport surface operation and presents certain reference value and practicability. Full article

The trim flap is an aerodynamic control surface capable of allowing Mars entry vehicles to improve landing performance during the most dangerous entry, descent, and landing (EDL) phase. In present work, a deployable trim flap system was proposed to meet the aerodynamical trim requirement of the Tianwen-1 Mars probe, which provided a mass-saving alternative to the conventional use of the center-of-gravity (CG) offset of ballast mass. In order to guide the trim flap design, theoretical and finite element (FE) models were established to predict and evaluate the deployment performance. Then, a full-scale physical prototype was manufactured for deployment experiments to verify the design effectiveness as well as validate the theoretical and FE models. Results predicted by theoretical and FE models were in good agreement with deployment experiments. Furthermore, the effects of three factors on the deployment performance were investigated, including the non-linear behavior of the damping, acceleration environment, and backshell flexibility. The manufactured prototype was installed on the Tianwen-1 Mars probe, saving more than 300 kg when compared to the conventional use of ballast mass CG offset, and assisted Tianwen-1 in achieving a successful landing, making China the first country in the world to utilize the trim flap technology for Mars EDL. Full article

The design of a vehicle launch comprises many factors, including the optimization of the climb path and the distribution of the mass in stages. The optimization process has been addressed historically from different points of view, using proprietary software solutions to obtain an ideal mass distribution among stages. In this research, we propose software for the separate optimization of the trajectory of a launch rocket, maximizing the payload weight and the global design, while varying the power plant selection. The launch is mathematically modeled considering its propulsive, gravitational, and aerodynamical aspects. The ascent trajectory is optimized by discretizing the trajectory using structural and physical constraints, and the design accounts for the mass and power plant of each stage. The optimization algorithm is checked against various real rockets and other modeling algorithms, obtaining differences of up to 9%. Full article

The paper presents the concept of a component of an aircraft’s automatic flight control system, controlling the airplane when in longitudinal motion (i.e., pitch angle, sink rate, airspeed channels) during automatic landing, from a final approach until a touchdown. It is composed of two key parts: a vision system and an automatic landing system. The first part exploits dedicated image-processing algorithms to identify the number of red and white PAPI lights appearing on an onboard video camera. Its output data—information about an aircraft’s position on a vertical profile of a landing trajectory—is used as one of the crucial inputs to the automatic landing system (the second part), which uses them to control the landing. The control algorithms implemented by the automatic landing system are based on the fuzzy logic expert system and were developed to imitate the pilot’s control actions during landing an aircraft. These two parts were teamed together as a component of a laboratory rig, first as pure software algorithms only, then as real hardware modules with downloaded algorithms. In two test campaigns (software in the loop and hardware in the loop) they controlled an aircraft model in a simulation environment. Selected results, presenting both control efficiency and flight precision, are given in the final section of the paper. Full article

In recent decades, the rapid development of alternative methods for launching satellites into space has been observed. The main purpose of this work is to obtain reliable information about aerodynamic properties, which will be useful in the preliminary design of a low-cost satellite launch system based on a system consisting of a carrier aircraft and a space rocket orbiter. The numerical geometry of the aircraft carrier was developed as a result of the digitization process of the external surface of a real aircraft. Aerodynamic analysis was performed using specialized software based on solving partial differential equations using the finite volumes method. The results of the aerodynamic analysis were presented in a quantitative and qualitative manner. Furthermore, in order to confirm the correctness of the chosen method, the obtained results were compared with the results of experimental tests carried out in a wind tunnel. This will also prove that the adopted method is sufficient for solving this type of problem. The main advantage of the presented method is obtainment of reliable results in a relatively short time, which is extremely important during the preliminary design stage. The results presented in this paper will certainly be helpful for all researchers involved in the development of new and low-cost methods for launching small satellites into LEO. Full article

Previous staring attitude control techniques utilize the geographic location of a ground target to dictate the direction of the camera’s optical axis, while the assembly accuracy and the internal structure of the spaceborne camera are not considered. This paper investigates the image-based staring controller design of a video satellite in the presence of uncertain intrinsic and extrinsic camera parameters. The dynamical projection model of the ground target on the image plane is firstly established, and then we linearly parameterize the defined projection errors. Furthermore, a potential function and a self-updating rule are introduced to estimate the parameters online by minimizing the projection errors. As the parameters are updating constantly, an adaptive control algorithm is developed, so that the errors between the current and the desired projections of the ground target converge to zero. The stability is proved using Barbalat’s lemma. Simulation results show that the designed controller can successfully move the target’s projection to the desired coordinate even though the camera parameters are unknown. Full article

As to an aerospace vehicle, the flight span is large and the flight environment is complex. More than that, the existing navigation algorithms cannot meet the needs to provide accurate navigation parameters for aerospace vehicles, which results in the decline of navigation accuracy. This paper proposes a multi-layer, fault-tolerant robust filtering algorithm of aerospace vehicle in the launch inertial coordinate system to address this problem. Firstly, the launch inertial coordinate system is used as the reference coordinate system for navigation calculation, and the state equation and measurement equation of the navigation system are established in this coordinate system to improve the modeling accuracy of the navigation system. On this basis, a multi-layer, fault-tolerant robust filtering algorithm is designed to estimate and compensate the unknown input in the state equation in real time and adjust the noise variance matrix in the measurement equation adaptively. Simulation results show that the errors about the integrated navigation system output parameters are reduced, through this algorithm, which improves the attitude, velocity and position estimation accuracy of the integrated navigation system. In addition, the algorithm enhances the fault tolerance and robustness of the filtering algorithm. Full article

In this paper, we propose a novel time and control effort optimal aggressive trajectory synthesis and control design methodology. The trajectory synthesis is a modified minimum snap design but with specific position and orientation constraints on a multi-copter, such as flying through tight spaces (windows) at specific orientations. The paper also introduces a means to stitch together multiple flight segments, enforce smoothness, and minimize segment times as well as the overall time, thereby resulting in very aggressive and feasible trajectories. A novel analysis for a specific scenario when no yaw angle specifications are provided is conducted, wherein a trade-off results in additional aggressiveness. The control algorithms to follow these trajectories are based on an inverse dynamics approach. Several candidate high-fidelity simulations are performed to verify the effectiveness of the proposed approach. Full article

A software-controllable, consumer-grade, single-chip transceiver integrated circuit (IC) has multiple applications because it can generate a continuous-wave beacon while providing the basic functions of frequency shift keying digital communication as well. In addition, such ICs are low-cost. The above characteristics are advantageous for CubeSats with limited space and for university satellites with development cost constraints. In this study, we conduct radiation tolerance evaluation and Doppler shift tolerance tests to evaluate the feasibility of a single-chip consumer transceiver IC for space applications. In the radiation tolerance evaluation test, we compare the IC radiation tolerance to that of a single-chip microcomputer implemented in space and confirm the good resistance of the former based on the predictive analysis of the single-event upset incidence. Through the Doppler frequency shift tolerance test, we confirm suitable receiving sensitivity. Furthermore, we develop a transceiver IC as a CubeSat-class satellite component and successfully establish communication in an in-orbit demonstration, where the transceiver IC is employed as a CubeSat communication module released from the International Space Station. Thus, the feasability of space utilization of the consumer communication IC is demonstrated, which has implications for the development of more flexible and challenging system designs using newly introduced consumer devices. Full article

The present work demonstrates the impact of future airframe and propulsion technologies on the sustainability of potential future medium-range commercial jets with design specifications similar to the Airbus A320-200. Advanced airframe and engine technologies include laminar flow control (LFC), active load alleviation, new materials and structures, and ultra-high bypass ratio turbofan engines. Two aircraft configurations with various design options were compared to determine potentially the best option for the mission profile, which tends to minimize the environmental impact. Each configuration was designed to balance the equivalent CO₂ emissions and Direct Operating Costs. Technology sensitivity analyses were performed to investigate the significance of particular technology combinations and determine the ones that improve aircraft sustainability the most. All studies were performed at a conceptual design level using a multi-fidelity design approach to investigate the system-level effects of the technologies. The open-source aircraft design environment SUAVE was extended and integrated with other aircraft design and analysis tools to obtain all required correlations. The aircraft with advanced technologies showed an average reduction in equivalent CO₂ emissions of 36% and a 23% reduction in DOC compared to the reference aircraft for a similar mission profile, although aircraft with future technologies may have a 43% higher production cost. The given results indicate that the application of technologies may be commercially successful if technologies achieve expected performance values, despite high development costs. Finally, the technology sensitivity analysis demonstrated the most significant influence of engine-related technologies and laminar flow control compared to other technologies considered in this research. Depending on design and integration complexities, engine technologies can be more achievable in the near future and can substantially reduce the overall emission level. Full article

In order to improve the shortcomings of the traditional constant section and gradual section space elevator system, combined with the advantages of constant section and gradual section space elevator system, a model of segmented space elevator system is designed. This model has the characteristics of easier construction, more practical functions, and easier maintenance. The cyclic iterative method is proposed to calculate the stress distribution of the space elevator system. The maximum stress variation and system scale variation of segmented space elevator system with different segment numbers is analyzed and compared with the system scale of constant section and gradual section space elevator system. The results show that the segmented space elevator model can significantly reduce the peak stress of the space elevator system under the condition of limited increase in the system scale, and the peak stress is 56% lower than that of the constant section space elevator model. Considering the number of segments, peak stress, and system scale, the calculation results show that the optimal number of segments is 5 or 6. Full article

This paper presents a robust trajectory design method for approaching and rendezvous with a space target considering multi-source uncertainties. A nonlinear covariance analysis method based on the state transition tensor is presented to formulate the propagation of uncertainties including environment parameter uncertainty, actuator error, sensor noise, navigation error and initial state dispersion of the closed-loop GN&C system. Then, the robust trajectory design problem is defined based on the quantified effect of the uncertainties, and an improved self-adaptive differential evolution algorithm is presented to solve the robust trajectory design problem with uncertainties. Finally, four groups of numerical simulations are carried out to show that the designed robust trajectories can satisfy the final state dispersion constraint under multi-source uncertainties. Full article

Autonomous rendezvous and docking (RVD) fuel optimization with field-of-view and obstacle avoidance constraints is a nonlinear and nonconvex optimization problem, making it computationally intensive for onboard computation on CubeSats. This paper proposes an RVD fuel optimization and guidance technique suitable for onboard computation on CubeSats, considering the shape, size and computational limitations of CubeSats. The computation time is reduced by dividing the guidance problem into separate orbit and attitude guidance problems, formulating the orbit guidance problem as a convex optimization problem by considering the CubeSat shape, and then solving the orbit guidance problem with a convex optimization solver and the attitude guidance problem analytically by exploiting the attitude geometry. The performance of the proposed guidance method is demonstrated through simulations, and the results are compared with those of conventional methods that perform orbit guidance optimization with attitude quaternion feedback control. The proposed method shows better performance, in terms of fuel efficiency, than conventional methods. Full article

The manuscript presents the conceptual design phase of an unmanned aerial vehicle, with the objective of a systems approach towards the integration of a hydrogen fuel-cell system and Li-ion batteries into an aerodynamically efficient platform representative of future aircraft configurations. Using a classical approach to aircraft design and a combination of low- and high-resolution computational simulations, a final blended wing body UAV was designed with a maximum take-off weight of 25 kg and 4 m wingspan. Preliminary aerodynamic and propulsion sizing demonstrated that the aircraft is capable of completing a 2 h long mission powered by a 650 W fuel cell, hybridized with a 100 Wh battery pack, and with a fuel quantity of 80 g of compressed hydrogen. Full article

Due to sensor characteristics, geographical environment, electromagnetic interference, electromagnetic silence, information countermeasures, and other reasons, the phenomenon of track breakages occur in the process of aircraft track data processing. It leads to the change in target label attributes. In order to make the track segment association effect better, we studied several existing time series prediction methods, and proposed a track segment association method based on bidirectional Holt-Winters prediction and fuzzy analysis. This algorithm bidirectionally predicts and extrapolates track segments by the Holt-Winters method, and then uses the fuzzy track segment association algorithm to perform segment association and secondary association. The simulation results of this method show that the track segment association method based on Holt-Winters prediction and fuzzy analysis can effectively solve the track association problem where the target label attributes change before and after track breakage, demonstrating better association ability and robustness. Compared with the fuzzy association method without adding track prediction, our method generally improves the association accuracy by 35%. Full article