Aiming at the shortcomings of the minimal inter-satellite distance solving methods,such as the general low efficiency and weak applicability,a method that can balance the applicability,accuracy and computational efficiency when solving the minimal inter-satellite distance for non-periodic coplanar relative motion of a pair of satellites is proposed.The principal idea of this method is utilizing the advantage of Deep Neural Networks(DNN)to fit the relationship between the initial relative state of two satellites and the minimum inter-satellite distance.The proposed method is able to calculate the minimal distance only through the position and velocity information at any given initial time.The close-range relative motion equations between satellites are established,based on which the analytic inter-satellite distance function is obtained.Through the analysis and derivation of the function,the range of the minimal inter-satellite distance with time is analytically obtained.The construction method of the dataset,which maps the initial states and the minimal distances,is designed to obtain a great number of mappings.Then a model to train the DNN is established and the training process is conducted repeatedly until the convergence is achieved.The training results of the DNN are verified through different simulation examples.The results demonstrate that the DNN-based calculation method can compute the minimal distance nearly in real-time and the corresponding relative errors are almost below 0.2％.
The flight speed of the spacecraft is generally supersonic and hypersonic. The shock wave and boundary layer interaction（SWBLI） occur frequently. Complex aerodynamic phenomena caused by SWBLI often leads to extreme dynamic aero-loads, such as the strong pressure and heat pulsation in local regions. To accurately simulate complex unsteady and local separated flows of the spacecraft with most of attached boundary layer, the advanced RANS-LES methods need to be developed by importing synthetic turbulence.The synthetic particle group method（SPOM） with IDDES is introduced to resolve small-scale turbulent structures in the local separation. Then, IDDES-SPOM is applied to simulate the SWBLI flows at some typical locations of the spacecraft, including the compression ramp, inner flow channel and polyhedron. From the results, some complex separation flow phenomena are explored, such as the shock oscillation and breathing of separation bubble. It’s the main factor which leads to the increase of pressure pulsation rapidly. Therefore, the IDDES-SPOM method can accurately predict complex flows induced by SWBLI and it can provide the theoretical basis and analytical tools for the spacecraft design.
The service environment for combined power aerospace vehicles is extremely harsh, resulting in a series of mechanical problems that need to be solved. Technical characteristics of combined powered aerospace vehicles and the basic concepts of related extreme mechanics are introduced, and the research status of extreme mechanics of aerospace vehicles is compared. Key mechanical problems of combined power aerospace vehicles in the extreme service environment are sorted out, including wide speed range adjustable integrated intake and exhaust and mode conversion unsteady load action mechanism, prediction of high Mach cavity flow dynamics environment under complex interference conditions, prediction of thermal response of multi-scale structures with long flight time and thermal management, high-temperature acoustic-vibration coupling mechanism and vibration fatigue of composite materials, large-scale rudder surface nonlinear thermal flutter mechanism, multi-parameter refined simulation ground test design of force thermoacoustic in extreme mechanical environment, etc., providing references for the development of related research work.
针对敌方无人机来袭时,其集群队形识别易受传感器噪声等外界干扰的情况,提出了一种提取无人机集群连续帧内部关系结构特征的时序表征方法.该方法充分利用无人机集群的方位和距离两个主要元素,对连续帧无人机集群内部关系结构特征进行描述,利用帧与帧之间的参数变化趋势对无人机集群进行时序表征.通过仿真对比实验证明,该方法对无人机集群的特征描述具有较好的抗噪能力和鲁棒性,能够有效解决传感器噪声等外界干扰影响下的队形变形问题,实现无人机集群持续稳定识别.
针对零压气球升空过程运动特性,进行动力学和热力学分析,引入实测风场数据,建立一个可以用于计算零压气球升速变化、升空轨迹变化以及气球温度变化的综合模型,主要分析不同发放时刻对气球升空过程中的速度、高度、飞行轨迹以及温度特性的影响规律.研究结果表明:飞行实测数据验证了仿真程序的可行性;上升速度曲线呈现双"V"形特点与内部氦气和周围大气温差变化有关;球内氦气温度和运动特性随外界辐射增强而变化显著,适当选取发放时刻有利于保证升空速度的稳定性.理论分析结果和仿真模型可为后续零压气球设计和飞行试验提供指导.
