Advances in Astronautics Science and Technology最新文献

A numerical investigation is conducted to analyze the impact of increasing inflow air total temperatures on a scramjet combustor featuring a strut injector and cavity integration. The AnsysFluent tool is used for the computational analysis, employing RANS equations and an SST k-ω turbulence model. The cavities, which are fastened symmetrically to combustor walls, are situated downstream of the strut injector. To evaluate the performance of the cavity-coupled DLR scramjet model under varying inflow air total temperatures, flow patterns, and flow property distributions are analyzed. The cavity configurations, compared to the baseline model, enhance combustion efficiency by achieving complete combustion while reducing the length of the combustion chamber. However, the introduction of additional shock waves from the cavities results in an increased overall pressure drop. Additionally, as the inflow air total temperature rises, the combustion zone extends further along the flow direction, contributing to a prolonged combustion process.

This paper presents a stochastic control strategy for fixed-time safe attitude control of rigid bodies on SO(3), addressing stochastic disturbances while ensuring safety constraints are met with probabilistic guarantees. A stochastic fixed-time control Lyapunov function (SFxTCLF) is designed to ensure that the attitude error converges to zero in probability with fixed-time stability guarantees. To enforce safety constraints on attitude and angular velocity, stochastic control barrier functions are formulated and combined with the SFxTCLF as a quadratic programming framework, which synthesizes an optimal control input that satisfies both stability and safety conditions simultaneously while respecting actuator limits. Extensive numerical simulations validate the efficacy and resilience of the proposed approach, demonstrating superior convergence speed and safety enforcement compared to existing stochastic attitude control methods.

The article delineates an innovative ball-type locking device designed for the separation of structural elements in promising launch vehicles. It further substantiates the necessity of this mechanism by addressing the stringent requirements for reliable operation. A mathematical model has been developed to analyze the dynamics of the relative motion between the separable stages of the launch vehicle utilizing the ball-type locking device. Key parameters for ensuring reliable stage separation with minimal time delay have been identified. Comprehensive numerical simulations have been conducted to evaluate the stress-strain characteristics of structural elements within the ball-type locking device. Additionally, the rational quantity of the balls within the design of this device has been established.

Aiming at the problems of life cycle cost estimation and reasonable design of key parameters for cost reduction in engineering design of Reusable Launch vehicle (RLV), a comparative cost modeling method for RLV benchmark against Expendable Launch Vehicle (EELV) of the same scale is proposed, with which it is carried out the economic analysis of RLV projection such as Space Shuttle, SpaceX Falcon 9 and reusable conceptual configuration. It is found that: reusable launchers with reasonable parameter can significantly reduce the cost of EELV, but the goal of reducing the cost by one order of magnitude is difficult to realize with restricted by the theoretical upper limit; the life cycle cost of RLV tends towards constant values or exhibit extremum points; the reusable recovery and refurbishment cost is a key parameter affecting the life cycle cost, cost-effectiveness and maintainability constitute defining characteristics of RLV, necessitating per-flight refurbishment expenditure to be maintained at ultralow levels—ideally not exceeding 5% of the Theoretical First Unit (TFU) manufacturing cost—to ensure economic viability; boundary conditions are given for the economic superiority of full reuse over first-stage partially reuse.

Shock wave generator is an effective device for mixing enhancement in scramjet combustors. This paper employs the Reynolds-averaged Navier-Stokes (RANS) numerical simulation method to investigate the effects of different parameters of a wall-mounted ramp, which serves as a shock wave generator, on cold flow, reacting flow fields and the vorticity transport within the turbulent mixing region in a strut-based scramjet combustor. The parameters examined include the ramp angle (15°, 20°, 25°, 30°) and its position (110, 130, 150 mm). The results demonstrate that the introduction of the shock wave generator alters the shock wave distribution within the strut-based combustor, promoting rapid mixing between the hydrogen jet and the incoming air flow. In the cold flow field, volumetric expansion and diffusion are identified as the dominant mechanisms for vorticity transport in the mixing layer, whereas in the reacting flow field, the baroclinic torque and diffusion emerge as the primary mechanisms. Moreover, the shock wave generator with different structural parameters exhibit a more pronounced influence about shock wave and vorticity distribution on the reacting flow compared to the cold flow. Notably, in reacting flow field, compared to a single-sided shock wave, the simultaneous incidence of shock waves from both the upper and lower sides into the mixing layer and their interaction significantly enhances the baroclinic term and the diffusion term.

MXene has become a potential electromagnetic absorbing material due to its controllable and excellent electromagnetic parameters, which have attracted extensive attention from researchers. However, due to the two-dimensional nanosheet structure of MXene and the rich polar functional groups on its surface, the dispersion of MXene in the process of assembling composites becomes a challenge. Herein, from the perspective of preparation methods, the micromorphology design ideas and the corresponding electromagnetic absorbing performance of MXene-based absorbing composite materials in recent years are reviewed. Through the meticulous material structure design strategy, MXene-based composites are expected to become tunable electromagnetic wave absorbing materials with superior performance.

Space-based multi-target tracking is one of the key enabling technologies for space situational awareness. As to solve the multi-target passive tracking problem by a cooperative dual-observer system, a centralized parallel fusion method that considers measurement association probability is developed. Firstly, an orbital dynamics model perturbed by Earth’s oblateness and lunar gravity, together with a line-of-sight (LOS) angles measurement model are established. Secondly, a new centralized parallel fusion multi-target tracking frame considering measurement association probabilities is designed for dual-observer cooperative system. In detail, a dual-observer LOSs association evaluation metric and a two-stage measurements-to-measurements association algorithm are developed, where the measurement association probabilities are calculated to achieve high-precision cooperative data association. Subsequently, a centralized parallel tracking filter is proposed for accurately estimating the targets’ orbital states based on the frame of probability hypothesis density (PHD) filter. Multiple sets of augmented measurements based on the measurement association results are constructed, of which the associated measurement probabilities are incorporated into the Gaussian Mixture PHD (GM-PHD) filter to adjust the weights of the Gaussian components. Finally, numerical simulations are conducted with a GEO-type mission, where a 10-target’s tracking case is taken for validation. The results show that the accurate tracking is achieved, where the performance advantage is analyzed and confirmed by comparing with traditional distributed tracking methods.

With the rapid development of human space technology, space photography is increasingly being applied to tasks such as satellite observation, debris collection, and deep-space exploration. However, extreme space environments and inherent deviations of imaging systems may lead to the accumulation of degradations, not only results in low-quality imaging results, but also hampers the performance of downstream applications such as object detection, tracking, and attitude estimation. Under extreme space imaging conditions, we focus on four key image enhancement tasks, including image denoising, deblurring, super-resolution and multi-exposure image fusion. We review the classic and deep learning-based methods, summarize the characteristics and analyze the practical problems in the space imaging process. The paper also presents timelines of method development and lists databases for training, validating and testing, providing a comprehensive overview and a reference for research on extreme space image enhancement. Furthermore, we discuss critical directions that need to be addressed in the future to advance new technologies for high-resolution imaging in extreme space environments.

In this paper, to satisfy the impact angle constraint, a general formulation of the biased proportional navigation guidance is provided. The proposed guidance law is built on the missile-target distance domain (range domain) rather than time domain, which can enhance the guidance accuracy without estimating the flight time. The capture region of the proposed guidance law is fully investigated for all desired impact angles between (pm 180^circ) by studying the behavior of the look angle. The result can provide guidelines on the selection of the desired impact angle based on the initial conditions. For larger impact angles scenarios where the look angle does not converge to zero, the proposed guidance law is readily modified to fulfill the guidance objectives. Numerical simulation results are in complete agreement with theoretical analysis.

To tackle the challenges posed by disturbances and uncertainties in helicopters, this article introduces a neural-network-based anti-disturbance integral sliding mode control method. The proposed methodology employs feedback linearization technique to mitigate the nonlinear characteristics of the helicopter altitude and attitude system, thereby enabling the effective design of an integral sliding surface. To comprehensively handle both external disturbances and system uncertainties, the control architecture integrates a dual-observer system comprising a nonlinear disturbance observer and a neural network observer. The proposed control method enhances system robustness, demonstrating superior performance over traditional sliding mode control methods through faster response time and reduced chattering effects. The control system’s stability is conclusively demonstrated through Lyapunov stability theory. The simulation results confirm that our proposed method effectively improves system stability and robustness across diverse conditions.