Advances in Astronautics Science and Technology最新文献

This paper focuses on the locomotion planning for a quadruped robot walking on the lunar rough terrain. Firstly, the detailed terrain data of the explorable area acquired by the navigation camera is filtered. The terrain is afterwards triangular meshed and reconstructed as a simplified triangular grid model with terrain features retained. Then, the reinforcement learning method is used to plan the path of the robot in the grid-based environment. It employs terrain relief and roughness as the rewards, therefore intelligently determining the optimal detection route with maximum cumulative reward. Finally, gait planning is carried out to make the legs actuate adaptively to the path. Particularly, the step sequence is adjusted with different steering angles, and the footsteps are decided based on the robot mechanism constraints and uneven terrain conditions. Numerical simulations illustrate the walking process of the quadruped robot. The results show that the robot can learn the optimal path with fewer trunk undulations, and generate continuous, stable, and safe gaits. It proves that the locomotion planning method can effectively improve the mobile stability, efficiency, and adaptability of the quadruped robot when walking on the lunar surface.

The main research question that this study tries to answer is how to produce and install a geostationary crane in space for raising and lowering payloads with the focus on how to install the counterweight, which will be presented the concept of an orbital loom factory to reach the geostationary stability. The strict objective of this study is to answer how to stabilize the space crane with the same Earth rotation that requires a counterweight at 36,000 km altitude. This study presents a proposal to solve this problem, by means of an orbital loom factory satellite in space to manufacture the cable in sections. Through the method of producing little by little, and at each section, a set of tests would be carried out, mechanically analyzed to safety, structural, commissioning, and maintenance. The study found that with this method, it is possible to install the space crane, which means to be an economic interface between Earth and space. Another question was answered on materials requests for engineering strategies, above the strength of materials limits. It was found that it is possible to work to increase this structural capacity using academically the crane model project to analyze the engineering of materials strategically, in addition to the available capacity, formulating a methodology through a suspended cable to withstand extreme mechanical conditions. Finally, will be presented why it is worth building this structure, and how to use the spatial crane as a greener way to access the space.

Microwave power transmission (MPT) technology has been proposed to supply power to the long-reached systems, such as high altitude airships, unmanned vehicles, and far-reached wireless sensor networks, etc., and it is also the key technology of the solar power stations (SPS). Rectenna array, receiving the microwave (MW) and convert it into the direct current (DC) power, is one main component of an MPT system. In this paper, the development of rectenna arrays are reviewed. Second, the recent research work of rectennas and rectenna arrays at C-, X- and Ka-bands at Shanghai University are illustrated. Thirdly, based on the experimental results and reasonable evaluation, the designs of rectenna arrays for 1 kW DC power at different bands are evaluated and analyzed. Finally, prospects and challenges of rectenna array and MPT technology are discussed.

Accurate failure prediction is a sharp focus issue in engineering application and advanced science. In it, the most important technique is to properly define the failure criteria. This work presents the critical stress intensity factor and the critical defect size in serving environment, both of which are essentially connected with the environmental surface energy and the environmental plastic deformation work. The defect is further identified as a unified feature to predict serving lifetime of the systems and quantitatively evaluate structural properties in theory and in engineering. Also, a case of defect analysis in aerospace safety is listed at the final.

Space Power Satellite (SPS) is a huge spacecraft to utilize solar energy in space. Because of the huge size, immense mass and high power, there exist many technical difficulties. For a GW SPS system, the generated electric power in space will be over 2 GW, and the whole area of the solar array will be several square kilometers. The high-power electricity generation, transmission and management in space becomes a huge challenge. In the paper, the primary scheme of MR-SPS concept is presented and two important sub-systems, Solar Energy Collection and Conversion (SECC), Power Transmission and Management (PTM) are introduced. The SECC sub-system includes fifty solar sub-arrays. Each solar sub-array is composed of twelve solar array modules. The area of each solar sub-array is about 0.12 km². The solar sub-arrays transmit electric power to the cables installed on the main structure of MR-SPS by 100 middle power rotary joints. PTM sub-system converts, transmits and distributes the output electric power of SECC sub-system. Most of electric power is transmitted to the antenna and is distributed in the antenna. The remaining electric power is transmitted and distributed to the service equipments for the operation of SPS. The mix of distributed and centralized high-voltage PTM is adopted to meet the requirement of electric power supply of the electric equipments on SPS. Typical space environment influencing high-power electric system is analyzed. The key technologies need to be researched and solved including high-efficient, long-life thin-film GaAs PV cell, ultra-large–high-voltage (500 V) solar array module, high-power conductive rotary joint, ultra-high-voltage (20 kV) cables, high-power converter, high-power switch, etc., and assembly and maintenance of the sub-systems.

Light weight and flexible III-V multi-junction thin film solar cells play an important role as power energy supplying in space solar power satellites. In this work, we fabricated 3 J GaInP/GaAs/InGaAs solar cells on 30 μm thick polyimide film using temporary bonding and epitaxial layer lift-off via selective wet chemical etching. The thin film solar cells with an average conversion efficiency of 30% (AM0) were connected together in series to increase the module’s voltage up to 500 V. Increasing module’s voltage allows to reducing the resistive losses during long distance current transportation and is enable inverter simplification leading to more efficient. We investigated the influence of the electrostatic discharging on the flexible thin solar module with 500 V ultra-high voltage and the results were discussed.

In this work, a single-layer reflectarray antenna design operating at the center frequency of 5.8 GHz for microwave power transmission is proposed. The reflectarray unit embodies a slotted circular patch loaded with four symmetrical resonant phase delay lines. By adjusting the length of the phase delay lines, a reflection phase compensation range of about 400° is achieved. The reflectarray uses the low-cost F4B material as the substrate. The feed horn antenna adopts an offset angle of 15°, and the focal diameter ratio (F/D) is 1.2. Based on the reflectarray unit design, a 361-unit reflectarray antenna is designed with the desired pitch angle and azimuth of the reflected wave to be (0°, 0°). The measured gain is 27.3 dBi at the center frequency of 5.8 GHz. The aperture efficiency and 1 dB reflectarray bandwidth are 51% and 20.4% (5.01–6.15 GHz) respectively. In addition, at the center frequency of 5.8 GHz, the side-lobe level and cross-polarization level are lower than − 18 dB and − 30 dB, respectively.

There will be serious thermal problems in the photovoltaic system of sunlight-concentrating space solar power station (SSPS), which will reduce the conversion efficiency of the photovoltaic system and overall energy transmission of the whole system. In this paper, based on the thermal problems in the optoelectronic system of SSPS via Orb-shape Membrane Energy Gathering Array (SSPS-OMEGA), a thermal management strategy of full-spectrum selective photonic thin-film based on the photoelectric characteristics of photovoltaic cells and pump-driven fluid flow loop is proposed with combination of passive and active cooling methods. Simulation results indicate that the full-spectrum selective thin film can significantly reduce the parasitic heat source in ultraviolet band and sub-band gap, from 205 to 72.8 W/m² and from 46 to 4.5 W/m², respectively. Meanwhile, it can effectively increase the emissivity from 0.84 to 0.938. On the other hand, the pump-driven fluid flow loop is designed and the temperature of the PV cell array is well controlled below 50 ℃ for ground-based demonstration validation system of the SSPS-OMEGA project. Finally, a simple experiment investigation is carried out demonstrate the thermal control performance of pump-driven fluid flow loop for photoelectric system.

Rectifiers and rectennas have been receiving great attention for the applications of wireless power transmission and energy harvesting. This paper describes the challenges and solutions of the rectifiers and rectennas in enhancing conversion efficiency at low and high input power levels for the applications of space solar power station (SSPS). We reviewed the developments of the rectifiers for the applications of wireless power transmission, described the SSPS system, retrospect the history of SSPS, and presented the requirements of rectifiers and rectennas in SSPS systems. Key technologies of high-efficiency rectifiers and rectennas at various input power levels are also proposed. In high power levels, reducing harmonic loss and diode loss is valid to enhance rectifying efficiency. When the input power is low, using booster-voltage technology with low turn-on voltage diodes can improve rectifiers’ performance. To keep a high efficiency in low and high power levels, rectifiers with wide input power dynamic ranges are proposed with various structures.