Advances in Astronautics Science and Technology最新文献

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.

Electromagnetic formation flying technology makes use of the inter-satellite electromagnetic force and torque to control the relative position and attitude of the satellites. It has the advantages of no propellant consumption, long lifetime, and high flexibility. Since the electromagnetic formation dynamics is nonlinear and strongly coupled, the magnetic dipole assignment is difficult. This paper studies the electromagnetic formation capability and dipole assignment of double satellites. The feasible engineering constraints are given based on the overall energy consumption optimization goal, which significantly simplifies the electromagnetic model and reserves a certain degree of freedom to assign electromagnetic dipoles. The relationship among electromagnetic force, torque, and dipole is illustrated by the diagram method. We also calculate the envelope of electromagnetic formation capability. The analytical solution of the dipole with the optimal energy consumption and the numerical solution of the dipole with the least angular momentum is given via the typical dipole assignment strategies. The results of the calculation example show that the approaches of dipole assignment are effective.

In this paper, intelligent materials for flexible actuators are reviewed, including fiber knitted fabric, elastic polymer, electroactive polymer, shape memory alloy and shape memory polymer. This paper will discuss the current challenges in the development of flexible actuators, and analyze its future development.

A novel photonics-based RF reception approach is proposed as a competitive solution to meet the current challenges of photonics-based approaches and to realize high performances at the same time. The proposed approach adopts the superheterodyne configuration by a combination manner of electronic techniques and photonic techniques, including the ultra-wideband generation of optical LO, the two-stage photonic superheterodyne frequency conversion and the real-time IF compensation. An engineering prototype has been developed and its performance has been evaluated in the laboratory environment. The experiment results preliminarily verify the feasibility of the proposed approach and its engineering potential. The typical performances are as follows: 0.1 GHz ~ 45 GHz operation spectrum range (> 40 GHz), 900 MHz instantaneous bandwidth, 101 dB·Hz^2/3 SFDR and 130 dB·Hz LDR, image rejections of ~ 80 dB for 1st frequency conversion and > 90 dB for 2nd frequency conversion.

Facing the major scientific issues of the global carbon cycle and the monitoring demand for carbon emission reduction all over the world, this paper researches and develops a new calculation method for space-based remote sensing detection of greenhouse gas-flux based on the atmospheric boundary layer turbulence transport theory and the active detection of coherent differential absorption lidar system. By obtaining the atmospheric wind profile information, gas concentration profile information and the new calculation method for space-based gas-flux proposed in this paper, the near-surface gas-flux information in the detected area can be directly obtained. So it can innovatively realize the space-based active and direct remote sensing of the atmospheric boundary layer gas-flux. The method in this paper not only can make up the blank in the space-based active detection of greenhouse gas-flux, but also can realize the high spatial and temporal resolution measurement of the three-dimensional atmospheric motion. It reduces assumptions and errors of the existing model based on the column concentration assimilation inversion method, so it can realize a direct and active observation of global multi-scale, high-quality, long-sequence gas-flux.

The rapid development of space technology has made it increasingly important to use space robots for on-orbit services. Space crawling robots can perform extravehicular condition monitoring, spacecraft fault location and diagnosis, repair and maintenance by carrying different payloads and traversing the spacecraft surface, which has received wide attention from researchers. A prototype of space crawling robot has been designed in this work, which is a quadrupedal insect-like configuration with integrated bionic adhesion material on the bottom of the four feet, and can walk on the satellite surface in a gravity-free space environment. The design and implementation of the crawling robot control system is carried out based on Robot Operating System, including hardware system construction and software architecture design. The tripod gait was also designed to enable the robot to crawl more stably in space. At last, the basic capabilities of the designed space crawling robot are tested in the ground environment, and the results demonstrate the robot’s body control capability, omnidirectional walking capability, and obstacle crossing and avoidance capability.

BSPIF-S-7.5A, a kind of open cell and low-density polyimide foam was developed for Chinese satellite. The polyimide foam is thermal isolation material with low thermal conductivity and high glass transition temperature. Basic physical properties, thermal physical properties, mechanical properties have been studied. For validating space environment resistance of polyimide foam, outgassing in vacuum, thermal cycle, total dose radiation, thermal vacuum and atomic oxygen tests have been performed. The apparent core density of this foam is as low as 7.5 ± 0.5 kg m⁻³. Its volume percentage of open cells is over 98%, which is beneficial to outgas in orbit. Coefficient of thermal expansion is less than 40 × 10^–6 K⁻¹ in the temperature range from − 170 to 135 ℃. Thermal conductivity in vacuum increases from 2.7 to 42.3 mW (m K)⁻¹ with temperature rising from – 130 to 135 ℃. After severe space environment tests, thermal conductivity becomes even lower, compressive strength raises slightly, but shear property declines apparently. Covered with polyimide film, polyimide foam can resist atomic oxygen erosion effectively. Therefore, the polyimide foam is superior thermal insulation material for space application, which is ideal for satellite structure.