小型感性耦合射频等离子体中和器的实验研究

为了研究适用于百瓦级电推力器的离子束流中和技术,基于电子鞘层模型、射频等离子体最优放电技术和通过插入探针实现快速点火的方法,设计了一套小型感性耦合射频等离子体中和器(RF plasma neutralizer,RPN).实验研究了RPN中和器的稳定工作条件和电子引出特性,实现了RPN中和器稳定工作和电子有效引出.实验结果表明:电子引出特性主要取决于发射孔附近阳极斑的形成与否,而阳极斑的形成又主要受结构设计、工质流量和偏置电压等运行条件的影响;通过对RPN运行条件的优化试验,获得了55~150mA可调电子束流范围和较高的工质利用系数(3.9~10.5),满足离子束流中和需求;另外,实验中还观察到了电子束流随工质流量或偏置电压的迟滞现象

HYDROLOGICAL OBSERVATION IN AN EVERGREEN BROAD LEAVED FOREST IN THE WUYI MOUNTAINS

[中文文摘]对武夷山甜槠林成熟林水文学效应的研究结果表明：观测期间，年大气降水量2678.78ｍｍ，林内雨量2182.04ｍｍ，林冠截留量为496.74ｍｍ；林内雨中，穿透雨量2082.08ｍｍ，树干茎流99.96ｍｍ；到达甜槠林地作用面的林内雨量中，被地表枯枝落叶层截留的雨量为159.84ｍｍ，地表径流量11.6ｍｍ，地下渗流量109.32ｍｍ，其余林内雨量形成土壤含水量增量并由地表物理蒸发、根系吸收以及植物蒸腾所消耗；甜槠林地o~20０ｃｍ土层水分初渗率78.6ｍｍ·ｍｉｎ－１，稳渗率１５．５ｍｍ·ｍｉｎ－１，达到稳渗历时４５ｍｉｎ，地表枯枝落叶最大持水量5.2ｍｍ，土壤蓄水量154.0ｍｍ。与国内其它地区不同类型的森林相比较，武夷山甜槠林具有较强的水文学效能。[英文文摘]Hydrological observations were made in a 76 year old Castanopsis eyrei forest of the Wuyi Mountains.The results are as follows:(1)In the study period during 1993～1994,annual gross precipitation,net precipitation (throughfall was 208204mm and stemflow was 9996mm)and interception loss were 267878mm,218204mm and 49674mm respectively.Interception rate was 1845%.(2)Net precipitation,the part of gross precipitation appearing on the forest floor,was redistributed through different routes.The part absorbed by litter layer was an annual amount of 15984mm,and accounting for 733%.The parts as surface runoff and below ground drainage were annual amounts of 116mm and 10932mm respectively,and accounting for0.53% and 5.01%,respectively.The rest was kept in soil and then lost to the atmosphere by means of ground physical evaporation or plant transpiration as absorbed by the roots.Its amount was 190128mm,and accounting for 87.13%.(3) The initial infiltration rate and stable infiltration rate for the soil layer of 0～20cm were 786mm·min-1 and 155mm·min-1 respectively.The time needed to arrive at the stable state was 45min.Water storage capacity of soil was 15041t·hm-2.The maximum water holding capacity of litter layer was 52mm.福建省自然科学基金,武夷山自然保护区管理局资

Space advanced technology demonstration satellite

The Space Advanced Technology demonstration satellite (SATech-01), a mission for low-cost space science and new technology experiments, organized by Chinese Academy of Sciences (CAS), was successfully launched into a Sun-synchronous orbit at an altitude of similar to 500 km on July 27, 2022, from the Jiuquan Satellite Launch Centre. Serving as an experimental platform for space science exploration and the demonstration of advanced common technologies in orbit, SATech-01 is equipped with 16 experimental payloads, including the solar upper transition region imager (SUTRI), the lobster eye imager for astronomy (LEIA), the high energy burst searcher (HEBS), and a High Precision Magnetic Field Measurement System based on a CPT Magnetometer (CPT). It also incorporates an imager with freeform optics, an integrated thermal imaging sensor, and a multi-functional integrated imager, etc. This paper provides an overview of SATech-01, including a technical description of the satellite and its scientific payloads, along with their on-orbit performance

基于扩张状态观测器的无拖曳系统参数辨识

分析了卫星无拖曳控制系统的在轨参数辨识问题,由于无拖曳系统的不稳定性质,需要设计控制器使其稳定,在此基础上进行闭环辨识.根据自抗扰控制原理,设计了扩张状态观测器以估计系统不同控制回路的扰动和状态,基于状态和扰动估计值设计控制器使系统稳定.提出了基于扩张状态观测器(ESO)的多输入多输出系统闭环参数辨识方法.为提高实际应用中的辨识效果,引入积分型滤波器对观测状态中的噪声进行抑制.将这种方法应用于类似LISA Pathfinder的单轴无拖曳模型,对系统动力学参数进行估计,通过数值仿真实验验证了该辨识方法的有效性和实用性

Ground performance tests and evaluation of RF ion microthrusters for Taiji-1 satellite

The Taiji-1 satellite is a test satellite for the verification of those key technologies involved in the Taiji Program in Space, China's space gravitational wave detection project; and the spacecraft drag-free control technology is one of its key technologies used to improve the microgravity level of spacecraft. Thus, a demand for a high-precision and continuously adjustable micronewton-level thrust has been proposed on the spacecraft micro-propulsion system. In allusion to such a task, a set of micronewton-level RF ion propulsion system was designed based on the principle of self-sustained discharge of RF plasma so as to conduct studies on the parameter optimization and engineering of RF ion thruster, and an engineering prototype of the micronewton-level continuously adjustable RF ion thruster was successfully developed to meet the design index requirements. The operating parameters have been solidified through further studies on the extreme operating conditions of the engineering prototype, and a series of ground simulation tests of space environment were successfully passed. The ground test and calibration experiment results of the micro-propulsion engineering prototype show that the engineering prototype has fully met the requirements of the Taiji-1 mission, thus having laid a solid foundation for the successful space verification of the key technologies for the Taiji-1 satellite

亚微牛级推力测量系统设计及实验研究

空间引力波探测任务需要具有亚微牛级推力分辨率和推力噪声的微推力器来实现卫星平台高精度无拖曳控制任务,为了在地面对所需微推力器的推力进行标定,设计并研制了一套基于扭摆的亚微牛级推力测量系统。该系统选用高精度、高分辨率电容式位移传感器作为扭摆角位移传感装置,利用高精度电子天平对静电梳进行标定,再利用该静电梳标定扭摆,得到推力与角位移的关系。此外,研究了高精度弱力标定技术和亚微牛级微推力在线测量技术,分析了测量误差来源以及控制方案,最后利用静电梳产生标准弱力测量扭摆推力分辨能力和范围等。实验结果表明:该系统可测推力范围为0～400μN,分辨率达到0.1μN,背景噪声功率谱密度优于0.1μN/((Hz)~(1/2))(10 mHz～1 Hz),满足空间引力波探测在10 mHz～1 Hz频段推力测量需求

A torsional thrust stand for measuring the thrust response time of micro-Newton thrusters

Drag-free technology functions as the keystone for space-based gravitational wave detection satellites moving along a geodesic path, like the Laser Interferometer Space Antenna (LISA) Pathfinder, to achieve ultra-high microgravity level. Several prerequisites for micro-thrusters operated under the drag-free technique include constantly adjustable thrust, high resolution, low noise and fast response time. Accordingly, a torsional thrust measurement system was methodically devised to measure the thrust response time of such micro-thrusters on the ground. The characteristics of the dynamic thrust change with time are inverted by the angular displacement of the torsional pendulum, established by the dynamic equation of the same, thus, measuring the rise/fall time of the thrust applied to the torsional pendulum. Calibration of the torsional pendulum thrust measurement system is carried out by the standard electrostatic force generated by the electrostatic comb-drive or microelectromechanical actuator, facilitating the suitable identification of the pendulum parameters. Afterwards, the electrostatic and electromagnetic forces generated by the actuator are applied to validate the measurable thrust response time of the torsional thrust stand. The experimental results show that the above-mentioned thrust stand can effectively measure the thrust response time up to 10 ms for a thrust step in 10 s of micronewtons, which qualifies as the thrust response time required by micro-thrusters for space-based gravitational wave detection

Experimental Study on the Effects of Discharge Chamber Length on 5 cm Radio-Frequency Ion Thruster

For keeping microgravity level of microgravity and space science satellites, a kind of electric thruster, the radio-frequency ion thruster (RIT) has been designed and applied. The RIT produces thrust through ionizing neutral particles in the discharge chamber and extracting ions by the ion optics system. The length of discharge chamber affects the ionization of neutral particles as well as the performance of RIT. In this paper, an experimental study has been carried out for analyzing the influence of discharge chamber length. In the experiment, the RIT-5 with various discharge chamber lengths, 27.6 mm, 30.0 mm, 31.9 mm, 35.5 mm, 40.0 mm, has different performances under the same condition. With the same radio frequency power and propellant flow rate, the RIT-5 has the optimal performance in beam current and efficiency when the discharge chamber length is 30.0 mm or 31.9 mm