电学前沿计量技术在航天型号保障中的应用

针对航天器中电学基准的长期稳定性、多种传感器输出电信号的线性度、电脉冲测量的时延等多个航天电测领域的难题,提出采用电学量子计量技术和计算基准技术的解决方案,可以10^-9量级的不确定度测量航天器中电阻基准短期变化量,从而推算出长期变化量,对航天器的稳定控制具有重要作用;可以极小的不确定度校准多种传感器输出的毫伏、微伏量级电压的线性度,对航天传感器测量准确度具有重要意义;可在10^-9秒量级确定电脉冲测量中电阻引入的时延,对航天器电推进系统的控制具有重要作用。     

The ASTROCULTURE(TM) flight experiment series, validating technologies for growing plants in space.

A flight experiment, ASTROCULTURE(TM)-1 (ASC-1), to evaluate the operational characteristics and hardware performance of a porous tube nutrient delivery system (PTNDS) was flown on STS-50 as part of the U.S. Microgravity Laboratory-1 mission, 25 June to 9 July, 1992. This experiment is the first in a series of planned ASTROCULTURE(TM) flights to validate the performance of subsystems required to grow plants in microgravity environments. Results indicated that the PTNDS was capable of supplying water and nutrients to plants in microgravity and that its performance was similar in microgravity to that in 1g on Earth. The data demonstrated that water transfer rates through a rooting matrix are a function of pore size of the tubes, the degree of negative pressure on the 'supply' fluid, and the pressure differential between the 'supply' and 'recovery' fluid loops. A slightly greater transfer rate was seen in microgravity than in 1g, but differences were likely related to the presence of hydrostatic pressure effects at 1g. Thus, this system can be used to support plant growth in microgravity or in partial gravity as on a lunar or Mars base. Additional subsystems to be evaluated in the ASTROCULTURE(TM) flight series of experiments include lighting, humidity control and condensate recovery, temperature control, nutrient composition control, CO2 and O2 control, and gaseous contaminant control.     

A root moisture sensor for plants in microgravity.

Development of components for bioregenerative life-support systems is a vital step toward long-term space exploration. The culturing of plants in a microgravity environment may be optimized by the use of appropriate sensors and controllers. This paper describes a sensor developed for determining the amount of fluid (nutrient solution) available on the surface of a porous ceramic nutrient delivery substrate to the roots of conventional crop plants. The sensor is based on the change in thermal capacitance and thermal conductance near the surface as the moisture content changes. The sensor could be employed as a data acquisition and control sensor to support the automated monitoring of plants grown in a microgravity environment.     

电学前沿计量技术在航天型号保障中的应用

针对航天器中电学基准的长期稳定性、多种传感器输出电信号的线性度、电脉冲测量的时延等多个航天电测领域的难题,提出采用电学量子计量技术和计算基准技术的解决方案,可以10^-9量级的不确定度测量航天器中电阻基准短期变化量,从而推算出长期变化量,对航天器的稳定控制具有重要作用;可以极小的不确定度校准多种传感器输出的毫伏、微伏量级电压的线性度,对航天传感器测量准确度具有重要意义;可在10^-9秒量级确定电脉冲测量中电阻引入的时延,对航天器电推进系统的控制具有重要作用。     

First flight of the ASTROCULTURE (TM) experiment as a part of the U.S. Shuttle/MIR program.

A number of space-based experiments have been conducted to assess the impact of microgravity on plant growth and development. In general, these experiments did not identify any profound impact of microgravity on plant growth and development, though investigations to study seed development have indicated difficulty in plants completing their reproductive cycle. However, it was not clear whether the lack of seed production was due to gravity effects or some other environmental condition prevailing in the unit used for conducting the experiment. The ASTROCULTURE (TM) flight unit contains a totally enclosed plant chamber in which all the critically important environmental conditions are controlled. Normal wheat (Triticum aestivum L.) growth and development in the ASTROCULTURE (TM) flight unit was observed during a ground experiment conducted prior to the space experiment. Subsequent to the ground experiment, the flight unit was transported to MIR by STS-89, as part of the U.S. Shuttle/MIR program, in an attempt to determine if super dwarf wheat plants that were germinated in microgravity would grow normally and produce seeds. The experiment was initiated on-orbit after the flight unit was transferred from the Space Shuttle to MIR. The ASTROCULTURE (TM) flight unit performed nominally for the first 24 hours after the flight unit was activated, and then the unit stopped functioning abruptly. Since it was not possible to return the unit to nominal operation it was decided to terminate the experiment. On return of the flight unit, it was confirmed that the control computer of the ASTROCULTURE (TM) flight unit sustained a radiation hit that affected the control software embedded in the computer. This experience points out that at high orbital inclinations, such as that of MIR and that projected for the International Space Station, the danger of encountering harmful radiation effects are likely unless the electronic components of the flight hardware are resistant to such impacts.     

Earth life support for aquatic organisms, system and technical aspects.

The importance of the research on Bioregenerative Life Support has increased dramatically in the last decade not only with regard to possible space flight application but also as a way to obtain a better understanding of our Earth's ecology. A major goal was to reach long-term stability of artificial model systems. Preliminary data are presented on the development of an improved aquatic system, currently dedicated for ground-based research. Closed aquatic ecosystems require reliability of the key parameters of pH, O2 and CO2 concentration and stability of sensors for monitoring. Besides the integration of an artificial lung (holofiber system and air pump with valves, allowing controlled oxygen uptake of air), in parallel to the oxygen producing water plants. Our new approach is to implement opto-chemical sensors, for such environmental monitoring. One major advantage of the new sensor technique is their better long-term reliability as compared to the electrochemical sensors. Our experiment with the new sensor technique has demonstrated satisfactory performance in closed aquatic ecosystems.     

Improvements in and actual performance of the Plant Experiment Unit onboard Kibo,the Japanese experiment module on the international space station

In 2004, Japan Aerospace Exploration Agency developed the engineered model of the Plant Experiment Unit and the Cell Biology Experiment Facility. The Plant Experiment Unit was designed to be installed in the Cell Biology Experiment Facility and to support the seed-to-seed life cycle experiment of Arabidopsis plants in space in the project named Space Seed. Ground-based experiments to test the Plant Experiment Unit showed that the unit needed further improvement of a system to control the water content of a seedbed using an infrared moisture analyzer and that it was difficult to keep the relative humidity inside the Plant Experiment Unit between 70 and 80% because the Cell Biology Experiment Facility had neither a ventilation system nor a dehumidifying system. Therefore, excess moisture inside the Cell Biology Experiment Facility was removed with desiccant bags containing calcium chloride. Eight flight models of the Plant Experiment Unit in which dry Arabidopsis seeds were fixed to the seedbed with gum arabic were launched to the International Space Station in the space shuttle STS-128 (17A) on August 28, 2009. Plant Experiment Unit were installed in the Cell Biology Experiment Facility with desiccant boxes, and then the Space Seed experiment was started in the Japanese Experiment Module, named Kibo, which was part of the International Space Station, on September 10, 2009 by watering the seedbed and terminated 2 months later on November 11, 2009. On April 19, 2010, the Arabidopsis plants harvested in Kibo were retrieved and brought back to Earth by the space shuttle mission STS-131 (19A). The present paper describes the Space Seed experiment with particular reference to the development of the Plant Experiment Unit and its actual performance in Kibo onboard the International Space Station. Downlinked images from Kibo showed that the seeds had started germinating 3 days after the initial watering. The plants continued growing, producing rosette leaves, inflorescence stems, flowers, and fruits in the Plant Experiment Unit. In addition, the senescence of rosette leaves was found to be delayed in microgravity.     

天基微小空间碎片探测研究

随着空间碎片数量的不断增多,天基微小空间碎片探测已经成为一个热点．首先介绍了空间碎片在低地球轨道上的分布情况以及它对于航天器的危害,然后介绍了国外微小碎片探测器的基本情况,并在这些探测结果的基础上提出了一个探测器方案．这种探测器的传感器采用了新型的压电材料聚偏二氟乙稀(PVDF),使用了飞行时间法(TOF)准确测定空间碎片的飞行速度,以及快脉冲分析系统分析碎片的质量．     

Analysis of space debris impact source localization based on PVDF piezoelectric film

As the pace of human exploration and utilization of space continues to accelerate, space debris gradually becomes an inevitable problem affecting and threatening human space activities. When space debris strikes the spacecraft bulkhead, determining the impact source location timely and accurately is the foundation of the repair damage, and is also of great importance for the safety of astronauts' life. This paper analyzed the wave propagation law in thin plates, established a lightweight sensor array using PVDF (Polyvinylidene fluoride) circular thin-film sensors, and used a two-stage light-gas gun loading system to conduct hypervelocity collision localization experiments on impacting 2A12 aluminum plates to study the effects of sensor array radius and sensor size on localization results. The results show that the smaller the radius of the PVDF sensor array is, the more accurate the positioning result is under the premise of the same size of the PVDF circular film sensor array. On the premise of the same PVDF sensor array arrangement, the larger the PVDF circular membrane sensor is, the more accurate the positioning result is. ABAQUS finite element software is used to study the stress wave propagation of aluminum ball impacting aluminum plate at high speed, simulating space debris impacting spacecraft. The stress waveform obtained from the simulation is in good agreement with the experiment, which shows the accuracy of the numerical simulation method.     

A capillary-driven root module for plant growth in microgravity.

A new capillary-driven root module design for growing plants in microgravity was developed which requires minimal external control. Unlike existing systems, the water supply to the capillary-driven system is passive and relies on root uptake and media properties to develop driving gradients which operate a suction-induced flow control valve. A collapsible reservoir supplies water to the porous membrane which functions to maintain hydraulic continuity. Sheet and tubular membranes consisting of nylon, polyester and sintered porous stainless steel were tested. While finer pore sized membranes allow greater range of operation, they also reduce liquid flux thereby constraining system efficiency. Membrane selection should consider both the maximum anticipated liquid uptake rate and maximum operating matric head (suction) of the system. Matching growth media water retention characteristics to the porous membrane characteristics is essential for supplying adequate liquid flux and gas exchange. A minimum of 10% air-filled porosity (AFP) was necessary for adequate aeration. The capillary-driven module maintained hydraulic continuity and proper gas exchange rates for more than 80 days in a plant growth experiment.     

空间光学遥感器真空热试验工装模块化设计

针对空间光学遥感器在空间环境地面模拟试验中舱板温度分布不均的问题,运用模块化思想对某型号空间光学遥感器工装的舱板结构开展了优化设计。将舱板按照温度分布进行分块,提出模块化拼装和模块化热控2种设计方案,模块化拼装是对舱板及其表面加热片进行独立分块划分,模块化热控则是将舱板视为整体,仅对其表面的加热片进行分块设计。结果表明:模块化热控的舱板平均温度偏差为0.205 K,低于未模块化设计的0.87 K和模块化拼装的0.30 K,提高了舱板的温度均匀性。同时,模块化拼装改善了舱板温度分布,使得符合热控要求的测点比例由34.8%提高到96.7%,但独立划分的模块之间仍存在一定温差;模块化热控则消除了模块间的温差,将符合热控要求的测点比例进一步提高到100%,完全满足热控要求。      

Use of planetary soils within CELSS: the plant viewpoint.

The major functions of soil relative to plant growth include retention and supply of water and minerals, provision of anchorage and support for the root, and provision of an otherwise adequate physical and chemical environment to ensure an extensive, functioning root system. The physical and chemical nature of the solid matrix constituting a soil interacts with the soil confinement configuration, the growing environment, and plant requirements to determine the soil's suitability for plant growth. A wide range of natural and manufactured terrestrial materials have proven adequate soils provided they are not chemically harmful to plants (or animals eating the plants), are suitably prepared for the specific use, and are used in a compatible confinement system. It is presumed this same rationale can be applied to planetary soils for growing plants within any controlled environment life support system (CELSS). The basic concepts of soil and soil-plant interactions are reviewed relative to using soils constituted from local planetary materials for growing plants.     

一种薄膜热电堆热流传感器灵敏度系数的实验研究

为应对长时间、高频响、高热流密度条件下的热流密度测试要求，通过热沉体设计发展了一种新型热阻式薄膜热电堆热流传感器，并利用对比标定的方法、采用辐射标定方式确定各个此类型传感器的灵敏度系数。标定实验数据表明：该类型热流传感器的灵敏度系数与感应面温度相关，且在高于一定温度之上校正关系式不同于以往的线性关系而呈现出二次非线性关系。通过分析可知：呈现出二次非线性校正关系式的原因主要是依赖于温度的热阻层导热系数以及薄膜热电偶Seebeck 系数。实验数据以及分析结果为该类型热流传感器的标定和优化设计提供了参考，同时确保了该类型热流传感器在使用过程中获得准确、可靠的热流测试数据。     

基于薄膜热电堆的新型高温瞬态热流密度传感器的研制

目前针对国内薄膜瞬态热流传感器一致性较差、制备工艺不成熟等问题，提出了一种基于光刻工艺和离子束溅射镀膜工艺的制备方法，200对T型金属薄膜热电偶沉积在10mm×10mm的水冷块上，测量1μm的氧化铝热阻层温差，从而得到瞬态热流密度值。对新型高温瞬态热流密度传感器进行比对法标定，一致性误差为0.211%，即工艺的一致性约为99.79%。实验表明，研制的新型高温瞬态热流密度传感器的一致性好,制备工艺具备良好重复性和可移植性，能够满足高温瞬态热流检测需要，为热流传感器的推广应用及标准化、批量化生产提供了良好的技术支撑。     

基于薄膜热电堆的新型高温瞬态热流密度传感器的研制

目前针对国内薄膜瞬态热流传感器一致性较差、制备工艺不成熟等问题，提出了一种基于光刻工艺和离子束溅射镀膜工艺的制备方法，200对T型金属薄膜热电偶沉积在10mm×10mm的水冷块上，测量1μm的氧化铝热阻层温差，从而得到瞬态热流密度值。对新型高温瞬态热流密度传感器进行比对法标定，一致性误差为0.211%，即工艺的一致性约为99.79%。实验表明，研制的新型高温瞬态热流密度传感器的一致性好,制备工艺具备良好重复性和可移植性，能够满足高温瞬态热流检测需要，为热流传感器的推广应用及标准化、批量化生产提供了良好的技术支撑。     

空间目标在天基光学探测中的特性分析与仿真

分析了空间目标的分布及几何特性,研究了空间目标光学特性与天基探测系统、太阳以及目标自身参数的关系,提出了空间目标光学特性仿真的思路,建立的天基空间目标光学特性分析系统可以计算并绘制相对距离、太阳相位角及目标星等变化曲线.由于很难获取准确的空间目标实际光度数据,文中提出了对仿真结果的验证方法.通过对仿真结果的分析,得出了天基空间目标光学探测的特点,为天基光学探测和识别的研究提供了参考.      

同步轨道遥感器热设计和热分析

为解决遥感器在同步轨道环境温度场分析中热传导与热辐射的综合处理问题,热传导模型温度计算采用控制容积方法建立有限差分方程;热辐射模型采用奥本海姆方法计算设备表面单元之间辐射换热;根据是否被遮挡,辐射换热中表面单元角系数的计算分别采用积分和数值方法。计算结果表明,采用上述方法进行温度场分析能够有效解决热传导模型与热辐射模型的耦合,求解精度较高,遥感器设备部件稳态分析温度分布和在轨瞬态分析温度曲线变化清楚,可作为进一步精密热控设计的依据。     

压电自适应桁架结构主动控制模型及实验

为提高结构对外部环境的抗干扰能力,构造了压电柔性自适应桁架结构,并对其主动控制进行了研究.由传感器、作动器与柔性梁组成压电自适应桁架结构.基于自适应结构的机电耦合理论,在测量位移的情况下,采用改进的二次积分力反馈控制方法研究了空间压电柔性自适应桁架结构的振动主动控制问题.建立了压电柔性自适应桁架结构主动控制实验系统,并对这类自适应结构进行了实时计算机振动主动控制实验研究.实验研究表明柔性自适应桁架结构能够改善结构的动力学特性,对外界的干扰具有良好的自适应性.     

Chromosomes and plant cell division in space: environmental conditions and experimental details.

Details of the plant cultivation system developed for the CHROMEX experiment flown aboard the Shuttle Discovery (March, 1989) in NASA's Plant Growth Unit (PGU) are presented. The physical regime as measured during Spaceflight, both within the orbiter cabin environment and within the PGU itself, is discussed. These data function as a guide to what may be representative of the environmental regime in which Space-based plant cultivation systems will be operating, at least for the near-term. Attention is also given to practical considerations involved in conducting a plant experiment in Space. Of particular importance are the differences expected to occur in moisture distribution patterns within substrates used to cultivate plants in Space vs on Earth.     

Tolerance of wheat and lettuce plants grown on human mineralized waste to high temperature stress

The main objective of a life support system for space missions is to supply a crew with food, water and oxygen, and to eliminate their wastes. The ultimate goal is to achieve the highest degree of closure of the system using controlled processes offering a high level of reliability and flexibility. Enhancement of closure of a biological life support system (BLSS) that includes plants relies on increased regeneration of plant waste, and utilization of solid and liquid human wastes. Clearly, the robustness of a BLSS subjected to stress will be substantially determined by the robustness of the plant components of the phototrophic unit. The aim of the present work was to estimate the heat resistance of two plants (wheat and lettuce) grown on human wastes. Human exometabolites mineralized by hydrogen peroxide in an electromagnetic field were used to make a nutrient solution for the plants. We looked for a possible increase in the heat tolerance of the wheat plants using changes in photosynthetically active radiation (PAR) intensity during heat stress. At age 15 days, plants were subjected to a rise in air temperature (from 23 ± 1 °C to 44 ± 1 °С) under different PAR intensities for 4 h. The status of the photosynthetic apparatus of the plants was assessed by external СО₂ gas exchange and fluorescence measurements. The increased irradiance of the plants during the high temperature period demonstrated its protective action for both the photosynthetic apparatus of the leaves and subsequent plant growth and development. The productivity of the plants subjected to temperature changes at 250 W m⁻² of PAR did not differ from that of controls, whereas the productivity of the plants subjected to the same heat stress but in darkness was halved.