高分辨力机载毫米波FM-CW SAR的研发

紧凑的FM—CW（调频-连续波）雷达技术和高分辨力SAR（合成孔径雷达）处理技术的结合将为体积小、重量轻且性价比高的成像雷达的发展铺平道路。然而，在空中观察地球表面这一领域中，将SAR用于FM—CW雷达是比较新颖的。通信传输和雷达国际研究中心（IRCTR）启动了一项关于FM—CW SAR的可行性研究。在该研究项目框架中，开发并测试了一种完全运转的机载FM—CW SAR验证系统。文中综述了地面测试的情况。此外，2004年6月在柏林附近的Strausberg机场进行了一次非常成功的空中试验。本文将介绍这些机载试验的初步结果。     

在直升机平台上进行高分辨率SAR／ISAR成像

海上监视对高分辨率雷达成像模式特别感兴趣。在海上监视应用中，可以使用高分辨率雷达成像模式来支持对已经用传统搜索功能和跟踪功能检测到的海面目标的分类和可能的识别。     

Humans to Mars: a feasibility and cost-benefit analysis

Mars is a compelling astrobiological target, and a human mission would provide an opportunity to collect immense amounts of scientific data. Exploration alone, however, cannot justify the increased risk. Instead, three factors drive a human mission: economics, education, and exploration. A human mission has a unique potential to inspire the next generation of young people to enter critically needed science and engineering disciplines. A mission is economically feasible, and the research and development program put in place for a human mission would propel growth in related high-technology industries. The main hurdles are human physiological responses to 1–2 years of radiation and microgravity exposure. However, enabling technologies are sufficiently mature in these areas that they can be developed within a few decade timescale. Hence, the decision of whether or not to undertake a human mission to Mars is a political decision, and thus, educational and economic benefits are the crucial factors.     

Ozone concentrations and ultraviolet fluxes on Earth-like planets around other stars

Coupled radiative-convective/photochemical modeling was performed for Earth-like planets orbiting different types of stars (the Sun as a G2V, an F2V, and a K2V star). O(2) concentrations between 1 and 10(-5) times the present atmospheric level (PAL) were simulated. The results were used to calculate visible/near-IR and thermal-IR spectra, along with surface UV fluxes and relative dose rates for erythema and DNA damage. For the spectral resolution and sensitivity currently planned for the first generation of terrestrial planet detection and characterization missions, we find that O(2) should be observable remotely in the visible for atmospheres containing at least 10(-2) PAL of O(2). O(3) should be visible in the thermal-IR for atmospheres containing at least 10(-3) PAL of O(2). CH(4) is not expected to be observable in 1 PAL O(2) atmospheres like that of modern Earth, but it might be observable at thermal-IR wavelengths in "mid-Proterozoic-type" atmospheres containing approximately 10(-1) PAL of O(2). Thus, the simultaneous detection of both O(3) and CH(4) - considered to be a reliable indication of life - is within the realm of possibility. High-O(2) planets orbiting K2V and F2V stars are both better protected from surface UV radiation than is modern Earth. For the F2V case the high intrinsic UV luminosity of the star is more than offset by the much thicker ozone layer. At O(2) levels below approximately 10(-2) PAL, planets around all three types of stars are subject to high surface UV fluxes, with the F2V planet exhibiting the most biologically dangerous radiation environment. Thus, while advanced life is theoretically possible on high-O(2) planets around F stars, it is not obvious that it would evolve as it did on Earth.     

Dosimetric measurements in manned missions

Detector packages consisting of thermoluminescence detectors (TLDs), nuclear emulsions and plastic nuclear track detectors were exposed in different sections of the MIR space station, inside the Spacelab during the IML1 mission, and inside Spacelab module and tunnel during the D2 mission. This report concentrates on total dose measurements with TLDs during these mission. The results are discussed and compared to results of former missions and to calculations. Finally, dose equivalents and mean quality factors for each mission are presented which are derived from the TLD results and results obtained from the other detector systems. Dose equivalents range between 200 μSvd⁻¹ and 700 μSvd⁻¹.     

中心孔药柱中燃速的径向变化

大西洋研究公司提出了一种分析固体发动机药柱燃烧状况的计算机程序化方法,本法可直接计算局部燃速对已燃药厚的平均燃速的比。包括使用标准批检验发动机的某些特殊试验在内,对几种不同构形的中心孔药柱燃速比的药厚变化效应(“虹效应”)及数值进行了评估。分析表明这种燃速比的药厚效应是由制造方法引起的.实际上与尺寸、长径比、控制温度、燃速和药厚等发动机参数无关。提出了一种假说,认为此种药厚效应的起因与推进剂富粘合剂层的条痕结构有关,而条痕的形状又与制造方法及药柱构形有关。迄今积累的数据表明,对圆孔药柱而言,事先固定芯子的装药比先浇注后插入芯子的装药燃速约高3—4%。药柱上的各种槽沟往往限制了各点虹效应的精度确定,尽管在全部的构形中均可看到总的虹效应,且最大与最小值的差一般均在3—6%范围内变动。本文给出了各种发动机的燃速比数据,其推进剂重量从10磅左右至2000磅,长径比1:1至8:1,药厚从小于1英寸到大于7英寸,药形有槽管状、锥柱状、一端和两端的圆柱状。     

火箭喷管的二维两相流

本文介绍了编制一组解轴对称喷管气体/粒子流动方程组的计算机程序的进展情况。已经编写了两个程序,是用来解喷管喉部跨声速区的方程组的。第一个程序把两相流体看成是一种具有修正等熵指数和修正分子量的重理想气体,并解跨声速等熵流动方程组,得到的初始流场形状作为第二个程序的输入。第二个程序包含有气体/粒子混合物非平衡效应。这两个程序为进行超声速计算提供准确的初始线数据,这些数据将用作第三个程序的输入。第三个程序是解喷管超声速区两相流动方程组的,不久即将写成。     

Effects of microgravity on muscular explosive power of the lower limbs in humans

The maximal explosive power of the lower limbs of one astronaut has been measured before launch, and 2, 6 and 11 days after re-entry from 31 days on the MIR Station (EUROMIR '94). The subject, sitting on the carriage-seat of a Multipurpose Ergometer-Dynamometer (MED) constructed ad hoc in our laboratory, pushed maximally with both feet on two force platforms (knees angle 110 degrees). The carriage was free to move backwards on two rails inclined 20 degrees upwards. The force (F) of the lower limbs and the speed of the carriage (v) were recorded and the instantaneous mechanical power (w) was calculated as w = F * v. The average value of the mechanical power (w max) throughout the explosive effort was then obtained. The overall duration of the push was on the average about 0.3 s. It was observed that, at day R+2, mean force, maximal velocity, maximal power (mean and peak), maximal acceleration and overall mechanical work, were all reduced between 60 and 80% of pre-flight values. However, the recovery was remarkably fast, since all these parameters attained about 90% of pre-flight values by day R+11.     

Role of nutrition during long-term spaceflight

The authors discuss changes in macro- and micro-nutrients which occur in weightlessness and consider factors which help maintain appropriate nutrition during extended space flight. Basic energy requirements and metabolism are reviewed. The discussion of handling of foodstuffs includes protein, fats, carbohydrates, vitamins, folic acid, iron, and selenium. The discussion of fluids and minerals includes fluid intake, sodium, potassium, and calcium. Changes in gastrointestinal function are examined.     

Separation of bacterial cells by free flow electrophoresis under microgravity: a result of the SpaceLab-Japan project on Space Shuttle flight STS-47

We demonstrated free flow electrophoresis (FFE) of charged cells under microgravity, where gravitational effects are almost eliminated. Separation of a mixture of three bacterial strains (mutants of Salmonella typhimurium LT2) by FFE was conducted on NASA Space Shuttle flight STS-47 (September 1992). The experiment was designed to differentiate three strains having different lipopolysaccharide core structures in the cell membrane. The results were compared to those of ground experiments, in order to examine whether or not FFE in a weightless environment provides distinct advantages. Smooth strain SL1027 and rough strain SL3749 migrated to two separated fractions. The quality (viability) and the yields of the separated samples were sufficient to show the advantage of microgravity. Another rough strain, SL1102, exhibited unexpected electrophoretic behavior, which prevented the complete resolution of the three strains. All the strains were recovered as viable cells after 8 days of flight. The present study suggests that electrophoretic separation of bacterial cells is much more effective under microgravity conditions with relatively good resolution in comparison with the ground operation.