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81.
Mendell WW 《Acta Astronautica》2005,57(2-8):676-683
The Vision for Space Exploration invokes activities on the Moon in preparation for exploration of Mars and also directs International Space Station (ISS) research toward the same goal. Lunar missions will emphasize development of capability and concomitant reduction of risk for future exploration of Mars. Earlier papers identified three critical issues related to the so-called NASA Mars Design Reference Mission (MDRM) to be addressed in the lunar context: (a) safety, health, and performance of the human crew; (b) various modalities of mission operations ranging surface activities to logistics, planning, and navigation; and (c) reliability and maintainability of systems in the planetary environment. In simple terms, lunar expeditions build a résumé that demonstrates the ability to design, construct, and operate an enterprise such as the MDRM with an expectation of mission success. We can evolve from Apollo-like missions to ones that resemble the complexity and duration of the MDRM. Investment in lunar resource utilization technologies falls naturally into the Vision. NASA must construct an exit strategy from the Moon in the third decade. With a mandate for continuing exploration, it cannot assume responsibility for long-term operation of lunar assets. Therefore, NASA must enter into a partnership with some other entity--governmental, international, or commercial--that can responsibly carry on lunar development past the exploration phase. 相似文献
82.
Blood pressure at 30-sec intervals, heart rate, and percentage increase in leg volume continuously were recorded during a 25-min protocol in the M092 Inflight Lower Body Negative Pressure (LBNP) experiment carried out in the first manned Skylab mission. These data were collected during six tests on each crewman over a 5-month preflight period. The protocol consisted of a 5-min resting control period, 1 min at -8, 1 min at -16, 3 min at -30, 5 min at -40, and 5 min at -50 mm Hg LBNP. A 5-min recovery period followed. Inflight tests were performed at approximately 3-day intervals through the 28-day mission. Individual variations in cardiovascular responses to LBNP during the preflight period continued to be demonstrated in the inflight tests. Measurements of the calf indicated that a large volume of fluid was shifted out of the legs early in the flight and that a slower decrease in leg volume, presumably due to loss of muscle tissue, continued throughout the flight. Resting heart rates tended to be low early in the flight and to increase slightly as the flight progressed. Resting blood pressure varied but usually was characterized by slightly elevated systolic blood pressure, lower diastolic pressure, and higher pulse pressures than during preflight examinations. During LBNP inflight a much greater increase in leg volume occurred than in preflight tests. Large increases occurred even at the smallest levels of negative pressure, suggesting that the veins of the legs were relatively empty at the beginning of the LBNP. The greater volume of blood pooled in the legs was associated with greater increases of heart rate and diastolic pressure and larger falls of systolic and pulse pressure than seen in preflight tests. The LBNP protocol represented a greater stress inflight, and on three occasions it was necessary to stop the test early because of impending syncopal reactions. LBNP responses inflight appeared to predict the degree of postflight orthostatic intolerance. Postflight responses to LBNP during the first 48 hours were characterized by marked elevations of heart rate and instability of blood pressure. In addition, systolic and diastolic pressures were typically elevated considerably both at rest and also during stress. The time required for cardiovascular responses to return to preflight levels was much slower than in the case of Apollo crewmen. 相似文献
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84.
本文利用DYL多元逻辑电路的特点,提出求极值和中间值的“地址”的方法和电路。使DYL多元逻辑电路的应用更加完善。 相似文献
85.
用于导弹系统性能统计分析的统计线性化伴随法 总被引:1,自引:0,他引:1
本文在研究SLAM方法基础上,进行了理论推导和计算方法方面的改进,并将此方法应用于导弹系统性能的统计分析,计算机仿真结果表明该方法与采用CADET方法的结果完全一致。 相似文献
86.
安全是民航工作永恒的主题,是民航发展的生命线。国际航空运输协会(IATA)航空中心的统计表明,有80%的事故与人为因素有关。因此,必须开展人为因素的研究,以提高航空安全管理水平,逐步减少人为差错事故。心理素质作为人为因素的重要组成部分,也应引起我们的重视。一、航空气象预 相似文献
87.
低成本INS/GPS组合导航系统算法研究及其实现 总被引:3,自引:0,他引:3
采用基于 MEMS技术的低成本 IMU和 GPS接收机 ,以 DSP为信息处理核心 ,实现了 GPS/SINS组合导航系统。文中详细描述组合算法和算法的软件实现 ,并对模样机在实验室的静态实验结果进行描述和分析。实验结果表明 ,系统组合滤波器的设计和参数选择正确 ,模样机取得了较好的导航解算精度 相似文献
88.
自由—自由结构振动模态的一阶导数 总被引:1,自引:0,他引:1
空间飞行器和车辆等一大类结构属于自由—自由结构。本文讨论这类结构的振动模态-阶导数计算问题,提出了一种改进的截尾模态展开法,将未知模态对模态导数的贡献用已知模态和系统矩来表达。针对刚度阵奇异问题,提出了移位措施,通过选择的移位系数,不仅解决了奇异问题,而且加速了算法的收敛速度。给出了一个数值例子,算例表明本文方法十分有效。 相似文献
89.
90.
有分布质量系绳的卫星系统的动力学 总被引:2,自引:0,他引:2
以一组偏微分方程建立起的数学模型和采用距离速率控制算法来描述系统的受控运动。创建的递推算法用于计算系统的定常运动和称驻形。根据求解小偏差运动方程和通过边界条件求解特征根以判定驻形的稳定性。给出了模拟结果。 相似文献