利用比力多重积分作为输入信号的捷联导航算法

本论文提出了异于传统的推导捷联导航算法的方法，现在常用的仍然是传统的推导方法，且不久前Paul Savage做过总结(Savage，P．G，“Strapdown Inertial Navigation Integration Algorithm Design Part2：Velocity and Position Algorithms”，Journal of Guidance，Control，and Dynamics，V01．21，No．2，1998，PP．208—221．)。新方法的要点是利用了额外的加速度计的输出信号，它是比力多重积分在迭代周期的增量。由此产生了比力转换算法新的家族，它有效地消弱所谓的假振摆效应(它在线性振动和高频陀螺仪误差存在时产生)，以较低的速度计算且无须采用抗混叠预滤波。     

软土地层中的地铁工程

美国华盛顿特区的地铁工程，其中穿越城市西北部的中城Ｅ路工程，它代表了大华盛顿市区公共交通局系统的最后主要的软土地层隧道。全部线路开挖都在水位线以下，工程遇到了重重困难。在交通繁忙的大道下施工，要求把地面的沉降减少到最低限度。该文着重介绍了Ｅ路工程采用的施工方法、排水措施，使之地面沉降得到控制，完成了地铁工程。     

卫星及星上固体发动机之间的相互要求

本文讨论了对用于卫星的固体火箭发动机所提出的要求和技术条件的依据。列举了已经采用的典型的技术条件。所讨论的技术条件项目是:总冲、推力值、推力偏心校准、温度、羽流及羽流污染、自旋速度、振动和冲击、重心和平衡。     

基于目标机动新模型的被动寻的导弹制导律

假设某些目标能作正交于其速度矢量的规避机动,提出一种新的随机动态目标模型.利用增益修正广义卡尔曼滤波器来估计目标状态和在线建立目标机动的角速率.推导出可使二次型性能指标极小化的制导律,对于二维的只有角测量的情况,数值仿真表明,所提出的目标模型会使目标状态的估计得到明显的改进.此外,还给出采用这种新制导方法对终端脱靶距离的影响,并与高斯-马尔可夫模型作了比较.     

靶场标准化及自动化计划第二阶段

一、靶场背景 美国主要的航天发射场,包括东靶场(位于弗罗里达州卡纳维拉尔角)和西靶场(位于加利福尼亚州范登堡空军基地)起源于50年代,在随后的几十年内进行了逐步扩展和改进。直到前不久移交给空军空间司令部时,这些靶场才更多地用作研究和开发单位,而不只是操作运行单位。逐步改造使它们具备了支持发射新型航天器、弹道导弹以及逐步发展起来的     

Analysis of a spacecraft life support system for a Mars mission

This report summarizes a trade study conducted as part of the Fall 2002 semester Spacecraft Life Support System Design course (ASEN 5116) in the Aerospace Engineering Sciences Department at the University of Colorado. It presents an analysis of current life support system technologies and a preliminary design of an integrated system for supporting humans during transit to and on the surface of the planet Mars. This effort was based on the NASA Design Reference Mission (DRM) for the human exploration of Mars [NASA Design Reference Mission (DRM) for Mars, Addendum 3.0, from the world wide web: http://exploration.jsc.nasa.gov/marsref/contents.html.]. The integrated design was broken into four subsystems: Water Management, Atmosphere Management, Waste Processing, and Food Supply. The process started with the derivation of top-level requirements from the DRM. Additional system and subsystem level assumptions were added where clarification was needed. Candidate technologies were identified and characterized based on performance factors. Trade studies were then conducted for each subsystem. The resulting technologies were integrated into an overall design solution using mass flow relationships. The system level trade study yielded two different configurations--one for the transit to Mars and another for the surface habitat, which included in situ resource utilization. Equivalent System Mass analyses were used to compare each design against an open-loop (non-regenerable) baseline system.     

A viable microbial community in a subglacial volcanic crater lake, Iceland

We describe a viable microbial community in a subglacial lake within the Grímsv?tn volcanic caldera, Iceland. We used a hot water drill to penetrate the 300-m ice shelf and retrieved lake water and volcanic tephra sediments. We also acquired samples of borehole water before and after penetration to the lake, overlying glacial ice and snow, and water from a nearby subaerial geothermal lake for comparative analyses. Lake water is at the freezing point and fresh (total dissolved solids = 260 mg L(-1)). Detectable numbers of cells were found in samples of the lake water column and tephra sediments: 2 x 10(4) ml(-1) and 4 x 10(7) g(-1), respectively. Plate counts document abundant cold-adapted cultivable organisms in the lake water, but not in the borehole (before penetration) or glacial ice. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments amplified from genomic DNA extracted from Grímsv?tn samples indicates that the lake community is distinct from the assemblages of organisms in borehole water (before penetration) and the overlying ice and snow. Sequencing of selected DGGE bands revealed that many sequences are highly similar to known psychrophilic organisms or cloned DNA from other cold environments. Significant uptake of 14C-labeled bicarbonate occurred in dark, low-temperature incubations of lake water samples, indicating the presence of autotrophs. Acetylene reduction assays under similar incubation conditions showed no significant nitrogen fixation potential by lake water samples. This may be a consequence of the inhibition of diazotrophy by nitrogen in the lake.     

Hydrogen in rocks: an energy source for deep microbial communities

To survive in deep subsurface environments, lithotrophic microbial communities require a sustainable energy source such as hydrogen. Though H2 can be produced when water reacts with fresh mineral surfaces and oxidizes ferrous iron, this reaction is unreliable since it depends upon the exposure of fresh rock surfaces via the episodic opening of cracks and fissures. A more reliable and potentially more voluminous H2 source exists in nominally anhydrous minerals of igneous and metamorphic rocks. Our experimental results indicate that H2 molecules can be derived from small amounts of H2O dissolved in minerals in the form of hydroxyl, OH- or O3Si-OH, whenever such minerals crystallized in an H2O-laden environment. Two types of experiments were conducted. Single crystal fracture experiments indicated that hydroxyl pairs undergo an in situ redox conversion to H2 molecules plus peroxy links, O3Si/OO\SiO3. While the peroxy links become part of the mineral structure, the H2 molecules diffused out of the freshly fractured mineral surfaces. If such a mechanism occurred in natural settings, the entire rock column would become a volume source of H2. Crushing experiments to facilitate the outdiffusion of H2 were conducted with common crustal igneous rocks such as granite, andesite, and labradorite. At least 70 nmol of H2/g diffused out of coarsely crushed andesite, equivalent at standard pressure and temperature to 5,000 cm3 of H2/m3 of rock. In the water-saturated, biologically relevant upper portion of the rock column, the diffusion of H2 out of the minerals will be buffered by H2 saturation of the intergranular water film.     

Application of hyperspectral infrared analysis of hydrothermal alteration on Earth and Mars

An integrated analysis of both airborne and field short-wave infrared hyperspectral measurements was used in conjunction with conventional field mapping techniques to map hydrothermal alteration in the central portion of the Mount Painter Inlier in the Flinders Ranges, South Australia. The airborne hyperspectral data show the spatial distribution of spectrally distinct minerals occurring as primary minerals and as weathering and alteration products. Field spectral measurements, taken with a portable infrared mineral analyzer spectrometer and supported by thin-section analyses, were used to verify the mineral maps and enhance the level of information obtainable from the airborne data. Hydrothermal alteration zones were identified and mapped separately from the background weathering signals. A main zone of alteration, coinciding with the Paralana Fault zone, was recognized, and found to contain kaolinite, muscovite, biotite, and K-feldspar. A small spectral variation associated with a ring-like feature around Mount Painter was tentatively determined to be halloysite and interpreted to represent a separate hydrothermal fluid and fluid source, and probably a separate system. The older parts of the alteration system are tentatively dated as Permo-Carboniferous. The remote sensing of alteration at Mount Painter confirms that hyperspectral imaging techniques can produce accurate mineralogical maps with significant details that can be used to identify and map hydrothermal activity. Application of hyperspectral surveys such as that conducted at Mount Painter would be likely to provide similar detail about putative hydrothermal deposits on Mars.     

Lessons learned from the Space Flyer Unit (SFU) mission

The Space Flyer Unit (SFU) system and mission chronology are briefly introduced. Lessons learned from the SFU mission are categorized as programmatic and engineering lessons. In the programmatic category are dealt with both international and domestic collaborations. As for the engineering lessons safety design, orbital operation, in-flight anomaly, and post flight analyses are the major topics reviewed.