固体火箭发动机点火期间的瞬态流动

本文用处理流体动力学方程的计算机程序研究燃烧室中的非稳态流场、并对计算值和试验值作了比较。压力首先在燃烧室尾部上升,随后在头部上升,头、尾两区域间的压力差可能引起推进剂药柱的快速位移(爆裂效应)或过早的破坏。本文介绍了该分析方法应用于一个典型发动机的情况。     

跨音速翼型激波的被动控制(英文)

本文提出了在超临界流中减弱翼型激渡的方法。通过数值求解定常跨音速流的无粘、小扰动方程,根据实心翼型或多孔翼型的边界条件,获得了相应的压力分布。比较这两种情况下的压力分布后可以看到,在相当大的M数范围内,多孔冀型出现向后缘逐渐再压缩,未出现强激波。这与人们熟知的超临界翼型的最优化只有在非常接近设计M数和迎角时才是有效的这一事实相反。给定M数和迎角时,可利用计算的多孔翼型的压力分布,来产生外形类似于超临界翼型的实心翼型的压力分布。     

未填充氯丁胶与黄铜粘接性能的研究

本文研究了未填充氯丁胶WRT的硫化特性和应力——应变特性,并研究分析了试验温度和速度对未填充氯丁胶与黄铜粘接性能的影响。结果表明,对于配方中不加硫磺的样品,在各种温度和速度下的破坏能Gi值可以应用WLF方程进行变换,并得到一条平滑的组合曲线。然而在足够高的速度下,出现一条不连续的线段,这可能是由于橡胶在较高应力下诱导结晶所至。对于配方中加硫磺的样品,当试验温度升至60℃时,会出现一个从界面破坏到内聚力破坏的转变现象。文中也解释了橡胶配方中不含硫磺样品和只含少量硫磺样品中Gi与温度关系之间所出现的完全不同的行为。     

实现555时基电路频率的线性控制

大家熟悉的555集成时基电路,虽则广泛地用作非稳态多谐振荡器,但一直有频率响应不是线性的缺点。本文图1中的线路却能使555时基电路提供极易实现的线性频率     

导弹的整体级方案——系统研究结果

为美国空军研制的导弹整体级方案(ISC),采用一般的结构件将两级火箭发动机组合在一起,从而提高了多级导弹系统的性能,使现有推进系统体积得到更有效的利用,并能得到更高的发动机可靠性和明显地降低制造成本。在以往的几年中,航空喷气战略推进公司(ASPC)曾经研究将整体级方案应用到采用部件设计概念和新材料的几种未来系统上。近期完成的详细研究表明,对于限定体积的系统级性能约提高30%和限定重量的系统级性能约提高15%。本文概述了这些系统的研究结果,所介绍的一些特定系统包括:先进的洲际弹道导弹,空中发射的助推滑翔飞行器,速燃助推器和轨道转移飞行器。最后,讨论了整体级降低成本预估的基础和将来发展的计划。     

Temperature and moisture conditions for life in the extreme arid region of the Atacama desert: four years of observations including the El Niño of 1997-1998

The Atacama along the Pacific Coast of Chile and Peru is one of the driest and possibly oldest deserts in the world. It represents an extreme habitat for life on Earth and is an analog for life in dry conditions on Mars. We report on four years (September 1994-October 1998) of climate and moisture data from the extreme arid region of the Atacama. Our data are focused on understanding moisture sources and their role in creating suitable environments for photosynthetic microorganisms in the desert surface. The average air temperature was 16.5 degrees C and 16.6 degrees C in 1995 and 1996, respectively. The maximum air temperature recorded was 37.9 degrees C, and the minimum was -5.7 degrees C. Annual average sunlight was 336 and 335 W m(-2) in 1995 and 1996, respectively. Winds averaged a few meters per second, with strong f?hn winds coming from the west exceeding 12 m s(-1). During our 4 years of observation there was only one significant rain event of 2.3 mm, which occurred near midnight local time. We suggest that this event was a rainout of a heavy fog. It is of interest that the strong El Ni?o of 1997-1998 brought heavy rainfall to the deserts of Peru, but did not bring significant rain to the central Atacama in Chile. Dew occurred at our station frequently following high nighttime relative humidity, but is not a significant source of moisture in the soil or under stones. Groundwater also does not contribute to surface moisture. Only the one rain event of 2.3 mm resulted in liquid water in the soil and beneath stones for a total of only 65-85 h over 4 years. The paucity of liquid water under stones is consistent with the apparent absence of hypolithic (under-stone) cyanobacteria, the only known primary producers in such extreme deserts.     

Response to hypogravity of normal in vitro cultured follicular cells from thyroid

Aim of this investigation is the study of molecular modifications occurring in differentiated mammalian cells exposed to gravitational changes. The test system chosen is a well characterized clone of differentiated, normal thyroid follicular cells (FRTL5) in long-term culture. As a follow-up to our recent experiment performed during the MASER-7 sounding rocket mission, flown for European Space Agency by Swedish Space Corporation in May 1996, we evaluated FRTL5 cells responses to Thyroid Stimulating Hormone dependent cAMP production under acute hypogravity conditions obtained in a fast rotating clinostat. Following this approach, we evaluated the FRTL5 cells response to TSH under microgravity conditions in order to optimize experimental tools and strategies in preparation to, and in between real flight missions.     

Relative efficacy of the proposed Space Shuttle antimotion sickness medications

Space motion sickness has been estimated as affecting between 1/3 and 1/2 of all space flight participants. NASA has at the moment proposed a combination of promethazine and ephedrine (P/E) and one of scopolamine and dextroamphetamine (S/D), both given orally, as well as a transdermally applied scopolamine (TAS), as preventive and ameliorative measures. The reported double-blind study, tests the early phase actions and efficacy of the transdermal scopolamine (Transderm (TM)-V of ALZA Corporation) and compares these in detail to the oral medications. Motion sickness resistance was tested by standardized head movements while accelerating at 0.2 degree/sec2 to a maximum rotation of 240 degrees/sec, with an intermediate plateau of 10 min at 180 degrees/sec. To permit weighting motion sickness protection against other system influences, cardiovascular, psychological (subjective and objective), and visual parameter changes were documented for the three therapeutic modes. The relative impact of the various modalities on operational and experimental components of space missions is discussed. A comparison to intramuscularly administered promethazine (a backup therapeutic mode suggested for Space Shuttle use) is also included.     

Life science experiments during the German-Russian MIR '97 mission

Manned spaceflight has been an important element of the German space program over the last decades. This is demonstrated by the nationally managed space missions Spacelab D-l (1985), D-2 (1993), and MIR '92 as well as by the participation in the 1st Spacelab mission FSLP (1983), the NASA missions IML-1 (1992) and IML-2 (1994), as well as in the ESA missions EUROMIR '94 and '95. On February 12th, this year, the German cosmonaut Reinhold Ewald was launched together with his Russian colleagues Wasilij Zibliew and Alexander Lasudkin onboard of a Soyuz spacecraft for another stay of a German cosmonaut onboard of the Russian Space Station MIR. This mission--the so-called German/Russian MIR '97--was, of course, another cornerstone with regard to the cooperation between Russian and German space organizations. The cooperation in the area of manned missions began 1978 with the flight of the German cosmonaut Sigmund Jahn onboard of Salyut 6, at that time a cooperation between the Soviet Union and the German Democratic Republic in the frame of the Interkosmos Program. In March 1992, it was followed by the flight of Klaus Dietrich Flade with his stay onboard of MIR. After two further successful ESA missions, EUROMIR '94 and '95 with the two German cosmonauts Ulf Merbold and Thomas Reiter and with a marked contribution of German scientists, the decision was taken to perform another German/Russian MIR mission, the so-called MIR '97. In Germany, MIR'97 was managed and performed in a joint effort between several partners. DARA, the German Space Agency, was responsible for the overall program and project management, while DLR, the German Aerospace Research Establishment, was responsible for the cosmonaut training, for medical operations, for the mission control at GSOC in Oberpfaffenhofen as well as for user support.     

A Sensate Liner for personnel monitoring applications

This program develops and demonstrates technologies useful for implementing a manageable cost effective systems approach to monitoring the medical condition of personnel by way of an instrumented uniform hereafter referred to as a Sensate Liner (SL). The SL consists of a form fitting garment which contains and interconnects sensing elements and devices to an electronics pack containing a processor and transmitter. The SL prototype requires fiber, textile, garment and sensor development. The SL textile consists of a mesh of electrically and optically conductive fibers integrated into the normal structure (woven or knitted) of fibers and yarns selected for comfort and durability. A suite of SL garment compatible embedded biological and physical sensors are then integrated into the SL. The initial SL sensor suite is selected to improve triage for combat casualties. Additional SL sensor concepts for medical monitoring will be discussed.