GENERATION AND APPLICATION OF UNSTRUCTURED ADAPTIVE MESHES WITH MOVING BOUNDARIES

INTRODUCTIONMany engineering applications require thenumerical prediction of strongly unsteady flowsinteracting with moving bodies.A case in pointis that the detailed calculation of sphere motionsin an unsteady field induced by blast waves is akey issue to determine the drag force exerting up-on the sphere by the surrounding gas and,inturn,to reveal the mechanism of unsteady effectson the drag coefficient.To cope with such pro-blems,one should simulate unsteady flows withmoving boundary co…     

Adaptational changes in the neural control of cardiorespiratory function in a confined environment: the CNEC#3 experiment

The goal of the study was to characterize the changes in neurovegetative control of the circulation, attending the presumed physiological and psychological stress originated by the isolation and confinement typical of the living condition of space stations, as simulated in a ground based unit, using time and frequency domain analysis. As a secondary goal we sought to verify the implementation of real time data acquisition, for off line spectral analisys of R-R interval, systolic arterial pressure (by Finapres) and respiration (by PVF2 piezoelectric sensors).

We addressed the cardiorespiratory and neurovegetative responses to standardized, simple Stressors (active standing, dynamic and static handgrip) on the EXEMSI 92 crew, before, during and after the isolation period.

On average the appropriate excitatory responses (to stand, dynamic and static handgrip) were elicited also in isolation and confinement.

Active standing and small masses muscular exercises are easy to be performed in a confined and isolated environment and provide a valuable tool for investigating the adaptational changes in neural control mechanisms.

The possibility there exists of using this time and frequency domain approach to monitor the level of performance and well being of the space crew in (quasi) real time.     

Meteors do not break exogenous organic molecules into high yields of diatomics

Meteoroids that dominate the Earth's extraterrestrial mass influx (50-300 microm size range) may have contributed a unique blend of exogenous organic molecules at the time of the origin of life. Such meteoroids are so large that most of their mass is ablated in the Earth's atmosphere. In the process, organic molecules are decomposed and chemically altered to molecules differently from those delivered to the Earth's surface by smaller (<50 microm) micrometeorites and larger (>10 cm) meteorites. The question addressed here is whether the organic matter in these meteoroids is fully decomposed into atoms or diatomic compounds during ablation. If not, then the ablation products made available for prebiotic organic chemistry, and perhaps early biology, might have retained some memory of their astrophysical nature. To test this hypothesis we searched for CN emission in meteor spectra in an airborne experiment during the 2001 Leonid meteor storm. We found that the meteor's light-emitting air plasma, which included products of meteor ablation, contained less than 1 CN molecule for every 30 meteoric iron atoms. This contrasts sharply with the nitrogen/iron ratio of 1:1.2 in the solid matter of comet 1P/Halley. Unless the nitrogen content or the abundance of complex organic matter in the Leonid parent body, comet 55P/Tempel-Tuttle, differs from that in comet 1P/Halley, it appears that very little of that organic nitrogen decomposes into CN molecules during meteor ablation in the rarefied flow conditions that characterize the atmospheric entry of meteoroids approximately 50 microm-10 cm in size. We propose that the organics of such meteoroids survive instead as larger compounds.     

STARDUST: finessing expensive cometary sample returns

The STARDUST Discovery mission will collect samples of cometary coma and interstellar dust and return them to Earth. Five years after launch in February 1999, coma dust in the 1- to 100-micrometers size range will be captured by impact into ultra-low-density silica aerogel during a 6 kms-1 flyby of Comet Wild 2. The returned samples will be investigated at laboratories where the most critical information on these primitive materials is retained. The Jet Propulsion Laboratory will provide project management with Lockheed Martin Astronauts as the spacecraft industrial partner. STARDUST management will aggressively and innovatively achieve cost control through the use of Total Quality Management principles, the chief of which will be organization in a Project Engineering and Integration Team that "flattens" the traditional hierarchical structure by including all project elements from the beginning, in a concurrent engineering framework focusing on evolving Integrated Mission Capability.     

MX导弹第一级发动机

MX导弹第一级发动机在系统论证阶段后,现在正进入研制阶段。其设计原则是选择能使性能、成本和进度三者之间得到平衡的技术。由于MX导弹第一级发动机是为弹道导弹研制的迄今最大的固体动力装置,因而其设计具有普遍意义。     

复合固体推进剂浇入发动机时的流变学

浇铸时未固化的复合固体推进剂的流动特性是十分重要的,因为它直接关系到发动机装药的完整性。增加推进剂的固体含量,可以提高能量特性,却导致药浆的流动性变坏。固体含量高的推进剂呈现非牛顿假塑性流动特性,即表观粘度依赖于剪切应力,以及随着未固化推进剂存放时间的增长,假塑性也增加。本文介绍了在 NASA 主办下进行浇铸研究的一些情况。对浇铸过程中剪切应力的三个明显不同区域和每一区域中推进剂的流动特性,进行了讨论。叙述了推进剂组分和工艺条件的变化对表观粘度的影响和浇铸过程中形成药柱缺陷的有关流变性能的实验结果。     

Isolation,confinement, and sensory deprivation

Long-duration space flight involves sensory monotony, isolation, and confinement. Obviously, data from other such environments are relevant to our concerns; and the application of the concept of arousal both to interpersonal relations and to task performance in space can point to appropriate selection, training, and spacecraft design features. In the context of space flight, all of these leads remain conjectural--simulation as well as laboratory research and initiation of long-duration flights will be the crucial test of the hypotheses.     

Preparing for life in space

The third team to inhabit the Advanced Life Support Test Chamber at the Johnson Space Center participated in an interview about life in the test chamber and program goals. Questions examine the air and water systems; human factors such as life in confinement, privacy, health, and training; and exercise. The test chamber is used to test life support systems for the International Space Station, lunar bases, and manned missions to Mars.     

Application of the mechanical oscillator technique to the investigation of EVA decompression

The ultrasonic bubble detection technique has been used as a versatile tool in the investigation of hypobaric decompression procedures for the last two decades. However, this method can only detect relatively large bubbles > 30-50 micrometers (usually in venous blood) and not the very first stages of bubble formation. Recently, the mechanical oscillator technique has been applied in air diving trials in order to detect small blood density changes due to hypothetical fluid shifts. However, sharp density drops were found in the decompression process, and these have been attributed to gas bubble formation. In this study, this method was applied together with Doppler controls to a series of altitude decompressions to 300 and 500 hPa, which represents the range of EVA operational pressures currently used or planned. Six subjects participated in both series; the oscillator sample tube could be pressurized. By the application of pressure on a blood sample containing questionable gas bubbles, these are reduced in volume, like in recompression therapy, and thus the density of the sample is increased. This effect has been shown in all 6 subjects undergoing decompression to 300 hPa, whereas in the 500 hPa series only 3 out of 6 subjects corresponded with gas phase formation immediately after decompression. Typically, Doppler bubbles appeared only after some latency time between 20 and 60 min; after this time, the density effect had nearly vanished. It is concluded that the mechanical oscillator technique represents a complementary research instrument to the Doppler method, because it is able to deliver a quantitative resolution of the early stage of gas phase formation.