液氧/煤油发动机地面试验故障紧急关机系统研制

论述了液氧／煤油发动机研制地面试车中，出现故障时所采用的紧急关机系统的原理和系统结构、设计程序、设计指标、关机判断准则、验证及应用等。     

The properties of alamethicin incorporated into planar lipid bilayers under the influence of microgravity.

During evolution, life on earth had adapted to the gravity of 1g. Due to space flight, in the last decades the question arose what happens to the brain under microgravity on the molecular level. Ion channels among others are the molecular basis of brain function. Therefore, the investigation of ion channel function under microgravity seems to be a promising approach to gather knowledge on brain function during space flight. In a first step, the ion channel forming peptide Alamethicin was used as a model channel in an artificial membrane. It is well suitable for this kind of investigation, since its properties are well described under standard gravity. For that reason, changes due to microgravity can be detected easily. All experiments were performed in the German drop tower at ZARM-FAB, Bremen. A special set-up was constructed based on the bilayer technique introduced by Mueller and Rudin. All functions of this set-up can be observed and controlled remotely. In the first set of experiments, a dramatic change of electrical properties of Alamethicin under microgravity could be observed. Mainly, the pore frequency is significantly reduced.     

Prediction of solar particle event proton doses using early dose rate measurements

A methodology for predicting solar particle event doses using Bayesian inference is being developed. As part of this development, we have tested criteria for categorization of new solar particle events (SPE) using calculated asymptotic doses and dose rates for the 22 SPEs that occurred in 2001. In 9 out of 22 events, our criteria for categorization would have over-predicted the range of asymptotic doses in which the tested events would have fallen. In two cases, our methodology under-predicted the dose range in which the event would have fallen. In order to better predict a new event's group category and thus, to better restrict the Bayesian inference predictive model parameter space, we have reexamined our dose rate criteria for categorization of new events. We report the updating of the grouping criteria using data from the 22 SPEs of 2001, as well as five additional SPEs. Using the revised grouping criteria, we present an analysis of group categorization prediction results for the first ten SPEs of 2002.     

Infrared sensor for hot spot recognition for a small satellite mission

High temperature events strongly influence the environmental processes. Therefore, their observation is an important constituent of the global monitoring network. Unfortunately the current remote sensing systems are not able to deliver the necessary information about the world wide burn out of vegetation and its consequences. For global observations a dedicated system of small satellites is required. The main components of the corresponding instrumentation are the infrared channels. The proposed HSRS (HOT SPOT RECOGNITION SENSOR) has to demonstrate the possibilities of an such instrumentation and its feasibility for small satellites. The main drawbacks of the HSRS design are the handling of the hot spot recognition in the subpixel area and of the saturation in the case of larger hot areas by a suitable signal processing hardware.     

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.     

Measuring performance: Moving NASA Earth science products into the mainstream user community

Demonstrating performance of the applications of Earth observation satellite-based science data products and services is increasingly a requirement of government research agencies. We present efforts from the NASA-funded Earth Observing System Data and Information System's Synergy Project to measure performance in the development of applications from NASA research and development projects. We summarize challenges in monitoring performance and share our experience in evolving metrics over a 5-year project life. We demonstrate how to adapt project management processes and metrics from the information technology (IT) industry to Earth observation applications research and development. A roadmap for adapting IT processes and developing metrics and examples of quantitative and qualitative metrics are provided. Our findings suggest that designing and implementing these IT metrics will enhance project success, as defined by the degree of penetration of NASA products into the user community and level of non-NASA funding secured.     

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.     

On the solar pressure damping and attitude control

Librational control of satellites using solar radiation pressure is investigated using a nonlinear optimization technique. The control strategy specifies only the direction in which a relatively weak solar pressure induced moment should be applied irrespective of its magnitude. The analysis suggests that a simple two-vane configuration can damp, rather effectively, severe disturbances over a range of satellite and orbital parameters. The controller is also successful in imparting any desired orientation to the satellite thus giving it a degree of versatility in undertaking diverse missions. The semi-passive character of the controller assures longer lifespan with an associated saving in cost.     

Artificial gravity--head movements during short-radius centrifugation: influence of cognitive effects

Short-radius centrifugation is a potential countermeasure against the effects of prolonged weightlessness. Head movements in a rotating environment, however, induce serious side effects: inappropriate vestibular ocular reflexes (VOR), body-tilt illusions and motion sickness induced by cross-coupled accelerations on a rotating platform. These are well predicted by a semicircular canal model. The present study investigates cognitive effects on the inappropriate VOR and the illusory sensations experienced by subjects rotating on a short-radius centrifuge (SRC). Subjects (N=19) were placed supine on a rotating horizontal bed with their head at the center of rotation. To investigate the extent to which they could control their sensations voluntarily, subjects were asked alternatively to "fight" (i.e. to try to resist and suppress) those sensations, or to "go" with (i.e. try to enhance or, at least, acquiesce in) them. The only significant effect on the VOR of this cognitive intervention was to diminish the time constant characterizing the decay of the nystagmus in subjects who had performed the "go" (rather than the "fight") trials. However, illusory sensations, as measured by reported subjective intensities, were significantly less intense during the "fight" than during the "go" trials. These measurements also verified an asymmetry in illusory sensation known from earlier experiments: the illusory sensations are greater when the head is rotated from right ear down (RED) to nose up (NU) posture than from NU to RED. The subjects habituated, modestly, to the rotation between their first and second sequences of trials, but showed no better (or worse) suppression of illusory sensations thereafter. No significant difference in habituation was observed between the "fight" and "go" trials.     

The influence of gravity on the process of development of animal systems

The development of animal systems is described in terms of a series of overlapping phases: pattern specification; differentiation; growth; and aging. The extent to which altered (micro) gravity (g) affects those phases is briefly reviewed for several animal systems. As a model, amphibian egg/early embryo is described. Recent data derived from clinostat protocols indicates that microgravity simulation alters early pattern specification (dorsal/ventral polarity) but does not adversely influence subsequent morphogenesis. Possible explanations for the absence of catastrophic microgravity effects on amphibian embryogenesis are discussed.