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31.
Cosmic Research - We have considered procedure and results of the experimental study for spectral characteristics of self emission from laboratory models of electric thrusters with closed electron... 相似文献
32.
R.M. Baevsky I.I. Funtova A. Diedrich A.G. Chernikova J. Drescher V.M. Baranov J. Tank 《Acta Astronautica》2009,65(7-8):930-932
Investigations of blood pressure, heart rate (HR), and heart rate variability (HRV) during long term space flights on board the “ISS” have shown characteristic changes of autonomic cardiovascular control. Therefore, alterations of the autonomic nervous system occurring during spaceflight may be responsible for in- and post-flight disturbances. The device “Pneumocard” was developed to further investigate autonomic cardiovascular and respiratory function aboard the ISS. The hard-software diagnostic complex “Pneumocard” was used during in-flight experiment aboard ISS for autonomic function testing. ECG, photoplethysmography, respiration, transthoracic bioimpedance and seismocardiography were assessed in one male cosmonaut (flight lengths six month). Recordings were made prior to the flight, late during flight, and post-flight during spontaneous respiration and controlled respiration at different rates.HR remained stable during flight. The values were comparable to supine measurements on earth. Respiratory frequency and blood pressure decreased during flight. Post flight HR and BP values increased compared to in-flight data exceeding pre-flight values. Cardiac time intervals did not change dramatically during flight. Pulse wave transit time decreased during flight. The maximum of the first time derivative of the impedance cardiogram, which is highly correlated with stroke volume was not reduced in-flight.Our results demonstrate that autonomic function testing aboard the ISS using “Pneumocard” is feasible and generates data of good quality. Despite the decrease in BP, pulse wave transit time was found reduced in space as shown earlier. However, cardiac output did not decrease profoundly in the investigated cosmonaut.Autonomic testing during space flight detects individual changes in cardiovascular control and may add important information to standard medical control. The recent plans to support a flight to Mars, makes these kinds of observations all the more relevant and compelling. 相似文献
33.
A.C. Levasseur-Regourd 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,17(12):117-122
In-situ space observations of dust in the solar system are seldom possible. On the opposite, remote observations of solar light scattered by dust are relatively easy to perform from Earth- or satellite-based observatories; the evolution of the polarization of light scattered by dust particles as a function of the phase angle may provide information on the physical properties of these particles. Unfortunately, since remote observations are integrated along the line-of-sight of the observer, they can hardly be used to determine local physical properties. We have precisely developed Optical Probe techniques to forge the link between the numerous remote observations and the unique in-situ measurements. A short review of the remote observations of light scattered by cometary dust is first presented. Then, the Optical Probe concept is analyzed. Finally, the OPE instrument, which had been designed to optically probe the inner coma of comet Halley is described; its limitations and its achievements during Halley and Grigg-Skjellerup encounters are discussed. 相似文献
34.
运用张量分析理论,比较简捷地导出了三维任意曲线坐标系上椭圆型N-S方程的通用形式。在对这些方程进行数值离散时,采用了有限控制体积的非交错网格设置,该算法以SIMPLE为基础,为了抑制压力振荡场的出现,在压力修正方程中对压力梯度的离散附加一项1—δx的差分。作为算例,本文给出了三维90°强曲率弯曲管道中气流的不可压缩紊流状态的数值计算结果,并与相关的实验数据进行了对比,结果是满意的。 相似文献
35.
C. Marchal 《Acta Astronautica》1979,6(9):1153-1161
Problems of Hamiltonian Mechanics can generally be simplified by some Von Zeipel transformations which reduce the influence of short period parameters and lead to very slowly variable functions: the “quasi-integrals”; however these transformations are implicit and then difficult to use.An explicit construction of the quasi-integrals is presented here and is used to integrate the motion of an artificial satellite perturbed by the zonal harmonics of the Earth gravitational potential; the quasi-integrals are also used to obtain informations on the stability of natural satellites, i.e. lower bounds on the duration of escape or capture. 相似文献
36.
J.C. Cretenet 《Acta Astronautica》1985,12(11):949-958
The presence of Europe in the future developments of spatial programs, which are foreseen, for the 1990s and further, needs the availability of vehicles, modules and all related technologies adapted to operational use of low earth orbit station.The manned HERMES vehicle shall be part of the in-orbit infrastructure realized either in the European context or in cooperation between Europe and the United States.The main mission for this vehicle will be to run a shuttle with the station that means transport and change of the crews, its safe return in abort condition and cargo transport of consumable and experimental equipment.Secondary missions could be servicing on automatic platform, making autonomous scientific experiments. Lastly, the vehicle, by means of its on-board propulsion capability, could be used to accomplish in-orbit tow and assembly missions.Studies which are undertaken now about the vehicle are devoted to the aerodynamic shape (research of a compromise between aerothermic and overall fitting), the system (functional architecture, ground and flight configuration); further works dealing with technology are presently on hand in the field of thermal protection, aerodynamics, power generation with a high massic yield. 相似文献
37.
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39.
Salwen Howard C. Zaorski Ralph 《IEEE transactions on aerospace and electronic systems》1968,(1):65-80
The ability to detect the presence or absence of a target is no longer the fundamental design criterion when the vehicle to be tracked is cooperative. In spacecraft tracking or navigation systems, for example, emphasis is placed on post-acquisition performance. Therefore, classical radar theory and design techniques are not specifically applicable. On the other hand, there are optimization techniques for extracting the tracking data from noise that are more to the point. In particular, optimum demodulation theory is directed specifically to the problem of continuously extracting data from a nonlinear modulation process. In this paper, the tracking properties of a multitone PM ranging signal are reviewed and are shown to be nearly optimum for cooperative vehicles. An optimum, but nonrealizable, maximum a posteriori (MAP) continuous estimator of range is derived for this signal. The linearized model of this receiver is the optimum nonrealizable Wiener filter for the data. Interpretation of this optimum nonrealizable estimator leads to a receiver design that is both practical and intuitively satisfying. With the aid of post-detection processing in the Wiener-Hopf sense, almost optimum performance is obtained from the resulting receiver, above threshold. 相似文献
40.
The potential of airborne radar to provide pictorial displays as an aid to low approach has stimulated invention of several aircraft approach systems. Early developments are reviewed briefly, and an experiment in producing and flight testing a two-dimensional, range and azimuth, pictorial radar display is described. The monopulse radar equipment and a monopulse display improvement (MDI) technique used in the flight test to enhance the B-scope display are also described in some detail. Representative radar scope photographs are used to illustrate the display available in the aircraft. 相似文献