Production of neutrons from interactions of GCR-like particles

In order to help assess the risk to astronauts due to the long-term exposure to the natural radiation environment in space, an understanding of how the primary radiation field is changed when passing through shielding and tissue materials must be obtained. One important aspect of the change in the primary radiation field after passing through shielding materials is the production of secondary particles from the breakup of the primary. Neutrons are an important component of the secondary particle field due to their relatively high biological weighting factors, and due to their relative abundance, especially behind thick shielding scenarios. Because of the complexity of the problem, the estimation of the risk from exposure to the secondary neutron field must be handled using calculational techniques. However, those calculations will need an extensive set of neutron cross section and thicktarget neutron yield data in order to make an accurate assessment of the risk. In this paper we briefly survey the existing neutron-production data sets that are applicable to the space radiation transport problem, and we point out how neutron production from protons is different than neutron production from heavy ions. We also make comparisons of one the heavy-ion data sets with Boltzmann-Uehling-Uhlenbeck (BUU) calculations.     

Radial velocity search for low mass companions of nearby stars

The detection of substellar companions of nearby stars is very difficult, because these objects are very faint and are located close to their bright parent stars. One way to attack this problem is to look for small periodic motion of the bright star, induced by the gravitational attraction exerted by the unseen small companion. Over the past decade stellar spectroscopy has been used by a few teams to monitor the radial velocities of several samples of stars, with a threshold for detection of companions well below the substellar limit of about 0.08 M. So far, only a few possible spectroscopic binaries have been identified where the unseen companions might be substellar.Recently, radio observers discovered that the millisecond pulsar PSR B1257+12 displays periodic variations in the pulse arrival times, indicating the existence of at least three unseen companions in circular orbits around the pulsar. This is the first convincing case for an extra-solar planetary system. This discovery suggests that planetary systems can form in very different situations, and therefore may prove to be common.     

航天飞行器防热部件烧蚀行为的数值模拟

对航天飞行器防热部件在氧－煤油发动机火焰喷吹下的烧蚀行为进行了有限元数值模拟。利用“杀死”单元的方法建立防热部件瞬态温度场的有限元模型，实现了烧蚀边界的退缩，从而完成了对烧蚀尺寸变化的定量描述。烧蚀开始于4．59s，到12s时线烧蚀量为1．47mm。计算结果与试验的实测结果一致。     

机动再入飞行器的复合制导方案研究

对机动再入飞行器弧段的复合制导方案进行了研究，首先提出了通过高低空复合制导控制再入飞行器的终端速度和弹道倾角的思路；然后分别给出了高空最优制导律和大气厚再入最优制导律；最后对此复合制导方案进行了数字仿真。仿真结果表明此方案在理论上是可行的。     

Electrostatic Instability and Plasma Irregularities in the Topside Ionosphere above the South-Atlantic Geomagnetic Anomaly

The data of measuring the plasma density in the topside ionosphere for the South-Atlantic geomagnetic anomaly region are presented. It is shown that irregular plasma structures with a wide spectrum of irregularity scale (including large-scale structures with a dimension of order of some hundred kilometers) can be generated in the fields of electrostatic turbulence in inhomogeneous plasma.     

Cave biosignature suites: microbes,minerals, and Mars

Earth's subsurface offers one of the best possible sites to search for microbial life and the characteristic lithologies that life leaves behind. The subterrain may be equally valuable for astrobiology. Where surface conditions are particularly hostile, like on Mars, the subsurface may offer the only habitat for extant lifeforms and access to recognizable biosignatures. We have identified numerous unequivocally biogenic macroscopic, microscopic, and chemical/geochemical cave biosignatures. However, to be especially useful for astrobiology, we are looking for suites of characteristics. Ideally, "biosignature suites" should be both macroscopically and microscopically detectable, independently verifiable by nonmorphological means, and as independent as possible of specific details of life chemistries--demanding (and sometimes conflicting) criteria. Working in fragile, legally protected environments, we developed noninvasive and minimal impact techniques for life and biosignature detection/characterization analogous to Planetary Protection Protocols. Our difficult field conditions have shared limitations common to extraterrestrial robotic and human missions. Thus, the cave/subsurface astrobiology model addresses the most important goals from both scientific and operational points of view. We present details of cave biosignature suites involving manganese and iron oxides, calcite, and sulfur minerals. Suites include morphological fossils, mineral-coated filaments, living microbial mats and preserved biofabrics, 13C and 34S values consistent with microbial metabolism, genetic data, unusual elemental abundances and ratios, and crystallographic mineral forms.     

自适应控制方法的直接命中目标本体的平行接近制导律

本文在最少量测条件下采用视线角速度ｑ趋于零的指标函数和低阶等效辨识模型与快速自适应控制方法实现了战术导弹的平行接近制导律。这种最优制导律可以实现直接命中目标本体，实现一弹多用，可以用于反导弹的控制。能使制导装置简化并使其尺寸和重量减小，算法简单易于工程使用。经过大量数学和半实物仿真试验表明，上述成果可应用于实际工程当中。     

Main medical results of extended flights on space station Mir in 1986-1990

During 1986-1990 seven prime spacecrews (16 cosmonauts) have flown on-board the Mir orbital complex. The longest space mission duration was 366 days The principal objectives of the medical tasks were the maintenance of good health and performance of the spacecrews and conducting medical research programs which included study of the cardiovascular, motor, endocrine, blood, immune, and metabolic systems. Results obtained point to the ability of humans to readily adapt to a year-long stay in space and maintain good health and performance. Readaptation had a similar course as after other previous long-term space flights of up to 8 months in duration. Primary body system changes were not qualitatively different from findings after flights aboard the Salyut 6 and 7 space stations. In this case, during and after an 11-12 month flight, body system alterations were even less severe which was a result of adequate countermeasure use, their systematic and creative employment and maintenance of required environments to support life and work in space.     

Electrostatic Noise Spectrum at the Electron Cyclotron Frequency and Electromagnetic Emission in the Inhomogeneous Plasma of the Topside Ionosphere

Measurements of the wave emission of the topside ionosphere made onboard the APEX satellite using the electric component of the wave field in the 0.1–10 MHz frequency band are presented. At middle latitudes a wave intensity decrease was observed in the broad-band spectrum of the electrostatic noise at the electron cyclotron frequency. It is shown that a break in the spectrum of electrostatic modes at the electron cyclotron frequency (the absence of the plasma eigen-frequencies) may be a cause of the observed effect. The increase of the intensity at the electron cyclotron frequency in the ionospheric trough and at latitudes above the trough region as compared to middle latitudes may be explained by the capture by plasma irregularities of the electromagnetic emission of the auroral electron fluxes.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 201–208.Original Russian Text Copyright © 2005 by Izhovkina, Prutensky, Pulinets, Kiraga, Klos, Rothkael.