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681.
The spatial motion relative to the center of mass is considered for a capsule on an elastic tether, when it is unrolled from a spacecraft by a special program. The spacecraft is in a circular orbit and oriented relative to the local vertical, which is guaranteed by operation of its own stabilization system. Angular motion of the capsule relative to the tether direction is studied, and the main factors influencing the stability of this motion are analyzed. An approximate quasi-linear mathematical model of the capsule attitude motion is obtained, which allows one to estimate the influence of major disturbances of its motion. The results of numerical simulations are presented for characteristic cases of the capsule motion.  相似文献   
682.
The goal is to study parameters of drifting type III bursts, and find out the emission mechanism of these bursts and understand what factors affect instantaneous spectral bandwidth of these bursts.  相似文献   
683.
A possibility to prevent collisions with the Earth of dangerous celestial bodies by directing at them small asteroids is considered. It is proposed to solve this problem using a gravitational maneuver near the Earth.  相似文献   
684.
Melting sulfur and mixing it with an aggregate to form “concrete” is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO2 powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.  相似文献   
685.
We compared fluxes of the 1–100 MeV solar energetic particles (SEP) measured in the interplanetary medium (ACE) and in the magnetosphere (Universitetsky-Tatiana, POES—in polar caps, and GOES-11—at geosynchronous orbit) during several SEP events of 2005–2006. Peak intensities of the SEP fluxes inside and outside the magnetosphere were compared for each event. It is shown that observed inside-outside difference depends mainly on direction of interplanetary magnetic field (IMF), on degree of the SEP anisotropy (pitch-angle distribution) in IMF, and on distance of the dayside magnetopause from the Earth.  相似文献   
686.
A problem of applying closed multiloop thermodynamic cycles with mixing of dissimilar working gases in spacecraft power plants has been considered. The advantage of these cycles that is due to reduction of a heat quantity being rejected into space has been shown for ecologically clean generation of electric energy in prolonged space flights.  相似文献   
687.
The mathematical models of the solid-liquid flow regimes in the vertical cylindrical channel are described. A two-speed flow based on the solid-liquid phase interaction is considered. The problem was numerically solved and the calculation results were compared with experimental data.  相似文献   
688.
A numerical and analytical method for constructing a shape of the axisymmetric body streamlined with jet blowout by the specified velocity distribution along its meridian section is proposed. The foundation of the method is the iteration process based on the solutions of an inverse problem in the plane case and a primal problem for the axisymmetric body. A program realizing the iteration process is set up and examples of numerical calculations are given.  相似文献   
689.
A recursive method for calculating decoupling zeroes in the linear multiconnected dynamic system based on the application of matrix canonization techniques is proposed. Its essence is that the problem dimension is successively decreased and reduced to finding eigenvalues of some matrix. The results obtained can be used to check controllability and observability as well as to calculate uncontrollable and unobservable modes of the dynamic system.  相似文献   
690.
It is commonly believed that comets are made of primordial material. As a consequence, they can reveal more information about the origin of our solar system. To interpret the coma composition measurements of comet Churyumov–Gerasimenko that will be collected by the Rosetta mission, models of the coma chemistry have to be constructed. However, programming the chemistry of a cometary coma is extremely complex due to the large number of species and reactions involved. Moreover, such a program needs to be very flexible as one may want to extend, change, or update the set of species, reactions, and reaction rates. Therefore, we developed software to manage a database of species and reactions and to generate code automatically to compute source/loss balances. This database includes the data from the UMIST database and the ion–molecule reactions collected by V.G. Anicich. To use all these databases together, a lot of practical problems need to be solved, but the result is an enormous source of information about chemical reactions that can be used in chemical models, not only for comets but also for other applications.  相似文献   
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