F.F. Gabdullin - Main Specialist, Central Research Institute of Machine Building. E-mail: flur.gabdullin@gmail.com
M.Yu. Kurshakov - Ph. D. (Phys.-Math.), Vice Head of Department, Central Research Institute of Machine Building. E-mail: mkurshakov@yandex.ru
E.M. Tverdokhlebova - Ph. D. (Eng.), Head of Laboratory, Central Research Institute of Machine Building. E-mail: tverdokhlebova@tsniimash.ru

The article is devoted to the problem of influence of a spacecraft's own external atmosphere (SCOA) on functioning of onboard systems. SCOA forms mainly due to processes of outgasing and dust exhausting from both construction materials of a spacecraft (SC) and external coverings of a SC - thermo stabilization system (mostly multilayer thermal covers), and the exhausts of engine jets. The short review of experimental data about the value of pressure in SCOA is presented. The data are obtained under flight conditions onboard the «Mir» Space Station and the geostationary communication satellite «Yamal­200». The results of these measurements show that the spacecraft is engulfed by products of the combustion during the operation of propulsion system and some time after its switching off. This cloud of products of combustion penetrates into unpressurized pallets, the pressure increases there and then rather fast by relaxes to the level of background pressure within several minutes. The method and algorithm of calculation of the values of SCOA flows to the SC surface are offered. The developed method is based on the model of a free molecular flow of gas and allow us to evaluate the influence of spacecraft's own external atmosphere on the operation of its onboard equipment. The method takes into account multiplex reflections of gas molecules from SC surfaces and shading of the design elements by each other under the presence of gas emission from surfaces and local sources of gas, vapor and dust particles emission (for example, onboard engines). On a base of the developed method the software was developed which allows to calculate parameters of own external atmosphere of the spacecraft of any geometry, SCOA density in the set line of sight, the values of SCOA flows to the set SC surface and total contamination by SCOA components on the set surface after the whole life time of the spacecraft. Examples of several special cases relating to the «Elektro­L», «KazSat», «Monitor­E» and «Spektr­UF» spacecrafts are given. Results of calculations of both the SCOA parameters during onboard systems operation and the effects of pollution of SC surface by SCOA particles illustrate possibilities of the software.

 

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