A. V. Paleshkin, V. V. Terent′ev, UDC 629.78 and S. O. FirsyukA methodological approach to determination of the thermal state at a point on the surface of an isothermal element of a small spacecraft has been developed. A mathematical model of heat transfer between surfaces of intricate geometric confi guration has been described. In this model, account was taken of the external fi eld of radiant fl uxes and of the differentiated mutual infl uence of the surfaces. An algorithm for calculation of the distribution of the density of the radiation absorbed by surface elements of the object under study has been proposed. The temperature fi eld on the lateral surface of the spacecraft exposed to sunlight and on its shady side has been calculated. By determining the thermal state of magnetic controls of the orientation system as an example, the authors have assessed the contribution of the radiation coming from the solar-cell panels and from the spacecraft surface.The most diffi cult thing about mathematical modeling of heat transfer of a nonhermetic spacecraft (sp) is to determine the external and internal radiant heat transfer. In engineering practice, there is a great need for a universal and rather userfriendly model of external and internal radiant heat transfer of a spacecraft. Considering the exterior and interior surfaces of the spacecraft as an aggregate of a fi nite number of isothermal elements, we determine the density of the radiant fl ux incident on each of these elements under the following conditions:(1) the spacecraft can be in an assigned fi eld of radiant fl uxes coming from the sun and, if the craft is on a low circumplanetary orbit, from the planet; (2) the spacecraft surfaces in heat transfer can have an intricate geometric confi guration, as a result of which there is a possibility for mutual occultation of some surfaces from the radiation of external sources of radiant fl uxes and from the radiation of the surfaces of the spacecraft itself; (3) within each isothermal element (portion of the spacecraft surface), the radiation characteristics of the surface must be uniform.The problem of radiant heat transfer was solved under the following simplifying assumptions:(1) the surfaces taking part in the heat transfer are diffuse-type, i.e., the directed emissivity factor and directed absorptivity of these surfaces, do not depend on the direction; (2) the surfaces are gray in two characteristic spectral ranges: in the range of wavelengths from 0.2 to 2 μm, where practically all the energy of solar radiation is concentrated, and in the range from 5 to 50 μm, in which there is a release of most of the energy of self-radiation of bodies having a moderate temperature at the level of 200-500 K; (3) within each portion of subdivision of the spacecraft surface into isothermal elements, the density of the incident radiation fl ux is uniform on the portion′s surface.
In order to mathematically simulate the thermal effect that radiation emitted by planets has on spacecraft, two intensity field models describing planetary radiation may be used depending on the emitter specifics: isotropic and anisotropic. The isotropic model is based on the assumption that the local surface density of outgoing radiation flux is the same for all surface regions visible from orbit. In the case of the anisotropic model this value is assumed to be proportional to the zenith angle cosine for each surface element on the side of the planet that is illuminated by the Sun. Published results of studies concerning developing planetary radiation field simulators indicate that thermal vacuum installations where the working volume is comparable to the total installation volume can only reproduce the sotropic planetary radiation intensity field model. It is a pressing issue to determine whether and when it is possible to replace the anisotropic model with an isotropic one when physically simulating the effect that the solar radiation reflected from a planet and intrinsic radiation flows generated by planets with no atmosphere have on spacecraft. The investigation that we conducted regarding this issue was based on comparing the results of computing the irradiance of spacecraft elements using the models under consideration. These computation results allowed us to conclude that it is possible to physically simulate the effect of solar radiation flows reflected from planets combined with intrinsic (infrared) radiation flows generated by planets with no atmosphere by means of using simulators reproducing isotropic radiation fields in their working volumes
Московский авиационный институт (национальный исследовательский университет) «МАИ», Москва, Российская Федерация Аннотация Ключевые слова Рассмотрены методы формирования потоков излучения с направленной силой, характеризуемой ламбертовскими индикатрисами в ограниченном телесном угле. Приведено описание радиационно-оптических схем модулей имитаторов внешних тепловых нагрузок, диффузно испускающих излучение. В состав модулей входят диффузно излучающие в полусферическом телесном угле диски или ленты, а также зеркальные отражатели, поверхностями которых являются параболоид вращения и параболический цилиндр с определенными геометрическими характеристиками направляющих линий. Используя изложенные методы в различных комбинациях, можно разработать принципиальные схемы оптических устройств для воспроизведения лучистых потоков с определенными направленными свойствами Имитация, тепловые нагрузки, космический аппарат, индикатриса излучения, диффузное излучение
This article describes the conditions of the spacecraft (SC) heat transfer at the stages of its operation. A methodical approach is developed, and algorithm for calculation of external and internal heat transfer of spacecraft is proposed. The calculations of the thermal modes and computer experiment to assess the possibility of placing electronic components on the surface of the plate inside nonhermetic SC are carried out. Modeling was carried out taking into account heat liberation of functioning equipment and requirements for the maintenance of a specified temperature range with passive temperature control means. Obtained using a mathematical model results could be used as input parameters for reproducing the calculated external heat loads on the SS irradiated surface during the thermal vacuum tests. The methods of model verification and confirmation of the adequacy of ground tests during the flight test are proposed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.