Astrosols in Near-Earth Space
Investigation of Astrosols in Near-Earth Space Using the Onboard Measurements and Computer Modeling. Analysis of Astrosol Effect on Components of a Spacecraft
Tech Area / Field
- SAT-SAF/Space Safety/Space, Aircraft and Surface Transportation
- ENV-EHS/Environmental Health and Safety/Environment
- SAT-EXP/Extraterrestrial Exploration/Space, Aircraft and Surface Transportation
8 Project completed
Senior Project Manager
Ryzhova T B
Research Institute of Aviation Systems, Russia, Moscow
- Institute of Applied Mechanics, Russia, Moscow\nSt Petersburg State University / Mathematic-Mechanical Faculty / Smirnov Scientific Research Institute of Mathematics and Mechanics, Russia, St Petersburg
- ONERA, France, Toulouse\nFraunhofer Institut Kurzzeitdynamik, Germany, Freiburg
A spacecraft in a near-earth orbit undergoes influence of many space factors including microparticles of sizes from fractions of a micron to hundreds microns of natural and man-caused origin. With growth of anthropogenic pollution of the Near Earth Space (NES) the concentration of the man-caused microparticles increases, and they already dominate in Low Earth Orbits in some size ranges now. As onboard measurements show (Mulholland & Singer 1992; Singer 1993; Maag, Deshpande & Johnson 1997; Mulholland, Kessler D.J. et al., 2001), man-caused particles form clouds with sizes from hundreds to thousands kilometers (the so-called “astrosols”). Existence of such populations with inhomogeneous distributions in space and time (not concerning Poisson one) is verified experimentally (Drolshagen et al. 1997, Smirnov, Semenov, Rebrikov et al. 2001). Such distributions are not considered in the modern space debris models. Astrosol clouds can have density in 2-3 orders of magnitude greater than background, and due to high relative impact velocities of ~10 km /s can seriously influence on functioning of spacecraft components (solar panels, windows, optic reflectors) (Schafer at el. (2001); McDonnel, Catling & Carey (2001); Hyde et al. (2001); Bernard, Christiansen, & Kerr (2001); Smirnov, Semenov, Sokolov et al. (2002)).
The objectives of the project are investigation of the man-made astrosol distributions in NES using results of the onboard experiments and computer modeling, and the analysis of their effect on exposed samples and construction components of spacecraft.
Scope of the project involves three problems.
- statistical treatment of results of the onboard investigations at the space stations “Salyut” and determination of characteristics for the astrosol particle distributions;
- analysis of impacts of the astrosol particles on returned samples, particularly, on solar-cell samples after their 10-years exploitation at the space station “Mir” (morphological and statistical characteristics of surface damages);
- development of propositions on new combined onboard measurements of parameters of micrometeoroids and debis microparticles (MM/SD)
As a result of this solution, new information concerning astrosol cloud distributions in the NES, damage effects of the MM/SD particles, material durability for long-term exposure will be obtained. This information will supplement the results of onboard experiments obtained in LDEF, Euro Mir'95 programs, etc. and morphological investigations of damages of solar-cells returned to the Earth. New schemes of onboard MM/SD combined experiments will be proposed.
- investigation of the microdebris sources;
- development of methods for computer simulation of astrosol evolution in NES;
- modelling of evolution of fine debris in NES and formation of man-caused astrosols.
Numerical results will be compared with results of onboard measurements by the first problem and other experiments (LDEF e.g.). Solution of these problems is necessary for development of new forecast tools for space distribution of astrosol debris in NES and mitigation measures in NES to minimize pollution with man-caused particles of different origin.
- experimental investigation of damage of glasses at hypervelocity impact of microparticles by a size from 0.5 µm up to 1000 µm of different density (aluminum, iron, oxide of aluminum);
- experimental and computer modeling of the results of the onboard experiments (morphology of craters and holes, spalls)
- statement and software development for the collision problem to evaluate astrosol flux on a detailed spacecraft structural component;
- experimental and theoretical investigation of ejecta produced upon hypervelocity impacts of projectiles on different shields (solid and mesh shields).
The results of experiments and the programs suppose to be used for analysis of MM/SD impacts on different components of spacecraft and to optimize protective constructions for these components.
Investigation of parameters and distribution functions for MM/SD particles in NES will be carried out using results of experiments performed in space stations “Salyut” and “Mir”. These measurements were made with two independent methods: 1) using onboard condenser-type sensors, 2) using samples retrieved after in-orbit exposure. The condenser-type sensors were made of aluminum foil layers with thickness of 10, 20, 60 or 200 microns. The exposure samples were 1 mm thick plates of duralumin 123 mm 86 mm or 115 mm 70 mm in sizes, or double plate spaced aluminum foil. These samples were exposed in space up to 1460 days. The five solar-cell samples of solar panels retrieved after their 10-years exploitation at the space station “Mir” will be also used for the MM/SD analysis. To study the exposed samples is planned to use special equipment: metallographical MMU-3 and “Latimed” optical microscopes, and electron microscope with a magnification of up to 3500.
Experimental investigation of the impact phenomena, including optical surface damages by microparticles of ≥ 100 µm, will be performed using GosNIIAS’s light gas gun. Experimental investigation of the damages caused by microparticles of ≤ 10 µm will be performed using “cascade generator” (KG-200 and KG-500) and “electrostatic generator” (EG-8) installed at the Institute of Nuclear Physics of Moscow State University. These facilities are commonly destined to accelerate particles with sizes of 0.5-10 µm at speed up to 1-30 km/s.
When the software to calculate evolution of the astrosol particles will be developing the main attention will be paid to “one-particle” model for astrosol dynamics. The dynamic model of sphere microparticle (aluminum, iron, carbon) in the various structural regions of the plasma shell of Earth (plasma-sphere, plasma sheet, ionosphere) will be developed. The following factors acting on the microparticles will be considered:
- gravitational field of the Earth (considering oblateness of the Earth);
- electrodynamic forces acting on the electrically charged particles in the magnetic and electrical fields in Near Earth Space;
- solar light pressure;
- drag force due to neutral component of background gas (determined by a piece-wise exponential approximation of altitude dependencies for upper atmosphere).
Note, that consideration of the electrodynamic forces and solar light pressure allows us to depict correctly the motion of submicron particles. It is planned to use the dipole model of the geomagnetic field. Electrical field in the NES will be assumed as superposition of corotational electric field and convective one. Absorption of incident electrons and ions of the space plasma, secondary electron emission, when electrons and ions impact on a microparticle, will be considered as the possible charging mechanisms.
Hypervelocity damage supposes to be modeled with the aid of gridless SPH method and also using an Eulerian grid-based method for two- and three dimensions. Both the methods can be applied to high deformation processes.
The application of kinetic theory methods and generalized functions (distributions) to the collision problem with orbital objects will be developed.
A competence of the project participants is clarified by the experience of GOSNIIAS in accomplished measurements of MM/SD using instruments installed at satellites and space stations “Salyut” and “Mir” since 1971. Some results of these unique measurements and their analysis were published (Smirnov, Semenov, Rebrikov et al. 2001; Smirnov, Semenov, Sokolov et al. 2002). The IMM SPSU is a known Russian leader in microparticle dynamics in NES. Their activity will be directed to the modeling of evaluation of fine debris in NES and to study formation the man-caused astrosols. The competence of the IAM RAS and GOSNIIAS on impact problems can be clarified by their development of protective constructions for the Functional Cargo Block of the ISS and participation in the ISTC project #1917 on optimization of the protection problem (IAM RAS and GosNIIAS are institutions- participants).
The project contributes to the next ISTC objectives: weapon experts will have an opportunity to redirect their possibilities to peaceful activities as well as the project will develop works on near Earth space ecology. Besides the project will made a direct input in mastering extraterrestrial space that has national and international character.
Cooperation with foreign collaborators in frame of the project brings about the next directions: providing information in the course of the project implementation; participation in choice of parameters of models; participation in working out of proposals on the complex experimental measurements of micriparticle parameters in Near Earth Space; holding joint symposiums and workshops.
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