New computer model for outgassing calculations

Hans Hartmann

doi:10.1117/12.400828

20 September 2000 New computer model for outgassing calculations

Hans Hartmann

Proceedings Volume 4096, Optical Systems Contamination and Degradation II: Effects, Measurements, and Control; (2000) https://doi.org/10.1117/12.400828
Event: International Symposium on Optical Science and Technology, 2000, San Diego, CA, United States

Abstract

A new computer model for the outgassing and potential contamination of S/C surfaces in orbit is described. It calculates the redistribution of contaminants on internal surfaces with time and their escape into space with time, based on the calculation of the various vapour pressures generated by the contaminated surfaces. These vapour pressures are a function of the type of the contaminant, of surface temperatures and of surface coverage. Different vapour pressures over different surfaces generate net flows of contaminants from higher to lower pressure, limited by the venting resistance between these surfaces. Calculating these net flows with time results in change of contamination layer thickness of all surfaces, as a function of temperature and size of vent holes. The advantage of this new model is that it is not limited to few wall collisions of a molecule, as it is the case in models calculating the movement of individual molecules by statistical methods. The model mainly was developed for the X-ray satellite XMM-Newton, to estimate the contamination with time of its cold experiments within the telescope tube. At the date of this publication, XMM-Newton results were not yet available, and therefore the model also was tested by comparison to results gained from a former outgassing test made for ROSAT. The coincidence between experimental results here can be made remarkably good, by assuming certain initial conditions.

Citation Download Citation

Hans Hartmann "New computer model for outgassing calculations", Proc. SPIE 4096, Optical Systems Contamination and Degradation II: Effects, Measurements, and Control, (20 September 2000); https://doi.org/10.1117/12.400828

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KEYWORDS

Contamination

Molecules

Resistance

Computer simulations

Mirrors

X-rays

Space telescopes

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