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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: The effects of selected orbital environmental factors on painted launcher upper stages and modelling of their contribution to the small size space debris population

Author: NOMBRO, JPA

Year: 2005

Supervisor(s): John Stark

Analysis of impacts from returned surfaces from orbit have indicated that paint is a common impactor. Paint flakes and pigments are suspected to originate from spent launcher upper stages left in orbit. Such particles are suspected to be released as a result of erosion via ATOX bombardment, cracking and delamination due to embrittlement of paint layers from exposure to UV and thermal cycling in orbit. This thesis presents the steps taken to understand and model these debris sources.

Ground based exposure of launcher upper stage paints to ATOX, UV, heat exposure in vacuum and thermal cycling was performed. The results of these experiments are presented.

The erosion of typical launcher upper stage paints due to ground based ATOX exposure is derived following the ATOX exposure. These are based on mass loss measurements. It is observed that ATOX erodes the polymeric paint binder which tends to free pigments. A size distribution of paint pigments is determined. A paint pigments release model is then derived using the measured erosion rates and pigment size range.

The changes in thermal and mechanical properties which affect the stresses in the paint layer are quantified following exposure to UV and heat exposure. It is shown that exposure to heat in vacuum cause the most considerable changes in the mechanical properties of paint. Such exposure alters the paint layer into a more brittle material. The formation of paint flakes via cracking and delamination of the stressed paint layer is considered.

The rate of release of paint pigments and flakes as a function of altitude and size is determined. Comparisons with debris models are made. Areas of where further research needs to be undertaken are then discussed.