AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Characterization of Soot Particles from Heat Insulation Foam Combustion
Jesse Fowler, DE-LING LIU, The Aerospace Corporation
Abstract Number: 632 Working Group: Combustion
Abstract Concerns were raised for potential spacecraft contamination inside a launch vehicle payload faring (PLF) from soot particles generated by the thermal decomposition of heat insulation foam during the rocket engine ignition process. Soot particles could be ingested through leak paths in PLF envelope, which in turn poses contamination risk to spacecraft optics, solar cells, and thermal control surfaces as soot particles exhibit strong light absorption properties and could alter thermal properties. To gain insights into the effect of soot contamination to spacecraft, measurements of light transmission attenuation and thermo gravimetric analysis were performed to assist in risk assessment due to soot particle contamination.
Soot particles were generated and collected in a test setup consisting of a diffusion burner, a smoke collection funnel, a condenser, a dryer, an agglomeration chamber, a neutralizer, and filter assemblies. High purity hydrogen and compressed air were used as the fuel and the oxidizer, and were pre-mixed prior to feeding into the diffusion burner. Heat insulation foam was cut to the desired size and placed above the hydrogen flame to generate soot particles. Glass frits served as filters to sample soot particles, which were subsequently subjected to thermal gravimetric analysis (TGA) up to 800 degree C in nitrogen or air. For light transmission measurements, soot particles were collected on fused silica plates via smoke impingement above the burner, and the soot transmission properties were characterized by a Lambda-900 Spectrometer (Perkin-Elmer). The TGA results indicate that the collected soot particles contained approximately 40% semi-volatile organic compounds (SVOC), which were generated in the insulation foam combustion process and subsequently condensed/adsorbed on soot particles as the smoke cooled. In terms of effects of soot contamination, light transmission attenuation was observed to first occur in the UV-visible regime, as attributed to light absorption by SVOC. As more soot particles accumulated on the fused silica plates, light transmission attenuation in UV-visible became more pronounced, and continued to evolve into the infrared (IR) region. The findings suggest that soot may serve as unit density filters thus reducing optical transmission throughput in the IR wavelength range once certain soot area coverage is achieved.