Engineering topics
Publications and source records attributed to Thomas, Michael E..
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Multi-wavelength laser transmittance was measured during a series of open-air propellant burn tests at Alliant Techsystems, Inc., in Elkton, MD, in May 2012. A Mie scattering model was combined with an alumina optical properties model in a simple single-scatter approach to fitting plume transmittance. Wavelength-dependent plume transmission curves were fit to the measured multi-wave- length transmittance data to infer plume particle size distributions at several heights in the plume. Tri-modal lognormal distributions described transmittance data well at all heights. Overall distributions included a mode with nanometer-scale diameter, a second mode at a diameter of ~0.5 µm, and a third, larger particle mode. Larger parti- cles measured 2.5 µm in diameter at 34 cm (14 in.) above the burning propellant surface, but grew to 4 µm in diameter at a height of 57 cm (22 in.), indicative of particle agglomeration in progress as the plume rises. This report presents data, analysis, and results from the study.
JHU/APL conducted solid propellant fire characterization tests in warm, humid, ambient conditions near sea level. Yttria and ceria surrogate materials were placed in the fires. The substrates simulating ground surfaces were concrete from a Kennedy Space Center launch pad, and steel covered with a protective ablative material representing a launch platform. In-situ instrumentation consisted of witness materials, thermocouples, air handlers, filters, and cascade impactors; remote instrumentation consisted of optical cameras and spectrometers. Test and analysis team members included the Naval Air Warfare Center Aircraft Division, Sandia National Laboratories (SNL), Alliant Techsystems, and the Johns Hopkins University. Test data were analyzed, reported, and delivered, including plume rise and transport captured on video. Derivation of the alumina particle size distributions formed the basis for condensing vapor and agglomeration estimates. Assessment of alumina mass in the plume, along with the surrogate fraction from filter forensics, provided an estimate of airborne surrogate mass. Technical interchange meetings were held with SNL and the Jet Propulsion Laboratory. Specifications for the fire environment were developed and delivered. A thermochemistry model that simultaneously provides the maximum temperature and heat flux was developed and delivered. An SPIE paper on 3D pyrometry of the fire was written and presented.