Solid rocket motor backflow analysis for CONTOUR mishap investigation

A procedure developed for free molecule modeling of plume backflow from a STAR (TM) 30BP solid rocket motor is presented for work performed in support of the Comet Nucleus Tour spacecraft mishap investigation. Good general agreement is established with DSMC flowfield results, with interesting deviations developing as the plume backflow approaches the spacecraft surfaces closely, providing insights regarding characteristics of the surface Knudsen layer. Also, investigation of related free expansion results indicate significant discrepancies exist between the rarefied techniques and the continuum results from which their starting surfaces were created. The nature of these differences suggests that convective fluxes to CONTOUR may have been much higher than the rarefied analyses indicated.