Al2O3 collection and sizing from solid rocket motor plumes

A unique dart system has been designed and built to collect aluminum oxide particles from the plumes of large-scale solid rocket motors, such as the Space Shuttle redesigned solid rocket motor (RSRM). The capability of this system to collect clean samples from both the vertically fired modified NASA (MNASA) (18.3% scaled version of the RSRM) motors and the horizontally fired RSRM motor has been demonstrated. The particle mass-averaged diameters d& measured from the samples for the different motors, ranged from 8 to 11 fun and were independent of the dart collection surface and the elapsed time during motor burn. The measured d& results agreed well with those calculated using the industry standard Hermsen's correlation within the standard deviation of the correlation. For each of the samples analyzed from both MNASA and RSRM motors, the distribution of the cumulative mass fraction of the plume oxide particles as a function of the particle diameter was best described by a monomodal log-normal distribution with a standard deviation between 0.13-0.17. This distribution agreed well with the theoretical prediction by Salita using the one-dimensional three phase code for the RSRM motor at the nozzle exit plane; this seems to confirm that droplet collision-coalescence removes most of the smoke mass from the plume flowfield.