Introduction of a nozzle throat diameter dependency into the SRM dust size distribution Original Research Article

The ESA space debris population model MASTER (Meteoroid and Space Debris Terrestrial Environment Reference) considers 1032 firings of solid rocket motors (SRM) with the associated generation of SRM slag and dust particles in its current version. The resulting dust population is a major contribution to the sub-millimetre size space debris environment in Earth orbit. For the modelling of each SRM dust release event a detailed knowledge of the particle size distribution is essential. However, the knowledge of the particle sizes after passing the nozzle throat is poor. The current dust implementation in the MASTER model assumes a fixed size distribution which is identically used for both large upper stages and small apogee motors. This assumption can lead to an over-representation of large dust particles in regions, where mainly apogee motors are used (i.e., Geostationary Earth Orbit) and an under-representation in lower altitudes, where large stages predominate. In this paper, a concept for the improvement of SRM dust size modelling is discussed. It will be shown that an introduction of a nozzle throat diameter dependency into the dust size distribution enables a more precise modelling of SRM dust release events. The improved SRM dust size distribution is going to be used by the MASTER-2005 space debris model which is currently under development by the Institute of Aerospace Systems and QinetiQ (UK) under ESA contract.