Experimental study of plume flow emanating from rectangular orifices

Abstract

In recent years several microthrusters based on MEMS technology were developed. They differ from conventional axisymmetric thrusters with regard to two aspects concerning plume flow and impingement, as they typically feature a rectangular cross-section, and a nozzle exit flush mounted into the surrounding spacecraft structure. Both features lead to expect plume expansions which also differ from those of axisymmetric thrusters. Plume characterisation is necessary to assess and, when indicated, to minimize plume impingement effects. The latter arise out of the interaction between flow and spacecraft surfaces and comprise forces and moments, heat load and contamination, all of them in general undesired. As a precursor activity to studying plumes from micronozzles, we investigate plumes from rectangular orifices. We report on ongoing research, aiming at analysing the flow structure and revealing impingement potential. Initial results from measurements in the DLR Göttingen High-Vacuum Plume Test Facility for Chemical Thrusters, STG-CT, are presented.