Experimental Investigation of a Small-scale Arc-jet for Earth Entry Simulation

This paper provides an introduction to the OPG2 plasma generator, with a particular emphasis on the modifications made to transition from argon flow to air flow. The modifications include tilted swirl injection of oxygen into a settling chamber to mix with nitrogen mimicking the composition of air. The plasma generator can be utilised as a stand-alone miniaturised arc-jet facility, or as a dedicated pre-heating device for a combined arc-jet and expansion tube arrangement. Emission spectra are used to determine molecular internal excitation temperatures which are between 3800K and 5800K for conditions using approximately 0.2 g/s of test gas and arc-currents between 250A and 300 A. Facility Mach numbers are determined through imaging of the plasma plume width and amount to values between 1.9 and 2.75.