ANALYSIS OF THE ARGON ADDITIVE INFLUENCE ON A NITROGEN ARCJET FLOW

Two plasma wind tunnels for the simulation of conditions encountered b y space vehicles during planetary entry, and for the development and q ualification of heat protection material, are in use at the Institute for Space Systems. The plasma is produced by a magnetoplasmadynamic (M PD) accelerator, specially designed for the use of gas mixtures such a s N2/O2 and carbon containing gas mixtures. At high mass flow rates an d low power levels a protective gas layer of argon is produced at the anode for a N2/O2 flow. The influence of the Ar additive on a nitrogen plasma is investigated experimentally by means of electrostatic probe s, mass spectrometry, pitot probes, and heat flux probes; and numerica lly with a program especially developed for the simulation of the high enthalpy flowfield of MPD accelerators. The existing numerical code f or solving the chemical reactions within an air plasma was extended by argon/air reactions. A comparison between the experimental data set a nd the numerical simulation of the plasma flow is made for a N2 and a N2/Ar plasma.