Characteristics of Arc-Heated Plasma Flow for Martian Atmosphere

Abstract

Characteristics of plasma flow in a 10.5kW arc-heated wind tunnel are investigated by spectroscopic measurement. The test gases are 100 % CO2 and 90 % CO2 - 10% N2 mixture which simulates the Martian atmosphere. In CO2 plasma, radiation of C2 Swan bands system is predominant and strong radiation of atomic oxygen is seen in the near-infrared light region. In CO2 - N2 plasma, radiation of CN violet band system is much stronger than those of C2 Swan band system and atomic oxygen. By using the multipoint spectroscopic system, spatial profiles of spectra are obtained with high accuracy. With approaching the stagnation point, radiation intensity increases caused by the formation of shock wave around the hemisphere model. Thickness of shock layer is estimated to be 3mm from the stagnation point. The rotational and vibrational temperatures of C2 and CN are estimated by the spectrum fitting method using the SPRADIAN 2 and spatial distribution of temperatures are obtained. For C2, the rotational temperature is higher than vibrational temperature ahead of shock wave. These temperatures are almost same in the shock layer. For CN, the rotational temperature is lower than vibrational temperature, showing the opposite tendency observed in C2. However, in the shock layer, rotational and vibrational temperatures are almost same.