Space Launch System Base Heating Test: Tunable Diode Laser Absorption Spectroscopy

摘要

This paper describes the Tunable Diode Laser Absorption Spectroscopy (TOLAS) measurement of several water transitions that were interrogated during a hot-fire testing of the Space Launch Systems (SLS) sub-scale vehicle installed in LENS Ⅱ. While the temperature of the recirculating gas flow over the base plate was found to increase with altitude, it was also observed that the gas motion parallel to the base plate has significant velocity along the optical path of the sensor at the higher altitudes. The line-by-line analysis of the H_2O absorption features must include the broadening effects of the Doppler shift phenomena particularly at high altitude. The TDLAS experimental measurements and the analysis procedure that incorporates the velocity dependent flow will be described.