Shock Layer Radiation Measurements at a Mars Entry Condition for Infrared Thermography

摘要

This paper presents experimentally measured shock layer radiation data relevant to a Mars Science Laboratory trajectory point in a 96% CO_2, 4% N_2 mixture. Tests were performed in the X2 expansion tube at The University of Queensland to characterise shock layer radiation. Results from these tests will assist in determining if infrared thermography can be used in expansion tubes for measuring heat transfer at Martian entry conditions. The radiance data was spectrally and spatially resolved and ranges the near to mid infrared region from 0.78 - 5.1 μm. Results indicated that the ideal region to perform thermography was from 3.5 - 4 μm as the shock layer radiation was found to be a minimum in this region. A pre-heat surface temperature of 1800 K is deemed to be necessary to obtain a good signal to noise ratio, so that the thermally emitted surface radiation was much higher than that from the gas in the shock layer. It was also found that using an Aluminium diaphragm rather than Mylar resulted in higher shock layer radiation.