Reconstruction of Mars 2020 backshell radiative heating via infrared emission spectroscopy of CO2/N2/Ar shockwaves

Journal article

A test series was performed in the Electric Arc Shock Tube (EAST) facility with the aim of reproducing flight conditions encountered during the Mars 2020 mission entry into the Mars atmosphere. For this test series, the EAST facility was instrumented with two spectrometers for optical emission spectroscopy (OES) measurements and three mid-infrared lasers for tunable diode laser absorption spectroscopy (TDLAS). This paper focuses on the spectrally and spatially resolved radiance measured with OES. Conditions were chosen to achieve similarity to backshell radiative heating measured with the MEDLI2 heat flux gauges near and after the time of peak heating. Comparisons were made against two candidate kinetic models for Mars entry. Below 2.7 km/s, the chemistry is effectively frozen, with measurements being above both models and CEA predictions. It is shown that taking into account shock deceleration in the tube explains most of the discrepancy between measured and frozen radiance. For velocities above 2.7 km/s, the data lies between the two models. However, adjusting for shock deceleration indicates that one of the models may be preferred for predicting CO₂ dissociation. Finally, comparisons between OES and TDLAS data are made and show a good agreement on the measured temperature and CO₂ number density profiles, typically within 10 and 5%, respectively. A good agreement is also observed for the radiance that would be inferred based upon the quantities measured by TDLAS.

Authors: Tibere-Inglesse, AC; West, TK; Jelloian, CC; Minesi, NQ; Spearrin, RM

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Institute of Aeronautics and Astronautics
• Journal: Journal of Thermophysics and Heat Transfer
• Volume: 38
• Issue: 4
• Pages: 568-585
• Publication date: 2024-08-09
• Acceptance date: 2024-03-13
• DOI: 10.2514/1.t6916
• EISSN: 1533-6808
• ISSN: 0887-8722
• Language: English
• Keywords: radiative heating; tunable diode laser absorption spectroscopy; electric arc shock tube; heat flux; planets; infrared spectrometers; emission spectroscopy; optical emission spectroscopy; planetary atmospheres; freestream conditions