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a jet flame illuminating a space at NASA Ames
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Many spacecraft thermal protection systems (heat shields) are tested at the NASA Ames Arcjet complex.

Arcjets are high-energy flow facilities where gases (often air, but sometimes the atmospheric compositions of other planets) are heated by an arc of electric current, expanded through a nozzle to supersonic speeds, and finally passed over a flow model to simulate the harsh conditions spacecraft experience during reentry.

The Hanson Research Group has a long-standing collaboration with NASA Ames to make quantitative spectroscopic measurements in such flow facilities. Our techniques provide value to NASA in assessing the temporal and spatial uniformity of the facility’s gas flow and characterizing gas conditions in comparison to realistic flight conditions. The Arcjet flow environment is extreme, reaching temperatures above 7000 K; spectroscopic measurements thus have a clear advantage over intrusive probes which cannot survive such intense heating. The Hanson Research Group collaboration with Ames has already led to modifications to the Arcjets, including the addition of a mixing volume for increased spatial uniformity.

diagram of an interactive heating facility arcjet, and a graph of temperatures during an experiment
Taken from [1]. At left, a schematic of the placement of an optical disk within the Interactive Heating Facility (IHF) Arcjet. The disk sits downstream of the electrodes and upstream of the nozzle. On a given optical disk, there are as many as 4 optical viewports (‘lines of sight’) at different transverse locations labelled alphabetically A-D. At right, spectroscopic measurements of temperature on those lines of sight during stable operation of the IHF. Different measured temperatures are evidence of thermal gradients due to proximity to the wall of the column.

To learn more, check out some of our publications:

[1] Nations, Marcel, Leyen S. Chang, Jay B. Jeffries, Ronald K. Hanson, Megan E. MacDonald, Anuscheh Nawaz, Jaswinder S. Taunk, Tahir Gökçen, and George Raiche. “Characterization of a large-scale arcjet facility using tunable diode laser absorption spectroscopy,” AIAA Journal 55, no. 11 (2017): 3757–3766. 10.2514/1.J056011

[2] Viveros Salazar, D., Strand, C. L., Hanson, R. K., and MacDonald, M. E., “Investigating Arcjet Mixing and Enthalpy Loss Using Atomic Oxygen Laser Absorption Spectroscopy,” AIAA Journal, Sep. 2021, pp. 1–9. DOI: 10.2514/1.J060274