What is it about?
At the 78 km W-2 trajectory point we ran both DSMC and CFD, then computed line-of-sight spectra with two radiation codes, HARA and NEQAIR, and compared them with OSPREE. HARA and NEQAIR disagree in both magnitude and shape. NEQAIR underpredicts spectral radiance by up to two orders of magnitude relative to HARA above 500 nm. We trace that gap to NEQAIR’s non-Boltzmann N2 emission band model.
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Why is it important?
Even with the same flow field, the radiation solver can swing the answer by orders of magnitude. Anyone using NEQAIR versus HARA for Vis-NIR shock-layer emission on a capsule needs to know that N2 band treatment is not a detail; it can dominate the comparison with flight data.
Perspectives
Companion to the Acta Astronautica DSMC paper and to 2026-0307. This one isolates the radiation-code disagreement at a single altitude rather than marching the whole trajectory.
Zach Davis
Space Dynamics Laboratory
Read the Original
This page is a summary of: Hypersonic Non-equilibrium CFD and DSMC Model Comparisons with the Varda Reentry Capsule, January 2026, American Institute of Aeronautics and Astronautics (AIAA),
DOI: 10.2514/6.2026-1469.
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