There is a need to calculate the radiative heating rate at the surface of a vehicle entering any atmosphere, (e.g., Earth, Saturn, Titan, Mars, Venus etc). NEQAIR simulates the actual chemical and physical actions and reactions of the gaseous species in high-temperature shock layers. NEQAIR has been NASA’s main radiation code for the past 30 years. It is a line-by-line radiation code that computes spontaneous emission, absorption, and stimulated emission due to transitions between various energy states of chemical species along a line of sight. There have recently been substantial updates to the physics in the code and the computational efficiency in NEQAIR; v14.0 is the first parallelized version that has resulted in calculations speeding up by a factor of approximately 30×.

NEQAIR v14.0 is a complex code that enables the calculation of non-equilibrium or equilibrium populations of excited energy levels for atomic and diatomic molecules, optical radiation emitted and absorbed by atomic and diatomic rotational lines along a line of sight or across a shock tube, transport of optical radiation through a non-uniform gas mixture to a solid surface, and detailed spectra at points along a line of sight. NEQAIR v14.0 uses the quasi-steady-state (QSS) method to calculate the populations for energy levels in low-density flows where the low collision rates cannot maintain Boltzmann population levels.

NEQAIR v14.0 has a wide range of capabilities in addition to its main function of calculating the radiative heating rate on entry vehicles. It can produce a Planck (black body) function, scan over any calculated spectrum to change the resolution and compare with laboratory spectra, simulate a shock tube configuration and calculate the spectral data for comparison with shock tube results, and show where in a radiative flow field the radiation is emitting and absorbing.

This work was done by Aaron M. Brandis and Brett A. Cruden of Engineering Research and Consulting, Inc. for Ames Research Center. This software is available for use. To request a copy, please visit