Modeling of Sodium Radiation from Reentry Flows at High Altitudes

DOI: 10.2514/1.40441 Akinetic-basedquasi-steady-statemodelisdevelopedtostudysodiumradiationintensityforreentryhigh-altitude flows of the blunt-body Stardust and a slender body. The sodium detected in the high-speed Stardust-reentry flow was from an impurity of the ablative thermal protection material. In this work, the particle-based direct simulation Monte Carlo method is used to obtain flow solutions, and a quasi-steady-state model is used to derive the sodium number-densitydistributionsinthegroundandexcitedelectronicstates.Thesodiumradiationintensityiscalculated based on the sodium number-density distributions in the excited states and agrees reasonably well with the observation data for the Stardust reentry at 81 km. It was also found that sodium radiation in the slender-body reentry flow will be orders of magnitude less than the value observed for the blunt body. Nomenclature A = coefficient, surface area B = coefficient c = light speed d = distance E = energy e � = electron h = Planck constant I = radiation intensity k = reaction rate, Boltzmann’s constant M = neutral species m = molecular mass N = number density Na = sodium atom T = temperature t = time x = distance along a line of sight � = wave length � = cross section � = lifetime of excited state Subscripts a = atomic species e = electron species g = ground state i = atomic ground or excited state 1= first excited state 2 = second excited state