# Study of the spectral nonequilibrium emissivity of strong shock waves

# Main results

- The program package was developed for the simulation of a nonequilibrium spectral radiation of the shock waves in the atmosphere of Eart, Mars, Titan (moon of Saturn). This package contains several modules which were disigned in order to calculate selfconsistently the gasdynamic parameters of shock wave, nonequilibrium physical and chemical relaxation processes behind the front of a shock wave, nonequilibrium chemical reactions in the gas mixtures and the nonequilibrium radiation in the absence of a Boltzmann distribution of particles in excited energy states;
- Systematic calculation and theoretical study of nonequilibrium radiation of the shock layer near the surface of a spacecraft entering in the atmosphere of Earth, Mars and Titan on the trajectories planned for the future space missions were carried out. A satisfactory description of an experimental data was obtained.

# Nonequilibrium radiation of strong shock waves

# Theoretical analisys of the Thomas-Menard experiments

(gas mixture: 9% CO_{2} - 90% N_{2} - 1% Ar,
p = 0.25 torr, U_{s} = 7620 m/s)

(a) | (b) |

Nonequilibrium radiation behind the strong shock waves (line is the calculation; dots are experimental data):

a) The calculation was performed under the assumption of the Boltzmann distribution for the electronic exited states;

b) The calculation was performed under the assumption that for the electronic exited states exist radiative-collisional equilibrium.

Distribution of the temperatures behind the shock wave. The calculation was performed under the assumption that for the electronic exited states exist radiative-collisional equilibrium

# Theoretical analisys of the Kozlov-Losev-Romanenko experiments

(gas mixture: 9.6% CO_{2} - 0.3% N_{2} - 90.1% Ar, p = 1 torr, U_{s} = 3450 m/s)

(a) | (b) |

Nonequilibrium radiation behind the strong shock waves (solid line is the calculation; dashed line is the result of the experiment):

a) The calculation was performed under the assumption of the Boltzmann distribution for the electronic exited states;

b) The calculation was performed under the assumption that for the electronic exited states exist radiative-collisional equilibrium.

# Analysis of new experimental data on non-equilibrium radiation, obtained on shock tubes of Institute of Mechanics MSU

(experiments performed: P.V. Kozlov, Yu.V. Romanenko, O.P. Shatalov, calculations: Dikalyuk A.S.)

(a) | (b) |

Distributions of temperatures in the relaxation zone behind the shock wave:

a) gas mixture 70% CO_{2} - 30% N_{2}, V_{sh}=6.76 km/s, p = 0.3 torr;

b) gas mixture 70% CO_{2} - 30% N_{2}, V_{sh}=5.81 km/s, p = 1 torr.

(a) | (b) |

Nonequilibrium spectral emissivity behind the shock wave front,
comparison of theoretical calculation (dashed curve) and experimental measurements (solid curve):

a) gas mixture 70% CO_{2} - 30% N_{2}, V_{sh}=6.76 km/s, p = 0.3 torr;

b) gas mixture 70% CO_{2} - 30% N_{2}, V_{sh}=5.81 km/s, p = 1 torr.

(a) | (b) |

Partial contributions of different molecular bands to the total emissivity of the gas behind the shock front:

a) gas mixture 70% CO_{2} - 30% N_{2}, V_{sh}=6.76 km/s, p = 0.3 torr;

b) gas mixture 70% CO_{2} - 30% N_{2}, V_{sh}=5.81 km/s, p = 1 torr.