Equilibrium temperature of ballistic capsule blunt surface when returning to the earth at a parabolic velocity

Аuthors

Zarubin V. S.^*, Zimin V. N.^**, Leonov V. V.^***, Zarubin V. S.

Bauman Moscow State Technical University, MSTU, 5, bldg. 1, 2-nd Baumanskaya str., Moscow, 105005, Russia

*e-mail: zarubin@bmstu.ru
**e-mail: zimin@bmstu.ru
***e-mail: lv-05@mail.ru

Abstract

The spacecraft return process at the atmospheric trajectory segment is being accompanied by rather high values of the air pressure and temperature in the zone between the shock wave and the blunted nose. This leads to the intensive convective and radiative heat exchange on the blunted surface, even in flight at high altitude in rarefied layers of the atmosphere. This article considers the descent of a stabilized spherical ballistic capsule entering the Earth atmosphere at a parabolic velocity at the Lunar mission completion. The equilibrium temperature of each of these segments, being determined form the density of the supplied total thermal flux and density of the thermal flux being removed due to the self-radiation ws selected as the reliable estimate of the thermal impact of the flow running on the separate areas of the blunted surface. Simplified engineering formulas that allow calculating the total heat flow in the full range of the capsule flow modes such as free-molecular, sliding, transition area and continuum are presented. The article presents the results of computing variation the equilibrium temperature maximum value on the blunted surface of the spherical stabilized ballistic capsule with a radius of 1.96 m and mass of 5500 kg for various descent trajectories by the descending time. It shows the descent tragectory rational selection, particularly using the trajectories, containing several consequtive segments of the Earth dense atmosphere layers entering, allows maximum value reducing of the equilibrium temperature to the level, comparable to the acceptable temperature of the heat-shielding material of the bluned nose.

Keywords:

ballistic capsule, equilibrium temperature, free-molecular flow-around mode, continuum flow-around mode, Knudsen number, multiple dense atmosphere layers reentry

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