Atmospheric Braking Entry and Associated Technologies

Abstract

The use of planetary atmospheres for planetocentric maneuvers offers itself in the case of the planets Venus, Earth and Mars. In all three cases, the atmospheres are comparatively fluffy and thin, if compared to atmospheres of the jovian planets, and the entry velocities are usually within the range of technical feasibility. The highest entry velocities are encountered upon return from Mars along a mono-elliptic transfer orbit. Maximum velocities are in the range of 70, 000 to 75, 000 ft/sec. It is possible, however, to reduce the speed at least as far down as 50, 000 to 60, 000 ft/sec, either by a properly arranged mission profile or by a braking maneuver or by Venus fly-by on return. The braking maneuver is most economically applied at perihelion transit rather than at Earth approach. If the velocity is reduced to the level of about 60, 000 ft/sec by mission profile adjustment, direct atmospheric entry along an unretarded approach hyperbola, is technically, as well as possibly space medically, the most difficult case of atmospheric braking; but also the most rewarding case in terms of effect on the reduction in orbital departure weight of the interplanetary vehicle.