A configuration for re-entry from mars missions using aerobraking.

A new concept in re-entry vehicle configuration is proposed which results in a family of compact shapes with lift-to-drag (L/D) ratios of 0.5 to 1 .0. The main heat shield consists of a circular cone raked off at an angle to provide sufficient lifting surface. The afterbody is an elliptical cone fitted to the cross section of the forecone. Trim at zero angle of attack results in a symmetrical flow field over the forebody which makes the shape amenable to reliable analysis. Re-entry criteria are evaluated in terms of aerodynamic and guidance requirements for speeds up to 65,000 fps. These criteria are satisfied with an L/D value as low as 0.6 if a closed-loop re-entry guidance system is used. Operational trajectories are described, and sufficient corridor and range maneuverability is demonstrated using trimmed lift roll control. A detailed analysis of the radiative and convective heating shows that ablation heat-protection methods are adequate. Important factors affecting the heat transfer are radiation loss from the airstream, mass transpiration effects on the boundary layer, and shock-layer vorticity. For re-entry at 65,000 fps, the heat-shield weight for a six man vehicle is about one-third of the total vehicle weight.