Application of the pitch modulation maneuver in the region of the ''limiting'' entry velocity.

Abstract

Future manned interplanetary missions to Mars arid beyond may require entry vehicles capable of sophisticated maneuvers in order to utilize aerodynamic braking on Earth return. The purpose of this paper is to analyze one such maneuver, pitch angle modulation for peak g alleviation, which allows extension of the maximum deceleration limited entry velocity beyond that attainable by the roll-control maneuver. It is also the purpose here to define the available entry corridors in this region of entry velocity. The ranges of variables considered in this study are lift-drag ratios of 0 to 3 and maximum deceleration loads of 6 to 14 g. It is shown that the use of pitch modulation is quite effective in increasing the entry corridor for velocities from below to slightly above the roll-controlled zero-corridor limiting entry velocity. For zero corridor width, use of the pitch modulation maneuver yields only a small increase in the limiting entry velocity above that obtainable by the roll maneuver. Large increases are obtainable, however, for realistic entry corridors. This increase is shown to be dependent on the lift-drag ratio and maximum deceleration limit. The unexpected result that both the overshoot and undershoot boundaries are skip limited is demonstrated. It is concluded that the use of pitch modulation may be desirable for entry at velocities in the region of the limiting velocity.