Range control during initial phases of supercircular reentries

Abstract

For direct reentry from a lunar or deep space mission, considerable variation in reentry plane, reentry point, and reentry angle must be anticipated. The returning vehicle must therefore, possess the ability to control its range after reentry in order to touch down in the desired recovery area.

Recent studies have indicated that considerable ranging capability is available with even low lift-drag ratio vehicles operating wholly within the atmosphere if aerodynamic maneuvering is initiated while the vehicle still possesses greater than satellite velocity. In these studies, maneuvering was initiated shortly after the initial pull-up. Range control is also available during the initial pull-up, but such control results in little gain in longitudinal ranging capability in most cases.

It is the purpose of the present thesis to investigate the feasibility of increasing lateral ranging capability by banking during the initial pull-up. Low lift-drag ratio vehicles reentering the atmosphere in a banked attitude are considered and the effects of such reentries on allowable corridor width, and lateral range capability are studied.

Equations are developed for the motion of a vehicle reentering the atmosphere of a spherical, non-rotating earth, and some permissible approximations applicable for the present problems are discussed. Numerical results obtained for the developed system of equations through use of an IBM 7090 high-speed computer are used throughout the investigation to furnish accurate evaluations of the effects being studied and to check the validity of some of the approximations used.

Particular emphasis is placed on reentry at escape velocity, but the effects determined apply in character to reentry at other supercircular velocities.