93-172
Description And Performance Analysis Of A Generalized Optimal Algorithm For Aerobraking Guidance
Steven w. Evans* and Greg A. Dukeman**
Abstract
A practical real-time guidance algorithm has been developed for aerobraking vehicles which nearly minimize the maximum heating rate, the maximum structural loads, and the post-aeropass delta v requirement for orbit insertion. The algorithm is general and reusable in the sense that a minimum of assumptions are made, thus greatly reducing the number of parameters that must be determined prior to a given mission. A particularly interesting feature is that in-plane guidance performance is tuned by adjusting one mission-dependent parameter, the bank margin; similarly, the out-of-plane guidance performance is tuned by adjusting a plane controller time constant. Other features of the algorithm are simplicity, efficiency and ease of use. The algorithm is designed for, but not necessarily restricted to, a trimmed vehicle with bank angle modulation as the method of trajectory control. Performance of this guidance algorithm is examined by its use in an aerobraking testbed program The performance inquiry extends to a wide range of entry speeds covering a number of potential mission applications. Favorable results have been obtained with a minimum of development effort, and directions for improvement of performance are indicated.
*Ph.D., Aerospace Engineer, Flight Mechanics Branch, NASA Marshall Space Flight Center, Mail Stop EL58, MSFC, Alabama 35812. Member AIAA
**Aerospace Engineer, Flight Mechanics Branch, NASA Marshall Space Flight Center, Mail Stop EL58, MSFC, Alabama 35812.