Accurate Guidance for Re-entry Vehicles Using Real-time Numerical Integration
by
Yoshiyuki Ishijima
NASDA(National Space Development Agency of Japan)
Coauthors: Hideto Suzuki, Hifumi Yamamoto, Hiroshi Yoneda, Atsushi Amito

Existing re-entry guidance laws were limited by the performance of on-board computers. Recent winged re-entry vehicles, such as Space Shuttle, adopt the closed-form guidance, which uses analytic solutions for range prediction based on specified drag acceleration profiles. Analytic formulae require little computational load, but, in the case of low L/D, extra modification of the formulae is required to be adjusted to the low L/D flight characteristics and the range prediction accuracy is low. By using real-time integration for the prediction, we can estimate precise down-range for the remainder of flight. As the first step, we investigated the model for range prediction in order to reduce computational load, maintaining its accuracy. And based on the assumed low L/D capsule model, we designed the guidance law and performed numerical re-entry simulations. As the results, the guidance accuracy is improved as to major error sources, such as aerodynamic coefficient error, atmospheric density error, compared with the existing closed-form guidance. And the calculation time per one guidance cycle is only several times as much as that of a proposed ascent guidance law for H-IIA, and we can conclude that the proposed law is feasible in view of the recent advancement of on-board computers.

Date received: January 30, 1998

Copyright © 1998 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caav-05.