Entry Guidance: A Unified Method

TLDR

Entry guidance methods have evolved over five decades, driven by vehicle types and computing advances, with recent predictor‑corrector algorithms poised to become the next dominant approach. This paper develops a unified predictor‑corrector method applicable to a wide range of orbital and suborbital vehicles with varying lift capabilities. The method augments a baseline predictor‑corrector with vehicle‑ and mission‑dependent altitude‑rate feedback to meet trajectory shaping and inequality constraint needs. The approach successfully enforces heating‑rate and load‑factor constraints for both low‑ and high‑lifting vehicles and is validated on a capsule, a shuttle‑class vehicle, and a hypersonic glider.

Abstract

During the past five decades, entry guidance methods have gone through major evolutions, largely driven by the needs of different types of entry vehicles and greatly increased onboard computation capabilities. Numerical predictor-corrector algorithms have emerged in recent years to hold the potential to become the next prevalent entry guidance method. This paper aims at developing a method that is centered on a single baseline predictor-corrector algorithm and will be applicable to a wide range of vehicles with varying lifting capabilities for orbital as well as suborbital entry missions. Different needs for additional (vehicle- and mission-dependent) trajectory shaping and inequality constraint enforcement are met by appropriate augmentations of altitude-rate feedback to the baseline algorithm. In particular, the long-standing challenge of enforcing common inequality trajectory constraints (such as the heating rate and load factor) with a predictor-corrector algorithm is now satisfactorily overcome, for either low-lifting or high-lifting vehicles. The method is successfully applied to three very different vehicles, a capsule, a shuttle-class vehicle, and a high-lifting hypersonic gliding vehicle.