Three-in-One Abort Trajectory Optimization for Launch Vehicles under Engine Failures

Abstract

Onboard trajectory optimization provides a flexible approach to generate launch vehicle abort trajectories. Although abort trajectory optimization methods have been proposed previously, they formulate each abort mode as an individual optimal control problem. Implementing an abort algorithm with multiple abort modes requires managing multiple optimal control problems. Unlike such one-to-one formulations, this paper presents a three-in-one formulation that unifies three abort modes into a single optimal control problem. The three abort modes are unified by introducing a novel parameter that takes values of zeros and ones to select abort modes. By scaling the performance index and constraints with the mode-selecting parameter, these parts can be numerically enabled or disabled, allowing the three-in-one problem to equivalently reduce to one of the abort modes. Due to a new formulation of orbital insertion conditions, the size of the three-in-one problem is only slightly larger than when the three abort modes are individually formulated, and it remains in a common form that can be solved by employing the sequential convexification approach. Numerical studies that compare robustness, real-time performance, and computing resource usage showed that the proposed three-in-one formulation requires a negligible increase in computation time but offers better mission adaptability, covering the entire ascent profile using three abort modes within a single optimal control problem.