Damage-Mitigating Control of a Reusable Rocket Engine: Part II—Formulation of an Optimal Policy

This sequence of papers in two parts investigates the feasibility of damage-mitigating control of a reusable rocket engine similar to the Space Shuttle Main Engine (SSME) where the objective is to increase structural durability without any significant loss of performance. To this effect, a fatigue damage model of the turbine blades has been reported in earlier publications, and a creep damage model of the main thrust chamber coolant channel has been formulated and tested in the first part. This paper, which is the second part, synthesizes an optimal policy for open loop control of up-thrust transients of the rocket engine. Optimization is based on the integrated model of the plant, structural and damage dynamics under the constraints of fatigue and creep damage in the critical components. The results are presented to demonstrate the potential of life extension of reusable rocket engines via damage mitigating control. The concept of damage mitigation, as presented in this paper, is not restricted to control of rocket engines. It can be applied to any system where structural durability is an important issue.