Life-extending control of a reusable rocket engine

The goal of life-extending control is to achieve a tradeoff between structural durability and dynamic performance of complex mechanical systems such as aircraft, spacecraft, and energy conversion systems. The paper presents a procedure for synthesis of output feedback life-extending controllers and explores the feasibility of its application to a reusable rocket engine such as the Space Shuttle Main Engine. The reported work focuses on: (i) reduction of fatigue damage in the blades of the oxidizer (O₂) and fuel (H₂) turbines and (ii) enhancement of engine performance, by simultaneously minimizing the turbine torques and the output tracking errors of the thrust chamber pressure and the O₂/H₂ mixture ratio. To realize different levels of performance/damage tradeoff, one performance (i.e. without any consideration to damage) controller and three damage-mitigating controllers have been synthesized by using an induced L₂-norm method applicable to sampled data systems. Simulation results are presented to demonstrate the effectiveness of the life-extending control concept