Design and performance evaluation of flow-control-valve-only deep throttle control system for liquid-propellant rocket for space exploration

Abstract

Thrust control is an ordinary requirement for modern liquid-propellant rocket engines. The thrust-controllable, often called throttle-able, liquid-propellant rocket engines make highly constrained missions possible: limiting the acceleration of a launch vehicle, safe planetary entry and/or decent, space rendezvous, and ballistic missile defense trajectory control. For future planetary exploration missions especially lunar-exploration missions the throttle-able liquid propulsion system must be developed. To develop the throttle-able propulsion system flight-proven methods for the liquid rocket engine throttling were reviewed and the propulsion system requirements for lunar-exploration mission were conceptually analyzed. The main difficulties for the system are to control the much more complicated system and possibility for instable combustion. The simplest throttling method is to use the high-pressure-drop injector with flow control valves. The solution for the combustion instability problem of the method is much higher pressurant pressure but it was reported that Mars Lander Engines for Mars Science Laboratory mission achieved an extremely wide throttle range with a relatively high pressurant pressure using a cavitating venturi-type flow control valve. Considering the precedent, feasibility analysis of a throttle-able space propulsion system with the cavitating venturi-type flow control valves and a thruster with normal-pressure-drop injector is being conducted. To analysis the feasibility based on experiments the cavitating venturi-type flow control valves were designed and tested. To design the valves, a design optimization was carried out for a small lunar lander to determine the minimum propulsion mass allowed using a H2O2/kerosene bipropellant rocket system. Specific impulse estimation based on two-temperature nonequilibrium nozzle flow analysis, propulsion system mass estimation by modeling the tank and the thrust chamber mass. The optimal design specifi...