Descent Propulsion Subsystem
The Descent Propulsion Subsystem consists of two fuel and two oxidizer tanks with interconnecting gas and liquid balance lines for the like tanks. The pressurization system consists of cryogenically stored helium and an auxiliary ambient start system. The system is centered about a deep-throttling ablative rocket engine which has restart capabilities. The maximum thrust level is approximately 10,000 Ibs. and the engine can be throttled to 1050 Ibs. The engine is mounted in the center compartment of the Descent Stage cruciform, suspended at the throat of the combustion chamber on a gimbal ring that is an integral portion of the engine assembly. The engine is gimballed to maintain thrust vector c.g. alignment. The propellants are identical to those used in the Ascent engine and Reaction Control thrusters.