Propulsion (Ascent Stage)
|The Ascent Propulsion
Subsystem uses a fixed, constant-thrust rocket engine. The system includes
the associated ambient helium pressurization and propellant supply components.
The engine develops 3,500 pounds of thrust in vacuum, sufficient to launch
the Ascent Stage from the lunar surface and place it in orbit. Two main
propellant tanks are used: one for fuel, the other for oxidizer. The tanks
are installed on either side of the Ascent Stage structure. The propellant
supply sections in this subsystem also provide for fuel and oxidizer interconnect
to the Reaction Control Subsystem as a propellant supply for the latter
during select mission phases. The fuel is a 50/50 mixture of hydrazine
and unsymmetrical dimethyl hydrazine. The oxidizer is nitrogen tetroxide.
These propellants constitute a hypergolic system, that is, engine ignition
results when the propellants come in contact with each other
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
Propulsion (Descent Stage)