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Titan IV Liquid Rocket Engine (LRE)

• Stage I Engine
  • Propellant: N2O4 - Aerozine 50
  • Thrust: 548,000lbs (2,438 kN) Vac
  • ISP: 302sec Vac
• Stage II Engine
  • Propellant: N₂O₄ - Aerozine 50
  • Thrust: 105,000lbs (467 kN) Vac
  • ISP: 316sec Vac

Stage I Engine: The booster vehicle has two Liquid Rocket Engine (LRE) assemblies, one for each stage. The Stage I engine (Aerojet LR87-AJ-11) has two subassemblies that operate simultaneously and independently, but under a single/common control system. Each assembly contains fuel and oxidizer pumps that are geared together and are turbine driven. The turbine is powered by a gas generator which uses the same liquid propellants as the main combustion chambers. They receive the propellants from the pump discharge lines. Hydraulic actuators, in response to vehicle guidance commands, vector the trust of the two combustion chambers to provide pitch, yaw and roll control. Hydraulic power is supplied by a single turbine-driven hydraulic pump mounted on the gearbox of subassembly two. The engine also provides hot gases to pressurize the main propellant tanks during engine operations. Each subassembly is started by a solid propellant start cartridge which drives the turbine until the gas generator "bootstraps" the engine to its steady-state operational level.

Stage II Engine: The Stage II engine, Aerojet LR91-AJ-11, operates in the same manner as the Stage I engine, except that it has only one combustion chamber. This chamber is hydraulically vectored to provide pitch and yaw control. The gas generator exhaust is ducted through a roll control nozzle, which is also hydraulically vectored to control vehicle roll. -Propellants: Both Stage I and Stage II engines use liquid hypergolic propellants that can remain aboard in a launch ready state for extended periods of time. The fuel (Aerozine-50) is nominally a 50-50 weight mixture of hydrazine and unsymmetrical dimehtylhydrazine (UDMH) and the oxidizer is nitrogen tetroxide (N2O4). These propellants are storable at ambient temperature and pressure, thus eliminating temperature conditioning equipment such as is required when handling cryogenic propellants. The hypergolic property (spontaneous ignition upon fuel oxidizer contact) eliminates the need for an ignition system and related checkout and support equipment.

Retrorockets: Four retrorocket motors with 440 lb thrust each, are mounted equally spaced around the aft edge of the Stage II Aft Oxidizer Skirt with their thrust nozzles positioned forward. These rocket motors are fired to retard Stage II after Upper Stage or Space Vehicle (SV) separation.

PROPELLANTS: Both Stage I and Stage II engines use liquid hypergolic propellants that can remain aboard in a launch ready state for extended periods of time. The fuel (aerozine-50) is nominally a 50-50 weight mixture of hydrazine and unsymmetrical dimethylhydrazine (UDMH) and the oxidizer is nitrogen tetroxide (N2O4). These propellants are storable at ambient temperature and pressure, thus eliminating temperature conditioning equipment such as is required when handling cryogenic propellants. The hypergolic property (spontaneous ignition upon fuel oxidizer contact) eliminates the need for an ignition system and related checkout and support equipment.