(U) Centaur

(The effects of any budget/program decisions made since the information was collected during 1997-98 are NOT reflected in the National Security Space Road Map (NSSRM).)

Overview: (U)
(U) Centaur is a family of liquid fueled upper stage vehicles designed to deliver a satellite to its operational orbit.  The Centaur is used on the Titan IV and Atlas family of space launch vehicles and has been developed in four versions.  These versions are the Centaur I, II, IIA and Titan IV Centaur, and each corresponds to the launch vehicle that it is integrated.  All Centaur versions share construction techniques and materials for propellant tanks and major subsystems such as propulsion, tank pressure control and avionics. The different versions are distinguished by tank capacities, shape and booster vehicle integration. The Centaur has two RL10A-3-3A engines,  which use LH2/LO2 to provide 30,000 pounds of thrust.

Description: (U)
(U)   The Centaur upper stage was originally designed to provide payload capacity for high altitude satellites, and lunar and planetary space probes.  The first successful flight took place on November 27,1963, marking the first flight of a space vehicle powered by a liquid hydrogen and liquid oxygen fuel combination.  The propellant tanks are a pressure-stabilized design constructed from stainless steel using resistance welding techniques similar to those proven on the Atlas booster.  Propulsion is provided by two turbopump-fed Pratt & Whitney RL10 engines, which are capable of multiple starts in space.  Two versions of the engine, which are uprated versions of the previously flown RL1OA-3-3A engines with the option of extendible nozzles, provide either 41,600 pounds of thrust (RL10A-4) or 44,000 pounds of thrust (RL10A4-1).  First flight of Centaur with RL10A-4 engines occurred in June 1992 on the INTELSAT K mission.  The inertial navigation unit (INU) located on the Centaur provides guidance control for both Atlas and Centaur, and controls both Atlas and Centaur tank pressures and propellant use.  A hydrazine reaction control system provides attitude control and propellant settling during coast phases.  The first Centaur burn lasts about five minutes after which the Centaur and its payload coast in a parking orbit.  The second Centaur ignition occurs about 24 minutes into the flight and continues for about one-and-a-half minutes followed three minutes later by the separation of the Centaur and the spacecraft.  In 1995, the 100th launch of the Centaur system occurred.

(U) The Centaur I is used on the Atlas I launch vehicle.  It has two RL10A-3-3A engines and 30,000 pounds of LH2/LO2.  The Centaur II is used on the Atlas II.  It is similar to the Centaur I, except it is three feet longer and holds 7,000 pounds more propellant.  The Centaur IIA is the same size as the Centaur II, but uses a different engine.   The Titan IV Centaur is a design based on the Atlas Centaurs.  It has two RL10A-3-3A engines and carries 46,000 pounds of propellant.  It can lift approximately 10,000 lbs from LEO to Geosynchronous Earth Orbit (GEO).  

User Impact: (U)
(U) Provides medium lift capability to launch communications satellites, which support DoD and national requirements.

Programmatics: (U)
(U) Operational.

Related Initiatives: (U)
(U) Advanced Upper Stage, Atlas, Milstar I, Milstar II, Titan IVA

Related Requirements: (U)
(U) None.

Related Categories: (U)
(U) Spacelift, Upper Stages

Road Map Placements: (U)
(U) SPACE FORCES SUPPORT.

Lead Office: (U)
(U) Air Force.

Date of Information: (U)
04 November 1997

(The effects of any budget/program decisions made since the information was collected during 1997-98 are NOT reflected in the National Security Space Road Map (NSSRM).)