Encyclopedia Astronautica
Delta 3-2


Lox/LH2 propellant rocket stage. Loaded/empty mass 19,300/2,476 kg. Thrust 110.03 kN. Vacuum specific impulse 462 seconds. The upgraded cryogenic second-stage Pratt & Whitney RL10B-2 engine is based on the 30-year heritage of the reliable RL10 engine. It incorporates an extendable exit cone for increased specific impulse (Isp) and payload capability.

The basic engine and turbo pump are unchanged relative to the RL10. The engine gimbal system uses electromechanical actuators that increase reliability while reducing both cost and weight. The propulsion system and attitude control system (ACS) utilize flight-proven off-the-shelf components. The second-stage propulsion system produces a thrust of 24,750 lb with a total propellant load of 37,090 lb, providing a total burn time of approxi-mately 700 sec. Missions requiring more than one restart are accommodated by adding an extra helium bottle for the additional tank repressurization. Propellants are managed during coast by directing hydrogen boiloff through aft facing thrusters to provide settling thrust. Propellant tank pressurization during burn is accomplished using hydrogen bleed from the engine for the LH2 tank and helium for the LO2 tank. After spacecraft separation, the stage is safed by dumping propellants followed by venting of the tanks.

Cost $ : 21.000 million.

Status: Retired 2000.
Gross mass: 19,300 kg (42,500 lb).
Unfuelled mass: 2,476 kg (5,458 lb).
Height: 8.80 m (28.80 ft).
Diameter: 2.44 m (8.00 ft).
Span: 4.00 m (13.10 ft).
Thrust: 110.03 kN (24,736 lbf).
Specific impulse: 462 s.
Burn time: 700 s.
Number: 3 .

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Associated Countries
Associated Engines
  • RL-10B-2 Pratt and Whitney lox/lh2 rocket engine. 110 kN. In production. Isp=462s. Used on Delta 3 , Delta IV launch vehicles. First flight 1998. Extendable exit cone for increased specific impulse; electromechanical actuators replace hydraulic systems. More...

Associated Launch Vehicles
  • Delta 3 American orbital launch vehicle. Delta 3 was an attempt by the manufacturer to provide the ultimate development of the original Delta booster. The core vehicle was beefed-up to accomodate much larger solid rocket boosters and a new cryogenic upper stage. However problems were incurred during development, resulting in the first two launches being failures. Meanwhile the satellite launch market crashed and the new vehicle was left without customers. The venerable Delta 7925 soldiered on for NASA, and the new Delta 4 series captured the USAF EELV requirement. More...

Associated Propellants
  • Lox/LH2 Liquid oxygen was the earliest, cheapest, safest, and eventually the preferred oxidiser for large space launchers. Its main drawback is that it is moderately cryogenic, and therefore not suitable for military uses where storage of the fuelled missile and quick launch are required. Liquid hydrogen was identified by all the leading rocket visionaries as the theoretically ideal rocket fuel. It had big drawbacks, however - it was highly cryogenic, and it had a very low density, making for large tanks. The United States mastered hydrogen technology for the highly classified Lockheed CL-400 Suntan reconnaissance aircraft in the mid-1950's. The technology was transferred to the Centaur rocket stage program, and by the mid-1960's the United States was flying the Centaur and Saturn upper stages using the fuel. It was adopted for the core of the space shuttle, and Centaur stages still fly today. More...

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