Encyclopedia Astronautica
Delta 4H - 2

Lox/LH2 propellant rocket stage. Loaded/empty mass 30,710/3,490 kg. Thrust 110.05 kN. Vacuum specific impulse 462 seconds. Delta 4 second stage with hydrogen tank increased to 5.1 m diameter.

Status: Active.
Gross mass: 30,710 kg (67,700 lb).
Unfuelled mass: 3,490 kg (7,690 lb).
Height: 12.00 m (39.00 ft).
Diameter: 2.44 m (8.00 ft).
Span: 5.00 m (16.40 ft).
Thrust: 110.05 kN (24,740 lbf).
Specific impulse: 462 s.
Burn time: 1,125 s.
Number: 4 .

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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 IV Heavy American orbital launch vehicle. Heavy lift all-cryogenic launch vehicle using two Delta-4 core vehicles as first stage flanking a single core vehicle as second stage. A heavy upper stage is carried with a 5 m diameter payload fairing. 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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