Encyclopedia Astronautica
Ariane 5 ESC A


Lox/LH2 propellant rocket stage. Loaded/empty mass 16,500/2,100 kg. Thrust 64.70 kN. Vacuum specific impulse 446 seconds. Uses engine and oxygen tank from Ariane 4 + new liquid hydrogen tank.

Status: Active.
Gross mass: 16,500 kg (36,300 lb).
Unfuelled mass: 2,100 kg (4,600 lb).
Height: 9.00 m (29.50 ft).
Diameter: 5.46 m (17.91 ft).
Span: 5.46 m (17.91 ft).
Thrust: 64.70 kN (14,545 lbf).
Specific impulse: 446 s.
Burn time: 960 s.
Number: 26 .

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Associated Countries
Associated Engines
  • HM7-B SEP, Ottobrunn lox/lh2 rocket engine. 70 kN. Isp=447s. Increased performance version of the HM-7 engine for the Ariane 2 and 3. Combustion chamber pressure raised from 30 to 35 bar and nozzle extended. First flight 1984. More...

Associated Launch Vehicles
  • Ariane 5ECA French orbital launch vehicle, first version of the evolved Ariane 5. The solid booster motors propellant load was increased by 2.43 tonnes and the case was welded, for a weight saving in dry mass of 1.9 tonnes. The core was powered by an improved Vulcain 2 engine. The oxygen-rich cycle of the engine allowed the oxygen bulkhead to be moved within the stage, resulting in a 15.2 tonne increase in propellant in the core. A new Lox/LH2 upper stage, using the HM7B engine and oxygen tank from the Ariane 4 series, replaced the storable propellant EPS stage of earlier models. The result was an increase in payload to geoscynchronous transfer orbit from 6 tonnes to 10.5 tonnes. 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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