Encyclopedia Astronautica
Ottobrunn 300N

Ottobrunn lox/lh2 rocket engine. 300 N. Upper stages. Developed 2000. Isp=415s - highest value ever achieved in Europe for an engine of such small size.

This 300 N cryogenic propellant engine had a vacuum Isp of 415 seconds - the highest value ever achieved in Europe for an engine of such small size. Characteristic chamber length was 0.4 m; overall efficiency 91%; thrust could be varied from 240 to 480 N with the chamber pressure varying from 4 to 8 bar, mixture ratio from 3.5 to 6.5, and the propellant mass flow rate from 0.06 - 0.12 kg/s.

Application: Upper stages.


Engine: 1.88 kg (4.15 lb). Chamber Pressure: 5.00 bar. Area Ratio: 57. Oxidizer to Fuel Ratio: 5.5. Restarts: 4.

Status: Developed 2000.
Height: 0.39 m (1.27 ft).
Thrust: 300.00 kN (67,440 lbf).
Specific impulse: 415 s.

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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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