Encyclopedia Astronautica
Bell 8081


Bell Nitric acid/UDMH rocket engine. 71.2 kN. Out of production. Isp=285s. Used on Agena B stage atop Thor and Atlas. First flight 1960.

Engine: 130 kg (280 lb). Chamber Pressure: 10.00 bar. Area Ratio: 45. Propellant Formulation: RFNA/UDMH. Thrust to Weight Ratio: 55.8230769230769. Oxidizer to Fuel Ratio: 2.55. Coefficient of Thrust vacuum: 2.99603430168432. Restarts: 2.

AKA: XLR81-BA.
Status: Out of production.
Unfuelled mass: 130 kg (280 lb).
Diameter: 1.52 m (4.98 ft).
Thrust: 71.20 kN (16,006 lbf).
Specific impulse: 285 s.
Burn time: 240 s.
Number: 156 .

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Associated Countries
Associated Spacecraft
  • Agena B American space tug. 94 launches, (1960) to (1967). Upper stage / space tug - out of production. Launched by Atlas Agena B; Thor Agena B. More...

See also
Associated Launch Vehicles
  • Thor Agena B American orbital launch vehicle. Two stage vehicle consisting of 1 x Thor DM-21 + 1 x Agena B More...
  • Atlas Agena B American orbital launch vehicle. Atlas D with improved, enlarged Agena upper stage. More...
  • Thor Agena D American orbital launch vehicle. Two stage vehicle consisting of 1 x Thor DM-21 + 1 x Agena D More...

Associated Manufacturers and Agencies
  • Bell American manufacturer of rockets, spacecraft, and rocket engines. ARC Liquid Propellant Division, Niagara Falls, NY, USA. More...

Associated Propellants
  • Nitric acid/UDMH Drawing on the German World War II Wasserfall rocket, nitric acid (HNO3) became the early storable oxidiser of choice for missiles and upper stages of the 1950's. To overcome various problems with its use, it was necessary to combine the nitric acid with N2O4 and passivation compounds. These formulae were considered extremely secret at the time. By the late 1950's it was apparent that N2O4 by itself was a better oxidiser. Therefore nitric acid was almost entirely replaced by pure N2O4 in storable liquid fuel rocket engines developed after 1960. Unsymmetrical Dimethylhydrazine ((CH3)2NNH2) became the storable liquid fuel of choice by the mid-1950's. Development of UDMH in the Soviet Union began in 1949. It is used in virtually all storable liquid rocket engines except for some orbital manoeuvring engines in the United States, where MMH has been preferred due to a slightly higher density and performance. More...

Associated Stages
  • Agena B Nitric acid/UDMH propellant rocket stage. Loaded/empty mass 7,167/867 kg. Thrust 71.17 kN. Vacuum specific impulse 285 seconds. More...

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