Encyclopedia Astronautica
Bell 8247

Bell Nitric acid/UDMH rocket engine. 71.2 kN. Out of Production. Isp=291s. Version of Agena engine for the Gemini-Agena Target Vehicle. Minimum capability of five restarts and a demonstrated capability of fifteen restarts. First flight 1963.

The Gemini-Agena Target Vehicle design was an adaptation of the basic Agena-D vehicle using the alternate Model 8247 rocket engine and additional program-peculiar equipment required for the Gemini mission. The XLR-8I-BA-13 was a liquid bi-propellant rocket engine with a minimum capability of five starts and a demonstrated capability of fifteen starts under vacuum conditions. This rocket engine consisted of the following major components:

  • Thrust-chamber assembly
  • Multiple-restart assembly
  • Turbine-pump assembly
  • Overspeed shutdown electronic-gate and cable assembly
  • Turbine-exhaust duct
  • Propellant manifolds
  • Thrust-chamber nozzle extension

Fuel used was unsymmetrical dimethylhydrazine (UDMH); oxidizer used was inhibited red fuming nitric acid (IRFNA). The propulsion system provided the thrust necessary to place the GATV into a selected orbit and to accomplish major orbital changes. A minimum of five starts was available for performing these maneuvers.

Engine: 132 kg (291 lb). Chamber Pressure: 34.00 bar. Area Ratio: 45. Propellant Formulation: RFNA/UDMH. Oxidizer to Fuel Ratio: 2.57. Coefficient of Thrust vacuum: 1.829. Restarts: 13.

AKA: XLR81-BA-13.
Status: Out of Production.
Unfuelled mass: 132 kg (291 lb).
Diameter: 1.52 m (4.98 ft).
Thrust: 71.20 kN (16,006 lbf).
Specific impulse: 291 s.
Burn time: 240 s.
First Launch: 1962-1964.
Number: 248 .

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Associated Countries
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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...

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