Encyclopedia Astronautica
Agena D


American space tug. 205 launches, (1963) to (1987). Upper stage / space tug - out of production. Launched by Atlas Agena D; Thor Agena D; Titan 3B; Titan 34B.

One of the real workhorses of U. S. space exploration, the Agena upper stage which was also employed as a spacecraft, the whole vehicle going into orbit. Agena played a key role in manned space flight; it was the target vehicle for rendezvous and docking maneuvers in NASA's Gemini project. Agena had a main rocket engine capable of multiple re-starts in space; in the modified target vehicle version it also had two secondary engines to provide small changes in velocity and position in orbit. In the Gemini Agena, a control system could handle 96 commands from the astronauts or from ground stations. Agena was used as an upper stage with the Thor, augmented Thor, Atlas and Titan boosters; it played important roles in such military and NASA programs as Corona, Keyhole, Discoverer, Samos, Mariner, OGO, Lunar Orbiter, Ranger and Orbiting Astronomical Observatory.

The Agena D was essentially a standardized version of the Agena B. The restartable Agena D could accept a range of payloads and be fitted to Atlas, Thor, or Titan boosters without modification. Its outstanding dry weight fraction, resulting in it being selected for use in preference to the heavier Transtage for many Titan missions.

Unit Cost $: 8.700 million.

Gross mass: 6,821 kg (15,037 lb).
Unfuelled mass: 673 kg (1,483 lb).
Height: 7.09 m (23.26 ft).
Diameter: 1.52 m (4.98 ft).
Span: 1.52 m (4.98 ft).
Thrust: 71.17 kN (15,999 lbf).
Specific impulse: 300 s.
Number: 205 .

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Associated Countries
Associated Engines
  • Bell 8096 Bell Nitric acid/UDMH rocket engine. 71.2 kN. Out of production. Isp=292s. Used in Agena stage on top of Thor, Atlas, and Titan launch vehicles. First flight 1963. More...

See also
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...

Bibliography
  • NASA Report, Reusable Agena, Web Address when accessed: here.

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