Encyclopedia Astronautica
Agena D


Nitric acid/UDMH propellant rocket stage. Loaded/empty mass 6,821/673 kg. Thrust 71.17 kN. Vacuum specific impulse 300 seconds. One of the real workhorses of US space exploration, Agena was a restartable upper stage which was also employed as a spacecraft, the whole vehicle going into orbit. A mainstay of the US Air Force reconnaisance satellite program, it also boosted early NASA probes to the moon and planets. Agena played a key role in manned space flight as the target vehicle for rendezvous and docking manoeuvres in NASA's Gemini project. It

Agena had a main rocket engine capable of multiple re-starts in space; in the modified target vehicle version it also had 2 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 had played important roles in such military and NASA programs as Discoverer, Samos, Mariner, OGO, Lunar Orbiter, Ranger and Orbiting Astronomical Observatory.

Cost $ : 8.700 million.

Status: Retired 1987.
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.
Burn time: 265 s.
Number: 380 .

More... - Chronology...


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...

Associated Launch Vehicles
  • Thor Agena D American orbital launch vehicle. Two stage vehicle consisting of 1 x Thor DM-21 + 1 x Agena D More...
  • Atlas Agena D American orbital launch vehicle. Atlas D with further improved and lightened Agena upper stage. More...
  • Thorad Agena D SLV-2H Thor Agena upgraded with Long Tank Thor stage. Variant with straight tank from Delta was Thorad (Long Tank Augmented Thrust Thor Delta) More...
  • Thorad Agena D SLV-2H Thor Agena upgraded with Long Tank Thor stage. Variant with straight tank from Delta was Thorad (Long Tank Augmented Thrust Thor Delta) More...
  • Titan 23B American orbital launch vehicle. Basic Titan 3A core, originally developed for Titan 3C, with Agena D upper stage replacing Transtage. New radio guidance system, 1.5 m diameter fairing atop Agena. Payload remained attached to the Agena. More...
  • Titan 33B American orbital launch vehicle. Basic Titan 3A core, except guidance provided by the Agena upper stage. The Agena and its payload were completely enclosed in a new 3.05 m diameter shroud. 'Ascent Agena' seperated after orbital insertion and did not remain attached to the payload. More...
  • Titan 24B American orbital launch vehicle. Stretched first stage, originally developed for the cancelled MOL program, with Agena D upper stage. Radio guidance system, 1.5 m diameter fairing atop Agena. Payload remained attached to the Agena. More...
  • Titan 34B American orbital launch vehicle. Stretched Titan core, originally developed for Titan 3M MOL, with Agena D upper stage. Guidance provided by the Agena upper stage. The Agena and its payload were completely enclosed in a 3.05 m diameter shroud. 'Ascent Agena' seperated after orbital insertion and did not remain attached to the payload. 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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