Agena in orbit Credit - NASA

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. Length: 7.09 m (23.26 ft). Basic Diameter: 1.52 m (4.98 ft). Span: 1.52 m (4.98 ft). Mass: 6,821 kg (15,037 lb). Main Engine: Bell 8096. Main Engine: 132 kg (291 lb). Main Engine Thrust: 71.166 kN (15,999 lbf). Main Engine Propellants: Nitric acid/UDMH. Main Engine Propellants: 6,148 kg (13,554 lb). Main Engine Isp: 300 sec.

• NASA Report, Reusable Agena, . Accessed at: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740023215_1974023215.pdf. -right click to download pdfs!