RM-81 Agena
The RM-81 Agena (
On some missions, the payload was built directly into the Agena, which provided it with electric power, communications and
The Agena name was suggested by the Department of Defense's
The final launch was of an Agena D on February 12, 1987, configured as the upper stage of a Titan 34B. In all, 365 Agena vehicles were launched by NASA and the US Air Force.[5]
Characteristics
The Agena was 5.0 feet (1.5 m) in diameter, three-axis stabilized (for the benefit of the reconnaissance system cameras) and its
Attitude control of the horizontal flying Agena was provided by an inertial reference package with three
As the Agena was designed to hold a fixed orientation in space while orbiting Earth, a passive thermal control system was devised.[1]
The main source of the Agena's electrical power was
Versions
Three versions of the Agena were flown:
Variant | Engine | Thrust | Burn time | Rockets | number of launches |
---|---|---|---|---|---|
Agena-A | Bell 8048
|
69 kN | 120 seconds | Atlas, Thor | 20 |
Agena-B | Bell 8081
|
71 kN | 240 seconds | Atlas, Thor | 76 |
Agena-D | Bell 8247 on Agena Target Vehicle[2] )
|
71 kN | 265 seconds | Atlas, Thor, Thorad, Titan IIIB | 269 |
Agena-A
The Agena A was the first type of Agena to be built. It was launched atop Thor and Atlas rockets, mostly into polar orbits from
Agena-B
Agena-D
The Agena D was the result of a proposal by Lockheed engineering executive Lawrence Edwards, who suggested standardizing the basic Agena configuration (up to this point, each Agena was custom-built for both the payload and the launch vehicle it was used with), and adding additional features depending on payload requirements, and a requirement from the Pentagon that the Agena be made compatible with the Titan rocket. This proposal originated in late 1962 when mounting frustration over the high failure rate of Thor and Atlas-Agena prompted the suggestion that greater standardization of launch vehicles would improve reliability. David N. Spires summarizes the standardization as follows:
The Agena D's common configuration included four usable modules containing the major guidance, beacon, power, and telemetry equipment, a standard payload console, and a rear rack above the engine for plug-in installation of optional gear-like solar panels, "piggyback" subsatellites, and an optional Bell Aerosystems engine that could be restarted in space as many as sixteen times.[8]
Its orbital configuration had a diameter of 60 in (1.5 m) and a length of 248 in (6.3 m), and provided 19,500 Wh of electrical power from batteries.[9] As of 2014, the Agena-D is the most-launched US upper stage.[10] A special production line was set up to turn out 40 Agena-D spacecraft per year. Edwards remained responsible for the engineering for several years, until the Air Force declared the Agena-D as operational and froze its design. By the time of its retirement, the reliability of the Agena-D exceeded 95 percent. The first Agena D launch was of KH-4 #7 on June 28, 1963, and a total of 269 Agena Ds were launched.
Thor-Agena flew for the last time in 1972 when it launched a KH-4B satellite. The last Atlas-Agena used an Agena D stage atop a refurbished Atlas F missile to launch Seasat in 1978. Twelve more Agenas were launched on Titan vehicles through 1987 before the stage was completely retired.
The Agena-D was used to launch
Agena Target Vehicle
The Agena Target Vehicle was based around the Agena-D, with equipment fitted to support use as a rendezvous and docking target for missions conducted as part of
Other variants
In the early 1970s Lockheed studied the use of Agena as a payload booster in the Space Shuttle payload bay. An Agena-C with an increased diameter was proposed, but never built.
The Agena-2000 was intended as a modernized Agena, and would have been used on the
Launches
The first launch of an Agena-D was Agena Flight #64 on 27 June 1962. By the end of 1967, a total of 162 Agena-D had been launched:[12]
1962 | 1963 | 1964 | 1965 | 1966 | 1967 | 1968 | 1969 | 1970 | 1971 | 1972 | 1973 | 1974 | 1975 | 1976 | 1977 | 1978 | 1979 | 1980 | 1981 | 1982 | 1983 | 1984 | 1985 | 1987 | Total | ||
Launches | 8 | 23 | 35 | 29 | 39 | 28 | 21 | 17 | 14 | 12 | 8 | 5 | 3 | 4 | 4 | 4 | 4 | 1 | 1 | 2 | 1 | 2 | 2 | 1 | 1 | 269 | |
Success | 8 | 18 | 32 | 26 | 36 | 26 | 20 | 17 | 14 | 10 | 6 | 4 | 3 | 4 | 4 | 4 | 4 | 1 | 1 | 2? | 1 | 2 | 2 | 1 | 1 | 245? | |
Failure | Agena | – | 3 | 3 | 1 | 2 | 1 | – | – | – | ? | ? | ? | – | – | – | – | – | – | – | – | – | – | – | – | – | 10? |
Booster | – | 2 | – | 2 | 1 | 1 | 1 | – | – | ? | ? | ? | – | – | – | – | – | – | – | – | – | – | – | – | – | 6? | |
Cumulative | 8 | 31 | 66 | 95 | 134 | 162 | 183 | 200 | 214 | 226 | 234 | 239 | 242 | 246 | 250 | 254 | 258 | 259 | 260 | 262 | 263 | 265 | 267 | 268 | 269 | – |
Debris
Since many of the Agenas have remained in orbit long after they were needed, they've had time to break-up resulting in more orbital debris.[13] They are thought to have exploded due to residual propellant igniting.[14]
See also
Related lists
- List of military aircraft of the United States
- List of missiles
References
- ^ a b c d Jacob Neufeld; George M. Watson, Jr. & David Chenoweth (1997). "Technology and the Air Force A Retrospective Assessment" (PDF). Air Force History and Museums Program. Archived from the original (PDF) on October 7, 2012.
- ^ a b c Lockheed Missiles & Space Company (1972-02-25). "Shuttle/Agena study. Volume 1: Executive summary". NASA.
- ^ Space and Missile Systems Organization. June 1969. Archived from the original(PDF) on 2011-10-16.
- ^ Helen T. Wells; Susan H. Whiteley & Carrie E. Karegeannes. Origin of NASA Names. NASA Science and Technical Information Office. pp. 6–7.
- ^ "Lockheed RM-81 Agena". www.designation-systems.net.
- ^ "Bell Model 8048". National Museum of the U. S. Air Force. Retrieved 24 March 2018.
- ^ "Factsheets: Bell Model 8048". National Museum of the USAF. Archived from the original on 2010-12-25. Retrieved 2011-01-29.
- ^ David N .Spires (2004). "Orbital Futures: Selected Documents in Air Force Space History, Vol II". Air Force Space Command., page 1122.
- ^ "Feasibility Study, Final Report, Geodetic Orbital Photographic Satellite System, Volume 2" (PDF). NRO. June 1966. Archived from the original (PDF) on 2012-03-16. Retrieved 2011-01-28.
- ^ Genesis of Agena D: America's Most-Used Space Vehicle, lead article in Cold War Space History: Programmes, Space Chronicle, May 2006. Edited by Dwayne A. Day.
- ^ Krebs, Gunter. "Atlas-5". Gunter's Space Page. Retrieved 20 July 2010.
- Space and Missile Systems Organization. 2017-08-28 [November 1971].
- ^ "50 Year Old Agena-D Rocket Photographed in Orbit". Retrieved 15 February 2023.
- ^ @@planet4589 (September 26, 2020). "The Delta, Agena and CZ-4B stages are thought to have broken up due to residual propellant igniting many years after the stages were abandoned in orbit" (Tweet) – via Twitter.