Agena

The title of this article is ambiguous. Further meanings are listed under Agena (disambiguation) .

The Agena was a varied set up US school for aerospace - launchers . Its development was based on the knowledge gained after the first satellite launches at the end of the 1950s that precisely defined orbits are necessary for the successful use of a satellite (e.g. for reconnaissance ) . These could not be realized by the single ignitable solid rocket stages used up to now .

Development history

From 1955 it became clear to the military that an essential application of satellite technology would be the reconnaissance of the foreign territory. The WS 117L program (WS for Weapons System) was founded for this purpose. The core was a photo reconnaissance satellite, the recordings of which were to be taken back to earth on films in capsules ( keyhole CORONA ). When returning, the idea was to have the capsules hanging on the parachute caught by airplanes in order to allow as little "enemy loss risk" as possible. The prerequisite was a satellite that could maneuver in orbit (i.e. had a re-ignitable engine and attitude control). In October 1956, the Lockheed company got the contract because it was able to fall back on developments (which had already been discontinued at the time) for a controllable missile projectile for nuclear warheads of the B-58 Hustler bomber . The US Air Force designated this missile as the RM-81 Agena. The satellites became known as the Discoverer . The storable combination of nitric acid / UDMH was selected as the fuel . The specialty of the Agena upper stage was that in most cases it stayed together with the actual payload. Only parts were separated after a long joint flight to return or as a space probe.

Agena A

Agena A with Discoverer payload

The first Agenas used the Bell XLR81-BA-3 (Model 8001) engines, but most of them used the XLR-81-BA-5 (Model 8048) with approximately 69 kN (15,500 lb) of thrust for a burn time of 120 s. The engine had gimbaled nozzles for pitch and yaw control. The Thor Agena A launched the first optical CORONA -Aufklärungssatelliten the Discoverer series (KH-1 for Keyhole on German keyhole ). The combination Atlas-Agena A was used for the Midas (Missile Detection and Surveillance) early warning system before missile launches and the ELINT system called Samos (Satellite and Missile Observation System) for electronic surveillance.

Agena B

The Agena B represented a further development of the Agena A by extending the tanks and using Bell XLR-81-BA-7 (model 8081) engines. These engines were re-ignitable in a vacuum, had approx. 71 kN (16,000 lb ) Thrust, and the total burn time doubled to 240 s. Later variants used the Bell XLR-81-BA-9 (model 8096) engine. The Thor-Agena B was used again for satellites of the Keyhole series (KH-2/3/4/5) and partly for the Samos program. The Atlas-Agena B for Midas and Samos . The Ranger moon and space probes were also launched with it.

Agena C

Planned further development with tank capacity doubled again - not implemented

Agena D

Agena D as GATV target satellite Gemini 10

Agena D with integrated KH-4B spy satellite

While the Agena A and B were specially adapted for each mission, the Agena D was created on the basis of the Agena B, the first standardized platform for payloads for Thor, Atlas and Titan missiles . The payload was accommodated in the nose cone or, as in the case of the Keyhole satellites, remained firmly attached to the Agena. In addition, small secondary payloads could be attached to the stern of the step . Payloads included a. the Mariner planetary probes, but also the Gemini Agena Target Vehicles , target satellites for coupling experiments as part of the Gemini program . However, the majority of the payloads were military. The satellites of the optical CORONA reconnaissance satellites (KH-4 / 4A / 4B), ARGON (KH-5) and LANYARD (KH-6) were launched with the Thor variants. The Atlas (LV-3A / SLV-3) launched the optical GAMBIT (KH-7), the Atlas SLV-3A launched the CANYON / RHYOLITE / AQUACADE satellites for electronic reconnaissance ( ELINT / SIGINT ) into geostationary orbits. The GAMBIT optical reconnaissance program (KH-8) was continued with the Titan 3B / 23B / 24B. The larger Titan 33B / 34B were again used for the SIGINT-JUMPSEAT satellites.

Technical specifications

Upper grades

Type	Agena A	Agena B	Agena D
length	5.94 m	7.56 m	7.09 m
diameter	1.52 m
Dimensions	3850 kg	7167 kg	6821 kg
Empty mass	885 kg	867 kg	673 kg
Fuel weight	2945 kg	6115 kg
drive	Bell 8001/8048 (XLR81-BA-3/5) 68.9 kN for 120 s	Bell 8081 (XLR81-BA-7) 71.1 kN for 240 s	Bell 8096 (XLR81-BA-9) 71.1 kN for 240 s

Engines

Engine	Bell 8048 (Agena A)	Bell 8081 (Agena B)	Bell 8096 (Agena D)	Bell 8247 (GATV)
thrust	68.9 kN	71.2 kN
Weight	127 kg	130 kg	140 kg	132 kg
length	2.16 m		2.11 m
Max. Diameter	1.52 m
Specific impulse (vacuum)	2707 m / s	2834 m / s	2874 m / s	2855 m / s
Combustion chamber pressure	10 bar	17.5 bar	35 bar	34 bar
Expansion ratio	10: 1	45: 1
Burn time	120 s	240 s
Reignitions			2, later 3	> 15
ignition			pyrotechnic	Starting tanks

Agena level start list

Missile type	Number of starts	First start	Last use
Thor (SLV-2) + Agena A	16	01/21/1959	09/13/1960
Atlas (LV-3A) + Agena A	4th	02/26/1960	01/31/1961
Overall Agena A	20th
Thor (SLV-2) + Agena B	44	10/26/1960	08/28/1964
Thrust-Augmented Thor (SLV-2A / C) + Agena B	3	06/29/1963	05/15/1966
Atlas (LV-3A) + Agena B	28	07/12/1961	03/21/1965
Atlas (SLV-3) + Agena B	1	06/09/1966
Overall Agena B	76
Thor (SLV-2) + Agena D	22nd	06/28/1962	05/31/1967
Thrust-Augmented Thor (SLV-2A / C) + Agena D	60	02/28/1963	January 17, 1968
Long-Tank Thrust-Augmented Thor (SLV-2G / H) + Agena D	22nd	08/09/1966	07/16/1971
Thorad (SLV-2G / H) + Agena D	21st	05/18/1968	May 25, 1972
Atlas (LV-3A) + Agena D	15th	07/12/1963	07/20/1965
Atlas (SLV-3) + Agena D	48	08/14/1964	05/11/1967
Atlas (SLV-3A) + Agena D	12	03/04/1968	04/07/1978
Atlas F + Agena D.	1	07/27/1978
Titan IIIB (SLV-5B)	29	07/29/1966	October 23, 1970
Titanium 23B	2	01/21/1971	04/22/1971
Titanium 33B	3	March 21, 1971	08/21/1973
Titanium 24B	23	08/12/1971	08/21/1973
Titanium 34B	11	03/10/1975	02/12/1987
Overall Agena D	269

See also

• List of missile types

swell

• Agena in the Encyclopedia Astronautica (English)
• Lockheed RM-81 Agena (English)

Web links

• The Agena with Bernd Leitenberger

Individual evidence

1. ↑ Bernd Leitenberger: US launch vehicles . 2nd Edition. BoD - Books on Demand, Norderstedt 2013, ISBN 978-3-7392-3547-9 , pp. 35, 36, 38 .