Atlas I

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Atlas I
Atlas I launching CRRES satellite1.jpg
Launch of the maiden flight of the Atlas I, with the CRRES satellite
Function Expendable launch system
Manufacturer Convair
Country of origin United States
Height 43.90m (144.00 ft)
Diameter 3.05m (10 ft)
Mass 164,300kg (362,200 lb)
Stages 2.5
Associated rockets
Family Atlas
Launch history
Status Retired
Launch sites LC-36B, Cape Canaveral
Total launches 11
Successes 8
Failures 3
First flight 25 July 1990
Last flight 25 April 1997

The Atlas I was an American expendable launch system, used in the 1990s to launch a variety of different satellites. The "I" in "Atlas I" can cause confusion, as all previous Atlas rockets were designated using letters, ending with the Atlas H, however subsequent rockets were designated using Roman numerals, starting with the Atlas II. Officially, the "I" is the Roman numeral "1".

The first stage of the Atlas I was derived from Atlas G, and the second stage was a Centaur. The first stage had an improved MA-5A propulsion system, consisting of the LR-89 booster engine with dual thrust chambers and a more powerful RS-27 replacing the traditional LR-105 sustainer engine. With the new RS-27 sustainer engine, all three of the large Atlas thrust chambers produced equal thrust.[1] Booster engine jettison occurred prior to sustainer engine cut-off for stage-and-a-half staging of the Atlas. (Used in conjunction with the Centaur, this gave the Atlas I 2.5 stages).

Launch history

Date/Time (GMT) Serial Number Payload Outcome Remarks
Atlas Centaur
25 July 1990, 19:21 AC-69 5049 CRRES Successful Maiden flight of Atlas I, spacecraft later failed
18 April 1991, 23:30 AC-70 5050 Yuri 3H Failure One Centaur engine failed to start due to debris lodged in the LH2 turbopump. RSO destruct at T+441 seconds.
14 March 1992, 00:00 AC-72 5052 Galaxy 5 Successful
22 August 1992, 22:40 AC-71 5051 Galaxy 1R Failure Centaur engine failure followed by RSO destruct. Unlike the 1991 launch, this incident was caused by LH2 mixing with atmospheric nitrogen to form a plug in a valve caused by an experimental procedure to increase performance by cooling the Centaur engines prior to ignition.
25 March 1993, 21:38 AC-74 5054 UHF F-1 Failure An improperly torqued set screw caused the Atlas sustainer engine to drop to 75% thrust starting at T+25 seconds. By booster staging at T+120 seconds, sustainer thrust was down to 60%. The payload was placed in an unusable orbit. This was the last failed launch involving an Atlas vehicle.
3 September 1993, 11:17 AC-75 5055 UHF F-2 (USA-95) Successful
13 April 1994, 06:04 AC-73 5053 GOES-8 (GOES-I) Successful
24 June 1994, 13:50 AC-76 5056 UHF F-3 (USA-104) Successful
23 May 1995, 05:52 AC-77 5057 GOES-9 (GOES-J) Successful
30 April 1996, 04:31 AC-78 5058 BeppoSAX Successful
25 April 1997, 05:49 AC-79 5059 GOES-10 (GOES-K) Successful Final flight of Atlas I[2]

See also


  1. Dennis R. Jenkins, "Stage-and-a-Half, The Atlas Launch Vehicle", To Reach the High Frontier (University Press of Kentucky, 2002) p. 92
  2. "Atlas I Successfully Launches GOES-K". International Launch Services. April 25, 1997. Retrieved 2013-03-16.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>