Atlas I

The Atlas I was a US expendable launch system used in the 1990s to launch a variety of 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". Eleven launches took place, with three failures.

Atlas I
Launch of the maiden flight of the Atlas I, with the CRRES satellite
FunctionExpendable launch system
ManufacturerGeneral Dynamics Space Systems Division
Country of originUnited States
Height43.90m (144.00 ft)
Diameter3.05m (10 ft)
Mass164,300kg (362,200 lb)
Associated rockets
Launch history
Launch sitesLC-36B, Cape Canaveral
Total launches11
First flightJuly 25, 1990
Last flightApril 25, 1997

Though the Atlas I was marketed as a new rocket, it was mostly a re-brand of the Atlas G/H for commercial payloads. The Atlas G and H launched mostly governmental satellites.

Atlas I was the last use of the classic Atlas design with three engines, jettisonable booster section, and two vernier engines. Atlas II, while retaining most of those features, replaced the verniers with a hydrazine roll control system.

Launch history

Date/Time (GMT) Serial Number Payload Outcome Remarks
Atlas Centaur
July 25, 1990, 19:21 AC-69 5049 CRRES Successful Maiden flight of Atlas I, spacecraft later failed
April 18, 1991, 23:30 AC-70 5050 Yuri 3H Failure RSO destruct at T+441 seconds. Due to management[1] schedule and cost pressure during the postflight analysis, engineers made a quick but wrong conclusion that one Centaur engine failed to start due to debris lodged in the LH2 turbopump. The real problem was LH2 mixing with atmospheric nitrogen to form a plug of solid nitrogen in a Centaur engine valve. This resulted in the engine not developing thrust and the twin engine Centaur tumbled out of control. The problem would resurface again in Atlas AC-71.
March 14, 1992, 00:00 AC-72 5052 Galaxy 5 Successful
August 22, 1992, 22:40 AC-71 5051 Galaxy 1R Failure Centaur engine failure followed by RSO destruct. Just like the 1991 launch, this incident was caused by LH2 mixing with atmospheric nitrogen to form a plug of solid nitrogen in a Centaur engine valve. The condition was caused by an experimental procedure to increase performance by cooling the Centaur engines prior to ignition. The procedure was not fully tested under flight like conditions. This time management gave full authority to examine every possible cause until the root was found.
March 25, 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.
September 3, 1993, 11:17 AC-75 5055 UHF F-2 (USA-95) Successful
April 13, 1994, 06:04 AC-73 5053 GOES-I (GOES-8) Successful
June 24, 1994, 13:50 AC-76 5056 UHF F-3 (USA-104) Successful
May 23, 1995, 05:52 AC-77 5057 GOES-J (GOES-9) Successful
April 30, 1996, 04:31 AC-78 5058 BeppoSAX Successful
April 25, 1997, 05:49 AC-79 5059 GOES-K (GOES-10) Successful Final flight of Atlas I[2]

See also


  2. "Atlas I Successfully Launches GOES-K". International Launch Services. April 25, 1997. Retrieved March 16, 2013.

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