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 considered to be is the roman numeral "1".

The first stage of the Atlas I is an Atlas H, and the second stage is a Centaur. The first stage has an MA-5 booster unit, consisting of two LR-89 engines, for stage-and-a-half staging (used in conjunction with the Centaur, this gives 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	Unknown	Yuri 3H	Failure	Centuar turbopump malfunction
14 March 1992, 00:00	AC-72	5052	Galaxy 5	Successful
22 August 1992, 22:40	AC-71	5051	Galaxy 1R	Failure	Centaur turbopump failed to start
25 March 1993, 21:38	AC-74	5054	UHF F-1	Failure	Atlas engine failure, satellite placed in unusable orbit
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	Beppo-SAX	Successful
25 April 1997, 05:49	AC-79	Unknown	GOES-10 (GOES-K)	Successful	Final flight of Atlas I