Atlas G

Atlas G
	Launch of FLTSATCOM-7 on an Atlas G.
Function	Expendable launch system
Manufacturer	Convair; General Dynamics
Country of origin	United States
Launch history
Status	Retired
Launch sites	LC-36B, Cape Canaveral
Total launches	7
Successes	5
Failures	2
First flight	9 June 1984
Last flight	25 September 1989

The Atlas G, also known as Atlas G Centaur-D1AR[1] was an American expendable launch system derived from the Atlas-Centaur. It was a member of the Atlas family of rockets, and was used to launch seven communication satellites during the mid to late 1980s. Atlas G consisted of an improved Atlas core with modernized avionics and stretched propellant tanks. The Centaur stage also had several updated components and other technical improvements. It was replaced by the Atlas I, which had an improved guidance system.

The maiden voyage of Atlas G was the launch of Intelsat 5 on June 9, 1984. Atlas performance was normal as was Centaur orbital injection, but during the coasting phase prior to the second Centaur burn, the stage's LOX tank split open. The Centaur and Intelsat tumbled end-over-end and were left in a useless orbit where they remained until reentering the atmosphere four months later.

Investigation into the failure found that a minor fatigue crack developed in the Centaur LOX tank during staging and orbital injection, which eventually led to complete tank failure and loss of the mission. The uprated Centaur flown on Atlas G, among other changes, deleted the propellant boost pumps in the interest of greater simplicity and weight-saving. To compensate for this, LOX tank pressure was increased 25%. Although the tank had been designed to accommodate higher pressure, technicians at Convair inexplicably failed to test Centaur 5402 for leaks before shipping it to Cape Canaveral. In addition, engineers had not tested the Centaur G stages to verify if they could handle the shock from the explosive bolts on the booster firing during staging, but this test was performed later and the stage passed it.

Finally, the leak testing program and tools used at Convair were outdated and less reliable than newer methods and the tech personnel in charge of fabricating the Centaur's balloon tanks were badly inexperienced. Ultimately, this was a symptom of the entire US space program in the 1980s as plans to entirely replace expendable launch vehicles with the Space Shuttle had resulted in large-scale budget cutbacks and layoffs of experienced technicians.

Six more Atlas G/Centaur launches took place through 1989. These were:

Intelsat 5A F-10, March 22, 1985
Intelsat 5A F-11, June 30, 1985
Intelsat 5A F-12, September 28, 1985
FLTSATCOM 7, December 5, 1986
FLTSATCOM 6, March 26, 1987 (launch failed after the booster was struck by lightning)
FLTSATCOM 8, September 25, 1989

The first stage was derived from the SM-65 Atlas missile, and a Centaur was used as the second stage.[2] The first stage was also flown without the Centaur, as the Atlas H.

References

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[1] Gunter's Space Page - Atlas-G Centaur-D1AR

[EA-2] Encyclopedia Astronautica - Atlas

Orbital launch systems
List of orbital launch systems Comparison of orbital launch systems
Current	Angara A5 Antares 230+ Ariane 5 Atlas V Delta IV Heavy Electron Epsilon Falcon 9 Block 5 Falcon Heavy GSLV Mk II Mk III H-IIA Hyperbola-1 Jielong 1 Kuaizhou 1 1A 11^† Kaituozhe 2 LauncherOne^† Long March 2C 2D 2F 3A 3B/E 3C 4B 4C 5 5B 6 7 7A^† 11 Minotaur I IV V C OS-M1^† Pegasus XL Proton-M PSLV Qased Safir Shavit Simorgh^† Soyuz-2 2.1a / STA 2.1b / STB 2-1v Unha Vega Zenit 3SL 3SLB 3F Zhuque-1^†
In development	Angara 1.2 Ariane 6 Bloostar Cyclone-4M Eris Firefly Alpha Beta H3 Hyperbola-2 Irtysh Kuaizhou 21 31 Long March 8 9 Miura 5 New Glenn New Line 1 Nuri OmegA OS-M2 OS-M4 Orbex Prime SLS Soyuz-7 SSLV Starship Terran 1 Vega C Vega E Vulcan Zero Zhuque-2
Retired	Antares 110 120 130^† 230 Ariane 1 2 3 4 ASLV Athena I II Atlas B D E/F G H I II III LV-3B SLV-3 Able Agena Centaur Black Arrow Conestoga^† Delta A B C D E G J L M N 0100 1000 2000 3000 4000 5000 II III IV Diamant Dnepr Energia Europa^† Falcon 1 Falcon 9 v1.0 v1.1 v1.2 "Full Thrust" Feng Bao 1 GSLV Mk I H-I H-II H-IIB Juno I Juno II Kaituozhe-1 Kosmos 1 2I 3 3M Lambda 4S Long March 1 1D^† 2A 2E 3 3B 4A Mu 4S 3C 3H 3S 3SII V N1^† N-I N-II Naro-1 Paektusan Pilot-2^† R-7 Luna Molniya M L Polyot Soyuz original FG L M U U2 Soyuz/Vostok Sputnik Voskhod Vostok L K 2 2M R-29 Shtil' Volna^† Saturn I IB V Scout SLV Space Shuttle SPARK^† Sparta SS-520 Start-1 Thor Able Ablestar Agena Burner Delta DSV-2U Thorad-Agena Titan II GLV IIIA IIIB IIIC IIID IIIE 34D 23G CT-3 IV Tsyklon 2 3 Universal Rocket UR-500 Proton Proton-K Rokot Strela Vanguard VLS-1^† Zenit 2 2M
Classes	Sounding rocket Small-lift launch vehicle Medium-lift launch vehicle Heavy-lift launch vehicle Super heavy-lift launch vehicle
This Template lists historical, current, and future space rockets that at least once attempted (but not necessarily succeeded in) an orbital launch or that are planned to attempt such a launch in the future Symbol ^† indicates historical or current rockets that attempted orbital launches but did not ever succeed (never did or has performed a successful orbital launch)

Orbital launch systems developed in the United States
Active	Antares 230+ Atlas V Delta IV Heavy Falcon 9 Block 5 Falcon Heavy Minotaur I IV V C Pegasus
In development	Astra Firefly Alpha Beta LauncherOne New Glenn OmegA SLS Starship Terran 1 Vulcan
Retired	Antares 110/120/130/230 Athena I II Atlas B D E/F G H I II III LV-3B SLV-3 Able Agena Centaur Conestoga Delta A B C D E G J L M N 0100 1000 2000 3000 4000 5000 II III IV Falcon 1 Falcon 9 v1.0 v1.1 v1.2 "Full Thrust" H-I* Juno I Juno II N-I* N-II* Pilot Saturn I IB V Scout Space Shuttle SPARK Sparta Thor Able Ablestar Agena Burner Delta DSV-2U Thorad-Agena Titan II GLV IIIA IIIB IIIC IIID IIIE 34D 23G CT-3 IV Vanguard
* - Japanese projects using US rockets or stages