The Atlas G, also known as Atlas G Centaur-D1AR
/ref> was an American expendable launch system derived from the

Atlas-Centaur The Atlas-Centaur was a United States expendable launch vehicle derived from the SM-65 Atlas D missile. Launches were conducted from Launch Complex 36 at the Cape Canaveral Air Force Station (CCAFS) in Florida. Early development Convair, ...

. It was a member of the

Atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geograp ...

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 The Atlas I was a US expendable launch system manufactured by General Dynamics in the 1990s to launch a variety of satellites. In June 1987, General Dynamics committed $100M to acquire long-lead procurement items to support build of 18 vehicles ...

, 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. The first stage was derived from the

SM-65 Atlas The SM-65 Atlas was the first operational intercontinental ballistic missile (ICBM) developed by the United States and the first member of the Atlas rocket family. It was built for the U.S. Air Force by the Convair Division of General Dy ...

missile, and a Centaur was used as the second stage.Encyclopedia Astronautica - Atlas
/ref> The first stage was also flown without the Centaur, as the

Atlas H The Atlas H was an American expendable launch system derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was used to launch five clusters of NOSS satellites for the US National Reconnaissance Office. Two fli ...

References

Rockets and missiles Atlas (rocket family) {{rocket-stub