page_title: Atlas V
section_title: Versions
hierarchical_section_title: Atlas V / Versions
context_page_description: Atlas V is the fifth major version in the Atlas rocket family. It is an expendable launch system originally designed by Lockheed Martin, now being operated by United Launch Alliance, a joint venture between Lockheed and Boeing.
  Each Atlas V rocket consists of two main stages. The first stage is powered by a Russian RD-180 engine manufactured by RD Amross and burning kerosene and liquid oxygen. The Centaur upper stage is powered by one or two US RL10 engine manufactured by Aerojet Rocketdyne and burning liquid hydrogen and liquid oxygen. AJ-60A strap-on solid rocket boosters are used in some configurations and will be replaced by GEM-63 SRBs in the near future. The standard payload fairings are 14 or 18 feet in diameter with various lengths.
context_section_description: Each Atlas V booster configuration has a three-digit designation. The first digit shows the diameter (in meters) of the payload fairing and has a value of "4" or "5" for fairing launches and "N" for crew capsule launches (as no payload fairing is used when a crew capsule is launched). The second digit indicates the number of solid rocket boosters (SRBs) attached to the base of the rocket and can range from "0" through "3" with the 4-meter (13 ft) fairing, and "0" through "5" with the 5-meter (16 ft) fairing. As seen in the first image, all SRB layouts are asymmetrical. The third digit represents the number of engines on the Centaur stage, either "1" or "2".
  For example, an Atlas V 551 has a 5-meter fairing, 5 SRBs, and 1 Centaur engine, whereas an Atlas V 431 has a 4-meter fairing, 3 SRBs, and 1 Centaur engine. The Atlas V N22 with no fairing, two SRBs, and 2 Centaur engines was first launched in 2019. The flight carried the Starliner vehicle for its first orbital test flight.
  As of June 2015, all versions of the Atlas V, its design and production rights, and intellectual property rights are owned by ULA and Lockheed Martin.
caption: Atlas V family with asymmetric SRBs. The HLV was not developed
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