The Atlas V rocket is an expendable launch vehicle formerly built by Lockheed Martin and now built by the Lockheed Martin-Boeing joint venture United Launch Alliance. Aerojet develops and manufactures the Atlas V boosters. The rocket, built in Decatur, Alabama, consists of a first stage powered by kerosene and liquid oxygen, which uses a Russian-made RD-180 engine, and a liquid hydrogen–liquid oxygen powered Centaur upper stage. Some configurations also use strap-on booster rockets. Together these components are referred to as the Atlas V launch vehicle.