Each Atlas V rocket consists of two main stages. The first stage is powered by a Russian RD-180 engine manufactured by Energomash and burning kerosene and liquid oxygen. The Centaur upper stage is powered by one or two American RL10 engine(s) manufactured by Aerojet Rocketdyne and burning liquid hydrogen and liquid oxygen. The Star 48 upper stage was used on the New Horizons mission as a third stage. AJ-60A strap-on solid rocket boosters (SRBs) are used in some configurations. In November 2020, they were replaced by the GEM-63 SRBs. The standard payload fairings are 4.2 or 5.4 m (14 or 18 ft) in diameter with various lengths. YouTube Video Streamed Live on May 18, 2021 | ULA's Atlas V rocket launches SBIRS GEO-5 \ufeff Boeing and NASA will hold a news conference today (Aug. 13) to discuss the delay of the Starliner Orbital Flight Test 2 (OFT-2) mission to the International Space Station. Starliner was scheduled to launch to the orbiting laboratory July 30, but a mishap with the docking of Russia's new Nauka module \u2014 followed by newly discovered valve issues on Starliner \u2014 have delayed the mission indefinitely. Hear NASA and Boeing officials provide an update on Starliner's latest launch delays in a teleconference beginning at 1 p.m. EDT (1700 GMT). You can tune in live in the window above, courtesy of NASA, or directly via the agency's website.