United States · 2006–
United Launch Alliance
Joint venture between Lockheed Martin Space and Boeing Defense, Space & Security that designs, integrates and launches rockets (Atlas V, Vulcan Centaur), mainly for the Department of Defense and NASA.
Catalog — Rockets
- 2006
Atlas V 551
The Atlas V 551 is the most powerful faired configuration of the Atlas V, not a separate rocket. Atlas V is an expendable launch system, the fifth major version of the Atlas family, developed by Lockheed Martin and operated since 2006 by United Launch Alliance. Each vehicle has two main stages: a first stage, the Common Core Booster, powered by a single Russian RD-180 engine burning kerosene and liquid oxygen, and a Centaur upper stage with one or two RL10 engines burning liquid hydrogen and liquid oxygen. Each configuration is identified by three digits. The first indicates the payload fairing diameter, the second the number of solid rocket boosters, and the third the number of Centaur engines. The 551 is therefore the variant with a 5.4-metre fairing, five solid rocket boosters — the maximum possible — and a single-engine Centaur. It is the most capable configuration of the faired series: about 18,814 kg to low Earth orbit and 8,900 kg to geostationary transfer orbit, with an advertised base price of US$153 million, the highest in the Atlas V catalogue. That capability made it the choice for the programme's most demanding missions: interplanetary probes such as New Horizons and Juno, MUOS and AEHF military communications satellites, and, in its final years, Amazon's internet constellation deployments. Atlas V is being retired; the 551 configuration flew for the last time on 2 July 2026, after 23 launches.