United Launch Alliance in the context of "Atlas V"

A launch service provider or launch vehicle provider is a type of company that delivers a payload into space, including the delivery of satellites, spacecraft, cargo, astronauts, and potentially space tourists. Services provided may include furnishing launch vehicles, launch support, equipment and facilities, for the purpose of launching satellites into orbits or deep space. These companies and their launch vehicles are in various stages of development, with some (such as SpaceX, Rocket Lab, and ULA) already in regular operation, while others are not.

In 2018, the launch services sector accounted for $5.5 billion out of a total $344.5 billion "global space economy". It is responsible for the ordering, conversion or construction of the carrier rocket, assembly and stacking, payload integration, and ultimately conducting the launch itself. Some of these tasks may be delegated or sub-contracted to other companies. For example, United Launch Alliance formally subcontracted the production of GEM solid rocket motors for their Delta II and Delta IV (Medium version) rockets to Alliant Techsystems. (Both vehicles are now retired.) An LSP does not necessarily build all the rockets it launches.

Delta IV was a group of five expendable launch systems in the Delta rocket family. It flew 45 missions from 2002 to 2024. Originally designed by Boeing's Defense, Space and Security division for the Evolved Expendable Launch Vehicle (EELV) program, the Delta IV became a United Launch Alliance (ULA) product in 2006. The Delta IV was primarily a launch vehicle for military payloads for the United States Air Force (USAF), but was also used to launch a number of United States government non-military payloads and a single commercial satellite.

The Delta IV had two main versions, which allowed the family to cover a range of payload sizes and masses: Medium, which had four configurations, and Heavy. The final flight of a Medium configuration occurred in 2019. The final flight of Heavy was in April 2024.

The Centaur is a family of rocket-propelled upper stages that has been in use since 1962. It is currently produced by United Launch Alliance (ULA) in two main versions. The 3.05 m (10 ft) diameter Centaur III (also known as the Common Centaur) serves as the second stage of the retiring Atlas V rocket, and the 5.4 m (17.7 ft) diameter Centaur V is used as the second stage of the Vulcan Centaur rocket. Centaur was the first rocket stage to use hydrolox propellant—liquid hydrogen (LH₂) and liquid oxygen (LOX)—a high-energy combination well suited for upper stages but difficult to handle because both propellants must be stored at extremely low cryogenic temperatures.

The Delta IV Heavy (Delta 9250H) was an expendable heavy-lift launch vehicle, the largest member of the Delta IV family. Following the retirement of the Space Shuttle in 2011, it was the most capable operational launch vehicle until the Falcon Heavy's debut in 2018. At the time of its retirement in 2024, it ranked third among active rockets in payload capacity. Developed by Boeing and later manufactured by United Launch Alliance (ULA), it first flew in 2004. The Delta IV Heavy was retired after its 16th and final launch on 9 April 2024 and was succeeded by ULA's Vulcan Centaur rocket, which can offer similar heavy-lift capabilities at a lower cost with a single-core and six solid rocket boosters.

The vehicle consisted of three Common Booster Cores (CBCs), each powered by an RS-68 engine. Two served as strap-on boosters attached to a central core. During ascent, all three engines ignited at liftoff, with the central engine throttling down partway through flight to conserve propellant before throttling up again after booster separation.