EELV

Evolved Expendable Launch Vehicle (EELV) is a United States government program to develop a family of expendable launch vehicles designed to provide reliable and cost-effective access to space for national security payloads and other government missions.

The program began in the 1990s as an effort by the U.S. Air Force and NASA to replace aging Atlas and Delta launch systems with a more capable, standardized set of launch vehicles. Key goals included improving reliability, reducing life-cycle costs, and standardizing interfaces and production processes to enable competition and streamlined procurement.

Two primary families emerged from the EELV program: Atlas V and Delta IV. Both are produced and managed by the United Launch Alliance (ULA), a joint venture between Lockheed Martin and Boeing established to oversee EELV development and production. The Atlas V and Delta IV have been used for a wide range of national security payloads and other missions, benefiting from common design principles and production efficiencies.

Atlas V configurations vary by payload fairing size and launch vehicle length, and it has historically used the Russian RD-180 engine on the first stage for many variants. Delta IV offers several variants, including heavier lift versions, with different core configurations and engines such as the RS-68 family.

Future plans include the Vulcan Centaur, intended to replace both Atlas V and Delta IV in the evolving launch landscape. Vulcan Centaur is designed to use BE-4 engines and an upgraded upper stage, aligning with longer-term national launch needs.

In common usage, EELV refers to the DoD/NASA program-driven family of expendable launch vehicles developed to ensure assured access to space.