United Launch Alliance (ULA) is preparing to launch its final Atlas 5 rocket for the U.S. military on July 30.

The mission, designated USSF-51, will carry a classified payload to geostationary Earth orbit from Cape Canaveral Space Force Station. This marks ULA’s 100th national security launch and the 53rd for the Atlas 5 rocket.

USSF-51 is the first ULA mission under the National Security Space Launch (NSSL) Phase 2 contract, awarded in 2020 to ULA and SpaceX.

While SpaceX has already conducted a Phase 2 launch, ULA’s Vulcan Centaur rocket, intended to replace the Atlas 5 and Delta 4, has faced delays, pushing its first launch to January 2024.

Consequently, USSF-51 was reassigned from Vulcan to Atlas 5 to ensure schedule reliability, Space News has reported.

Although the Atlas 5 will retire from the NSSL program, ULA plans to use the remaining rockets for 16 commercial and non-defense missions.

Meanwhile, ULA is preparing two additional NSSL missions for the Vulcan Centaur, with a certification launch scheduled for September 2024.

Written by B.C. Begley