United Launch Alliance, formed in 2006 to merge the Boeing and Lockheed Martin launch vehicle programs, has flown 100 national security missions over the last 18 years using the Delta II, Delta IV, and Atlas V rocket families. USSF-51 was ULA’s 100th national security launch, and the last ever flown by an Atlas-family rocket.
An Atlas V 551, AV-101, was rolled out to Space Launch Complex-41 at the Cape Canaveral Space Force Station to fly a classified national security payload for the US Space Force. The USSF-51 mission successfully launched on Tuesday, July 30, at 6:45 AM EDT (10:45 UTC), at the beginning of a five-hour launch window. This window closed at 11:45 AM EDT (15:45 UTC).