The final half-decade of launches in the Thor/Delta family consisted of one Delta IV Heavy each year from 2020 through 2024. This followed the retirement of Delta II in 2018 and single-stick (non-Heavy) variants of the Delta IV in 2019. With the start of 2024, Vulcan Centaur took its first flight in time to maintain continuity of ULA's service in the heavy-lift launch vehicle market before the Delta IV Heavy program came to an end three months later on April 9, 2024.
Reconnaissance satellite, likely an Orion satellite.[2] Launch attempts on 29 August and 30 September were aborted due to problems with the Ground Service Equipment (GSE).[3][4] The rocket finally lifted off on 11 December.