Delta IX Rocket

In 2020, the  was commissioned by the USSA. The Delta IX Rocket was the last of the manned rockets to the Moon. Almost 15 years later, the Delta IX Rocket was converted for U.S. military purposes. Crew and instrument sections were replaced with a nuclear warhead. The last manned mission to the moon occurred in 2052.

Museum of Technology: Plate transcript
The  is mentioned in Fallout 3's Museum of Technology on a description plate. There's a crashed one located in Vernon Square.