A Delta IV Heavy booster from a United Launch Alliance barge, known as the RocketShip, proceeds to the Horizontal Integration Facility May 4, 2020, at Vandenberg Air Force Base, Calif. A HIF is a building within which the stages of a multistage rocket are brought together before the assembled stack is rolled out to the launch pad or space launch complex and raised into a vertical position for final integration and launch. (Courtesy photo)