The Lunar Module Adapter is shown here attached to the Saturn IV-B stage.
In this historical photo from the U.S. space agency, attached to the Saturn IV-B stage on Oct. 11, 1968, the Lunar Module Adapter's four panels are retracted to the fully open position. This is where the Lunar Module (LM) is stored during launch. On missions requiring the use of a LM, the four panels would be retracted and jettisoned before rendezvous and docking.
This photo was taken during the Apollo 7 mission, when no Lunar Module was carried. The SIV-B stage flew as the second stage on a Saturn IB rocket. It is also used as the third stage on the Saturn V. The Apollo 7 mission was designed to test the Apollo Command and Service Module spacecraft systems specifically. Apollo 9 was the first mission to fly the Lunar Module.
Each weekday, SPACE.com looks back at the history of spaceflight through photos (archive).