The Post Boost Vehicle, fourth stage of the Peacekeeper Intercontinental Ballistic Missile, is installed for testing in the Arnold Engineering Development Center J-3 test cell at Arnold Air Force Base in the early 1990s. The Post Boost Vehicle provided all the propulsion for the fourth stage. This year marks the 60th anniversary of completion of the construction on J-3 and the initiation of the first operational test in the cell. (U.S. Air Force photo)