The Minuteman third stage, that originally contained three 440 pound nuclear weapons, is being replaced with the more capable one from the Peacekeeper ICBM. The Minuteman III is 70 feet long, 5.5 feet in diameter and weighs 32 tons. The Peacekeeper is a four stage missile that carried ten warheads. The Peacekeeper is 71 feet long, 7.7 feet in diameter and weighs 88 tons. The Peacekeeper is being taken out of service because not many (50) were put into service before the Cold War ended, and disarmament treaties outlawed some of its features.
The upgraded Minuteman III is expected to remain in service until 2020, at which point it will be replaced by a new missile design. Current disarmament treaties have the United States reducing nuclear warheads to fewer than 2,200 in the next few years.
The U.S. Air Force continues to upgrade its Minuteman III missiles, a process that will continue through the end of the decade. The upgrades include new electronics and rocket motors, as well as improvements in the silos and communications. The air force is also looking into using ICBMs with conventional warheads, and GPS guidance to enable the Minuteman to take out small targets quickly.