Martin Marietta LGM-118A Peacekeeper The Peacekeeper served as the U.S. Air Force’s most powerful, accurate and technologically advanced Intercontinental Ballistic Missile (ICBM) deterrent from 1986 to 2005. Conceived to replace the Minuteman ICBMs, its development began in the early 1970s under the name “Missile, Experimental,” or MX. Later, it received the official name “Peacekeeper,” and the first test flight took place in 1983 at Vandenberg AFB, Calif. It became operational in 1986, when 10 missiles were deployed at F.E. Warren AFB, Wyo. By 1988, the USAF had 50 missiles in service there. Whether to base the missile inside a stationary, hardened silos or on mobile railways to keep the Soviets guessing at the missiles’ true location was a major issue during Peacekeeper's development. Funding problems and competing ideas about the wisdom of each basing solution delayed Peacekeeper production and deployment. Eventually, the USAF decided to place all LGM-118As into hardened, underground silos previously used by Minuteman ICBMs. Many contractors worked on the Peacekeeper, but Martin Marietta and Denver Aerospace (now Lockheed Martin) assembled and tested the Peacekeepers. Constructed with an airframe made of a Kevlar epoxy composite, the Peacekeeper was much lighter than previous ICBMs, and it could carry more warheads. When combined with new Multiple Independently Targeted Re-entry Vehicles (MIRV) technology, one Peacekeeper could accurately deliver a number of nuclear warheads on different targets at the same time. A four-stage missile, Peacekeeper was the first Air Force ICBM to use the “cold launch” technique similar to the system used to launch missiles from submarines. This procedure shot the missile out of a modified Minuteman underground silo with a massive burst of high-pressure steam, and its first-stage solid-rocket motor ignited only after the missile cleared the silo. The next two stages, also solid-fuel rockets, boosted the missile's payload into space. The fourth stage, also known as the post-boost vehicle, was liquid-fueled, and it contained the missile’s guidance and re-entry systems. After maneuvering in space to properly orient the re-entry system, the fourth stage activated and released up to 10 nuclear warheads. Each warhead -- contained in a small, unpowered MK-21 re-entry vehicle -- descended on an independent ballistic path to its target. Accuracy depended on the warheads being released in the right direction at the proper altitude and speed. The Peacekeeper modernized and improved the United States’ nuclear deterrence, but the end of the Cold War made its mission less crucial. The Strategic Arms Reduction Treaty (START) II, signed in 1993 with Russia, removed all multiple-warhead ICBMs. As a result of the changed strategic world situation and START II, the United States deactivated all 50 LGM-118As between 2003 and 2005. Some Peacekeepers were eventually used as satellite launch vehicles. TECHNICAL NOTES: Payload: 10 Avco MK-21 re-entry vehicles Stages: (1st) solid fuel, by Thiokol; (2nd) solid fuel, by Aerojet; (3rd) solid fuel, by Hercules; (4th) storable liquid fuel, by Rocketdyne Maximum speed: Approx. 15,000 mph Range: Greater than 6,000 miles Guidance: Inertial Height: 71 feet Weight: 195,000 lbs. Click here to return to the Missile Gallery. Find Out More Related Fact Sheets Peacekeeper Re-entry Vehicles & Deployment Bus Other Resources Air Force Space Command: ICBM 50th Note: The appearance of hyperlinks does not constitute endorsement by the National Museum of the USAF, the U.S. Air Force, or the Department of Defense, of the external website, or the information, products or services contained therein.