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Home > Fact Sheets > Boeing LGM-118A Peacekeeper


Posted 11/13/2014 Printable Fact Sheet
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Missile & Space Gallery
DAYTON, Ohio (04/2008) - The Peacekeeper missile (bottom right corner) is the most recent missile added to the Missile & Space Gallery at the National Museum of the U.S. Air Force. (U.S. Air Force photo)
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Note: The Missile & Space Gallery will close temporarily, beginning Dec. 8, 2014, for approximately five months for construction linking the gallery to the museum's new fourth building. This exhibit will not be accessible during that time. Click here for more information.

The Peacekeeper was the U.S. Air Force's most powerful, accurate and technologically advanced intercontinental ballistic missile (ICBM) when it served as a deterrent from 1986 to 2005. The USAF began planning for a missile to replace Minuteman ICBMs in 1972, and named the projected weapon "missile X," or MX. It would use the latest targeting technology to deliver many independently targeted nuclear warheads by each missile. The ability to deliver several warheads on one missile is known as MIRV, or Multiple Independently targeted Re-entry Vehicles. MX eventually was named Peacekeeper and designated LGM-118A. 

Full-scale development of the Peacekeeper began in 1979, and the first test flight took place in 1983 at Vandenberg AFB, Calif. It became operational in 1986, when ten missiles were deployed at F.E. Warren AFB, Wyo. By 1988, 50 missiles were in service there. 

Basing--whether in stationary hardened silos or on mobile railways that would 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, it was decided to base all LGM-118As in hardened, underground silos. 

Peacekeeper was a four-stage missile, and it was the first U.S. ICBM to use "cold launch" technology. This meant the missile was shot out of a storage canister in a modified Minuteman underground silo by 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, or post-boost vehicle, contained the missile's guidance and re-entry systems. This liquid-fueled stage maneuvered in space to properly orient the re-entry system, which activated and released up to ten nuclear warheads. Each warhead was contained in a small MK-21 re-entry vehicle, and each followed an independent ballistic, or unpowered, path during descent 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 U.S. 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, and thus, spelled the end for Peacekeeper. As a result of the changed strategic world situation, deactivation of all 50 LGM-118As began in 2003 and was completed in 2005. Some Peacekeepers, no longer needed as ICBMs, were used as satellite launch vehicles.

Payload: 10 Avco MK-21 re-entry vehicles
Stages: (1st) solid fuel, Thiokol; (2nd) solid fuel, Aerojet; (3rd) solid fuel, Hercules: (4th) storable liquid fuel, Rocketdyne
Maximum speed: Approximately 15,000 mph
Range: Greater than 6,000 miles
Guidance: Inertial
Height: 71 ft
Weight: 195,000 lbs

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Air Force Space Command: ICBM 50th
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