Sputnik Escalates the Cold War
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MX Missile System

Title: MX Missile (Peacekeeper MGM-118A)
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The Mobile Experimental (MX) missile was a U.S. intercontinental ballistic missile (ICBM) and centerpiece of the U.S. arms buildup of the late 1970s and 1980s. The MX, formally known as the LGM-118A Peacekeeper, was a four-stage rocket. The largest ICBM ever in the U.S. arsenal, the MX was 71′ in length and 7′8″ in diameter and weighed at launch some 198,000 pounds. The first three stages were of solid propellant, while the fourth was liquid propelled. The MX had a range of greater than 6,000 miles and a speed at burnout of up to 15,000 miles per hour. The MX carried ten Avco MJ 21 multiple independently targeted reentry vehicles (MIRVs)—its predecessor, the Minuteman III had only three, less powerful warheads—and was believed to be more accurate than any other ICBM. The MX missiles were ultimately placed in canisters in former Minuteman silos to protect them against damage and give them a cold-launch capability. At launch, the Peacekeeper was ejected by pressurized gas some 50 feet in the air before first-stage ignition occurred, the first ICBM to employ such technology.

Development of the Peacekeeper began in 1971 with the search for a successor to the Minuteman, sparked by a perceived growing threat from Moscow in the form of more accurate Soviet missiles. The Strategic Air Command (SAC) sought a missile with greater range, increased accuracy, and variable yield warheads that could take advantage of MIRV technology and counter the new monster Soviet SS-18 missile capable of launching ten warheads at separate targets. Many experts held that deployment of such a missile with a first-strike capability would be destabilizing, and this, along with funding issues and basing questions, impeded development.

Concerned about vulnerability to a Soviet first strike, in 1976 Congress passed legislation blocking funding for any ICBM situated in a fixed silo. The U.S. Air Force then presented a variety of different plans. Finally, in 1976 President Jimmy Carter's administration adopted the shell game plan in which 200 MX missiles would each be shuttled around among 23 different silos. The logic behind this plan was that the Soviets would have to employ 23 warheads to ensure that they had destroyed one MX, or 4,600 warheads to hit them all. When Ronald Reagan became president, he scrapped the Carter mobile plan in favor of placing the MX missiles in existing Minuteman silos.

In 1983 Congress and the Reagan administration reached a compromise. While the MX missiles would be placed in silos, the United States would also build 500 single-warhead ICBMs, dubbed the Midgetman. The Midgetman was never built, however.

The air force successfully carried out the first test of the Peacekeeper missile from Vandenberg Air Force Base, California, on 17 June 1983. Additional tests were conducted from Minuteman test silos. Production of the Peacekeeper began in February 1984, with the first fifty missiles deployed in the Minuteman silos at F. E. Warren Air Force Base, Wyoming. The fiftieth missile was delivered in December 1988.

Additional deployments were halted when in July 1985 Congress cut the total number of MX missiles to only fifty until the Reagan administration could produce a more survivable basing plan. The Reagan administration proposed a rail garrison concept with two missiles on each of twenty-five special trains to be deployed onto the national rail net in periods of international tension. This plan was never implemented, and all fifty missiles were based at F. E. Warren Air Force Base.

As a part of the Strategic Arms Reduction Treaty II (START II), the United States agreed to eliminate its MIRV Peacekeeper ICBMs by the year 2003. The last of the MX missiles went off alert status on 19 September 2005.

Spencer C. Tucker

Further Reading
Graham, Thomas, Jr., and Damien J. LaVera. Cornerstones of Security: Arms Control Treaties in the Nuclear Era. Seattle: University of Washington Press, 2003.

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