LGM-118 Peacekeeper
The LGM-118 Peacekeeper, originally known as the MX for "Missile, Experimental", was a MIRV-capable intercontinental ballistic missile (ICBM) produced and deployed by the United States from 1985 to 2005. The missile could carry up to twelve Mark 21 reentry vehicles (although treaties limited its actual payload to 10), each armed with a 300-kiloton W87 warhead. Initial plans called for building and deploying 100 MX ICBMs, but budgetary concerns limited the final procurement; only 50 entered service. Disarmament treaties signed after the Peacekeeper's development led to its withdrawal from service in 2005.
"MX missile" redirects here. For the early USAAF missile equipment designation system, see MX missiles.LGM-118 Peacekeeper
United States
- Boeing
- Martin Marietta
- TRW
- Denver Aerospace
US$70,000,000 (equivalent to $194,571,949 in 2023)
87,750 kg
193,460 lb[3]
21.8 m
72 ft[3]
2.34 m
7.7 ft[3]
Ground-burst and/or air-burst fusing modes
- Three-stage solid-fuel rocket
- First stage: Thiokol SR118 solid-fuel rocket motor
- Second stage: Aerojet General SR119 solid-fuel rocket motor
- Third stage: Hercules SR120 solid-fuel rocket motor
- Post-boost vehicle: Rocketdyne restartable liquid-propellant rocket motor; storable hypergolic fuel
First stage: 500,000 pounds-force (2.2 MN)
Approximately 15,000 miles per hour (Mach 20; 24,000 km/h) at burnout[1]
Fixed silo
Studies on the underlying concept started in the 1960s. The idea was to allow the U.S. to absorb a sneak attack by the USSR with enough warheads surviving to attack the remaining Soviet missile silos. To do so, the missiles had to be highly accurate, be based in such a way that enough would survive a nuclear attack, carry a large number of warheads so the survivors would still inflict massive damage, and be able to rapidly re-target so they could be aimed at only those missiles the Soviets had not yet fired. Ultimately, the only problem that was never completely solved was the issue of basing; over its development through the 1970s, MX emerged as a highly accurate, rapid-firing, and quickly retargeted system.
Initial development began in 1971, with full-scale development starting in 1974. President Jimmy Carter ordered initial production in 1979 but was overturned by Congress. After considerable debate about the system, in October 1982, President Ronald Reagan announced that 50 of the newly named Peacekeepers would be put into service in existing LGM-30 Minuteman silos, a temporary measure until final basing was decided. The first flight test took place in 1983, which included the successful launch of six inert re-entry vehicles, each hitting pre-planned targets. It was the first U.S. ICBM to use a cold launch system, and it reached initial operational capability in 1986.
Meanwhile, the United States and the Soviet Union were negotiating the START II treaty, under which ICBMs were allowed to carry only a single warhead each. Because the Minuteman could carry a single warhead for far less money, the United States agreed to remove the Peacekeeper from their nuclear force in this treaty.
Despite the U.S. withdrawal from the Anti-Ballistic Missile Treaty and the subsequent Russian withdrawal from the START II on 14 June 2002, the last Peacekeeper missile was deactivated on 19 September 2005. Their advanced W87 warheads were moved to the Minuteman III.
The private launch firm Orbital Sciences Corporation has developed the Minotaur IV, a four-stage civilian expendable launch system using old Peacekeeper components.
Retirement and deactivation[edit]
The missiles were gradually retired, with 17 withdrawn during 2003, leaving 29 missiles on alert at the beginning of 2004, and only 10 by the beginning of 2005. The last Peacekeeper was removed from alert on 19 September 2005 during the final deactivation ceremony when the 400th Missile Squadron was inactivated as well. During the ceremony an Under Secretary of the Air Force credited the Peacekeeper with helping to end the Cold War.[2]
The Peacekeeper rockets were converted to the satellite launcher role by Orbital Sciences, as the Minotaur IV (OSP-2), while the warheads were redeployed on the existing Minuteman III missiles. Parts of the missile Roll Control System (RoCS) were reused during the Ares I-X test for the Constellation program.