MX missile

LGM-118 Peacekeeper
Test launch of a Peacekeeper ICBM by the 1st Strategic Aerospace Division(1 STRAD), Vandenberg AFB, CA (USAF)
Type	Intercontinental ballistic missile
Place of origin	United States
Service history
In service	1986–2005
Used by	United States Air Force
Production history
Manufacturer	Boeing, Martin Marietta, TRW, and the Denver Aerospace company
Unit cost	Approximately $70 million
Specifications
Weight	96.75 tons (195,000 lb; 88,450 kg)
Length	71 ft 6 in (21.8 m)
Diameter	7 ft 7 in (2.3 m)
Warhead	Up to 10 Avco Mk21 re-entry vehicles each carrying a 300 kt W87-0 warhead or a 475 kt W87-1/W88 warhead; or 12 Avco Mk12 re-entry vehicles each carrying a 335–350 kt W78 warhead plus decoys
Detonation mechanism	Ground-burst and/or air-burst fusing modes
Engine	Three-stage solid-fuel rocket. First stage: 500,000 lbf (2.2 MN thrust) 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
Operational range	7,560 nmi (14,000 km; 8,700 mi)
Guidance system	Inertial (AIRS)
Accuracy	393 ft 7 in (120 m) CEP
Launch platform	Fixed silo

The LGM-118 Peacekeeper, also known as the MX missile (for Missile-eXperimental), was a land-based ICBM deployed by the United States starting in 1986. The Peacekeeper was a MIRV missile that could carry up to 10 re-entry vehicles, each armed with a 300-kiloton W87 warhead in a Mk.21 reentry vehicle (RV). A total of 50 missiles were deployed starting in 1986, after a long and contentious development program that traced its roots into the 1960s.

MX was designed to allow the US to ride out a sneak attack by the Soviet ICBM fleet and then launch a counterattack. In order for the counterattack to be effective, MX had to have three qualities; the ability to be rapidly re-targeted so it would only be attacking those Soviet missiles known to still be in their silos, enough accuracy to allow a small warhead to kill an enemy silo so more warheads could be packed on a single MX missile, and a basing system that meant enough of the missiles would survive an attack that the counterattack would be effective. Among these three, the basing issue remained an unsolved problem and the subject of much criticism during the MX's development.

After considerable debate, President Reagan announced that the newly named Peacekeeper would be put into service in existing LGM-30 Minuteman silos, a temporary solution until a final basing solution was decided on. During the same period, the US and USSR were involved in negotiations on the START II treaty, under which ICBMs were allowed to carry only a single warhead. As the Minuteman fleet could carry a single warhead for far less money, and the Peacekeeper was proving highly unreliable in the field, the US agreed to remove the Peacekeeper from their nuclear force as part of this treaty. Although START II was not ratified by the United States, the missiles were removed anyway, with the last one going out of service on 19 September 2005. Their advanced W87 warheads were slated to be 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.