page_title: LGM-118 Peacekeeper
section_title: MX
hierarchical_section_title: LGM-118 Peacekeeper / Development and deployment / MX
context_page_description: The LGM-118 Peacekeeper, first known as the MX or "Missile-X", was an MIRV-capable intercontinental ballistic missile produced and deployed by the United States from 1985 to 2005. The missile could carry up to 12 re-entry vehicles, each armed with a 300-kiloton W87 warhead in a Mk.21 reentry vehicle. Initially, 100 MX ICBMs were planned to be built and deployed, but budgetary concerns eliminated the final procurement. Disarmament treaties signed after the Peacekeeper's development concluded in its eventual withdrawal from service in 2005.
  Although larger than the LGM-30 Minuteman, the MX was designed to fit inside existing hardened LGM-30 Minuteman ICBM silos as a silo-based ICBM and later as a mobile ICBM via the Peacekeeper Rail Garrison. The first 50 MX ICBMs were scheduled to be deployed and full initial operational capability achieved by the United States beginning and ending in 1986. The first 50 missiles were deployed starting in 1986, after a long and contentious development program that traced its roots into the 1960s with the first generation ICBMs. Initial LGM-118A missile testing began in 1971, with full-scale development starting in 1974.
context_section_description: In 1971, the Air Force started a requirements development process combining the ICBM-X and SABRE concepts into a single platform, "Missile, Experimental", or MX. The new missile would have enough accuracy and warhead payload that even a few survivors would be able to destroy enormous numbers of any remaining Soviet force. The specifications for MX were fixed in February 1972, and the advanced development program started in late 1973. At the time, MX was to be based in existing Minuteman silos, in keeping with the original ICBM-X concept of MX as essentially a bigger Minuteman. The larger size of the missile being stationed in a tighter silo, not initially designed for it, resulted in the missile-body notably including graphite lubrication blocks being fixed to the midsection of the missile, as seen in pictures and being jettisoned in videos of the missile launching.
  For MX, the Draper Laboratory developed SABRE into the "Advanced Inertial Reference Sphere" (AIRS). AIRS would have a drift rate of only 1.5 x 10⁻⁵ degrees per hour, allowing it to be periodically referenced to an external point, like the silo wall, and then left for extended periods of time. Over the period of the flight the drift would be so low that any inaccuracies in the platform would account for a maximum of 1% of the warhead's final accuracy–the rest would be due to issues like the timing of the firing of the rocket engines, minor differences in warhead construction, and unavoidable randomness in the atmosphere. The Air Force also contracted with Autonetics for a backup design using mechanical gimbals, the "Advanced Stable Platform" (ASP). In May 1975 the first hand-built AIRS was transferred from Draper's laboratory to Northrop for further development.
caption: Advanced Inertial Reference Sphere
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