LGM-30 Minuteman

The LGM-30 Minuteman is an American land-based intercontinental ballistic missile (ICBM) in service with the Air Force Global Strike Command. As of 2025^[update], the LGM-30G (Version 3) is the only land-based ICBM in service in the United States and represents the land leg of the U.S. nuclear triad, along with the Trident II submarine-launched ballistic missile (SLBM) and nuclear weapons carried by long-range strategic bombers.

Development of the Minuteman began in the mid-1950s when basic research indicated that a solid-fuel rocket motor could stand ready to launch for long periods of time, in contrast to liquid-fueled rockets that required fueling before launch and so might be destroyed in a surprise attack. The missile was named for the colonial minutemen of the American Revolutionary War, who could be ready to fight on short notice.

The Minuteman entered service in 1962 as a deterrence weapon that could hit Soviet cities with a second strike and countervalue counterattack if the U.S. was attacked. However, the development of the United States Navy (USN) UGM-27 Polaris, which addressed the same role, allowed the Air Force to modify the Minuteman, boosting its accuracy enough to attack hardened military targets, including Soviet missile silos. The Minuteman II entered service in 1965 with a host of upgrades to improve its accuracy and survivability in the face of an anti-ballistic missile (ABM) system the Soviets were known to be developing. In 1970, the Minuteman III became the first deployed ICBM with multiple independently targetable reentry vehicles (MIRV): three smaller warheads that improved the missile's ability to strike targets defended by ABMs. However, the Minutemen III missiles were later "de-MIRVed"; since 2016 they have had only a single warhead per missile, either a W78 (335 kT) or W87 (300 kT).

By the 1970s, 1,000 Minuteman missiles were deployed. This force had shrunk to 400 Minuteman III missiles as of September 2017^[update], deployed in missile silos around Malmstrom AFB, Montana; Minot AFB, North Dakota; and Francis E. Warren AFB, Wyoming. The Minuteman III will be progressively replaced by the new LGM-35 Sentinel ICBM, to be built by Northrop Grumman, beginning in 2030.

Minuteman owes its existence largely to Air Force Colonel Edward N. Hall, who in 1956 was given charge of the solid-fuel-propulsion division of General Bernard Schriever's Western Development Division, which was originally created to lead development of the SM-65 Atlas and HGM-25A Titan I ICBMs. Solid fuels were already commonly used in short-range rockets. Hall's superiors were interested in short- and medium-range missiles with solids, especially for use in Europe where the fast reaction time was an advantage for weapons that might be attacked by Soviet aircraft. But Hall was convinced that they could be used for a true ICBM with a 5,500-nautical-mile (10,200 km; 6,300 mi) range.

To achieve the required energy, that year Hall began funding research at Boeing and Thiokol into the use of ammonium perchlorate composite propellant. Adapting a concept developed in the UK, they cast the fuel into large cylinders with a star-shaped hole running along the inner axis. This allowed the fuel to burn along the entire length of the cylinder, rather than just the end as in earlier designs. The increased burn rate meant increased thrust. This also meant the heat was spread across the entire motor, instead of the end, and because it burned from the inside out it did not reach the wall of the missile fuselage until the fuel was finished burning. In comparison, older designs burned primarily from one end to the other, meaning that at any instant one small section of the fuselage was being subjected to extreme loads and temperatures.

Guidance of an ICBM is based not only on the direction the missile is traveling but the precise instant that thrust is cut off. Too much thrust and the warhead will overshoot its target, too little and it will fall short. Solids are normally very hard to predict in terms of burn time and their instantaneous thrust during the burn, which made them questionable for the sort of accuracy required to hit a target at intercontinental range. While this initially appeared to be an insurmountable problem, it ended up being solved in an almost trivial fashion. A series of ports were added inside the rocket nozzle that were opened when the guidance systems called for engine cut-off. The reduction in pressure was so abrupt that the remaining fuel broke up and blew out the nozzle without contributing to the thrust.

The first to use these developments was the US Navy. It had been involved in a joint program with the US Army to develop the liquid-fueled PGM-19 Jupiter, but had always been skeptical of the system. The Navy felt that liquid fuels were too dangerous to use onboard ships, especially submarines. Rapid success in the solids development program, combined with Edward Teller's promise of much lighter nuclear warheads during Project Nobska, led the Navy to abandon Jupiter and begin development of their own solid-fuel missile. Aerojet's work with Hall was adapted for their UGM-27 Polaris starting in December 1956.