The Minuteman missile system was a radical departure from regular Intercontinental Ballistic Missile development. While the Atlas and Titan missiles were very large, used liquid fuels and required a great deal of maintenance – Minuteman was about the opposite of all of those things.
Seen from left to right, Atlas, Titan-I, Titan-II and Minuteman
Minuteman-II would greatly improve on Minuteman-I by the mid-1960s by incorporating enhanced electronics, better accuracy, increased survivability against attack and a longer range. Minuteman-II would prove such a good weapons system that then Secretary of Defense Robert McNamara decided that only one wing (later a squadron) would be built expressly for Minuteman-II (Grand Forks) while many original Minuteman-I sites would merely be updated to accept the new model. The type would serve in the U.S. arsenal until 1995.
Development on the Minuteman system was not yet complete however as development of the MIRV (Multiple, Independent Reentry Vehicle) was ongoing and soon to be deployed atop the Minuteman III missile. Built upon the successful Minuteman II missile, aside from MIRV Minuteman III could boast even greater accuracy with an improved “third-stage” thrust system (providing finer control over a portion of the missile’s flight time) and a post third-stage “Bus” – a sort of a “fourth-stage” that carried the warheads and could fine-tune the trajectories of its MIRVs.
So what are MIRVs anyway? Before Minuteman III ICBMs could only deploy a single warhead to their targets. The U.S. Navy Polaris A-3 missile meanwhile deployed in 1964 could deliver MRVs (Note: not MIRVS). The MRV (this variant sometimes called “The Claw”) lacked the “independent” ability to maneuver warheads to specified targets and could “shotgun” a target area with multiple warheads.
A Minuteman III Re-entry shroud (right) with its “bus” or reentry system (left)
A MIRV could be guided independently, meaning in the Minuteman III the post-boost “bus” could maneuver in space and point each of its warheads towards specific targets miles a part. MIRVs would enhance the U.S. nuclear arsenal without the cost of building more ICBMs and could potentially overwhelm Anti-Ballistic Missile (ABM) measures to intercept individual warheads. The Soviet Union would later deploy MIRVs of its own, the SS-18 specifically was to be armed with such warheads and was thought to target Minuteman missile fields in the United States.
After a relatively short development time, Minuteman IIIs were deployed beginning in 1970, 1972 at Grand Forks AFB sites. With the Minuteman III still in service, it’s MIRV potential has been downgraded due to international treaties. Many (unknown if all) Minuteman IIIs possess a single nuclear warhead today. Today the U.S. Navy’s Trident II submarine force remain equipped with MIRVs, providing a portion of the American nuclear “triad”.