March 14,2008: The U.S. Air Force has completed upgrading the guidance systems of its 450 LGM-30 Minuteman III ICBMs. The new guidance system, the NS50, has about the same performance as the one it replaced, but is more reliable and easier to maintain. Each new guidance system cost about $4 million.

The upgrading of the older Minuteman III missiles has been under way for nearly a decade now. The air force has also replaced decades old solid fuel rockets in its missiles. Actually, a test of a 33 year old Minuteman I rocket motor showed that it (actually, a long tube full of slow burning explosives) still performed according to specification. The last of the Minuteman III missiles will receive their new motors this year. It costs about $5.2 million to replace the rockets on each missile. Finally, to comply with disarmament agreements, the Minuteman third stage, that contains three 440 pound nuclear weapons, will be replaced with a warhead containing one 600 pound nuclear weapon. Also part of meeting disarmament treaty obligations, the most recent U.S. ICBM design, the Peacekeeper LGM-118A (formerly called the MX), has been retired. The Peacekeeper entered service in 1986, as the ultimate Cold War era ICBM. Three years ago, the last Peacekeepers were taken out of service.

The Minuteman III entered service in 1968, while the Minuteman I became operational in 1962, as the first solid fueled ICBM. The Minuteman III is 70 feet long, 5.5 feet in diameter and weighs 32 tons. The Peacekeeper is 71 feet long, 7.7 feet in diameter and weighs 88 tons. It is a four stage missile that carries ten warheads. The Peacekeeper has the same range as the Minuteman III, but greater accuracy. The refurbished Minuteman IIIs will have the same accuracy as the Peacekeeper.

Because the Peacekeeper came into use just as the Cold War unexpectedly ended, only fifty were ever put into service. The upgraded Minuteman III is expected to remain in service until 2020, at which point it will be replaced by a new missile design. Current disarmament treaties have the United States reducing nuclear warheads getting below 2,200 in the next few years.

Some $600 million also went to upgrading the computers and equipment in the control rooms from which the missiles are launched. The first six test flights have shown that the new and improved missiles are less accurate and had shorter range than the missiles they replaced. This was somewhat expected. The accuracy problem appears to arise from the decision to keep the 1960s era inertial measurement and just replace the electronics that worked with it. The air force says a software change has fixed the accuracy problem. The shorter range can be attributed to Environmental Protection Agency (EPA) regulations. The old motors did not have to comply with EPA rules, the replacement ones do. This meant the new rocket motors were heavier, which resulted in shorter range. The older Minuteman III motors provided a max range of 9,600 kilometers. Actually, that's an estimate, as the actual range is classified, as is the new, shorter, one. In any event, it's probably much ado about nothing. Losing ten percent of its range won't change anything and, unless the US government is secretly planning to take out Russian missile silos (most Chinese ICBMs are still unprotected), the loss of accuracy is meaningless as well.