New Sentinel ICBM set to replace aging Minuteman III by 2031

By the decade's end, the United States Air Force will introduce the new intercontinental ballistic missile LGM-30A Sentinel into service. It is designed to replace the aging Minuteman family of missiles. This program is one of the key components for the future of American strategic nuclear deterrence, forming the land-based foundation of the nuclear triad.

In addition to land-based ballistic missiles, the United States has shorter-range ballistic missiles launched from specially designed nuclear-powered submarines. They also maintain an air component consisting of atomic bombs (technically thermonuclear) and cruise missiles with nuclear warheads.

The Minuteman family of missiles has been in service since 1962, with the current version being the LGM-30G Minuteman III (its first version entered service in 1970). It is the only variant used by the U.S. Air Force (USAF), which is responsible for the triad's land and air components.

Intercontinental missiles produced by Boeing range from up to 8,700 miles and reach an altitude of 680 miles. In the final phase of flight, the third stage can reach speeds up to 17,400 mph. The Minuteman III is equipped with the MIRV system, allowing it to carry more than one (up to three) warhead carrier (reentry vehicle RV) and launch them independently in different directions. The number was limited to one due to the 1993 START II disarmament treaty, although in practice, most Minuteman missiles were not modified until 2010 (and possibly even later).

It's no surprise since only the U.S. ratified the treaty. RVs of the Mk 12 type with the W78 warhead and the Mk 21 with the W87 warhead remain in use. Due to their significant size (over 60 feet in length) and weight (approximately 79,000 lbs), the three-stage missiles are launched from well-protected underground silos.

Three missile wings—the 90th, 91st, and 341st—are armed with about 400 missiles. All three fall under the Global Strike Command (AFGSC), which also oversees the air wings armed with B-2A and B-52H strategic bombers and soon the B-21 (and the B-1B, though it doesn't carry nuclear weapons).

In the 1980s, the Minuteman III was anticipated to be replaced by the LGM-118 Peacekeeper, which carried up to 6 RVs with higher accuracy at the time (mean error of around 130 to 295 feet). The missile entered service in 1984 but was withdrawn 21 years later due to the ratification of the START II treaty and budgetary issues. Therefore, the aging Minuteman IIIs were modernized.

Currently, the GBSD program is underway, involving the development of the LGM-35A Sentinel. This program is essential due to the expiring life spans of the Minuteman III missiles (already extended multiple times) and the need to maintain the scientific and production capabilities necessary for building such crucial weaponry for the U.S.

The program for developing a new missile and modernizing silos and command centers began in 2016. Lockheed Martin, Boeing, and Northrop Grumman applied to participate in the project. In 2017, the USAF awarded the latter two companies initial work contracts. In 2019, the USAF selected the reentry vehicles and warheads for the new missile: older Mk 21s with the W87 warhead or newer Mk 21As with the W87-1 warhead.

Ultimately, Northrop Grumman remained in the race for the lucrative contract. Boeing withdrew from the project at the end of 2019 because a competitor bought the key rocket engine manufacturer Orbital ATK. The winner had a lot at stake. The contract is valued at $13.3 billion, and the program's total value over the first 20 years is expected to reach $63 billion. When the missiles are retired from service, planned for 2075, this value could rise to $85 billion.

According to a 2023 GAO report (the American equivalent of the NIK), the missile was supposed to enter service in 2030, a year later than anticipated. However, the program's costs were expected to stay within the planned budget. The USAF quickly debunked this optimistic thesis, as by January 2024, it was known that the total costs had risen to $125 billion, and the delay had increased to two years. By July, the Department of Defense estimated costs at nearly $141 billion.

Little is known about the missile itself today. Based on the information disclosed, the USAF plans to purchase 642 production missiles, 400 of which will enter operational service, replacing the aging Minuteman IIIs. The remaining missiles will serve as reserves or be used in tests and exercises. According to current plans, initial operational readiness will be achieved no earlier than 2031, meaning the deployment of the first nine missiles in silos. Unless things change, the USAF is expected to receive one missile per week for about nine years.

Full operational readiness was initially projected for 2036 (after deploying 400 missiles), so today, we can probably talk about 2038. Both virtual prototypes and physical versions of future missile components are being tested in parallel.

Not all tests are successful; for example, on July 6, 2022, a Minotaur II+ rocket exploded 11 seconds into flight with a Mk 21A reentry vehicle on board. Despite this, most components have already been developed, although some still require minor adjustments. Wind tunnel tests and engine tests are also being conducted, and preliminary work is underway on the successor to the Mk 21 family of RVs, tentatively called the NGRV.

During a speech at the Mitchell Institute, Major General Andrew Gebara, Deputy Chief of Staff for Strategic Deterrence and Nuclear Integration, declared that the USAF does not want to slow down or stop the program. However, he indicated that the program requires restructuring, as the costs of the LGM-35A program have already increased by half.

Work on the successor to the Minuteman III is progressing well, and if there are any issues, they do not seem insurmountable. Until the restructuring is completed, there is no talk of achieving the so-called Milestone B, i.e., setting the final budget and schedule for the program, based on which the contractor would continue the work. This could mean further delays and the need to keep the Minuteman missiles in service. However, it seems that the Sentinel program remains secure, although its future may be somewhat rocky.