Ground-Based Strategic Deterrent concept art. Photo: Northrop Grumman

The United States has unveiled a new intercontinental ballistic missile (ICBM) to carry its nuclear arsenal to replace its aging LGM-30G Minuteman III fleet as tensions and threats rise around the world.

This month, the US Air Force officially designated its Ground-Based Strategic Deterrent project as the LGM-35A Sentinel, which aims to replace the long-serving LGM-30G Minuteman III ICBMs as the land-based leg of the US nuclear arsenal. 

The move ensures continuity of strategic deterrence and costs less than modernizing the 1970s LGM-30G Minuteman missiles, which have already been in service for 50 years.

The LGM-35A Sentinel is a fully integrated launch, flight and infrastructure system equipped with the latest command and control functions, which aims to replace LGM-30G Minuteman IIIs by 2029 and is planned to be in service until the 2070s.

This replacement program is estimated to cost up to US$100 billion, complementing the new B-21 Raider and upcoming Columbia-class ballistic missile submarine, which will form the US’ air and sea-based nuclear deterrent.

The LGM-35A Sentinel has several improvements over its predecessor. In contrast to the LGM-30G Minuteman III, it features a modular design and open architecture, allowing for easy replacement of aging and obsolete components.

Open architecture also allows the US Air Force to control the source code of the system, allowing for multiple contractors to compete for system upgrades and improvements. These may include new safety measures, guidance systems and penetration aids to defeat enemy missile defenses.

Modularity also reduces the LGM-35A Sentinel’s maintenance costs by allowing the replacement of missile subsystems called modules, without totally redesigning the entire weapons system.

This can potentially be a more cost-effective way to support the LGM-35A Sentinel’s life cycle, in contrast with the older program that kept the LGM-30G Minuteman III in service for 50 years. 

The LGM-35A Sentinel also features improved security features. The older LGM-30G Minuteman III requires silo doors to be open for warhead maintenance, which opens a potential vulnerability and necessitates a huge security detail.

In contrast, the modular design of the LGM-35A Sentinel allows warhead maintenance with closed silo doors, eliminating the threats inherent with the LGM-30G Minuteman III, and potentially saving on manpower requirements for the system.

Also, the LGM-35A Sentinel has improved throw weight due to the use of lighter composite materials to house its propellant, in contrast to the heavy steel casings used by the LGM-30G Minuteman III. This allows the former to carry heavier payloads and added mission flexibility.

An LGM-30G Minuteman III missile inside a silo about 60 miles from Grand Forks Air Force Base in 1989. Photo: WikiCommons

This increased capacity means that the LGM-35A Sentinel can potentially deploy up to three warheads, or increased penetration aids.

The US Air Force’s missile bases, including Wyoming, F.E. Warren, Montana, Minot and Malmstrom, will house the new LGM-35A Sentinel alongside the LGM-30G Minuteman III. Both systems will meet nuclear safety standards with available missile base infrastructure during the phase-out, phase-in period.  

The Ground-Based Strategic Deterrent project was started in 2020, when the US Air Force awarded a $13 billion contract to Northrop Grumman to develop a next-generation ICBM to replace the aging US land-based nuclear missiles.

This development potentially breaks a hiatus in US nuclear capability development. In the 2000s, the US may have potentially skipped a generation of nuclear arsenal modernization, as it put off modernizing its nuclear triad for 20 years.

Notably, US allies such as France and the UK reduced their nuclear arsenals but continued to modernize their sea and air-based nuclear delivery systems. In contrast, most of the US nuclear arsenal dates to the 1980s and is slipping into obsolescence. 

Against this backdrop of slow obsolescence, China, Iran, North Korea and Russia continued to modernize their own nuclear forces. Notably, these countries are exploring the applications of hypersonic technology to their respective nuclear arsenals, in contrast to the US which focuses its hypersonic research efforts on tactical rather than strategic missiles. 

US officials claim that China is on track to substantially increase its nuclear arsenal to 700 deliverable warheads by 2027, and 1,000 warheads by 2030.

China may have also established its own nuclear triad with air-launched ballistic missiles and aims to further improve the land and sea-based legs of its nuclear arsenal. 

In September last year, US open-source intelligence reported that China was constructing at least 250 new long-range silos at three different locations. The alleged missile sites are located at Yumen and Hami in North-western China, and a potential third in Inner Mongolia. 

In addition to its silo-based nuclear arsenal, China is re-exploring the concept of railway nukes, which utilize China’s extensive high-speed rail network for mobility, survivability and concealment.