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The US Office of the Secretary of Defense (OSD) has concluded that the US Air Force’s (USAF’s) LGM-35A Sentinel intercontinental ballistic missile (ICBM) programme, which is intended to replace the air force’s ageing LGM-30 Minuteman III ICBMs, must continue despite its estimated acquisition cost rising by 81% compared to estimates made in September 2020.

The USAF notified Congress on 18 January 2024 that the Sentinel had committed a so-called Nunn-McCurdy breach, caused by its programme acquisition unit cost or average unit procurement cost increasing by 25% or more over the current acquisition programme baseline. By statute such a programme must be terminated unless the US under secretary of defense for acquisition and sustainment (USD(A&S)) certifies to Congress that the programme meets established criteria to continue.

Based on the results of the review, USD(A&S) Dr William A LaPlante, who led it, certified that the Sentinel programme met the statutory criteria to continue because:

  • Continuation of the programme is essential to national security;
  • There are no alternatives to the programme that will provide acceptable capability to meet the joint requirements at less cost;
  • The new estimates of the programme acquisition unit cost or procurement unit cost have been determined by the director of Cost Assessment and Program Evaluation (CAPE) to be reasonable;
  • The programme is a higher priority than programmes whose funding must be reduced to accommodate the growth in cost of the programme; and
  • The management structure for the programme is adequate to manage and control programme acquisition unit cost or procurement unit cost.

In certifying the Sentinel programme to continue, LaPlante rescinded its Milestone B approval (the point at which an acquisition programme is authorised to enter the engineering and manufacturing development phase). He also directed the USAF to restructure the Sentinel programme to address the root causes of the breach and ensure an appropriate management structure is in place to control costs in the future.

Total programme acquisition costs for a reasonably modified Sentinel programme are estimated by CAPE to be USD 140.9 billion (EUR 130.34 billion): an increase of 81% compared to estimates at the programme’s previous Milestone B decision in September 2020. The Nunn-McCurdy review determined that the majority of the cost growth relates to the Sentinel’s command and launch segment, which includes the launch facilities, launch centres and the process, duration, staffing and facilities to execute the conversion from the Minuteman IIS to the Sentinels.

“We are fully aware of the costs, but we are also aware of the risks of not modernising our nuclear forces and not addressing the very real threats we confront,” LaPlante was quoted as stating in a USAF press relsease. “There are reasons for the cost growth, but there are no excuses. We are already working to address the root causes and, more importantly, we believe we are on the right path to defend our nation while protecting the sacred responsibility the American taxpayer has entrusted us with.

“The nuclear triad is the foundation of our national defence, and as our competitors modernise their own nuclear forces, the urgency of pacing the threat is reflected in our Nuclear Posture Review,” LaPlante added. “Sentinel is a truly historic programme to modernise the land leg of the triad and its scale, scope and complexity are something we haven’t attempted as a nation in 60 years. Having completed a comprehensive and objective assessment of the programme, it is clear that the Sentinel programme remains essential to US national security and is the best option to meet the needs of our warfighters.”

Preserving schedule will be a key consideration during the programme’s restructuring, although a delay of several years is currently estimated.

The prime contractor for the Sentinel programme is Northrop Grumman, which in December 2019 won the competition to build the future US ICBM because its bid was the only one left to be considered for what was then called the Ground Based Strategic Deterrent (GBSD) programme.

The LGM-35A Sentinel ICBM programme, which is intended to replace the USAF’s ageing LGM-30 Minuteman III ICBMs, will continue despite cost escalations because there is simply no alternative. (Image: USAF)