The military will continue developing its new LGM-35A Sentinel intercontinental ballistic missile but has told the U.S. Air Force to restructure the program to get its ballooning costs under control.

Even a “reasonably modified” version of the Northrop Grumman-made Sentinel will likely cost $140.9 billion, 81% more than the program’s original cost estimate of $77.7 billion, the Pentagon said in a statement. If Sentinel continues on its current path without being modified, the likely cost will be about $160 billion, it said.

And the military expects restructuring the program will delay it by several years.

“There are reasons for this cost growth, but there are also no excuses,” William LaPlante, undersecretary of defense for acquisition and sustainment, said in a conference call with reporters on Monday. “We fully appreciate the magnitude of the costs, but we also understand the risks of not modernizing our nuclear forces and not addressing the very real threats we confront.”

The Sentinel is intended to replace the Air Force’s half-century old Minuteman III nuclear missile, which is nearing the end of its life. In January, the Air Force announced Sentinel’s future costs were projected to run over budget severely enough to trigger a review process known as a critical Nunn-McCurdy breach.

Such a review can sometimes lead to a program being canceled. LaPlante said Monday he decided to proceed with Sentinel after concluding it met several criteria, including that it is essential to national security and there were no cheaper alternatives that would meet the military’s operational requirements.

Big changes are coming for Sentinel, however. LaPlante rescinded the program’s Milestone B approval, which in September 2020 authorized the program to move into its engineering and manufacturing development phase. He also ordered the Air Force to restructure the program to address the root causes of the cost overruns and make sure it has the right management structure to keep its future price down.

The per-unit total cost for Sentinel was originally $118 million in 2020, when its cost, schedule and performance goals were set. When the Nunn-McCurdy breach was announced in January, those per-unit costs had grown at least 37% to about $162 million.

Hunter said the per-unit cost for the revised Sentinel program — which include components in addition to its missiles — is estimated to be about $214 million. He said the estimates from the Pentagon’s Cost Assessment and Program Evaluation, or CAPE, office came with a 50% confidence level, meaning the costs could end up higher or lower.

Andrew Hunter, the Air Force’s assistant secretary for acquisition, technology and logistics, said he agreed with LaPlante’s decision and pledged to draw up a plan for restructuring Sentinel over the next few months and get to a new Milestone B approval. The entire process for revising the program and getting the Pentagon to approve its new plan, cost and schedule will likely take 18 to 24 months, Hunter said.

Command and launch

LaPlante and Hunter said most of the projected overruns are coming from Sentinel’s command and launch segment, which will include its missile silos and accompanying launch control centers where airmen operate the ICBMs. Revamping that segment will be a major part of the Air Force’s cost control effort, they said, as well as improving its systems engineering and changing how its contract is structured.

LaPlante said changes will include a “scaling back” of the launch facilities to make them smaller, simpler and more cost-effective. Paring down the launch facilities will also shorten the timeline needed to transition from the existing Minuteman III system and the new Sentinel facilities, he said.

Hunter said the new Sentinel facilities will need more communications infrastructure beyond the 7,500 miles of copper cabling now in use for the Minuteman silos and launch centers. The Air Force’s planned modifications to Sentinel include more affordable ways to do that work, he said.

In a statement, Northrop Grumman said it “is making important progress on this highly complex weapon system,” and continuing to achieve milestones to mature its design and reduce risk to prepare for production and deployment in the future.

Northrop said those milestones include designing and developing Sentinel’s facilities, support equipment and missile, and tests of components such as its nose cone and three booster stages.

“We continue to perform and meet our commitments under the EMD contract as we move toward delivery of this essential national security capability,” Northrop Grumman said.

LaPlante said that in “hindsight,” the department didn’t originally have enough information on how complicated Sentinel’s ground-based systems would be to accurately estimate its costs. In the nearly four years since, the Pentagon has much better information on hand, he said.

The Air Force also set up a committee chaired by its most senior leaders to oversee its nuclear enterprise, including its bombers, ICBMs and command-and-control, Hunter said. And the department dedicated a program executive officer to be in charge of ICBMs, set up a Nuclear Systems Center, and is changing the leadership of the Air Force Nuclear Weapons Center from a two-star general to a three-star general, he said.

Hunter said the Air Force will “do what it takes to sustain Minuteman III to meet these warfighter requirements in the interim.”

Gen. Jim Slife, the Air Force’s vice chief of staff, said Sentinel’s cost growth is not expected to kick in during the next five years, and the hardest choices on what to cut won’t be made until after the program’s new baseline is set.

“It is a decision for down the road, to decide what trade offs we’re going to need to make,” Slife said.

Stephen Losey is the air warfare reporter for Defense News. He previously covered leadership and personnel issues at Air Force Times, and the Pentagon, special operations and air warfare at Military.com. He has traveled to the Middle East to cover U.S. Air Force operations.

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