Whether or not the U.S. Air Force’s new Sentinel intercontinental ballistic missiles (ICBM) will carry multiple warheads remains to be seen now that a key arms control treaty has expired. The service is otherwise hopeful that the Sentinel program is now on the right track after years of major delays and ballooning costs, driven heavily by costs and complexities associated with building new infrastructure. A particularly key issue has been the matter of silos, with the original plan to repurpose the ones that currently house Minuteman III ICBMs having been abandoned in favor of all-new construction.
Air Force and other U.S. military officials, as well as a representative from the Sentinel’s prime contractor, Northrop Grumman, shared new updates about the program with TWZ and other outlets at the Air & Space Forces Association’s (AFA) annual Warfare Symposium today. Sentinel has been undergoing a complete restructuring since delays and cost overruns triggered a legal requirement for a full review back in 2024. The original plan had called for the new Sentinel ICBMs, also designated LGM-35As, to begin entering operational service in 2029. Minuteman III, of which there are 400 currently sitting in silos across five states, was to be phased out by 2036.
The setbacks also mean that ongoing work on Sentinel is now occurring free from the limits on America’s nuclear arsenal that were imposed by the New START treaty with Russia. That agreement sunset, as scheduled, earlier this month without a follow-on deal in place.
A Sentinel Program official declined to say how many warheads could be loaded onto a single Sentinel missile when asked at a press briefing earlier today. The publicly stated plan previously has been to load each missile with a single W87-1 warhead.
Each of the Minuteman III ICBMs in service today, which are also designated LGM-30Gs, is topped with either a single W78 or W87 warhead, the result of a succession of arms control agreements culminating in New START. The LGM-30G, which entered service in 1970, was originally designed to carry up to three warheads, and retains this so-called multiple independently targetable reentry vehicle (MIRV) capability.
“We have the ability to do that. That’s obviously a national-level decision that would go up to the President,” Navy Adm. Rich Correll, head of U.S. Strategic Command (STRATCOM), told TWZ and others at a separate roundtable today, speaking generally about the prospect of the U.S. fielding ICBMs in a MIRV configuration again. “Those policy levers, if needed, provide additional resiliency within the capabilities that we have.”
“Nothing’s changed since [the] expiration of the New START treaty. The threat environment that existed before [the] expiration of the New START Treaty exists today,” Correll added. “So that decision space is open, and discussions will occur at a senior policy-making level to make decisions with respect to that. I would reserve any recommendations I have for that discussion within the Department.”
Earlier this month, Air Force Global Strike Command (AFGSC), under which the currently Minuteman III force falls, also told TWZ that it “maintains the capability and training to MIRV the Minuteman III ICBM force” and that it would be prepared to do so “if directed by the President.”
We do know that the Sentinel missile is a new design with a three-stage solid fuel rocket booster that has been described as slightly larger than the Minuteman III. Under the shroud on top is a payload bus with a liquid fuel propulsion system.
Enabling Peace Through Deterrence
“Our liquid propulsion system, this is what gives us the fine point that allows us to place the re-entry vehicle precisely on target, that greater accuracy that comes with the Sentinel system,” the Northrop Grumman official explained at today’s press briefing.
Beyond improved accuracy, the Air Force and Northrop Grumman have said that Sentinel will also offer greater range, as well as reliability and sustainability benefits, compared to the Cold War-era Minuteman III. Though more specific details about Sentinel’s capabilities are classified, developing a new ICBM does provide the opportunity to incorporate various new features and functionality, including when it comes to survivability.
“At this point, we have completed testing on all of the major elements of the missile system. … We met all of our primary objectives and are [on] a good course to first flight, which is why we have confidence that we’re going to hit that pad launch in 2027,” the Northrop Grumman official added. “What we’re working on now are additional tests just to give us confidence” when it comes to “reliability and integrating that system.”
The Air Force first announced it was targeting a Sentinel first flight in 2027, from a launch pad above ground, last week. The service has yet to share when it expects to conduct the first test launch from a silo. Northrop Grumman is now building a full-scale prototype silo facility in Promontory, Utah, but it is unclear whether that will be constructed in a way that would allow it to be used for test launches in the future. As an aside, the New START treaty had also imposed limits on deployed and non-deployed “launchers,” which included silos for ICBMs.
As mentioned, the topic of silos has been absolutely central to the Sentinel program and its troubles over the years. Originally, the Air Force expected to be able to reuse Minuteman III silos, but subsequently determined that this was not the optimal course of action. The plan now is to construct 450 entirely new silos. The Air Force hopes this will actually save time and money now, in part because of the ability to leverage modern modular construction methods from the start rather than trying to repurpose decades-old structures.
“The original acquisition strategy for Sentinel was to use and reuse the Minuteman III silos for the housing of the Sentinel missile, with some upgraded communication rooms and things next to it. Over the past year, we’ve gone through multiple assessments to figure out what the right strategy is as we look forward, and we’ve changed our acquisition strategy to go after building and constructing new silos for Sentinel,” the Sentinel Program official explained today. “That came out of really kind of two primary things. The first reason we looked at this is just the variability of refurbishing Minuteman III silos. The Minuteman III silos are amazing, and they are incredibly efficient at executing the mission today. But as we were going down the path of trying to plan, just like trying to renovate a house built in the [19]60s, there was variability in understanding how you would attack refurbishment, how you would understand the conditions, and the timing, and the cost associated with that.”
The Air Force also sees new silos as helping ease the transition process from Minuteman III to Sentinel. Both missiles will be in service simultaneously for a time to ensure the land-based leg of America’s nuclear deterrent triad remains credible throughout the process.
“As we were looking at opportunity space, we found a squadron at Malmstrom [Air Force Base in Montana], which was the first one, that was still owned Air Force land, but allowed us what I would call swing space,” the Sentinel Program official noted. “If we constructed there, how we sequence and how we choreograph, taking down Minuteman and bringing Sentinel up on alert, it allowed us the opportunity to do that without impacting operations today. And going after that swing space, it actually drove us to designing and constructing new silos, as there were not Minuteman III silos available to be reused on those sites.”
New silos “also captured a few things that we were working through on risk, primarily around human factors and some other things that were existing in the reuse of Minuteman, it allowed us to get those and reduce those as we went forward,” they added.
“We knew and had some assumptions at the beginning. We had to test out those assumptions,” they also said when asked about why these issues were not recognized earlier on. “As we’ve tested out those assumptions, some of them proved false, which is why we’ve been going down the path of laying in, prototyping, experimentation, and showing progress on how do we say, ‘Hey, this is a different way of approaching it.’”
“To suggest they weren’t thought about, I think that would be probably short-sighted. They were very much thought about. I think that we often forget that these are very challenging programs. This is something we have not done in over six decades,” Air Force Gen. Dale White, Director of Critical Major Weapon Systems and direct reporting portfolio manager to the Deputy Secretary of War, also said at the roundtable. “Some of the assumptions that did come to fruition have actually provided more operational advantages. We’ve made changes along the way.”
“With the decision to recapitalize the intersite communications and build new launch silos, it’s opened up a lot of additional possibilities,” AFGSC commander Air Force Gen. Stephen Davis also said at the roundtable. “And I would tell you, I don’t think we have the answer exactly how we’re doing that yet, but we have more flexibility.”
The aforementioned prototype silo in Utah is being built to help further burn down risk.
“There are many things that we’re looking to prove out through this risk reduction activity, excavation techniques, how we integrate the modular elements of the silo, too. How we protect from weather conditions and how we do transportation to and from the site – critically important,” the Northrop Grumman official said. “And we will ultimately use this as we start to integrate and perform operations around missile emplacement, those kinds of things.”
Despite the “swing space” found to exist on Air Force-owned land, the Sentinel program is still expected to require the use of other U.S. government-owned land and the acquisition of additional land from private entities. The full extent of those additional land requirements is still being assessed. What will happen to the decommissioned Minuteman III silos is still to be determined, as well.
Though they are the most important aspect, silos are only one part of the massive infrastructure development plans baked into the Sentinel program. A total of 24 new launch centers and three new missile wing command centers are also set to be built. The new ICBM force will be spread across 32,000 square miles in five states and linked together by more than 5,000 miles of new fiber optic lines.
“The wing command center is actually a new capability being provided by Sentinel that doesn’t exist today for Minuteman,” the Sentinel Program official said. “Today at Minuteman, the information is more siloed. The structure of Minuteman is built around the [missile] squadron, and there isn’t a sole place where the information is pulled together, to give you the battlespace awareness of the entire wing at one time.”
“So the wing command center is where that fiber backbone is incredibly important,” they continued. “The quantity of data that can be pushed on fiber, from my physical security monitoring for health and status of the missiles and of the launch facilities, all can be integrated here into a common picture that allows the operational commander the ability to see what is going on in the missile field and take the appropriate action and prioritize where they are using their resources, their Airmen, to tackle the problems and the solutions.”
The first of these facilities is now being built at F.E. Warren Air Force Base in Wyoming. That base is also set to host initial prototyping efforts related to the fiber optic cable laying, which is set to be a huge undertaking led by the U.S. Army Corps of Engineers.
The Air Force is now aiming to start fielding Sentinel sometime in the early 2030s. How long it will take to complete the transition from Minuteman III to the ICBMs is unclear. The service has said it is at least “feasible” to keep some number of Minuteman IIIs on alert until 2050, according to a past report from the Government Accountability Office (GAO), a congressional watchdog.
The U.S. military continues to stress that the new Sentinel ICBMs and modernized infrastructure that will come with them are top national security priorities. Despite debates in the past about the utility of the land-based leg of the triad, it does remain the fastest nuclear response option in the Pentagon’s strategic portfolio. It also has a continued purpose to act as a ‘warhead sponge’ that would force any opponent to expend substantial resources on trying to neutralize it in a future nuclear exchange.
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The global geostrategic environment has also evolved in ways that further bolster the case for Sentinel, particularly when it comes to China drastically expanding its nuclear arsenal. Other global crises, including Russia’s ongoing war with Ukraine, together with other proliferation and strategic weapons development concerns, are factors, as well.
“The fact of the matter is that both the offense and defensive threats … have evolved significantly” since Minuteman III was fielded, Gen. Davis said today. “We’ve gotten all the capability that we can out of the Minuteman, but Sentinel will bring Air Force Global Strike Command and USSTRATCOM important new capabilities that we need to keep up with the threat and to stay ahead of it.”
There are many questions the Sentinel program clearly still has to answer, including how many warheads each missile should carry, as it moves toward finally reaching an operational capability in the next decade.
Contact the author: joe@twz.com