Sentinel ICBM ‘on track’ for flight test this year: Senior USAF official

WASHINGTON — Development of the Air Force’s next-generation intercontinental ballistic missile, the LGM-35A Sentinel, remains “on track” to undergo a flight test later this year, according to a senior Air Force official — despite a Defense Department report to Congress in September showing an estimated 10-month slip in contractor Northrop Grumman’s development effort.

“The first flight test is still on track, and are still scheduled for this year. We’re not gonna fly it, obviously,, until it’s ready to go. And so without getting into any more detail than that, we would expect first flight tests coming in ’23,” Brig. Gen. Ty Neuman, Air Force director of concepts, said Wednesday.

Neuman, who is also the deputy of the service’s “futures” division looking at long-term requirements, has a long career in the nuclear weapons domain, including as an adviser to the National Security Council on nuclear matters from June 2020 to May 2022.

His reassurances as to the schedule for the replacement to the aging Minuteman III ICBM arsenal, made during the Exchange Monitor’s 15th Annual Nuclear Defense Summit, come in the wake of a November report by Aviation Week that Air Force Secretary Frank Kendall is “concerned” about the program’s schedule slip.

DoD’s most recent Selected Acquisition Report [PDF] on the progress of the Sentinel, formerly called the Ground Based Strategic Deterrent, said that due to “a schedule variance” in Northrop Grumman’s “baseline plan,” Critical Design Review is estimated to move from July this year to May 2024 — a date that nonetheless is within the Air Force’s “threshold” (read: wiggle room) for declaring initial operating capability with nine missiles on alert in 2029.

Northrop Grumman, for its part, today announced it has successfully completed a series of wind tunnel tests using scale models of the missile, as well as digital modeling and simulations, that the company says has “proved design maturity.”

“This wind tunnel campaign is an opportunity to put our digitally engineered designs to the test, under conditions that mimic a missile launch,” said Sarah Willoughby, vice president and program manager, Sentinel, Northrop Grumman. “Predictions from the modeling correlated with the testing results, giving us confidence in our model-based engineering approach.”

The company also touted the program’s “advancements in technology with the use of digital engineering, advanced tooling, and a modular, open-architecture approach.”

Neuman cited the use of open architectures as key to the Sentinel’s ability to keep pace with changing threats over the course of its planned 40-year lifetime.

“[T]he way we’re designing all of our weapon systems at this point in time is the modularity and ability to adapt and change. And what we realized is a rigid requirement that doesn’t have an open architecture in the future is just not sustainable. By the time it’s actually delivered, it’s OBE because the threat environment changes so much. So, Sentinel is going to be one of those systems — it’s gonna have an open architecture that allows it to have flexibility in the future,” he said.

Of MIRVs And MARVs And Modularity

However, Neuman wouldn’t be drawn out on what types of changes to the missile’s capabilities might be made possible by the modular design and the open architecture, especially with regard to what upgrades the Air Force might see as necessary to meet future threats — mainly, the continued modernization and proliferation of China’s nuclear weapons arsenal.

“Well, I don’t want to get into a whole lot of details with respect to how we’re going to get after some of the challenging stuff from a threat perspective,” he said. “The key to success right now is to maintain a single requirement, so that we can actually get systems fielded and then work on the modularity and adaptability.”

However, a January “primer” by the Congressional Research Service (CRS) on the ICBM modernization effort noted a number of advantages to the current development approach, well beyond the ability to outsource future upgrades to vendors who might provide faster and/or cheaper solutions, rather than being stuck with Northrop Grumman.

For example, CRS said, “These types of upgrades might become important as technology evolves and could allow for improvements in the safety and reliability of the missile system. They could include better guidance systems or new types of countermeasures that might allow the missile to penetrate an adversary’s ballistic missile defensive systems.”

The report explained that the modular design coupled with the Sentinel’s increased “throw weight” (payload carrying capacity) over the Minuteman III would allow the new ICBM to potentially carry “different payloads” such as ballistic missile countermeasures.

Further, CRS said, while the current service plan is to field 400 Sentinels each equipped with one warhead — i.e., a one-on-one replacement of the Minuteman III arsenal — the modular design and the increased throw weight all would enable each Sentinel to be equipped “with two or three warheads to meet the international security environment.”

In other words, the Sentinels could carry what are known in nuclear weapons jargon as multiple re-entry vehicles (MIRVs), or potentially even maneuverable re-entry vehicles (MARVs). MIRVs were banned by the 1993 Strategic Arms Reduction Treaty (START) II between the US and then Soviet Union. However, Moscow withdrew from START II in 2002 following the US move to withdraw from the 1972 Anti-Ballistic Missile Treaty.

CRS added that “some argue” that MIRVing the Sentinels might allow the Air Force “to meet targeting requirements with a smaller number of deployed missiles,” thus reducing costs, although it also would reduce the resiliency of the ICBM force.

DoD’s Selected Acquisition Report put the total cost of the Sentinel acquisition program, including construction of new silos, at $95.8 billion.