To make sure the nose cone shroud of the LGM-35A Sentinel wouldn’t collide with the nuclear intercontinental ballistic missile within, Northrop Grumman tested the shroud in a fly-off test.

Saturday’s solid-rocket motor test for the LGM-35A Sentinel intercontinental ballistic missile program was conducted by the U.S. Air Force and two primary contractors. The motor powers the third stage of the nuclear bomb.

The test was conducted in a confined chamber at the Tennessee-based Arnold Engineering Development Complex and also involves Northrop Grumman and Aerojet Rocketdyne. It came after the rocket motors for the first and second stages underwent static fire tests in March 2023 and January 2024, respectively.

The tested stage of propulsion on Sentinel is the smallest of its three phases. The Air Force withheld information on the test’s outcome and did not offer any more details.

Commander of the Air Force Nuclear Weapons Center and the service’s program executive officer for strategic systems, Maj. Gen. John Newberry, said, “This test is the latest in our ground and flight test program and is designed to help us refine Sentinel’s air vehicle design.” “It shows the advancements the Air Force is making in updating the strategic land-based nuclear deterrent of our country.”

The outdated LGM-30G Minuteman III ICBM, a vital component of the US nuclear triad throughout the Cold War, is to be replaced by the Sentinel program. Currently, the Air Force maintains over 400 Minuteman III warheads in silos located in North Dakota, Wyoming, Montana, Colorado, and Nebraska.

In lieu of releasing a press release on the test, Northrop Grumman sent Defense News the following succinct statement: “We continue to make significant progress on the Sentinel program in partnership with the Air Force, achieving key milestones to mature the design and reduce risk.”

In a press statement from February, Northrop claimed to have successfully tested a number of additional missile components. In order to gather information regarding the weapon’s in-flight structural dynamics, this involved assessing the forward and aft parts of a Sentinel ICBM at its Strategic Missile Test and Production Complex in Promontory, Utah.

Northrop also conducted a fly-off test at Naval Air Weapons Station China Lake in California to test the Sentinel’s shroud, which encloses the payload inside the missile’s nose. This test confirmed the shroud wouldn’t collide with the encapsulated payload as it descended from the missile, and the corporation declared it successful.

The cost of the Sentinel program has increased to the point where a Nunn-McCurdy breach—a mechanism for cost overrun—has been triggered. Leading Air Force officials have determined that the majority of the cost increase is attributable to its extremely intricate command and launch division, which entails obtaining land from hundreds of Midwest landowners, constructing over 400 launch facilities, constructing 7,500 miles of utility corridors, and installing thousands of miles of fiber-optic networks.

According to the Air Force, other parts of the program are experiencing more significant cost rise than the Sentinel missile itself.

According to the Air Force’s announcement earlier this year, Sentinel is likewise running around two years behind schedule. Originally scheduled to attain first operational capability in 2029.

Nonetheless, senior officials have stated that replacing the Minuteman III is so crucial that they would find money elsewhere in the budget to pay for the new ICBMs, therefore it is doubtful that the military will abandon the Sentinel program due to cost overruns and delays. Sentinel is now being reviewed by the Pentagon to see how best to reorganize the program in order to save expenses and get it back on schedule.