WASHINGTON — Northrop Grumman on Tuesday announced it successfully test fired the second-stage solid-rocket motor for the LGM-35A Sentinel nuclear missile now under development.

The full-scale static fire test was carried out in a vacuum chamber at the U.S. Air Force’s Arnold Engineering Development Complex in Tennessee, which Northrop said simulated the high-altitude and space flight conditions the intercontinental ballistic missile’s rocket motor would encounter during an actual launch.

The company said it will study the data from this test to determine how well the motor’s actual performance matched predictions made in digitally engineered models, as it aims to rein in risks facing the program.

“The test’s data gives us an accurate reading of our design’s performance and now informs our modeling and designs,” said Sarah Willoughby, a Northrop Grumman vice president and Sentinel program manager. “This lowers risk and builds confidence in our approach to deliver the next-generation ICBM capability to the Air Force.”

Sentinel is the Air Force’s program to build a new nuclear-armed intercontinental ballistic missile to succeed the aging LGM-30G Minuteman III. The program is expected to cost a total of about $100 billion. Northrop Grumman received a $13.3 billion contract in 2020 to build Sentinel, which is now in the engineering, manufacturing and development phase.

But the Government Accountability Office in June 2023 reported the program was experiencing staffing shortfalls, supply chain issues and software challenges that would cause the weapon’s rollout to slip from 2029 to roughly spring of 2030.

Air Force Secretary Frank Kendall also said during a November 2023 discussion that Sentinel is “struggling” and he is “more nervous” about its development than the B-21 Raider stealth bomber, also built by Northrop. Kendall also said Sentinel’s costs may rise.

The sheer scale and complexity of Sentinel is daunting, Kendall said, and is “probably the biggest thing … that the Air Force has ever taken on.” The program includes not just the production of the missile itself, but also real estate development, civil engineering, and the creation of both communications and command-and-control infrastructure, such as the complexes missileers would use to launch the weapons.

Northrop now plans to start a series of rocket motor qualification tests, alongside the Air Force, for both the first and second stages of the three-stage missile. The firm previously announced in early 2023 it had conducted a static test of the missile’s first-stage motor and hypersonic wind tunnel tests to validate its design.

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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