Northrop Grumman fires LGM-35A Sentinel second-stage motor

An artist's portrayal of the Northrop Grumman LGM-35A Sentinel ICBM. (Northrop Grumman)

Northrop Grumman has fired the second-stage solid-fuel rocket motor for the LGM-35A Sentinel nuclear missile for the first time, the company announced on 16 January.

The test was conducted inside a vacuum chamber at the US Air Force's Arnold Engineering Development Complex in Tullahoma, Tennessee, intended to simulate the high-altitude and space environments in which the motor would operate. Data from the test is to be compared against digitally simulated models, said Northrop Grumman.

The LGM-35A's first-stage motor was tested in March 2023, according to the company. That and the latest test-fire are conducted under the missile programme's engineering, manufacturing, and development (EMD) phase, scheduled to wrap up in 2027. The LGM-35A is scheduled to enter production in 2026 and operational service in 2029, with a planned fleet of 634 Sentinels to be produced.

US Secretary of the Air Force Frank Kendall hinted at potential delays to the Sentinel programme during a November 2023 talk at the Center for a New American Security.

“Sentinel is one of the most large, complex programmes I've ever seen,” Kendall said. “It's probably the biggest thing in some ways that the air force has ever taken on, because it's a vast real estate development [and] civil engineering programme, a fairly vast communications command-and-control programme, as well as of course, the missile itself.”

A June 2023 report from the US Government Accountability Office said that the programme's schedule “contains many deficiencies”.

The Sentinel is intended to replace the LGM-30G Minuteman as the US' sole ground-based nuclear intercontinental ballistic missile (ICBM).