WASHINGTON — Northrop Grumman announced Jan. 16 it conducted a successful static fire test of the second-stage solid rocket motor for a new intercontinental ballistic missile the company is developing for the U.S. Air Force. 

The Air Force in 2020 awarded Northrop Grumman a $13.3 billion contract to design and develop a next-generation intercontinental ballistic missile (ICBM) to replace the nation’s aging Minuteman 3 missiles that make up the land-based leg of the nuclear triad, ensuring the ability to retaliate following any nuclear attack on the homeland. 

Northrop Grumman was the only bidder for the program after Boeing dropped out of the competition, arguing that Northrop Grumman’s dominance of the solid rocket motors market gave it an overwhelming pricing advantage it could not compete against.

Test simulated real-world conditions

The second-stage motor for the new missile, named LGM-35A Sentinel, was tested at the Air Force Arnold Engineering Development Complex in Tennessee. It was conducted in a vacuum chamber simulating real-world environmental conditions the solid-rocket motor would experience during high-altitude and space flight, Northrop Grumman said. During a static fire test, engineers ignite the engine for a controlled period, typically a few seconds, observing its performance.

“Test data will be analyzed to determine how motor performance matched digitally engineered model predictions, critical to maturing the design and lowering risk,” the company said.

Northrop Grumman’s update follows a Jan. 12 announcement by the Air Force Nuclear Weapons Center, which noted that the recent test is the second in a series of static fire tests to validate the design and performance of Sentinel’s three-stage propulsion system. The stage-two that completed the test is the second largest of Sentinel’s three stages and the second solid rocket motor to fire following the missile’s launch. 

“This test is just a part of our comprehensive ground and flight test program designed to help us shake down the design as we approach its critical design review,” said Maj. Gen. John Newberry, commander of the Air Force Nuclear Weapons Center.

Other milestones previously completed include hypersonic wind tunnel testing and a stage-one solid rocket motor static fire.

Program schedule still TBD

The Air Force previously estimated the Sentinel missile to be ready for its first test launch in 2025 and to reach “initial operational capability” by 2029 but the timeline is likely to change, officials said. By recent DoD estimates, Sentinel is projected to cost at least $96 billion for 400 missiles. However, Air Force Secretary Frank Kendall recently expressed worries about the Sentinel program’s complexity and projected cost growth. 

Brig. Gen. Colin Connor, the Air Force’s director of ICBM modernization, said the Sentinel program is “one of the most complex things we’ve done.” Speaking Nov. 29 at a forum hosted by the Advanced Nuclear Weapons Alliance Deterrence Center, Connor said the Air Force is waiting for updated Sentinel schedule and cost estimates from Northrop Grumman. 

The requirements for the program have not yet been finalized, said Connor. “It’s premature to lay out exactly what it’s going to cost … We expect costs will be higher than expected.”

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...