Overheating problems with a test motor being developed Navy’s next nuclear ballistic missile submarine has not thrown the “no-margin-for-error” program off-schedule, senior service leaders have told Congress.

Testifying Tuesday before the House Armed Services seapower and projection forces subcommittee, Rear Adm. John Tammen Jr. said the problem, discovered before the motor arrived at Philadelphia “consumed considerable flex time” in the program. But “the risk is manageable and well in hand,” Rear Adm. Michael Jabaley, program executive officer for submarines, added.

Last week before the Senate Armed Services strategic forces subcommittee, Navy nuclear programs director Adm. James Caldwell said “it required us to have another motor built” by the subcontractor. The overheating problem was traced to faulty insulation. The new motor has not yet been tested.

By overlapping some other testing in the program and other tweaks, the overall Columbia program is on schedule. “We’re managing it very tightly” to meet the 2021 date to begin construction, Caldwell said.

James Geurts, the assistant secretary for Research, Development and Acquisition, said at Tuesday’s hearing “early work on missile tubes” for the new submarine also was a factor in keeping to schedule. Also having 83 percent of the ship’s design done at this stage of production, versus 42 percent for Virginia-class at a comparable time helps the program’s on-time prospects.

Delivery for the first Columbia boomer is expected in 2031. The no-margin-for-error comes with that date because the first Ohio–class ballistic missile submarine is set to retire.

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