Faulty missile tubes that earlier consumed months of schedule margin on the next-generation U.S. nuclear-armed, ballistic missile submarines are not pacing the schedule for the boats anymore, the admiral in charge of the U.S. program said Thursday.

“I retain margin on missile tubes,” Read Adm. Scott Pappano, the U.S. Navy’s program executive officer for strategic submarines, said in a webcast meeting hosted by the Washington-based non-government group, Advanced Nuclear Weapons Alliance.

In 2018, BWX Technologies

[BWXT] incorrectly welded a dozen missile tubes intended for Columbia-class boats, which are set to replace the existing U.S. Ohio fleet starting around 2031. These were “large, volumetric welds that we hadn’t done in the industrial base for a long, long time,” Pappano said Thursday.

The botched welds whittled the margin for the first Columbia boat — now under construction by prime contractor General Dynamics [GD] Electric Boat in Quonset Point, R.I., — down to about two months, Pappano said in November during the Naval Submarine League’s annual symposium.

Now, however, “we’re delivering the missile tubes at the quality and throughput that we need not only to maintain the Columbia class but also the common missile compartment that we’re supporting for the Dreadnought class in the U.K.,” Pappano said. 

Dreadnought, the future U.K. ballistic missile submarine, will share among other things the common missile compartment tubes with Columbia.

On Thursday, Pappano said vendors had delivered all the tubes necessary for the first Columbia boat to General Dynamics. In November, the admiral said to expect the delivery to the U.S. submarine prime by the end of 2021. All the tubes for the first U.K. Dreadnought had shipped by November, Pappano told the Naval Submarine League last year.

The U.S. Navy plans to replace the current fleet of 14 Ohio-class ballistic missile submarines with 12 Columbia boats. The vessels will carry Trident II D-5 ballistic missiles made by Lockheed Martin [LMT] tipped with a mixture of W76-1 and W88 Alt 370 warheads, with a smaller complement of W76-2 lower-yield warheads provided by the Department of Energy’s National Nuclear Security Administration (NNSA).

Dreadnought subs will replace Vanguard-class boats. U.K. submarines carry anglicized versions of the W76 nuclear warhead on Trident missiles. The next British nuclear warhead will be based on the U.S. W93, which is in its nascent design phase, though slated for a big ramp up in the NNSA’s fiscal year 2023 budget request. The U.K. nuclear arsenal consists solely of submarine-launched ballistic missiles.