NG: Composite superstructure on DDG on track

Northrop Grumman has refuted claims that it encountered problems in the construction of the composite superstructure for the DDG 1000 destroyer.

Shipbuilder Northrop Grumman (Los Angeles, Calif.) on Sept. 22 refuted assertions that serious problems have arisen with fabrication of the composite superstructure for the U.S. Navy's Zumwalt-class DDG 1000 destroyer.

"The DDG 1000 deckhouse has been through a very thorough development process, yielding a deckhouse design that meets all technical and load requirements, including apertures," Brian Cuccias, Northrop Shipbuilding's vice president of surface combatant programs, said in a statement Sept. 19. "We are on track for DDG 1000 composite deckhouse to start fabrication in February 2009."

The story alleging problems with the superstructure was first reported in the Sept. 15 issue of Defense News. Sources told the newspaper that serious concerns exist inside Northrop and in the Navy that construction problems might threaten construction of the deckhouse superstructure.

The Navy on Sept. 16 issued a statement on the issue.

"Northrop Grumman Shipbuilding [NGSB] has experience with the vacuum-assisted resin transfer molding [VARTM] process since 1994," the Navy said. "Beginning in 2001, the DDG 1000 program has manufactured multiple test articles that have demonstrated NGSB's ability to manufacture high quality parts. While there have been challenges, NGSB has continued to identify and pursue process improvements that have resulted in an increasingly mature manufacturing process.

"Navy subject matter experts have participated in all key technical, design and manufacturing decisions involved with the qualification of the material system, the modifications of the manufacturing process used to manufacture parts with the material system, and the validation through test of the material system. The design of the deckhouse has been conducted to support the weight/stresses of the Dual Band Radar and other topside sensors and systems, and the deckhouse structure meets all load requirements. The Navy continues to conduct production readiness reviews by which it assesses NGSB's capabilities and performance."

Northrop challenged the story's reporting that the Navy had been canvassing other composite manufacturers, calling it "incorrect or speculative."

The shipbuilder also said that reported problems in guaranteeing seals between composite structure panels is "completely incorrect - our structure is an integrated product and does not have seals between the panels."

In its statement, Northrop pointed to its extensive experience with "carbon fiber applications" of composite components.

"During the DDG 1000 engineering development phase, NGSB produced more than 6,000 carbon fiber/vinyl ester test articles that were successfully tested and validated for ship designs in radar cross section, co-site, material properties, joints, fire, corrosion, shielding effectiveness, fragmentation and blast," Northrop said. "We are committed to meeting our customers' requirements and will meet all technical specifications," Cuccias said.

The building schedule for the deckhouse already has slipped this year - in February, Northrop said construction was to begin in the fourth quarter of 2008. While Northrop will share in construction of the DDG 1000 with rival General Dynamics, Northrop is responsible for building the composite structures for all the Zumwalts at its facility in Gulfport, Miss.