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Bigger often means better, especially when the discussion is about one gun versus another. But a decision to replace a secondary weapon on the US Navy’s new Zumwalt-class destroyer with a smaller gun caliber is raising some eyebrows within the surface warfare community.
And the reason for dropping a 57mm weapon for a 30mm may be more surprising.
The Mark 110 57mm gun, “was nowhere near meeting the requirements,” said Capt. Jim Downey, program manager for the DDG 1000 Zumwalt class.
In fact, Downey said, the 57mm gun — selected years ago for the DDG 1000 as a close-in weapon and in service as the primary gun for the littoral combat ship and Coast Guard national security cutters — is overrated.
“They were significantly over-modeled on the lethality,” he said. “The results of the actual live test-fire data was that the round was not as effective as modeled.”
What’s more, Downey said, when the program asked the Naval Weapons Laboratory at Dahlgren, Virginia, to re-evaluate the two guns, the Mark 46 30mm came much closer to meeting the program’s requirements.
“The Mark 46’s lethality of its rounds met or exceeded the requirement,” he said.
BAE Systems, which makes the 57mm gun, declined to comment.
Downey declined to discuss specifics of the requirement, repeatedly citing classification concerns. But, he said, the 30mm was nearly equal to the 57mm or better, in multiple areas.
“It is classified but it gets into the range of the threat — the approach of the threat, what the make-up of the threat is and how it would maneuver, how it would fire against our ship. There is a whole series of parameters that are very specific on what the threat is and how you take it out through a layer of defenses.”
Downey admitted that when told the Mark 110 was no longer on track to meet his program’s requirements, it “was not what we expected to see.”
The review’s results led to a decision in late 2012 to replace the DDG 1000’s two 57mm guns with 30mm mounts. The move was not widely publicized, and that became more apparent to the outside world this spring when the event program for the Zumwalt’s christening ceremony in April depicted the ship with the newer weapon.
Many observers, however, quickly questioned the decision. The surface warfare community, when discussing the 57mm, has long compared it with the Mark 75 76mm gun, a weapon installed on frigates and Coast Guard cutters. Those discussions most often concern the LCS. Consideration of replacing the 57mm with a 30mm is rare, even though the LCS surface warfare mission module includes two Mark 46s in a temporary installation.
One retired senior surface warfare officer questioned the choice of the 30mm, which, he said, was effective only to about 2,200 yards.
“If they’re going to use the 30mm as the answer, they’re going to let some ships get in pretty close,” he said.
“When you look … at engaging swarm boats, [the 30mm] can’t even begin to engage effectively until they’re about a mile from the ship, and by then you’re in rocket-propelled grenade range,” the retired senior officer said. “The 57,” he added, “has an effective range of about two to three miles.”
For the DDG 1000’s particular requirements, however, Downey said the 30mm met more overall performance points than the 76mm or 57mm guns. All three guns were part of his program review, with the 30 coming in just ahead of the 76 and significantly ahead of the 57.
Other observers point at a comparison of the relative weights of the gun mounts, where the difference is striking. The 57mm mount weighs 12 to 14 tons with ammunition, the DDG 1000 program office said, while the 30mm comes in around 2 tons.
Downey virtually spat out his disdain for suggestions the swap had anything to do with weight.
“That is absurd, the fact that we changed the guns for weights,” he said in a September interview. “The weight had zero, absolutely, 100 percent nothing to do with the decision on the guns.”
The weight issue could be significant. Zumwalt has a unique, tumble-home, wave-piercing hull design that has never been tried out on a full-scale ship, and many are waiting to see the concept prove itself at sea.
But Downey brushed off suggestions his ship is overweight, or even weight-critical, citing measurements about the ship’s KG, or center of gravity.
“We meet or exceed all the weight in all the KG requirements. It is a complete non-issue in this ship,” he said. “That is a total red herring to say they changed the gun because of weight.”
Zumwalt, he said, is meeting the requirement to be completed with a 10 percent weight margin for growth over a 35-year period.
Commonality Questions
So if the 57mm gun doesn’t cut it, why keep it on the LCS?
While Downey’s program review resulted in an exchange of weapons on the DDG 1000, no similar review was done for the LCS program. In fact, although the 1000 program began its weapon review in 2012, it appears little of the information was conveyed to other program offices within Naval Sea Systems Command (NAVSEA).
“It is correct that that process does not exist right now,” Chris Johnson, a NAVSEA spokesman, said on Oct. 9. “And it is clear that your line of questions has started a discussion. So how is that going to be formalized? I don’t know right now.”
Johnson pointed out that the program offices have no responsibility to inform other programs of internal developments.
“Both programs now have gun systems that meet their individual requirements. Both are very confident in their individual systems,” he said.
That no structure exists to routinely inform offices of developments on common systems struck many observers as strange, whether the discussion is about weapons, engines, sensors, pumps or hatches, particularly since NAVSEA leaders have placed great emphasis in recent years on reducing possible features that may be needlessly duplicated.
A structure that could function as an information clearinghouse was set up in April under Rear Adm. Thomas Kearney, NAVSEA’s deputy commander. The Acquisition and Commonality directorate, Johnson said, “was established to improve our efforts to reduce variation and increase the use of common parts, systems and processes across acquisition programs.”
The directorate has yet to have an effect, however.
“The office is currently establishing their policies and procedures so that program offices can use them as a resource when designing or upgrading ship classes,” Johnson said. “Our belief is that by centralizing these responsibilities, the Navy will be able to increase the use of common parts and systems across the fleet as well as challenging requirements which may increase variation across the fleet.”
But the questions about the LCS program’s awareness of the DDG 1000’s tests and decisions might be prompting a greater emphasis on better information sharing.
“The commonality directorates and the program executive officers are aware that there is a component of knowledge-sharing that isn’t there yet, and that’s a conversation those organizations will need to have,” Johnson said. ■
