WASHINGTON — The latest U.S. Navy Aegis ships fitted for the ballistic missile defense (BMD) program can now handle anti-air warfare roles as well, according to Navy and industry sources.

More Arleigh Burke-class destroyers may get the ballistic-missile modification, as well.

Ships used in early BMD tests have been unable to handle air-defense roles due to processing limitations on older military computers and the nature of the test program. But the latest Aegis BMD ship, the cruiser Shiloh, is fitted with Aegis BMD version 3.6, restoring the multimission capabilities of the Aegis system.

“We spiraled for the research and track mission and for search, track and engagement,” Jimmy Carter, Lockheed Martin’s director of sea-based missile defense systems, said Sept. 26. “Those were not certified loads, they were only for emergency capability. You’d have to reboot the system under anti-air warfare or reboot under BMD.”

That’s no longer the case for the latest BMD upgrades.

“Everything before in engagement capability was done in special configuration for emergency activation,” Rear Adm. Brad Hicks, Aegis program director for the Missile Defense Agency, said in late August. “This is our first capability that is a full-up, tactical capability that’s a normal fleet-issue software for the Aegis ships that … returns the ship’s multimission capability. So when they load the Aegis BMD 3.6, they not only have a BMD capability — a tracking and engagement capability — they also get back their anti-air warfare capability. And will be able to conduct self-defense.”

The new system was tested June 22 near Hawaii when the Shiloh combined its 3.6 Aegis system with the new Standard SM-3 Block IA missile to intercept a separating target warhead in its terminal phase.

Three Aegis destroyers also took part in the June test. One ship, fitted with the 3.0 upgrade, linked with a land-based radar to evaluate the Shiloh’s ability to track the incoming warhead. Two other destroyers, including the Japanese Aegis destroyer Kirishima, performed long-range surveillance and tracking.

After returning to Japan, the Kirishima is the first Japanese Aegis ship to be upgraded with Aegis BMD software.

Eighteen U.S. Navy Aegis ships — three cruisers and 15 destroyers — are being modified for the BMD mission. Two ships already are fitted with Aegis 3.6, the Shiloh and destroyer Stethem, according to Lockheed Martin. The other two cruisers, Lake Erie and Port Royal, will have it by the end of the year, along with the destroyers Curtis Wilbur and Decatur. All the ships will be capable of launching the SM-3 missile, which designed to intercept a ballistic missile or warhead.

Ships already fitted with Aegis 3.0 include the destroyers John S. McCain, Fitzgerald, Russell, Milius, Paul Hamilton, John Paul Jones, Benfold, Hopper, O’Kane and Higgins. Those ships will be upgraded to the full 3.6 version by 2009, according to the Navy.

Some critics of the Navy BMD program have feared the ships would not be available for normal missions, such as escorting an aircraft carrier. But that won’t be the case, Hicks said.

“When those 18 ships are there, we’ll have to work out with the operational and combatant commanders … how we will deploy those ships as part of their normal battlegroup operations,” he said.

That’s a key element in allocating so many ships to the BMD role, one analyst said.

“It seems to me the Navy was reluctant to fully embrace the BMD missions for fear that more of the fleet would be dedicated to national missile defense,” said Bob Work, a naval analyst with the Center for Strategic and Budgetary Assessments in Washington. “This provides a much more flexible missile defense force.”

More BMD Ships?

The Navy also is considering adding the BMD upgrades to the DDG destroyer modernization program scheduled to begin in 2010, shortly before the last new DDG 51 Arleigh Burke-class destroyer is completed. That program currently is limited to hull, mechanical and electrical system improvements and some minor combat system upgrades.

But open architecture efforts and inclusion of more commercial-off-the-shelf elements into the Aegis system could make it easier and more affordable to add BMD functions to all the ships, the sources said, and the upgrades also could be applied to Aegis systems on non-U.S. ships.

Japan, Spain and Norway currently field the Aegis on naval vessels, and Australia and South Korea are building new Aegis destroyers. Saudi Arabia also has expressed serious interest in acquiring an Aegis version of the U.S. Navy’s Littoral Combat Ship.

“That’s the beauty of having allies that have Aegis,” said a Pentagon source. “They can use it for this purpose.”