The future of U.S.-led missile defense around the world could come down to hard decisions about two ships that were never intended for the mission.

As defense budgets tighten, questions continue to mount about the U.S. Navy's decision to truncate the fleet of DDG-1000 Zumwalt-class destroyers to three ships and restart the legacy DDG-51 Arleigh Burke line. Neither ship was originally envisioned for a national missile defense mission, but both lie at the heart of looming budget decisions whose ramifications could affect the proposed Phased Adaptive Approach (PAA) and Air and Missile Defense Radar (AMDR) systems.

An Aviation Week Intelligence Network (AWIN) examination since last summer into the Navy's destroyer programs and accompanying combat systems and missile defense applications indicates the Navy may have to overhaul $121.8 billion worth of plans.

Besides affecting shipbuilding, renewed uncertainty about these destroyer programs also puts at risk the Obama administration's PAA plan to protect U.S. allies from missile attacks, starting in Europe later this decade and possibly being repeated in Asia-Pacific.

After earlier Aviation Week reporting, the Government Accountability Office (GAO) started its own investigation into Navy decisions about the fleet, and that report is due to be published as soon as this month.

The DDG-51 restart is needed, the Navy says, to fulfill the service's ballistic missile defense (BMD) mission obligations, which envision the destroyers equipped with Lockheed Martin's venerable Aegis Combat System, ready to take down enemy targets with Raytheon's Standard Missile-3 interceptor.

But some defense analysts believe the GAO will recommend that the Navy ditch its current plan to buy more Burkes—including redesigned models in years to come—and build more Zumwalts instead because the DDG-1000s will offer greater growth potential for more weapons and lower life-cycle costs.

Regardless, the Navy has provided contradictory public statements about which destroyers they need and why. Neither Burkes nor Zumwalts were designed specifically for BMD, but some Navy brass have asserted that the DDG-1000s could not accommodate Standard Missiles. Yet other Navy documents, analysts and industry sources do not support that conclusion.

Moreover, the current fleet of destroyers and their Aegis systems needed for missile defense are a maintenance headache, to say the least. Just to get the vessels and systems shipshape could cost the price of an entire new destroyer, and an additional untold sum of money might be needed to keep the Burkes and their radar systems in good working order through coming decades.

It is this huge repair bill, plus mounting maintenance costs and the budgetary battles being waged on Capitol Hill, that led naval analysts to believe it is unlikely the Navy will be able to afford the proposed next-generation Burkes, planned improvements to the ships' Aegis combat systems or the AMDR, the supposed linchpin for maritime-based BMD.

Still, a course correction also could be a blow to the Navy, which has been bolstered in recent years through its BMD role. “The Navy is becoming the centerpiece of national missile defense,” says Lexington Institute defense analyst Loren Thompson. “But it can't afford to stick with the program of record.”

At particular risk is the Navy's proposed AMDR, with its estimated price tag of $15.7 billion. “There doesn't seem to be enough money to develop it,” says Norman Friedman, an author on naval issues.

Navy officials say forgoing AMDR and relying on Aegis is simply not an option because the threats are too complex and dangerous. Further, they say, costs are coming down on the new proposed radar system.

But a cursory analysis shows the service could save up to $14.3 billion if the Navy bought DDG-1000s in the coming decades instead of newly designed variants of the DDG-51s, assuming further major programmatic changes are not planned.

Ironically, the systems' potentially high price tag can be linked partly to the starts, stops and sudden shifts in shipbuilding plans during last decade. Debate over these issues should gather steam as soon as this month with the GAO report, followed by the president's fiscal 2013 request and congressional hearings through the spring.

Editor's note: This article is an abstract of a five-part series based on data analysis and interviews with Navy and contractor program officials, defense analysts, service and Pentagon leaders, testing officials and others associated with the destroyer programs. The full “Come About” series is available to AWIN subscribers online.