The long-stalled future of the U.S. special warfare community's troubled mini-submarine is even cloudier after a serious explosion and fire struck the craft last month, ironically on the cusp of a new mission and a new way ahead for the program.

The Advanced SEAL Delivery Vehicle 1 was having its lithium-ion batteries charged Nov. 9 when an explosion started a battery fire that burned for about six hours. No one was aboard the 60-ton craft, which was on shore at its base in Pearl Harbor.

Federal firefighters sealed the ASDS to put out the fire and continued to hose it down for several hours to cool hot spots. The mini-sub remained sealed for more than two weeks before the hatch was opened.

"The Navy has not yet determined the cause of the fire or the extent of the damage," Lt. Clay Doss, a Navy spokesman at the Pentagon, said recently. Two investigations are under way to determine the fire's cause and the extent of the damage, he added.

Sources familiar with the incident said that, in addition to fire damage, the craft likely would have significant water damage from having its interior flooded to fight the fire.

The Navy's one and only ASDS arrived at Pearl Harbor in 2000 and was heralded as leap-ahead technology that would deliver SEAL commandos dry and rested rather than shivering and cold in the existing SEAL delivery vehicle, a cramped open-water design requiring scuba tanks.

KEY JUNCTURE

The fire came at a key time for the mini-sub program. The ASDS was to have deployed in November attached atop the submarine Michigan — the first deployment for the former ballistic missile submarine that was converted to carry commandos and Tomahawk cruise missiles.

And, more than two years since U.S. Special Operations Command canceled further ASDS acquisitions, Pentagon officials reportedly were preparing to submit new program plans in the fiscal 2010 budget due to be sent to Congress on Feb. 2.

No details of the new way ahead for the program have been revealed, although Pentagon sources said the submission would need to be reviewed in light of the ASDS fire.

A primary question investigators will have is whether the craft's new lithium-ion batteries caused or contributed to the explosion.

The ASDS' original silver-zinc batteries provided insufficient power for the craft's missions, and more powerful lithium-ion batteries recently were substituted. Built at Yardney Technical Products in Pawcatuck, Conn., the lithium-ion batteries are known to present hazards if not properly handled, particularly when the batteries are being recharged.

The 65-foot-long mini-sub is intended to be carried to operational areas aboard submerged submarines and has an operational range of more than 100 nautical miles.

HISTORY OF PROBLEMS

The ASDS has had a long, checkered history. The first batch of six craft was to have been completed in the late 1990s, but technical problems led to long delays and a twelvefold cost overrun — the original $70 million contract for the first boat in 1994 ballooned to expenditures of at least $883 million by 2007, according to the Government Accountability Office.

Despite the problems, the ASDS has been used on several classified missions while improvements continue to be made.

One submarine expert familiar with the program expected, before the fire, a new program for three boats at a cost of about $1.2 billion. Early, unofficial estimates of about $100 million to repair the damage to ASDS-1 are "very uninformed" and likely very low, the source said.

Several sources said they expected the explosion and fire would not end the use of lithium-ion batteries in the ASDS.

"Lithium-ion batteries can be quite dangerous but they've been safely used many times before, and these batteries have gone through many cycles," a Pentagon official said.

"It almost certainly was a procedural issue," the submarine expert said. "Like most things, it is very safe if you follow the procedures. But if you don't follow the procedures, things can happen that you don't expect."