WASHINGTON — A ten-thousand-pound explosive charge set off close to the littoral combat ship (LCS) Jackson caused minimal shipboard damage, the US Navy said today, and the ship is back at Mayport, Florida, for more detailed examination.

"The ship performed exceptionally well, sustaining minimal damage and returned to port under her own power," the Navy said in a statement.

The July 16 test was the third and last Full Scale Shock Trial (FSST) to be performed on the Jackson, which had been outfitted with around 260 sensors and gauges to measure the effects of the explosion on the ship and many pieces of on-board equipment.

Earlier tests were carried out June 10 and June 22. A 10,000-pound charge was used in each of those tests as well, with the charge being moved closer to the ship with each test.

The Jackson is an all-aluminum trimaran, the first Independence-class variant and the first LCS to undergo FSSTs. The Milwaukee, of the steel-hulled Freedom class, is being prepared for another series of FSSTs to begin in August and continue into September.

Unofficially, the Jackson has been reported to have performed better than expected during the trials, in many cases meeting or exceeding modeling predictions done prior to the Florida tests.

While the Navy routinely performs FSSTs on all its combat ship designs, the timing of these tests came earlier than scheduled, driven by complaints about LCS survivability from Michael Gilmore, director of the Pentagon's Office of Test and Evaluation. Gilmore had been expected to be aboard the Jackson for the last test, but his office confirmed he did not attend.

But the Jackson's crew and dozens of technical representatives and observers from interested commands and offices — including DOT&E — were aboard.

The July 16 explosion was large enough for the US Geological Survey (USGS) to have reported a 3.7 magnitude earthquake about 168 kilometers east northeast of Daytona Beach Shores, Florida — an area confirmed by the Navy to be within the region where the Jackson test took place. The report set off a flurry of media reports about a possible connection with the LCS tests.

The Navy did not confirm the connection but, in its statement, noted "there were reports of increased seismic activity around the time of the test."

On Tuesday, the USGS reclassified the event as an "experimental explosion."