WASHINGTON (AP) \u2014 A hundred years ago, a mysterious explosion hit the only major U. S. warship to sink during World War I. Now the\u2026<\/b>
\nWASHINGTON (AP) \u2014 A hundred years ago, a mysterious explosion hit the only major U. S. warship to sink during World War I. Now the Navy believes it has the answer to what doomed the USS San Diego: An underwater mine set by a German submarine cruising in waters just miles from New York City.
That\u2019s the conclusion of an investigation by scientists, archaeologists and historians convened by the U. S. Naval History and Heritage Command. Last summer, the researchers sent an unmanned underwater vessel to inspect the site off New York\u2019s Long Island. Their analysis ruled out a torpedo and sabotage, two other possible scenarios.
The San Diego was sailing to New York on July 19,1918, when an external explosion near the engine room shook the armored cruiser. Water rushed into the hull. Within minutes, the 500-foot warship began to capsize. Weighed down with 2,900 tons of coal for a planned voyage across the Atlantic Ocean, the vessel sank in less than a half hour. Six crew members died.
\u201cThe explosion felt like a dull heavy thud,\u201d Capt. Harley Hannibal Christy, commander of the USS San Diego, wrote in a naval inquiry commissioned shortly after the warship sank. He had been standing on the bridge of the ship, on a clear day with light winds.
German naval records recovered after the war revealed that U-boat 156 had sailed just off the coast of New York, planting explosives.
\u201cWe believe that U-156 sunk San Diego,\u201d said Alexis Catsambis, an underwater archaeologist with the Navy. He presented the findings this week in Washington at the annual meeting of the American Geophysical Union.
Today, the shipwreck of San Diego is a rusting but well-preserved sanctuary for fish and lobsters. The researchers used information from the underwater vessel to create high-resolution 3D maps of the wreck. They modeled impact and flooding scenarios to analyze how the ship might have been attacked.
The flooding patterns weren\u2019t consistent with an explosion set inside the vessel. And the hole didn\u2019t look like a torpedo strike.
\u201cTorpedoes of the time carried more explosives than mines \u2014 and would have shown more immediate damage,\u201d said Arthur Trembanis, at University of Delaware marine scientist who collaborated on the study.
The mine was anchored at optimal depth to tear open a warship, said Ken Nahshon, a research engineer at the Naval Surface Warfare Center in Maryland, who also assisted the investigation.
The underwater explosive hit an unguarded lower part of the ship, where the hull was only about a half inch thick, said Nahshon. Had it struck the warship\u2019s armored band, the 5-inch thick steel plating would have minimized the impact.
After the blast, the commander directed the ship\u2019s gunners to \u201copen fire on anything resembling a periscope.\u201d Between 30 and 40 rounds were fired, in case an enemy submarine was nearby. The captain was aware German U-boats may have operating in the area. As the ship began to sink, Christy ordered the crew to pile into life rafts and dinghies. A passing whaleboat and two steamships helped rescue most of the San Diego\u2019s 1,100 sailors.
Follow Christina Larson on Twitter at @ larsonchristina .<\/p>\n