Key point: It is still unknown what exactly sunk the submarine.

In May 1968, a U.S. nuclear-powered attack submarine was sent on a secret mission to spy on the Soviet navy. Seven days later, with the families of the crew waiting dockside for the USS Scorpion to return from a three-month patrol, the U.S. Navy realized that the submarine was missing. Scorpion had been the victim of a mysterious accident, the nature of which is debated to this day.

The USS Scorpion was a Skipjack-class nuclear attack submarine. It was one of the first American submarines with a teardrop-shaped hull, as opposed to the blockier hull of World War II submarines and their descendants. It was laid down in August 1958 and commissioned into service in July 1960.

The Skipjacks were smaller than nuclear submarines today, with a displacement of 3,075 tons and measuring just 252-feet long by 31-feet wide. They had a crew of ninety-nine, including twelve officers and eighty-seven enlisted men. The class was the first to use the Westinghouse S5W nuclear reactor, which gave the submarine a top speed of fifteen knots surfaced and thirty-three knots submerged.

The primary armament for the Skipjack class was the Mk-37 homing torpedo. The Mk-37 had an active homing sonar, a range of ten thousand yards with a speed of twenty-six knots, and a warhead packed with 330 pounds of HBX-3 explosive.

Scorpion was only eight years old at the time of its loss, relatively new by modern standards. Still, complaints from the crew that the sub was already showing its age were rampant. According to a 1998 article in the U.S. Naval Institute Proceedings, Scorpion had 109 unfulfilled work orders during its last deployment. It had “chronic problems” with its hydraulics, its emergency blow system didn’t work and emergency seawater shutoff valves had not yet been decentralized. At the start of its final patrol, 1,500 gallons of oil leaked from its conning tower as it left Hampton Roads.

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