We have some theories.
Key point: Bad parts were most likely to blame for the sub’s untimely demise.
What sank Thresher? The best available theory is the extensive use of silver brazing on piping throughout the ship. An estimated three thousand silver-brazed joints were present on the ship, and the theory goes that up to four hundred of them had been improperly made. Experts believe that a pipe carrying seawater experienced joint failure in the aft engine spaces, shorting out one of the main electrical bus boards and causing a loss of power.
In the United States Navy, submarines lost at sea are said to be on “eternal patrol.” One such submarine was USS Thresher. Meant to be the first in a new generation of fast nuclear-attack submarines, today it rests in more than eight thousand feet of water, along with its crew. Thresher is one of two American submarines lost since the end of World War II.
In the mid-1950s, the U.S. Navy was still pushing nuclear propulsion out to the submarine fleet. USS Nautilus, the world’s first nuclear submarine, had just been commissioned in 1954, and nine classes of submarines were created, including the Sailfish, Barbel, Skate and Skipjack classes, before the Navy felt it had a design worthy of mass production. Preceding classes of nuclear submarines were built in small batches, but Thresher would be the first class to build more than five. Altogether fourteen Threshers would be built.
The Threshers were designed to be fast, deep-diving nuclear attack submarines. They were the second class, after the pioneering Skipjack class, designed with the new streamlined hull still in use today. They were the first submarines to use high strength HY-80 steel alloy, which was used through the 1980s on the Los Angeles class.
The submarines were just 278 feet long, with a beam of thirty-one feet. They weighed 4,369 tons submerged, making them about 30 percent larger than the Skipjacks. Their S5W pressurized water reactor drove two steam turbines, which turned a single propeller to a combined thirty-thousand-shaft horsepower. This gave them a surface speed of twenty knots, and thirty knots submerged. This was a noticeable improvement over the underwater speed of the older Skate class, which could manage only twenty-two knots underwater.
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