The Thresher Tragedy

 

Today is the anniversary of the loss of the USS Thresher, a particularly devastating blow to the tiny US Submarine Force. At the time, there were only about 4,000 of us in US submarines, so the loss of 129 men was a terrible blow.

As it happened, the next day my San Diego submarine was leaving for a Dependent’s Cruise” where our spouses have the opportunity to go to sea on our submarine, to see what it is we do.

Submarines are a mystery not just for the usual citizen, but our families as well.

In that early morning, our Executive Officer told the assembled wives that he knew that all of us had friends on the Thresher (I had Annapolis Classmates, and Submarine School Classmates), and that if any spouses wanted to fore-go going out that day, everyone would understand.

About 15 of the assembled 30 wives decided to go home. My wife stayed — she never missed a Cruise — and she has probably 20 dives to her credit, and probably five or more on the periscope.

The Thresher, it is reported on the CBS Evening News, crushed when a seam ruptured and caused a cascading series of events. I suspect that what actually killed my friends was a bit of nuclear hubris.

Submarines need to seek “neutral buoyancy” — they normally float just like a ship and they sink when certain tanks are flooded to make them negatively buoyant. Even negatively buoyant they can be maintained at a depth within six inches by using power.  Once submerged they pump water out of the tanks while slowly taking off submerged speed until they can literally “hang” in the water submerged without any speed.

Submarines need to go through this exercise because they do things in port to mess up their weight — they load torpedoes or remove them, gain or lose people, add or reduce food, etc.

Submarines do this exercise of determining neutral buoyancy regularly, but nuclear submarines had so much power available that they didn’t care how much they weighed — they had excess power always available to hold them at whatever depth they wanted to go. A nuclear submarine never had to “Go Silent, Go Deep” — if they were discovered they just cranked up the nuclear power and outran the surface ships. Problem solved.

When the Thresher hull developed a manageable leak, the nuclear power plant was designed to shut down. Suddenly there was no power to keep the submarine at a safe depth if it was negatively buoyant. Apparently it was so negatively buoyant that all the compressed air and pumps combined could not bring it to the surface — it continued to sink until the hull crushed.

Subsequently, Nuclear Submarines were directed to find and maintain neutral buoyancy, just like every other submarine. Good engineering practices are good engineering practices, regardless of power plant.

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