How a Tiny Swedish Sub Took Down an Entire US Aircraft Carrier

In a war game for the ages.
Ameya Paleja
The USS Nimitz, an aircraft carrier of the same class.US Navy / Wikimedia

The Nimitz-class aircraft carrier, USS Ronald Reagan, can carry up to 90 aircraft on its surface and boasts of multiple radar systems, measures to counter torpedoes, and even electronic warfare. But a small diesel-powered submarine built for the Swedish Navy 'ran rings' around it and sunk it during the war games of 2005, Business Insider reported.

Interestingly, the U.S.Navy decommissioned its diesel submarines in the 1990s in favor of nuclear ones. Though costing just a few hundred million dollars to make, diesel-powered submarines need air to combust their fuel and often need to emerge to restock their air supplies. Even while using a snorkel, the detection of a diesel submarine is easier as it rises to the surface every few days. On the other hand, nuclear-powered submarines can stay underwater for longer, emerging only to restock supplies needed for their crew. So, it does make sense to switch to nuclear-powered submarines to retain the element of surprise. 

However, even after the U.S. switched to nuclear-powered subs, Sweden continued to develop its diesel-powered submarines. The Gotland class features the noise-less Stirling engines that do not need air for their propulsion, allowing them to stay underwater for weeks when needed or switching to diesel power when traveling longer distances. 

By charging the batteries on the submarine, a navy unit can take up a noise-less stealth operation as well. Even though nuclear-powered submarines have batteries, they need to run a coolant to keep the reactor temperatures low, which can be a giveaway of their location. However, with a Stirling engine by its side, the Swedish submarine was able to run a quieter operation, which proved fatal for the aircraft carrier, not once or twice but for two years, Business Insider reported. 

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Aiding its success were other design modifications on the submarine such as sonar-resistant coatings on its hull, radar-absorbent on its tower, slow-turning propeller, acoustic deadening buffers on its inner machinery, and 27 electromagnets that counter detection from magnetic anomaly detectors. 

With abilities to turn sharply and computerized steering that allows only one operator to control the depth and the course, the submarine has higher maneuverability when compared to other submarines making it even harder to be detected, following a strike. Following the exercise, the U.S. Navy requested for the submarine to be deployed with the U.S. forces to improve their antisubmarine warfare which was then extended for a total of two years. 

The U.S. Navy has, however, stuck to its policy of using nuclear-powered submarines. 

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