The US Navy were surprised when a Swedish diesel submarine sank a powerful US carrier, USS Ronald Reagan in wargames. Furthermore, the sub maneuver stealthily without getting detected by ships in the carrier strike group.

In 2005, the world's powerful warship with the best defensive ships ever devised for sea combat were all defeated like what the German U-Boats did in prior wars. Sinking the US carrier represented weaknesses that were revealed.

In contrast, the Ronald Reagan cited by 19Forty Five cost $6.2 billion for all its systems, getting sunk by a cheaper sub was not acceptable for the USN.

The HSMS Gotland always triumphed

It was the same result over and over again for two years of wargames that ended with US ships and nuke subs dying via virtual attacks. In all that time, the Swede sub won on all occasions prompting a rethink of US naval strategy, reported the Business Insider.

It was a mere drill when the carrier was sunk, but the circumstance of the HSMS Gotland victory took the US by surprise. A small Swedish sub powered by diesel is at a mere 1,600 tons that is able to outsmart what the best-equipped navy that was never detected once.

According to naval expert and analysts, Norman Polmar, the feat of one sub winning over a carrier strike group gave US antisubmarine specialists an education that would have been costly in real combat. When the Swedish diesel submarine sank a powerful US carrier, it virtually caused concern.

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David versus Goliaths

To be exact, the USN was curious how the Gotland was able to bypass all the ships and sensors looking for it. Another is how a diesel sub attacked and succeeded to sink ships. By contrast, the US had no diesel subs in service since 1990, noted TakTikz.

Submarines driven by diesel engines used to be limited by the need to run noisy, air-consuming engines, which necessitated that they could only stay underwater for several days before requiring to surface. When a submarine surfaces, that is when it's most defenseless and could be easily detected, also when using the snorkel.

Nuclear-powered submersibles can stay submerged longer, and the air is not a problem. They can stay underwater for months, and move faster in water.

The secret of the Gotland which is relatively small at 200-feet long that served first in 1996 which had the first Air Independent Propulsion system or Stirling engine. The engine is used to power the 75-kilowatt battery with liquid oxygen to move it in the water.

Using the Stirling engine, the Swedish sub can stay submerged for two weeks and keep a steady 6-mph speed, or travel faster at 23-mph but it runs down the batteries faster.

When it's above the waves, it uses a snorkel. It lacks the equipment to make it less detectable to other sub hunters and ships.

But the Swedish sub has good maneuverability due to the x-type rudder, allowing it to make tight turns and hug the sea bottom. It has 27 magnets on the hull to scramble metal detectors, rubber buffer inside to lessen sonar returns.

The success of this AIP power sub as the first Swedish diesel submarine sank powerful US carrier has encouraged its use by other naval forces. Designs are getting better to threaten American carriers.

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