Strategy Page on the US Navy’s need to work with — and even consider buying — modern diesel-electric submarines:
The U.S. Navy continues to debate the issue of just how effective non-nuclear submarines would be in wartime, and whether the U.S. should buy some of these non-nuclear boats itself. This radical proposal is based on two compelling factors. First, the U.S. Navy may not get enough money to maintain a force of 40-50 SSNs (attack subs.) Second, the quietness of modern diesel-electric boats puts nuclear subs at a serious disadvantage, especially in coastal waters. With modern passive sensors, a submerged diesel-electric sub is often the best weapon for finding and destroying other diesel-electric boats. While the nuclear sub is the most effective high seas vessel, especially if you have worldwide responsibilities and these nukes would have to quickly move long distances to get to the troubled waters, the diesel electric boat, operating on batteries in coastal waters, is quieter and harder to find.
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For much of the past decade the U.S. Navy has been trying to get an idea of just how bad the threat it. Thus from 2005 to 2007 the United States leased a Swedish sub (Sweden only has five subs in service), and its crew, to help American anti-submarine forces get a better idea of what they were up against. This Swedish boat was a “worst case” scenario, an approach that is preferred for training. The Gotland class Swedish subs involved are small (1,500 tons, 64.5 meters/200 feet long) and have a crew of only 25. The Gotland was based in San Diego, along with three dozen civilian technicians to help with maintenance.
For many years before the Gotland arrived, the U.S. Navy had trained against Australian diesel-electric subs, and often came out second. The Gotland has one advantage over the Australian boats, because of its AIP system (which allows it to stay under water, silently, for several weeks at a time). Thus the Gotland is something of a worst case in terms of what American surface ships and submarines might have to face in a future naval war. None of America’s most likely naval opponents (China, North Korea or Iran), have AIP boats yet, but they do have plenty of diesel-electric subs which, in the hands of skilled crews, can be pretty deadly.