With news that the Nimitz-class aircraft carrier USS Carl Vinson (CVN 70) is en route to the Korean peninsula with three other ships, there is no doubt that tensions are high. With two carriers, there is a lot of striking power, but it is also a target for the North Koreans.
This is not an idle thought. On March 26, 2010, the Pohang-class corvette ROKS Cheonan was torpedoed and sunk by a North Korean mini-sub firing a 21-inch torpedo. So, the concern is what one of these subs could do to a carrier.
Let's look at what these subs are. The North Koreans have two front-line classes of mini-sub, according to the 16th Edition of Combat Fleets of the World. The Yono — the type of sub believed to have fired the torpedo that sank the Cheonan — is about 110 tons and carries two 21-inch torpedoes. The Sang-O is 295 tons and also has a pair of 21-inch torpedo tubes.
North Korea also has Romeo-class submarines, which have eight 21-inch torpedo tubes (six forward, two aft), with a total of 14 torpedoes. North Korea also has some mini-subs built to a Yugoslavian design with two 16-inch torpedoes, but those are believed to be in reserve.
That said, American aircraft carriers are very tough vessels. In World War II, the carriers USS Yorktown (CV 5) and USS Hornet (CV 8) took a lot of abuse before they sank. The carrier USS Franklin (CV 13) had one of the great survival stories of the war, despite horrific damage.
But today's carrier are much larger.
In fact, the Russians designed the Oscar-class guided-missile submarine to kill America's Nimitz-class carriers – and those have 24 SS-N-19 "Shipwreck" missiles, plus four 21-inch torpedo tubes and four 25.6-inch tubes meant to fire torpedoes with either massive conventional warheads or even nuclear ones.
This points to a North Korean sub being unable to sink a Nimitz-class carrier on its own.
But two torpedoes will still force a carrier to spend a long time in the body shop. And the escorts are more vulnerable as well.
A U.S. carrier could take a couple of hits and in a worst case scenario, she'd have to fly her air wing to shore bases.