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Nuclear Power for Surface Combatants

A third advantage, related to the other two, is effectively infinite time on station, again without much afloat support. The Navy is currently intensely interested in the anti-missile mission, which is a key justification for the future cruiser. Anti-missile operations require such ships to loiter in forward areas. They must be survivable, which includes an ability to operate without giving an enemy the opportunity to cut them off by cutting their fuel support. Unlike most ships, the missile cruisers may be unable to withdraw every few days to fuel in a safe area; there may be no safe areas at all nearby.

USS South Carolina (CGN 37)

The nuclear-powered guided missile cruiser USS South Carolina (CGN 37) underway during a composite training unit exercise. Congress insisted that the California-class ships be nuclear-powered, but their weapons fit, including two 5-inch guns and two Mk. 13 missile launchers, was limited for such large and expensive ships, and they lacked a helicopter hanger, which was becoming of increasing importance. U.S. Navy photo

Yet another claimed advantage is the sheer power output of a reactor. When the Navy operated oil-fueled carriers, it was often said that they had to slow down when launching large numbers of aircraft because they could not generate enough steam for both flight operations and for full speed. In the late 1950s, when the Navy contemplated a new class of Typhon missile ships, it planned to give them nuclear power specifically to provide sufficient power for their massive radars. It may be argued that a future anti-missile ship will need similar radar energy output. That might also apply to the power required for future beam weapons.

Reactors need fueling well before they literally exhaust their uranium. As it reacts, uranium forms by-products, notably xenon, which gradually poison it. Changing the amount of uranium or the configuration of the fuel can extend lifetime. Even if the amount of uranium has to be changed drastically, that is far less expensive than refueling.

Once the Soviets deployed fast nuclear submarines, it seemed that carrier groups needed antisubmarine protection. To use sonar effectively, they could no longer rush along at 30 knots; they had to limit themselves to about 20 to 25 knots. Once the Navy was used to such speeds, some asked whether higher speed was even worthwhile. This was one factor that led, by the end of the 1990s, to the decommissioning of all the Navy’s nuclear-powered cruisers. Without any enemy filling the sea with fast-attack submarines today, however, the argument may reverse. High sustained speed is exactly what the fleet needs in order to deploy to meet distant emergencies. In the past, the Navy maintained battle groups on station near possible hot spots, but that limited the number available at any one time. More recent practice has been to keep carriers home, often deploying them en masse as needed. In that case, sustained deployment speed matters a lot more.

USS Arkansas (CGN 41)

The nuclear-powered guided missile cruiser USS Arkansas (CGN 41) pulling clear of the nuclear-powered carrier USS Enterprise (CVN 65). The Virginia class improved upon the armament of the California class with two Mk. 26 twin-arm missile launchers that could fire both the SM-2 and the ASROC, and a helicopter hanger accessible by an elevator aft. Unfortunately, the elevator/hanger arrangement never worked satisfactorily, and armored box launchers for Tomahawk cruise missiles were carried at the expense of helicopter capabilities. U.S. Navy photo

The other factor in the fall of the nuclear cruisers was the post-Vietnam crash in defense funding. Whatever its full-life cost, a nuclear cruiser cost a great deal more to buy. It needed a much larger crew, because its two reactors needed so many operators. In the 1960s, Congress mandated nuclear power for any surface warship of more than 8,000 tons. Post-Vietnam, that seemed more a matter of Rickover’s enormous political power than of naval logic. When Adm. Elmo Zumwalt Jr. became Chief of Naval Operations (CNO), he wanted to build a new cruiser or destroyer armed with the new Aegis system. Because of the law, he asked his ship designers to produce an Aegis destroyer, which turned out to be too small to be worthwhile. Ultimately, Aegis was shoehorned into the Spruance hull, which was just smaller than the mandated tonnage. It was generally understood that further nuclear surface combatants were not affordable. The existing nuclear cruisers were never fully modernized, and they were discarded at the end of the Cold War.

Currently the Navy operates two types of nuclear-powered warships: aircraft carriers and submarines. Carriers are powered by two huge reactors, producing at least 120,000 SHP each. Submarines occupy the other end of the U.S. scale. The Virginia class probably has about the same output as the earlier Los Angeles, about 30,000 SHP. Seawolf is more powerful. The much more massive (because inherently much quieter) reactor in Ohio-class missile submarines probably produces about 35,000 SHP. By way of comparison, a destroyer needs 80,000 to 100,000 SHP and a large amphibious ship 40,000 to 50,000 SHP. The missile cruisers of the 1960s were rated at 60,000 SHP, using two reactors like those in a Los Angeles. The big carrier reactors were developed as part of a program to reduce the number of reactors needed per ship, and hence the number of very expensive reactor operators. Its initial product was to have been a single destroyer reactor (i.e., 60,000 horsepower) and the carrier reactor is apparently the next step up in size.

USS Virginia (CGN 38)

The nuclear-powered guided missile cruiser USS Virginia (CGN 38) underway off the coast of Cape Henry, Va. U.S. Navy photo

At least in the Navy, the lifetime cost of a nuclear-powered ship follows a very different cycle from that of a conventional warship. The ship is refitted when the reactor is refueled, and typically that is when the most money is spent. That makes sense because refueling inevitably involves cutting the ship open for access to a reactor buried deep inside. The reactor is deepest in a carrier, with her flight, hangar, and other decks over the reactor. In a submarine, the reactor is nearer the outside of the ship, but cutting into her pressure hull is difficult and must preserve the hull’s strength. For these reasons, for decades, the main thrust in reactor development has been toward extending lifetime. Reactors need fueling well before they literally exhaust their uranium. As it reacts, uranium forms by-products, notably xenon, which gradually poison it. Changing the amount of uranium or the configuration of the fuel can extend lifetime. Even if the amount of uranium has to be changed drastically, that is far less expensive than refueling. In submarines, the time between fuelings began at little more than a year, but by the 1960s it was eight years or more. Submarine operating life began to be expressed in terms of the number of fuelings the ship needed. Current submarine reactors are described as one-shot: They are never refueled during the 25- or 30-year life of the ship. Carriers are expected to last much longer; they are one-refueling ships.

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Norman Friedman is an internationally known strategist and naval historian. He is the author of...