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Nautilus(SSN-571), the first nuclear-powered submarine, at her christening.
Photo Courtesy of General Dynamics Electric Boat

The United States Navy has a legacy of innovation in nuclear-powered submarine design. In fact, nine one-of-a-kind Navy nuclear-powered submarines have been designed and built, and they have all pushed the limits of undersea design and capabilities. In addition to the world’s first nuclear-powered submarine, USS Nautilus (SSN-571), these unique boats have included the only U.S. Navy submarine ever constructed with a liquid-metal cooled reactor, the only twin-reactor submarine, two prototype electric-drive submarines, and the Navy’s deep-diving research submarine, NR-1. The lessons learned from the problems encountered in these aggressive steps in undersea technology reside in one of the Navy’s most important resources—the designers and engineers who have designed and built the nine unique nuclear submarines in U.S. Navy history and those who have inherited their legacy.

The Nautilus Challenge

The design and construction of USS Nautilus (SSN-571) to accommodate a nuclear powerplant marked the birth of the Naval Nuclear Propulsion Program. Under the detailed supervision of then-Capt. Hyman G. Rickover, engineers teamed with the newly-formed Naval Reactors Branch of the Atomic Energy Commission to tackle the difficult project.

Nautilus presented a vast array of challenges that had never before been encountered in submarine construction, or in any engineering project. For example, there were the issues of balancing the submarine, given the weight of the reactor and the shielding in the neighboring bulkheads, and of designing a piping system that would accommodate the extremely high-pressure, high-temperature water that would cool the reactor. Even a small break in the piping system would cause large amounts of water to flash instantly to steam. The team was able to solve those obstacles, and in just over three years, the submarine advanced from Congressional authorization to commissioning. On Sept. 30, 1954, Nautilus became the first commissioned nuclear warship in the world.

Nautilus set not only speed and endurance records—she also became the first vessel ever to transit the Arctic region under the icecap and was the first to travel 20,000 leagues under the sea, a mark previously attained only by her fictional namesake. She was decommissioned on March 3, 1980, after steaming almost a half-million miles, and today is a museum ship at the Submarine Force Library and Museum just outside the main gate of the Naval Submarine Base in Groton, Conn.

Second Nuclear Sub, But Another First-of-a-Kind

The U.S. Navy’s second nuclear boat also presented unique design challenges. Preliminary development work on nuclear power involved the investigation of a number of reactor design concepts, but only two were chosen for construction: the pressurized water reactor used on Nautilus, and the sodium-cooled reactor used on the follow-on nuclear submarine USS Seawolf (SSN-575).

As with Nautilus, the development of Seawolf’s liquid sodium plant involved the construction of a land prototype plant. Seawolf was launched on July 21, 1955, and conducted sea trials in January 1957. After acceptance, Seawolf operated as an active unit of the Atlantic Fleet and in 1958 made a record-breaking submerged run of two months, traveling more than 13,000 miles submerged, producing air and water for her crew the entire time.

Seawolf operated more than two years and steamed 71,000 miles on her sodium-cooled reactor, but, in 1958, the Navy had her refitted with a pressurized water reactor similar to the one in Nautilus, and that design is still the standard today. On her replacement plant, Seawolf steamed for another 27 years, finally being retired in 1987.

Seawolf stands out in the record books for other reasons as well. A few months after she was placed into service, then-President Dwight D. Eisenhower rode aboard the submarine, making him the first U.S. commander in chief to go “underway on nuclear power.”

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USSSeawolf(SSN-575) enters the Thames River in Connecticut during her christening on July 21, 1955.
Photo courtesy of General Dynamics Electric Boat

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