Nuclear Reactors:
Are basically heat engines. As uranium fissions, the breaking apart of atoms releases energy, much of it in the form of
heat, which can then be used to do work. In a nuclear-powered submarine, reactor heat produces steam to drive the
turbines that provide the submarine's actual power. The development of compact, safe, and highly reliable pressurized
water reactors for naval use in the early 1950s was the major technological achievement that made nuclear-powered
submarines possible.

How Reactors Work:
Naval pressurized-water reactors include a primary coolant system and a secondary coolant system. The primary
system circulates water, which is pressurized to keep it from boiling, in a closed loop. As water passes through the
reactor, it is heated. It then goes through the steam generator, where it gives up its heat to generate steam in the
secondary system. Finally, it flows back to the reactor to be heated again. Inside the steam generator, heat energy is
transferred across a watertight boundary to the secondary system, also a closed loop. The unpressurized water in the
secondary system turns to steam when heated. The steam, in turn, flows through the secondary system to the
propulsion turbines, which turn the propellers, and to the turbine generators, which supply electricity. As it cools, it
condenses to water and is pumped back to the steam generator.

Steam Turbines:
Propel nuclear-powered submarines. Heat from the nuclear reactor, regulated from consoles in the maneuvering room,
generates the steam that drives the turbines, which are geared to a propeller shaft. The rotating propeller drives the
submarine through the water.

Model of Propeller:
From Sturgeon-Class Nuclear-powered Submarine (shown to the right)
Because propeller design is so important to both speed and noise levels, it remains one of the most secret aspects of
submarine technology. This declassified model of the propeller from a 1960s Sturgeon-class fast attack submarine is
the first ever put on public display. The model was used in tests at the David Taylor Model Basin, Carderock, Maryland,
to improve propeller design. Hydrodynamic testing focused on achieving the greatest submarine speed through the
water with the least noise and turbulence to reveal the boat's position.
Nuclear Reactor

Reactor-Generated:
Steam drives not only the propulsion system but also the turbine generators that provide the electricity submarines
require for their auxiliary systems. These systems furnish power for equipment cooling and the operation of weapon
systems, for lighting and cooking, for climate control and water distillation. Air must be purified and oxygen generated as
well, because the submerged submarine is a closed system and must maintain its own atmosphere.

The Loss of the Thresher:
In August 1963, the research vessel USS Trieste recovered the segment of brass pipe shown in this photograph from
the mid-Atlantic wreck of the USS Thresher (SSN-593). She had sunk on 10 April 1963 in 8,400 feet (2,600 m) of water
with the loss of 129 lives. The apparent cause, never proven, began with a leak in seawater piping that escalated into a
failure of the air-ballast system and an uncontrolled dive. The Thresher was the first of two U.S. nuclear-powered
submarines lost at sea. The second was the USS Scorpion (SSN-589), lost at sea in May 1968. Although propulsion
system malfunction has been ruled out, the cause of neither has been determined. Courtesy U.S. Naval Institute

USS Thresher (SSN-593), 1961-1963;
USS Thresher, lead ship of a class of 3700-ton nuclear-powered attack submarines, was built at the Portsmouth Naval
Shipyard, Kittery, Maine. Commissioned in August 1961, she conducted lengthy trials in the western Atlantic and
Caribbean areas in 1961 and 1962, providing a thorough evaluation of her many new technological features and
weapons. After the completion of these test operations, Thresher returned to her builders for overhaul.

On 10 April 1963, after the completion of this work, Thresher began post-overhaul trials. Accompanied by the submarine
rescue ship Skylark (ASR-20), she transited to an area some 220 miles east of Cape Cod, Massachusetts, and started
deep-diving tests. As these proceeded, garbled communications were received by Skylark, indicating trouble aboard the
submarine. It gradually became apparent that she had sunk, taking the lives of 129 officers, crewmen and civilian
technicians.

After an extensive underwater search utilizing the bathyscaph Trieste, oceanographic ship Mizar, and other ships,
Thresher's shattered remains were located on the sea floor, some 8400 feet below the surface. Deep sea photography,
recovered artifacts and an evaluation of her design and operations permitted a Court of Inquiry to determine that she
had probably sunk due to a piping failure, subsequent loss of power and inability to blow ballast tanks rapidly enough to
avoid sinking. Over the next several years, a massive program was undertaken to correct design and construction
problems on the Navy's existing nuclear submarines, and on those under construction and in planning. Following
completion of this "SubSafe" effort, the Navy has suffered no further losses of the kind that so tragically ended
Thresher's brief service career.
Taking the lives of 129 officers, crewmen and civilian technicians
Pelletier's Home Inspection
Alfred Leo Pelletier, CMI, HI36

Salute to the USS Thresher
Counter