From the days of ancient Greece it has been recognized that by diving beneath the surface of the sea a warship could become invisible and perhaps invincible. Alexander the Great used some form of submersible vessel during the siege of Tyre in 332 B.C., but it was not until 1620 that a Dutch physician, Cornelius van Drebel, built several submersibles that navigated submerged in the Thames, propelled by a “12-manpower” crew of rowers.
Around 1800, Robert Fulton, with no backing in America, turned to France and under a grant of money from Napoleon built the first Nautilus in Paris. She was propelled submerged by a crew of three, and by sail when surfaced. Her maximum submerged endurance was five hours. Whatever the technical merits of this submersible, the French considered the use of a submarine to attack ships of a blockade to be a dishonorable method of warfare. The British, when approached by Fulton, not only turned away, but Earl St. Vincent, First Lord of the Admiralty, set the basis of British policy for the next century with the statement that he did not support the submarine concept since to do so would “encourage a mode of war which those who command the sea do not want and which, if successful, will deprive them of it.”
In America, the first operational submarine effort was made by David Bushnell’s Turtle, during the American Revolution.
Submarines were tried in the United States, with relative ineffectiveness during the Civil War. Progress during the 19th century was limited by poor propulsion modes. Steam was used for surface propulsion and the storage battery-motor drive for submerged operation. It was not until the turn of the century—when the internal combustion engine and the electric battery combination made the technical breakthrough in propulsion—that submarine progress jumped forward. A submerged speed of 7 knots and a 24-mile range by battery, and a surface speed of 8½ knots by gasoline engine was finally attained just 70 short years ago under the pioneer work of men including John Holland and Simon Lake. One notes here the interesting sidelight that, just as steam had to give way to the gasoline internal combustion engine for this technical advance, so, too, did the diesel engine in turn step aside 55 years later for steam propulsion when the nuclear engine breakthrough was made.
For the first half of the 20th century, however, submarine propulsion progress was tied to the improved development of the gasoline/diesel engine. Its high-water mark in the United States was the Tang class of 1,800 tons displacement, with 6,500-h.p. diesels attaining a 20-knot surface speed, and two 126-cell batteries for 10-plus knots deep-submergence speed. The Schnorkel, or snorkel, introduced by the Dutchman Jan Wechers in 1933 (after the principle lay dormant since first crudely conceived in 1801 in Fulton’s Nautilus), was perfected by the Germans, and gave their 1,600-ton U-boats 16½ to 17 knots submerged speed for 60-80 minutes. The device was later adopted by the United States in the Guppy program, in which 17-knot submerged speed was obtained.
In 1937, the German scientist Hellmuth Walter submitted his plans to the German Navy for a turbine-powered submarine propulsion system using oxygen generated by hydrogen peroxide to operate the turbine while submerged. Permanganates of sodium, potassium, or calcium were considered for catalysts to break H2O2 to O2 + H2O. The generated oxygen and diesel oil were burned in a combustion chamber with a water spray; the resulting evolved steam and combustion gases were fed to drive the turbine. A 4,000-h.p. prototype plant was operated at Kiel. By December 1943, the first two Walter boats, the U-792 and U-794, were ready for sea trials. They demonstrated 25 knots underwater speed for short intervals, with 20 knots for 5½ hours.
After World War II, the United States obtained the Walter boat, U-1406, and set up a facility at the Engineering Experimental Station in Annapolis, where five advanced chemical power plants were tested.
Thus, by 1947, submarine development had progressed to diesel-battery type propulsion systems for 1,800-ton fleet boats with 20 knots surface speed, 15-plus knots snorkel speeds, and 10 knots deep-submerged speed at about one hour endurance. A significant propulsion improvement, the Walter cycle, appeared ready for final development and incorporation into future U. S. boats. Its prospects: 25-knot submerged speed for six-hour endurance, or a performance factor of about 15 better than the internal combustion engine-battery performance.
In 1938, the fission phenomenon was discovered by the German researchers Hahn, Strassmann, and Meitner, and the prospect of its usage to produce large amounts of energy was underscored in Albert Einstein’s 1939 letter to President Franklin D. Roosevelt which evoked the nation’s nuclear weapon effort. At about the same time, paper studies were generated by Gunn and Cooley of the Naval Research Laboratory for a fission chamber in which steam could be generated to operate a turbine for a submarine plant. The nation’s attention was turned, however, in the direction of fission energy for the bomb, and the giant effort of the Manhattan Project engulfed all scientific thoughts and national capabilities for the next seven years.
Late in 1945, Phillip Abelson, an associate of Gunn’s at NRL issued a report in which he removed the XXVI-model Walter cycle machinery from a submarine plan and replaced it—on paper—with his conception of a nuclear plant. NRL technical surveys predicted that with a concerted effort in about two years an atomic-powered submarine could be placed in operation capable of 26 to 30 knots submerged speed, with an endurance of many years without refueling. The report proposed a liquid metal, sodium potassium, as the heat transfer agent in the reactor, which was mounted, along with its shielding, outside of the vessel along the keel. In a prophetic prediction of the Polaris submarine weapon system, the report said “This fast, submerged submarine will serve as an ideal carrier and launcher of rocketed atomic bombs.” There being no directed interest in naval nuclear propulsion at the time, the report, along with others proposing naval plants, was pigeonholed.
Other events, however, were soon to occur which, though completely unrelated at the time, eventually became the nuclei around which the naval nuclear program coalesced.
In April 1946, the Manhattan Project, through its Oak Ridge Laboratory in Tennessee, invited selected large industrial companies, the Navy, and some other federal agencies to participate, with the loaned assignment of technical personnel, in developing, designing, and building the world’s first nuclear power reactor. Perhaps out of scientific curiosity, or of “not wanting to be left out if anything came of it,” or of far-sighted conviction of the dawn of the nuclear power era, the response was excellent. The large electrical companies, General Electric, Westinghouse, and Allis Chalmers; the boiler fabricators like Babcock & Wilcox, chemical companies like Monsanto; the universities, and the Navy and NACA contributed excellent talent. Later on, many of these scientists and engineers, as well as their parent companies and agencies, played important roles in the naval nuclear program. Farrington Daniels, professor of chemistry at the University of Wisconsin, and previously director of the Manhattan District’s University of Chicago Metallurgical Laboratory, became the chief technical consultant on the Project and it was appropriately named the “Daniels’ Pile.” The reactor was enriched uranium-fueled, beryllium-moderated, and high temperature helium-cooled. Although the reactor never progressed into the construction phase, the effort would be significant to the later naval nuclear program for at least five reasons. First, it represented an official national effort to develop nuclear power for non-weapon purposes. Second, work was done to outline the technical problems in developing, designing, and building a power reactor. Third, a reactor type was investigated which later was considered as one of the possibilities for naval application. Fourth, industrial, university, and federal agency scientific and engineering talent was brought together and jointly applied to a reactor development problem. Much of this talent eventually wound up as the technical leadership in evolving the Nautilus’ power plant. Finally, the Navy assigned five officers and three civilians to the Oak Ridge effort with one of the officers, Captain Hyman G. Rickover, as the senior officer. This team played the key headquarters role in eventually moving the Nautilus from concept to reality.
At about the same time, General Electric, as contractor-operator of the Manhattan District’s Hanford plutonium works, was directed to build the Knolls Atomic Power Laboratory in Schenectady, N. Y. This laboratory, assisted by company technical support, did the necessary research and development in support of the Hanford operation. In addition, it was authorized to investigate the feasibility of power reactors. Its effort soon was oriented toward a liquid metal-cooled, enriched-uranium power breeder reactor with an auxiliary effort studying the liquid metal-cooled reactor for naval propulsion. (The senior BuShips naval representative at General Electric’s Schenectady Works was Captain Harry Burris, originally scheduled to lead the Oak Ridge naval contingent, whose reassignment was supplanted by Vice Admiral Earle Mills’s orders to Rickover.)
As events were to turn, the G.E.-operated laboratory, in a few years, was to direct its major effort toward the development of this basic reactor type for what eventually became the propulsion plant for the USS Seawolf (SS(N)-575).
Parallel to this capability buildup and preliminary development work in the 1946-48 period, political maneuvering occurred, in both the Navy and Atomic Energy establishments which established the organizational, fiscal, and political base from which the naval reactor program was to springboard. Following a one-year assignment at the Oak Ridge Laboratory, Captain Rickover was transferred back to the Bureau of Ships as an assistant to Admiral Mills, and Captain A. G. Mumma was given responsibility for the Navy’s interest in nuclear ship propulsion.
A period of embryonic convulsions occurred from mid-1947 for the next year as the Navy and the Atomic Energy Establishment evolved, by cajoling and manipulation, a series of decisions which led, by late 1948, to the launching of the Nautilus Project.
First, there was the in-house struggle between Captain Rickover and Captain Mumma for leadership of the naval effort. Rickover emerged not only as the “leader,” but also as the “father.”
Second, there occurred the Navy decision to throw its principal new propulsion development effort not to the already partially-proven Walter hydrogen peroxide-cycle plant, but to the totally new and untried nuclear plant. This decision was made in an evolutionary fashion as the nuclear work, hesitatingly started, picked up momentum and demonstrated its advantages over the Walter cycle. A conviction had to be generated within high-level naval sources to go the nuclear route. The technical staff-work of Rickover and his Oak Ridge-assigned naval contingent, backed up by a strong assist from Edward Teller as to the feasibility of developing nuclear power in three years, and with Admiral Mills’s backing, finally convinced Admiral Chester Nimitz, Chief of Naval Operations, and through him, the Secretary of the Navy.
Third, was the matter of convincing the AEC to undertake the development of the naval nuclear plant. The 1946 Congressional Atomic Energy Act specified that all work involving nuclear materials would be assigned to the Atomic Energy Commission. This “nuclear package” was adjudged to include the reactor core, its pressure vessel, controls, and the primary coolant out to its thermal energy conversion boundary. Furthermore, all fissionable and special materials were to be owned solely by the AEC. Technical program and budgetary responsibilities involving this package were assigned to the AEC. Consequently, a nuclear reactor program could be undertaken only by the AEC, within its own approved efforts, and within its own direct or subcontracted facilities.
Having the support of responsible key naval leaders, albeit somewhat tenuous in parts of the entire BuShips/CNO organization, Rickover sponsored a 1948 letter from the BuShips’ Chief Mills to the AEC, which stated that the sea service felt a nuclear-powered submarine was possible, was needed, and, if given proper emphasis, could be completed by the mid-1950s. In Fiscal Year 1949, the AEC budgeted the first monies (about half a million dollars) for this effort.
Fourth, there was the establishment of a “double hat” organizational responsibility by the naval group in both the AEC and the Bureau of Ships. This was accomplished at the headquarters level by Rickover’s assignment as Chief of BuShips’ Nuclear Power Division, and at the AEC as Chief of the Naval Reactors Branch of the Division of Reactor Development. His Washington-assigned officers also peopled both organizations. Likewise, in the field, many of the assigned naval personnel had at least two, and sometimes three, hats as a BuShips representative, as an AEC Regional Operations Office Chief, and as a working scientist assigned to a National Laboratory.
And, fifth, there was not only the assignment of the submarine nuclear project to an AEC laboratory, but also the mustering of program resources and technical enthusiasm in its behalf. Early in 1948, the AEC assigned its Argonne National Laboratory (outside Chicago) the responsibility for the development of power reactors. The Daniels’ Pile technical group at Oak Ridge was reassigned to Argonne—then under the directorship of Walter Zinn, a reactor development-oriented scientist—with the engineering and technology-oriented people making the move, while the research and scientific-oriented people stayed behind.
Zinn had oriented the Laboratory’s effort toward development of the liquid metal-cooled fast breeder and was deeply involved in the design and construction of (Experimental Breeder Reactor No. 1)EBR1. As a result, many of the supporting functions at this national laboratory were heavily reactor development-oriented rather than tuned to basic research.
The funds and personnel available from Argonne were adequate to instigate a number of design studies and initiate the start of basic development. The Laboratory, however, had the breeder reactor as its first priority and could not devote the total engineering and scientific effort required for the execution of what emerged as the Naval Reactor Program.
As the program developed from reactor plant concept at Argonne to detailed design and hardware fabrication at Westinghouse, an experienced shipbuilder was required who would work under the direction of Rickover. The U. S. Naval Shipyard at Portsmouth, N.H., had the experience but was management-pledged to the regular BuShips line of control. Electric Boat Company, with the independence inherent in private business, could administer its regular submarine building program under conventional BuShips management direction, but could also undertake the nuclear program under Rickover’s direction. The resident superintendent of ships’ supervisor’s office had to satisfy two masters.
Rickover’s “two-hat” responsibilities gave him the technical, fiscal, and legal entries into two separate, yet companion organizations—the AEC and the Navy (particularly BuShips). Since, by law, the AEC controlled all “nuclear” hardware, Rickover’s AEC Naval Reactors Branch could authorize programs, funds, and nuclear materials into Argonne, its assisting laboratories, and their contractors for all the nuclear reactor work. The Navy could, through Rickover’s prodding of CNO, convey the national need of nuclear power for ships, and through Rickover’s BuShips Nuclear Power Division, could authorize programs, funds, technical guidance, and review for work on the energy conversion equipment, and, through the ship design codes for work on hull design and construction. Thus, with Westinghouse brought in on December 1948 as the overall nuclear propulsion plant designer, AEC set up the Company-operated, government-owned Bettis Atomic Power Laboratory (BAPL) to develop and design the reactor and its auxiliaries. The Navy then authorized and funded BAPL through BuShips contracts to develop and design the energy conversion equipment and to integrate the total plant into the Electric Boat Company’s ship-design and construction program, which was authorized by the Bureau of Ships.
From the start, the nuclear propulsion plant was considered, not as a developmental model to test a concept, but as an actual prototype which could be placed in an operational submarine hull to produce a useful fleet vessel.
First considerations were for a hull size similar to the fleet boats—i.e., 18-foot diameter, about 300-feet long—with a displacement in the 2,000-ton range.
Since the single greatest weight of the nuclear plant is the shielding which is essentially wrapped around the reactor, the smallest size reactor gives a plant of least weight. A small-size reactor must be fueled with highly enriched uranium. In the late 1940s, the amount of such material which could be allocated away from the weapons programs was very limited. Consequently, the reactor design was directed to the conservation of least-critical uranium mass.
Similarly, for least-reactor size, a high specific power density in the core was desired. And since the dynamics of reactor control was a new art, inherent stability against neutron flux transients was sought.
The resultant desired characteristics oriented the reactor design to: highly enriched uranium reactor core; thermal, or near-thermal, energy neutron flux; conservation of uranium, i.e., low neutron absorption materials; and high power density and structurally compact reactor core.
The Nautilus program therefore began with an examination of three reactor cycles responsive to the above criteria. These reactor cycles included:
- The gas-cooled reactor investigation was a takeoff from the Daniels’ Pile. Because of the poor heat transfer properties of gas, and because of the temperature limitations of materials available in the late 1940s, the reactor had to be relatively large; energy conversion equipment (from gas to steam) was large, and the resultant plant occupied too much space.
- The liquid sodium-cooled reactor provided the high power density because of excellent heat transfer properties associated with sodium; it could be moderated to be slightly more epithermal than a water reactor; steam conditions on the secondary side of the heat exchanger were compatible with modern turbine inlet design. However, liquid sodium posed chemical and metallurgical problems of unknown scope, required leak-tight systems to avoid the sodium-air reaction, and presented new machinery and hardware development problems for practically every piece of plant equipment.
- The light water-moderated-and-cooled reactor provided a thermal neutron energy spectrum, had moderately good heat transfer characteristics and therefore could be of small volume, did not require a large critical mass of enriched uranium if low neutron absorption structural materials were used in the reactor core, and appeared to pose no power (neutron flux) stability problems if the water coolant was not allowed to boil and change to a two-phase fluid. However, such a pressurized water reactor did require high primary system pressures and lower steam conditions on the secondary side than modern turbines were capable of using, along with the lower resultant plant thermal efficiency.
From an operational standpoint, the water coolant was chemically compatible with the normal environment, leaks and makeup presented no significant problem, and decades of equipment development and fabrication experience for most hardware components was available from an established industrial technical base.
As a result of these early studies at Argonne, the decision was made by the AEC and Navy to put primary emphasis on the water-cooled reactor concept. And so was launched the STR Mark I—a pressurized water-cooled Submarine Thermal Reactor, the second version of which, the Mark II, propelled the Nautilus.
There were technical risks and unknowns. Would neutrons and gamma rays in the core dissociate the water to H2 and 02 and other compounds in untenable amounts? Could corrosion resistant structural materials be found for the fuel which would withstand radiation damage to their structure and prevent deterioration of physical properties? Would the reactor be stable under all operating modes, including the displacements caused by ship motion? Would corrosion problems in high temperature water deteriorate materials or heat transfer surfaces?
Because so little information was available to answer these questions, the liquid metal-cooled reactor was considered to be a worthwhile alternate or backup. A second effort to the STR was seriously considered and, within a year or so later, was embarked upon by the AEC at the G.E.-operated Knolls Atomic Power Laboratory. This effort became the SIR Mark A (submarine intermediate spectrum reactor, with its slightly higher neutron energy spectrum than the STR). The Mark B version propelled the Seawolf.
To answer the technical uncertainties of the water-cooled reactor, a number of development programs were pursued at Argonne and other government, university, and industrial laboratories across the country.
Argonne and Oak Ridge did water capsule tests, under irradiation environments, which showed water dissociation to be a manageable phenomenon in an operating reactor.
A nuclear fuel development program was spread across the country in the Argonne, Oak Ridge, Brookhaven, Ames, and Bettis AEC laboratories, and at Battelle Memorial Institute, M.I.T., and Sylvania among private and university complexes. A Hanford production reactor was made available, without interrupting its weapons program function, to irradiate fuel. Out of this effort came a fuel element that met and then far exceeded its original-design life requirements.
The requirements of neutron economy in the core made stainless steel a poor alternate choice for fuel and structural purposes. The low neutron absorption of zirconium was proven at Oak Ridge; demonstrated to be corrosion resistant and strong enough by the fuel development laboratories; alloy developed largely at the Bettis Laboratory; and rushed into large scale production by Rickover.
The neutron physics of a compact thermal reactor were verified by a critical assembly (ZPR-1) at Argonne, with Bettis’ physicists participating. Because of the preciously small allocation of enriched uranium, each gram was hoarded into its fabricated shape for use in the critical assembly.
Heat transfer and mechanics experiments at Argonne, U.C.L.A., and NACA Cleveland verified the ability to safely transfer thermal energy from the fuel to water coolant at higher heat transfer rates than those available in high-power fossil boilers.
As the basic research and development progressed satisfactorily at Argonne and the AEC associate laboratories, the engineering phase was started at the Bettis Laboratory in Pittsburgh.
Under the integrating overlay of Rickover’s organization, the basic design concepts were transferred from Argonne to Bettis, and the hardware development and detailed design phase of the nuclear plant went into high gear in 1949-1950. The Bettis Laboratory grew from a handful to a few thousand people, and subcontractor work was farmed out to tens and then hundreds of industrial suppliers across the nation. Yet, every technical detail was minutely checked over, reviewed, and approved by Argonne and Rickover’s AEC Washington group for the nuclear part of the plant and by BuShips for the more conventional engine room equipment part of the plant. Even the conventional equipment, however, had elements of unconventionality. Completely enclosed water circulating pumps (canned rotor motor) were conceived by Argonne and Westinghouse and developed by the industrial firm. A low steam-pressure turbine was required, so industry turned its design requirements back 20 years and upgraded it with new materials, hydraulics, and mechanics technology developed in the interim.
Then General Dynamics Corporation’s Electric Boat Division, was brought into the overall design phase, to integrate the nuclear plant into the hull design limitations, and to fit it into the ship.
Believing that the development of the nuclear plant would have its own uncertainties, Rickover and BuShips planned to use a conventional submarine hull rather than undertake the simultaneous problems of a new hull type such as the Albacore. For machinery reliability reasons, a two-screw ship was planned. As the reactor and its shielding design went from paper concept to developed hardware, it grew in size and so did the required hull size, so that what started out as a more or less conventional 18-foot diameter, 2,000-plus-ton ship became a 30-foot diameter, three-deck hull of over 3,000 tons displacement. And so paper and design plans began at last to take shape as steel and hardware.
By 1950, the concept of the prototype plant fell into place. One approach was to design the prototype as a test facility, spreading the machinery out for ease of testing and replacement if found to be deficient or unworkable. The other approach was to gamble that test results would be favorable and design the prototype compactly as in an operating ship hull. Changes, if required, would be difficult and costly to make, but the advantage was in laying out a plant exactly as it would be in the ship and determining, early, both operational and design interferences.
The decision was made to design the prototype as close as possible to what would next go into the operational submarine. The AEC had designated the Nuclear Reactor Testing Station at Arco, Idaho, as its national testing site and a location was assigned to the Naval program. To continue the Westinghouse-Bettis-Electric Boat Division plant-ship integration effort, Rickover’s Naval Reactor Branch assigned Westinghouse the operating responsibilities of the site and contracted the plant construction to the Electric Boat Division.
A submarine hull section was to house the entire propulsion plant so that accessibility, maintenance problems, construction interferences, and hardware foundation problems would be surfaced on the prototype and corrected before the ship design was frozen. Since shielding had the determining effect on total plant weight and hull size, and since the ocean surrounding the hull would have neutron back-scattering effects, a simulated sea (in a tank) was placed around the hull section at Arco.
Idaho construction started in 1950, and was completed by early 1953. In parallel with this phase, vital plant equipment was built, installed on the submarine hull Ulua in the Chesapeake Bay, and shock-tested by the Navy to verify capability to withstand expected battle damage.
Simultaneously, an operating personnel development effort was undertaken to recruit and train the naval crew which would eventually man the Nautilus. Carefully selected officers and men, individually interviewed by Admiral Rickover or his Washington staff, were sent to the Bettis Laboratory for theoretical and engineering courses, followed by on-the-job training at key equipment vendor plants or at Bettis, and finally sent to the Idaho site during later stages of the Mark I construction. There, on 31 March 1953, the Westinghouse engineers and the naval crew brought the prototype plant to criticality and on 31 May produced power.
In 1951, the decision had been made to proceed with the design and procurement of the Mark II plant before Mark I was in operation. To have waited for the Arco plant to prove fully operational performance would have delayed the ship program by two years. On the other hand, the research and development phase of the Mark I had proceeded well enough to indicate an acceptable risk of this parallel, rather than series, approach. Further, the effort to make the Mark I and II plants almost completely identical meant that problems uncovered in the prototype plant could be more readily correctable for the ship propulsion unit.
Accordingly, in 1951, the Navy authorized the construction of the Nautilus to be built at the Electric Boat Division yards at Groton, Connecticut. The AEC authorized the Mark II nuclear portion of the plant and its fuel load, the Bureau of Ships the remainder of the propulsion plant.
On 14 June 1952, President Harry Truman laid the keel, welding his initials onto the keel plate. During the next two years, yard designers and supervisors shuttled between the full-size wood mock-up located at one end of the yard, where every pipe run, every cable, every piece of hardware was checked out in place for fit-up and interference, and the ship on the ways, where her real counterpart was carefully installed. After 1953, operational results from the Arco plant fed back to the Westinghouse engineers with corrections made, as necessary, for the Nautilus plant.
On 21 January 1954, Mrs. Dwight D. Eisenhower launched the world’s first nuclear-powered submarine. One year later, on 17 January 1955, Commander Eugene Wilkinson—who had started his nuclear preparations five years earlier at Argonne as a senior physicist on the basic reactor design—commanded the ship as she headed seaward from the Thames channel. Wilkinson’s engineers pulled out the control rods, water coursed past the uranium fuel elements and generated steam on the secondary side of the boilers, the turbines turned over, and the message went out to the world: “Underway on nuclear power.” Thus, five-and-a-half years after work was started on the Nautilus prototype concept in 1949, 19 months after this prototype generated power, 31 months after the ship’s keel was laid, and after approximately 200 million dollars’ worth of national effort, the Nautilus went to sea as an operational ship of the Fleet.
Neither the originally designed performance criteria of the nuclear propulsion plant, nor those actually achieved have ever been made completely public. Yet, published events have shown that the Nautilus’ operational performance has revolutionized propulsion capability and opened up tactical and strategic application of submarines previously only dreamed of.
One need only compare the capabilities of the Tang-class submarine, the “best” in 1948, to what the Nautilus type has done.
The 2,000-ton Tang was capable of 20 knots surfaced, and 17 knots snorkel-submerged, with an undersea range of about one hour. (The U. S. Walter cycle boats planned, but never completed, were 850-ton craft with a submerged speed of 15-25 knots and a maximum range of 275 miles.) The operational practice of the diesel submarines (because of limited undersea range) was to steam less than 15 per cent of the time totally submerged.
The nuclear submarines average about 40,000 miles per year, of which about 90 per cent is completely submerged. Although the maximum submerged speed has never been divulged except as “greater than 20 knots,” the available submerged range is practically limitless. So, too, compared with an oil burner, is the range of the vessel between refuelings. The Nautilus’ first core, according to Congressional public testimony, provided energy for about 1,000 equivalent full-power hours of cruise, which, at even the conservatively quoted 20 knots, provided a full power range of over 20,000 miles between refueling. The Navy has publicly reported that the first core steamed over 62,000 miles; the second was still going at 80,000 miles. In 1956, the Nautilus’ prototype plant at Idaho operated 66 days uninterruptedly at full power, which, if at the conservative 20 knots speed, would be a distance of between once and twice around the world.
In July and August 1958, the ship steamed nonstop from Honolulu to England, a distance of 8,000 miles, including 1,830 miles under the Polar ice cap in a 96-hour run from Point Barrow on the Pacific side to Spitsbergen on the Atlantic.
A later nuclear boat, the Sargo, (SS(N)-853) steamed two-and-a-half months nonstop for 19,000 miles, of which 18,880 miles were fully submerged. In 1960, the twin reactor submarine Triton steamed submerged around the world.
Thus, nuclear propulsion, first demonstrated by the Nautilus’ plant, technically has made possible unlimited submerged range for submarines and realized the true potential of a “submarine”—i.e., to remain undetected deeply submerged and to ply the ocean depths at high speeds without any umbilical cord to the surface.
The unqualified success of the Nautilus diverted the entire U. S. submarine shipbuilding program from diesel-battery to nuclear power. By 1967, 74 nuclear boats were at sea, and an additional 33 were building or authorized. In six years, 1948 to 1955, the Nautilus went from an idea to an operating nuclear ship of the Fleet; in the next 12 years, the Navy’s submarine force went from a one-ship demonstration to a 107-ship fleet. Simultaneously, fuel improvements were made which extended the Nautilus’ first core-life of 62,000 miles to approximately 400,000 miles, or more than sufficient for ten years of normal operation between refuelings. The Navy submarine force had made the complete transition from fossil to nuclear propulsion in less than 20 years.