Forerunner to the Future

Innovative Submarine Shapes the
Future of the U.S. Submarine Force

by Julie Scrafford


Photo caption follows.
(above) The auxiliary general submarine USS Albacore (AGSS-569) transiting on the surface off the Isles of Shoals, April 1954. Albacore served as a sea-going test platform from 1953 to 1972. Albacore’s teardrop-shaped hull was the prototype for the Navy’s nuclear powered submarine force and was the first boat optimized for submerged performance.

 

 

 

 

 

(left) Wind tunnel tests are performed on a scale model of Albacore’s revolutionary tear-drop shaped hull.

“When in doubt, think speed.” This was the guidance Vice Adm. Charles “Swede” Momsen, Assistant Chief of Naval Operations for Undersea Warfare, gave to designers in 1949 as they began work on the U.S. Navy’s newest submarine. During World War II, the Navy’s Submarine Force proved its combat capability by sinking 30 percent of Japan’s navy, including one of the six aircraft carriers that attacked Pearl Harbor on Dec. 7, 1941. All told, U.S. submarines destroyed over half of the Japanese tonnage lost in the war. During that earlier era submarines were primarily surface vehicles with the ability to submerge, but their outstanding war record inspired Momsen and a series of high-ranking naval officers to put scientists and engineers to work on a true submersible. Speed may have been an initial goal of this design effort, but through successive improvements and the incorporation of new technologies the end result would prove to revolutionize submarine performance and handling, and greatly influence modern submarine design.

The advent of nuclear energy was pivotal to the prospect of designing a true submersible. Since nuclear power plants could operate without the oxygen supply needed by conventional internal-combustion machinery, and because techniques were available for removing carbon dioxide from the ship's atmosphere and creating oxygen for the crew it was possible to envision a submarine that would operate almost exclusively submerged, limited only by the endurance of the crew and supplies. In 1949, the Bureau of Ships authorized the David Taylor Model Basin at what is now the Naval Surface Warfare Center, Carderock Division, to research the ideal architecture of a fast and capable underwater vessel. And thus began the story of a 204-foot submarine that would break the world speed record twice and establish key design parameters for virtually all future submarines – USS Albacore (AGSS-569).

From July 1949 to April 1951, the David Taylor Model Basin tested a variety of hull forms and associated appendages that would increase underwater speed without jeopardizing surface performance. Designers looked to aviation for inspiration – something aerodynamic would be hydrodynamic as well. Derived from the traditional shape of airships or blimps, a rounded hull in the form of a paraboloid was incorporated in the initial designs. This configuration was then tested in a wind tunnel at Langley Air Force base in two variants – dual and single propeller systems. Because the twin propellers on previous submarines were largely for surface maneuvering and not really required for submerged running, a single, 11-foot diameter, five-bladed propeller was tested. When tests proved that this configuration was the most efficient for propulsion and maneuverability, the single propeller and tear-drop shaped hull were adopted in the initial design of Albacore. HY-80 steel – the toughest and strongest steel yet produced – had just become available and was used for Albacore’s pressure hull. With these innovations, the new design was a milestone in imaginative submarine technology.

For nearly two decades, from 1953 to 1972, Albacore was used as a test platform to validate design features and techniques that made possible the advances in speed, maneuverability, and depth capability enjoyed by today’s Submarine Force. During that period, Albacore went through five design phases and a series of corresponding underwater trials that revolutionized undersea warfare on a step-by-step basis. Built at the Portsmouth Naval Shipyard and commissioned on Dec. 5, 1953 with the Latin motto Praenuntius Futuri, or “Forerunner of the Future,” Albacore would soon demonstrate the aptness of that particular choice.

In Phase I, increasing underwater speed was the primary goal. The ship’s designers made every effort to streamline the hull. The sail was smaller than normal and served only to house the necessary masts. The rudder and diving planes, or control surfaces, were placed behind the single propeller. Because of limited internal volume for both crew and equipment, the engineers adopted one-man aircraft-style controls that integrated the operation of planes and rudders. The single helmsman controlled depth by pushing the wheel fore and aft for down and up angles and turning it like a steering wheel for direction. Electronics Technician Jim Tyrell remembers being at the wheel. “I actually learned to control Albacore in that way. A few years after I got out of the Navy, I took flying lessons. The instructor was amazed I could fly a plane the first time I tried. It felt exactly like flying Albacore”.

As the ship-control team became more confident, Albacore was subjected to increasingly tight turns at high speed and surprised her crew with near “snap rolls” that caused extreme heeling. To minimize this dangerous effect, a dorsal rudder was attached to the rear of the sail. However, the rudder caused too much control sensitivity, turning Albacore at the slightest touch of the wheel. Small aircraft-type trim tabs were installed to minimize the use of the larger control surfaces and ensuing trials showed that the sail-mounted rudder was not necessary for adequate maneuverability. It was dropped in the next design phase but would be reintroduced in Phase III.

Photo caption follows.
Albacore, seen here in Oct. 1961, with it’s innovative “X” tail.

In Phase I, Albacore had shown that a single-stick control station for the bow planes, stern planes, and rudder allowed piloting to be a one-man job. Ultimately, however, the U.S. Navy would be one of few to reject this system because it was thought to be unreliable and that human error was too great a possibility. During Phase I, Albacore was also the first to use a single periscope that combined the functions of an attack periscope and a search/night periscope.

Albacore went through design Phase II from December 1955 to March 1956. During this phase, control surfaces were moved in front of the propeller and arranged to be horizontal and vertical, forming a “+” shape. The dorsal rudder on the sail was deactivated and the small forward planes were removed not only for the reasons given above, but because they created drag and slowed the boat down. The new design provided excellent high-speed maneuverability. In another change, the diameter of the propeller was increased from 11 to 14 feet, which could turn more slowly and was quieter, but it proved relatively less effective and was deleted in the next phase. Other tests evaluated a fiberglass sonar dome carrying the BQS-4 sonar and a towed array fitted to the end of the submarine.

Soon, the technologies which had thus far proven successful on Albacore were applied in new construction. USS Barbel (SS-580), commissioned in 1959, was the first of a three-boat, conventionally-powered class to incorporate the tear-drop hull design and HY-80 steel. At that same time, the Skipjack (SSN-585) program combined the Albacore’s hull shape, single axially-mounted propeller, and HY-80 steel with the nuclear propulsion system that had been pioneered on the USS Nautilus (SSN-571) to create the prototype of the modern attack submarine.

Phase III took place from 1957 to 1961. The designers again experimented with new control surfaces. In this phase, control surfaces were still forward of the propeller but were mounted diagonally, forming an “X”-shaped configuration. This new design was expected to facilitate sharper turns, so a larger dorsal rudder was installed on the sail and re-activated. Ten hinged panels ringing the aft part of the boat were installed on Albacore as speed brakes. These panels were hydraulically operated to slow the boat rapidly if necessary. In addition, a drag parachute from a B-47 bomber was installed on the aft edge of the sail, which could be opened and streamed in an emergency to slow the boat and decrease the down angle. As clever as this idea may have seemed, the parachute ripped out after three test runs and was deleted from future designs.

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