USS Albacore

  The USS Albacore (AGSS-569) is remembered mainly as the prototype for the hull form of fast, maneuverable submarines capable of reaching extraordinary underwater speeds. But her story is much more complex than that. She was conceived mainly as a test platform to address the problems of controlling the new generation of fast-attack submarines.

  xNaval architect Morton Gertler directs instrument maker Carson W. Caudle in preparing a model of the Albacore for tests at the David Taylor Model Basin in Carderock, Maryland, in 1956. Gertler designed and supervised the development and testing that resulted in the submarine’s hull form. Naval History and Heritage Command

No one was sure any practicable power plant could match what the Germans aimed for with the Type XXVI, but the possibility that the Soviets could use captured technical information to do so was a postwar nightmare for the West. At the very least, the major Western navies wanted fast submarines so they could learn to counter an expected Soviet fleet of such craft.

The main issue was propulsion. The U.S. Navy pursued a variety of alternatives, including the German Walter system, a hydrogen-peroxide, air-independent propulsion plant. But by the late 1940s, nuclear power appeared to be the best long-term possibility. Nuclear reactors might produce 15,000 shaft horsepower in a reasonably compact package. A combination of comparatively small size and high power might drive a large submarine at about 23 to 25 knots.

It soon became obvious that power was not the only issue, however. No one knew how to control a submerged submarine at such speeds. The crews of Greater Underwater Propulsion Power Program (GUPPY) submarines found it difficult to maintain trim at high speed in highly streamlined boats with powerful electric motors. Without constant attention from the planesmen, a small up or down angle could soon grow uncontrollable. The problem got worse as speed increased. How could a really fast submarine be controlled?

To gain insight, the Navy needed a submarine large and fast enough to simulate projected ones. It did not have to be suitable for operations, nor did it need much underwater endurance. It seems to have been fairly obvious that the hull form with the least drag was the blimp-shape selected. The British reached much the same conclusion when designing their two hydrogen-peroxide-powered submarines, the Explorer and Excalibur, which were completed well after the Albacore. These boats were roundly criticized for departing from a pure Albacore hull form, but their designers defended them on the ground that their hulls had key Albacore features such as a fat bow and a high beam-to-length ratio. They were slower than the Albacore and are remembered best for their dangerous and unreliable power plants.

The object of the Navy’s design was to reach high speed to test control; therefore hydrodynamics ruled. The David Taylor Model Basin conceived the body-of-revolution hull form. It turned out to have a major advantage. It resulted in “arrow stability,” meaning that an up or down angle generated forces that automatically returned the hull to the horizontal. This seems to have been an unexpected outcome. The Albacore also differed from existing submarines in having a single propeller on the axis of her hull, rather than the usual offset pair. But the Albacore was not an experiment in high speed; she was given high speed to support her role in control development. The test concept was classified, with budget documents reporting the Albacore as a target submarine.

One objective of building the Albacore seems to have been to develop an autopilot that could maintain stability underwater. The notion of the boat as like an underwater airplane seems to have resulted in new control systems, replacing the earlier hand wheels with airplane-type controls. Her early trials showed that she was remarkably fast and extraordinarily maneuverable. In interviews, her commanding officer spoke of “hydrobatics,” analogous to the aerobatics of an airplane.

The Albacore’s performance was so extraordinary that she inspired a radical rethink of the fast submarine program. By 1950, when the Albacore was being built, closed-cycle powerplants were proving extremely difficult to develop. Only nuclear power was really working out, and it was coming along quickly. The Albacore became the control test vehicle for the nuclear prototype USS Nautilus (SSN-571), which was expected to make about 23 knots.

The Nautilus was expensive and unusually large. Before she became operational, the best attributes of nuclear propulsion were not at all clear. Was it extraordinary submerged endurance? High submerged speed? Captain Hyman G. Rickover’s nuclear-power project offered a range of  possible reactors, with a variety of power ratings. Initially, it seemed that half the Nautilus’s power might be suited to an affordable submarine. Such a submarine would have much the same speed as the best existing diesel-electric submarines—but be sustainable for weeks or months. This became the USS Skate (SSN-578). The Nautilus had not yet entered service, so any judgment as to what nuclear power might offer was only theoretical.

Once the Nautilus was operational, the Navy discovered what high speed could mean for submarines. In early exercises, the Nautilus could always outrun pursuers; it would take an entirely new generation of sonars and weapons to deal with fast nuclear-powered subs. However, the Nautilus was not quite fast enough to be sure of attacking fast surface ships.

By this time, the Albacore was operational, too, and she was demonstrating that her unusual hull form dramatically reduced underwater resistance. In 1956, U.S. submarines were recast, first as an Albacore-type hull with a low-powered reactor, and then as an Albacore hull form with a redesigned Nautilus reactor. The latter was built as the Skipjack class, for many years the fastest U.S. submarines. The Albacore hull form was adapted for a diesel-electric submarine as well, the USS Barbel (SS-580). The Barbel design was adopted by the Royal Netherlands Navy and by the Japan Maritime Self-Defense Force; the Dutch also built a version of their Barbel for Taiwan.

The blimp form turned out to be not very suitable for an operational submarine, however. Previous submarines had one long deck inside a more-or-less cylindrical pressure hull. A cylinder was the most economical form possible in terms of weight, but its diameter had to be minimized. A submarine places particularly stringent requirements on the designer, because of the way in which weight and watertight volume must match. With further study, designers eventually realized that a body-of-revolution shape (revolving a two-dimensional shape around a central axis) was more efficient than the whale-like shape of the Albacore; Western submarines today generally combine body-of-revolution with the single screw pioneered by the Albacore.

As for the Albacore, her high-speed hull form made it worthwhile to fill her with high-performance batteries to give her short-term high speed, so she could test a variety of control innovations. The Albacore’s speed introduced the U.S. Navy to the problem of snap-rolls, and she tested some possible solutions. These included the way in which two control operators would coordinate, as well as physical solutions such as a rudder on her sail, an X-shaped stern, inline multiple propellers, and speed brakes.