USS Diodon conversion to GUPPY IIA
Since 09-09-05
The Greater Underwater Propulsion Power Program (GUPPY) was initiated by the United States Navy after World War II to improve the submerged speed, maneuverability, and endurance of its submarines. (The 'Y' in the acronym was added to increase pronouncability.)
The Navy began the program by reverse-engineering two captured Type XXI U-boats: U-2513 and U-3008. That analysis led to four goals: increase the submarines' battery capacities, streamline the boats' structures, add snorkels, and improve the fire control systems.
The Tang class was designed to incorporate these improvements, and proved to be so much better than the existing Gato-, Balao-, and Tench-classes that the Navy decided to upgrade the existing fleet as well as build new boats. Those upgrades proceeded in seven variants:
Fleet Snorkel, GUPPY I, GUPPY II, GUPPY IA, GUPPY IIA, GUPPY IB, and GUPPY III. (The apparently out-of-order sequence is correct; see below.)
Some boats that went through an early phase were then upgraded further in a later phase.
GUPPY IIA Program
Running from 1952 through 1954, GUPPY IIA streamlined the boat, installed a new sail, a guppy bow, and new motors where necessary, just as GUPPY II did. IIA, however replaced one forward engine with air-conditioning plants and refrigeration units.
Some boats had the high-pressure air compressors relocated to the lower level of the forward engine room. The chill box and freeze boxes were moved to the forward end of the after battery under the galley.
Sonar was moved to the space now available in the forward end of the pump room. GUPPY IIA boats had the same outward appearance as GUPPY II, except the IIA had only three diesel exhaust outlets and the II had four.
GUPPY IIA Boats
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