
The Greater Underwater Propulsion Power Program (GUPPY) was a US Navy program initiated after World War II to improve the speed, manoeuvrability, and endurance of its submarines. The name was chosen to be catchy and sound like a fish.
The program began with the testing and reverse engineering of two German Type XXI U-boats obtained as war reparations. The US Navy sought to improve four aspects of its submarines: battery capacity, streamlining of the structure, snorkels, and fire control systems.
The GUPPY program proceeded through several variants: GUPPY I, GUPPY II, GUPPY IA, Fleet Snorkel, GUPPY IIA, GUPPY IB, and GUPPY III. The first two Tench-class submarines, Odax and Pomodon, were upgraded under GUPPY I, which included streamlining of the bridge and periscope, the removal of deck guns, and the addition of an SV radar aerial. The GUPPY II program, which ran from 1947 to 1951, upgraded 24 submarines and introduced snorkels and new sail designs. GUPPY IA, Fleet Snorkel, GUPPY IIA, and GUPPY IB were subsequent iterations of the program, which continued through the 1950s. GUPPY III, the final variant, began in 1961 and ended in 1963. It involved extensive modifications, including lengthening the submarines to add new sonar rooms, berthing, electronics, and storerooms.
Characteristics | Values |
---|---|
Years of Operation | 1944-1960 |
Number of Conversions | 50 |
Purpose | To improve submarine speed, maneuverability, and endurance |
Variants | GUPPY I, GUPPY II, GUPPY IA, Fleet Snorkel, GUPPY IIA, GUPPY IB, and GUPPY III |
Submarine Classes Involved | Tench-class, Balao-class, Gato-class |
What You'll Learn
- The GUPPY program was initiated by the US Navy after World War II to improve submarine performance
- The GUPPY program was an extensive conversion that gave fleet boats a snorkel, a more streamlined hull, much greater battery capacity, and a BQR 2
- The GUPPY I conversion began in 1947, with upgrades to two Tench-class submarines, the Odax and the Pomodon
- The GUPPY II conversion, from 1947 to 1951, was generally similar to the GUPPY I except for the sail
- The GUPPY IB program, from 1953 to 1955, was another interim conversion that converted four boats for transfer to foreign navies
The GUPPY program was initiated by the US Navy after World War II to improve submarine performance
The GUPPY program started in 1945 when the US Navy obtained two German Type XXI U-boats as war reparations. The U-2513 and U-3008 were extensively studied and tested, and lessons learned included the need for large battery capacity, streamlined structure and hull, a snorkel, and better fire control system. This led to four goals for the GUPPY program: increasing the submarines' battery capacity, streamlining the boats' structures, adding snorkels, and improving fire control systems.
The GUPPY program began in 1946 with the approval of the Chief of Naval Operations. The initial two-boat test program, implemented by the Portsmouth Naval Shipyard, eventually grew into several successive conversion programs. The first prototypes for this program were the USS Odax and USS Pomodon, both Portsmouth-built Tench-class boats. These were chosen as they were recent, completed in 1945, and in pristine condition. The GUPPY I boats featured a brand new streamlined bridge and shears structures, new periscope and radar mast supports, and a distinctive rounded "Guppy bow" that improved performance underwater. Internally, there was a complete rearrangement to accommodate larger battery wells and fit much larger and more powerful batteries. The high-speed motors were replaced with slow-speed motors, and open-front switchboards were replaced with enclosed splash-proof cabinets.
The GUPPY I program was followed by GUPPY II, which ran from 1947 to 1951 and upgraded two dozen submarines. The GUPPY II design featured three new masts (snorkel induction, snorkel exhaust, and ESM mast) and two sail designs: the Electric Boat Sail and the Portsmouth Sail. The GUPPY I prototypes, Odax and Pomodon, were upgraded again under the GUPPY II program, along with 22 other submarines. Several GUPPY II submarines were later given to foreign navies.
The GUPPY program continued through the 1950s with GUPPY IA, Fleet Snorkel, GUPPY IIA, and GUPPY IB. GUPPY III, the program's last iteration, began in 1961 and ran until 1963. The GUPPY III, while the program’s last iteration, did entail extensive modifications. The Tiru, which was the GUPPY III prototype, was cut in half and lengthened with a 12.5-foot section forward of the control room, added to make space for a new sonar room, berthing, electronics, and storerooms. In all, the GUPPY program upgraded 50 submarines between 1946 and 1960.
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The GUPPY program was an extensive conversion that gave fleet boats a snorkel, a more streamlined hull, much greater battery capacity, and a BQR 2
The GUPPY program was an extensive conversion program initiated by the United States Navy after World War II to improve the submerged speed, manoeuvrability, and endurance of its submarines. The program aimed to enhance the capabilities of the existing fleet of submarines, particularly the Gato, Balao, and Tench-class vessels. The GUPPY conversion gave these fleet boats several significant improvements:
- Snorkel: The addition of a snorkel allowed the submarines to operate their diesel engines while submerged at periscope depth, providing air for the diesel engines and expelling exhaust fumes. This technology was adopted from the German Type XXI U-boats, which served as a model for the GUPPY program.
- Streamlined Hull: The outer hull was streamlined to reduce hydrodynamic drag and improve underwater performance. The distinctive sharp V-shaped "fleet boat bow" was replaced with a rounded "Guppy bow," which also housed sonar hydrophones.
- Increased Battery Capacity: The submarines underwent internal rearrangement to accommodate larger battery wells and new, more powerful batteries. These batteries had a greater number of thinner plates, generating higher current for longer periods. This resulted in doubled electrical power and improved submerged speeds.
- BQR-2: While specific details about the BQR-2 are scarce, it was likely a component of the fire control system, as improving fire control systems was one of the key goals of the GUPPY program.
The GUPPY program included several variants, such as GUPPY I, GUPPY II, GUPPY IA, and GUPPY III, each incorporating different combinations of these improvements. These modifications not only enhanced the performance of the submarines but also led to changes in their terminology and appearance. The GUPPY conversions played a crucial role in maintaining a capable submarine force during the Cold War era, bridging the gap until the advent of nuclear-powered submarines.
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The GUPPY I conversion began in 1947, with upgrades to two Tench-class submarines, the Odax and the Pomodon
The GUPPY I conversion involved several external and internal changes. Externally, the Odax and Pomodon featured a new streamlined bridge and shears structures, periscope and radar mast supports, and a distinctive rounded "Guppy bow". The V-shaped "fleet boat bow" was replaced with the Guppy bow to improve underwater performance. Deck guns and their associated containers were removed, and an SV radar aerial was added to the top of the sail. Capstans, cleats, and rail stanchion supports were also redesigned to be retracted or removed when rigged for a dive.
Internally, the boats underwent a considerable rearrangement to accommodate larger battery wells and batteries of greater electrical power. The new batteries used a greater number of thinner plates that would generate higher current for a longer time. Four 126-cell batteries were installed in enlarged battery wells that replaced former storage, ammunition, and refrigeration spaces. In the manoeuvring room, the high-speed motors and reduction gears were replaced by slow-speed motors. All open-front switchboards were replaced with enclosed splash-proof cabinets, and electrical loads were converted to use 120-volt 60-hertz alternating current. A new air conditioning system of greater capacity was also installed.
The GUPPY I conversion proved to be very successful, with the Odax achieving a submerged speed of 18.2 knots during trials, compared to its previous speed of 8.75 knots. The GUPPY I boats were then modified to the GUPPY II standard.
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The GUPPY II conversion, from 1947 to 1951, was generally similar to the GUPPY I except for the sail
The GUPPY II conversion, from 1947 to 1951, was generally similar to the GUPPY I conversion, except for the sail. The addition of three new masts—snorkel induction, snorkel exhaust, and ESM mast—required more room in the upper portion of the sail to support the new masts. The Bureau of Ships approved two different sail designs:
The "Electric Boat Sail" had a straight trailing edge, round windows, a wider top, and a more rounded forward edge.
The "Portsmouth Sail" had a thinner top, curved trailing edge, square windows, and a sharper lower forward edge. It was put on all boats that used the government plans for the conversion.
Some boats with a Portsmouth Sail had an SV radar and needed extra room to house the aerial, thus had a bulge at the sail top. Later modifications put the SS or SS2 radars on these and other boats that had a smaller aerial and had an indicator with interlocks, allowing the mast to be housed only with the aerial in certain angular positions. Also, some GUPPY II and GUPPY III boats had their sails extended higher above the waterline, the "Northern Sail", to raise the bridge, allowing it to be manned in more severe weather.
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The GUPPY IB program, from 1953 to 1955, was another interim conversion that converted four boats for transfer to foreign navies
The GUPPY IB program was an informal designation for a limited upgrade and modernisation of four submarines for transfer to foreign navies. The program ran from 1953 to 1955 and was an interim conversion, similar to the GUPPY IA program. The four submarines involved in the GUPPY IB program were the Barb, Dace, Hawkbill, and Icefish.
The GUPPY IB submarines were fitted with snorkels and were generally similar to the GUPPY IA submarines. However, they lacked the modern sonar, fire control systems, and ESM of the other GUPPY variants. The two Italian boats were of the thin-skinned Gato class, while the two Dutch boats formed the Walrus class.
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Frequently asked questions
GUPPY stands for the Greater Underwater Propulsion Power Program, a program initiated by the United States Navy after World War II to improve the speed, manoeuvrability, and endurance of its submarines. The name was chosen to be catchy and sound like a fish.
The GUPPY program had four main goals: increasing the submarines' battery capacities, streamlining the boats' structures, adding snorkels, and improving the fire control systems.
The GUPPY program proceeded through several variants: GUPPY I, GUPPY II, GUPPY IA, Fleet Snorkel, GUPPY IIA, GUPPY IB, and GUPPY III.