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Greater Underwater Propulsion Power Program

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USSGreenfishafter GUPPY III modernization. Visible on deck are the three distinctive shark-fin domes of thePUFFSsonar.

TheGreater Underwater Propulsion Power Program (GUPPY)was initiated by theUnited States Navyafter World War II to improve the submerged speed, maneuverability, and endurance of itssubmarines.(The "Y" in the acronym was added for pronounceability.)

The navy began the program by testing andreverse engineeringtwo GermanType XXI U-boats—U-2513andU-3008—obtained as war reparation. That analysis led[1]to four goals—increasing the submarines' battery capacity, streamlining the boats' structures, addingsnorkels,and improvingfire controlsystems. The navy immediately focused on designing a new class of submarine, but theBureau of Shipsbelieved the fleet of existingGato,Balao,andTench-classsubmarines could be modified to incorporate the desired improvements. In June 1946, theChief of Naval Operationsapproved the GUPPY project. The initial two-boat test program, implemented by thePortsmouth Naval Shipyard,eventually grew into several successive conversion programs. Those upgrades proceeded in seven variants, in the following order:GUPPY I,GUPPY II,GUPPY IA,Fleet Snorkel,GUPPY IIA,GUPPY IB,andGUPPY III.Some boats that went through an early phase were then upgraded further in a later phase. Most GUPPY phases were assigned a correspondingShip Characteristics Board / SCB project number.

A similar program for theRoyal Navyinvolved modifications to 24 wartime and post-warBritish T-andA-classsubmarines, which were provided with streamlined hulls,fin-typeconning towers,and increased underwater performance during 1948–60.

GUPPY I program

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Pomodonafter GUPPY I.

The prototype GUPPYs,OdaxandPomodon(both Portsmouth-builtTenchboats), appeared in 1947. Externally, they featured improved streamlining of the bridge and shears structures, andperiscopeandradar mastsupports. To reducehydrodynamicdrag,one of the periscopes was deleted. No snorkel was fitted, due to difficulties in adapting the snorkel to the fleet boat. Deck guns and their associated containers were removed. An SV radar aerial was added to the top of the sail, creating a distinctive side bulge. All capstans, cleats, and rail stanchion supports were redesigned so they could be retracted or removed when rigged for dive. Most notably, the sharpV-shaped "fleet boat bow" was replaced with a distinctive rounded "Guppy bow" that improved submerged performance.[2]

These modifications changed not only the boats' appearance, but also their terminology: After a GUPPY conversion, the faired structure around the boat'sconning towerand mast supports was called the "sail".

Internally, the boats underwent considerable rearrangement to accommodate largerbatterywells and batteries of greatly increased electrical power. The batteries were of a new design. Compared with the originalSargobattery, the Guppy battery used a greater number of thinner plates that would generate higher current for a longer time. However, these batteries had a shorter life, 18 months versus the five years of theSargobattery, and took longer to charge. They also required ventilation to remove hydrogen gas, and required cooling water to the battery terminals and termination bars. Four 126-cell batteries were installed in enlarged battery wells that replaced former storage, ammunition, and refrigeration spaces. These four batteries could be connected in series or parallel, providing a wide range of voltages and currents, and thus a wide range of speeds.[3]

In the maneuvering room, two or four of the earlier high-speed motors and reduction gears were replaced by slow-speed motors. All open-front switchboards were replaced with enclosed splash-proof cabinets. Lighting and other "hotel" electrical loads were converted to use 120 volt 60hertzalternating current,and ship electronics to use 120 volt 400 hertz AC. A newair conditioningsystem of greatly increased capacity was also installed.

In service, these boats offered greatly improved underwater performance.Pomodonreached 17.8knots(33.0 km/h; 20.5 mph) surfaced and 18.2 knots (33.7 km/h; 20.9 mph) submerged as compared to the previous performance of 20.25 knots (37.50 km/h; 23.30 mph) surfaced and 8.75 knots (16.21 km/h; 10.07 mph) submerged,Odaxslightly less.[4]

GUPPY I boats

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  • Tenchclass
    • Odax
    • Pomodon

GUPPY II program

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USSCubera,after GUPPY II modernization

The GUPPY II conversion (SCB 47), implemented from 1947 to 1951, was generally similar to the GUPPY I, except for retention of both periscopes and introduction of the recently perfected snorkel. The addition of three new masts—snorkel induction, snorkel exhaust, andESMmast—required more room in the upper portion of the sail.BuShipsapproved two different sail designs:

  • The "Electric BoatSail "had a straight trailing edge, round windows, a wider top and a more rounded forward edge.
  • The "PortsmouthSail "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.

All boats converted during the GUPPY II program that originally had high-speed drive motors with reduction gears had these replaced with low-speed direct-drive motors, producing 2500 horsepower (1.9 MW) per shaft.

The two GUPPY I boats,OdaxandPomodon,were modified to GUPPY II standard.

GUPPY II boats

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GUPPY IA program

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BuShips devised the GUPPY IA (SCB 47A) program of 1951 as a cheaper alternative to the GUPPY II conversion. While the GUPPY IA conversion included most features of the GUPPY II, it omitted the four-well battery configuration and extensive internal rearrangement associated with it. Instead, the GUPPY IA retained the original battery wells, fitted with four more powerful Sargo II batteries. The Sargo II was developed to be lower cost than the Guppy battery while providing most of the performance. It was intermediate in size between the Guppy andSargobatteries.[5]These batteries featured electrolyte agitation, battery cooling, and open tank ventilation. They also had a longer life than the Guppy batteries, though shorter than the originalSargobattery. The sonar room was relocated from the forward torpedo room to a space under the galley. Compared to the GUPPY II, the GUPPY IA offered lower cost, better habitability, and easier maintenance at the expense of underwater performance.

GUPPY IA boats

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Fleet Snorkel Program

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USSPiperwith BQR-4A bow sonar

When the navy realized that it would not be able to fund all the GUPPY conversions it desired, it devised the Fleet Snorkel Program (SCB 47B) as a means of adding the minimum necessary modifications to fleet boats. This modernization added a snorkel, a streamlined sail, a higher capacity air-conditioning system, and a more powerful electrical system. The deck guns and auxiliary diesel were removed. Unlike the GUPPY conversions, these boats retained their original deck structure, bow, and storage batteries. Submerged performance of the Fleet Snorkel boats was therefore significantly inferior to any GUPPY conversion. Despite their limited features, the Fleet Snorkel boats served almost as long as the more modern GUPPY boats. Three boats,Piper,Sea Owl,andSterlet,received a large BQR-4A bow sonar. The ex-USSChub) and ex-USSBrill,both transferred to Turkey in 1948 as TCGGürand TCG 1.İnönü,were converted to a Fleet Snorkel Submarine in 1953, the work being done first in Turkey's Gölcük Navy Yard and completed in the United States.

Fleet Snorkel boats

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GUPPY IIA program

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USSThornbackafter GUPPY IIA modernization

The GUPPY IA program was succeeded by the nearly identical GUPPY IIA program (SCB 47C), implemented from 1952 to 1954. The GUPPY IIA, however, further alleviated the cramped internal conditions of earlier conversions by removing one forward engine and replacing it with pumps and air conditioning machinery. Some boats had the high-pressure air compressors relocated to the lower level of the forward engine room. The freezer and refrigerator units were moved to the space under the galley, and the sonar room was relocated to the forward end of the pump room. Sargo II batteries were installed in the existing battery wells.

Externally, the GUPPY IIA differed from the GUPPY II and IA by having only three diesel exhaust outlets, whereas the earlier conversions had four.

GUPPY IIA boats

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GUPPY IB program

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GUPPY IB was an informal designation for a limited upgrade and modernization given to four boats for transfer to foreign navies. These boats had snorkels and were generally similar to the GUPPY IA, except that they were not equipped with the modern sonar, fire control systems, or ESM. The two Italian boats were of the thin-skinnedGatoclass. The two Dutch boats formed together theWalrusclass.[6]

GUPPY IB boats

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GUPPY III program

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USSClamagoreafter GUPPY III modernization, as formerly preserved at Patriot's Point, Charleston, South Carolina.

The GUPPY II conversions suffered from very cramped internal conditions due to the four-battery configuration. The GUPPY III program (SCB 223) was devised to address this problem. In 1959,Tirubecame the prototype conversion. It was cut in half and lengthened with a 12.5-foot (3.8 m) section forward of the control room to create space for a newsonarroom, berthing, electronics, and storerooms. The removal of the sonar room from the forward torpedo spaces allowed an increase in the number of reloads. Crew spaces were also refurbished. As in the GUPPY IIA conversion, one diesel engine was removed. The tall sail (or "North Atlantic Sail", as they were sometimes called) was a singular characteristic of the GUPPY III boats, distinct from the so-called "step sail" of all of the other GUPPY submarine classes.

From 1961 to 1963, eight more GUPPY II boats were upgraded to GUPPY III standard. These boats differed fromTiruby adding a 15-foot (4.6 m) section forward of the control room. They also retained all four diesel engines. This increased the boat's length to 322 feet (98 m) and raised surfaced displacement to approximately 1,975 tons.

All boats received the BQG-4PUFFSpassive ranging sonar, identifiable by the three shark fin-like sonar domes added to the topside superstructure. The conning tower in the sail gained an additional 5-foot (1.5 m) section to accommodate the Mk 101 fire control system and Mk 37 director. All GUPPY III boats received a plastic sail.

The fire control upgrades allowed GUPPY III submarines to fire theMark 45 nuclear torpedo.[7]

The GUPPY III conversion was part of theFleet Rehabilitation and Modernization(FRAM) program. All 24 GUPPY II boats were originally slated to receive the GUPPY III upgrade, but budgetary constraints limited the program to a total of nine boats. Despite their extensive modifications and upgrades, the GUPPY III boats served only slightly longer than the rest of the GUPPY fleet.

GUPPY III boats

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Note - All GUPPY III boats had previously received GUPPY II conversions.

  • Balaoclass
    • Clamagore
    • Cobbler(became TGCÇanakkaleTurkish Navy)
    • Corporal(became TCG 2InönüTurkish Navy)
    • Greenfish(becameAmazonasBrazilian Navy)
    • Tiru
    • Trumpetfish(becameGoiasBrazilian Navy)
  • Tenchclass
    • Pickerel(becamePrimo LongobardoMarina Militare)
    • Remora(becameKatsonisHellenic Navy)
    • Volador(becameGianfranco Gazzana-PriaroggiaMarina Militare)

Notes

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Citations

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  1. ^"Guppy class Submarines (1946-59)".Naval Encyclopedia.The U-2513 and U-3008 were extensively studied and tested, and lessons learned, like the large battery capacity, streamlined structure and hull, a snorkel, and better fire control system. This led to a USN design which over the years 1946-49 became the Tang class, which made all previous USN submersibles obsoletes.
  2. ^Friedman, pp. 40-41
  3. ^Friedman, pp. 25, 41
  4. ^Friedman, p. 40
  5. ^Friedman, p. 41
  6. ^van Amstel (1991), p. 57.
  7. ^Friedman, p.43

References

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