NSW Historical Perspectives
The Winter 2022 edition of Fire in the Hole outlined the World War II period surrounding development and employment of combatant submersibles for maritime special operations. This story outlines a chronological summary of swimmer vehicle developments in the Underwater Demolition Teams; focused on foreign and domestic efforts between 1947 and the early 1960s.
Throughout the 1950s and 1960s, the UDTs had a particular fascination with enabled swimmer-assist submersibles. Part II provides a photo history derived from a report sponsored by Naval Operations Support Group, Pacific (today Naval Special Warfare Group ONE). It was promulgated in June 1967 as “NOSGPAC RDT&E Project 501.” Photo scans for this story were made from a paper copy of this report. Where possible, better photographs have been provided. Once classified CONFIDENTIAL, the report has long since been declassified.
The NOSGPAC report concluded that a number of studies had been made and reports published “on the general subject of combatant submersibles.” The project report stated that such studies had considered the various missions and tasks performed by combat swimmers, and that these largely defined attributes judged to be desirable in a combatant submersible. It went on to say that [no other] studies involved: “…a comprehensive compilation or tabulation of information on all known combatant swimmer delivery vehicles.” Also, that: “…[no] studies had been written from the operational viewpoint, [nor addressed] what had already been accomplished; including many practical considerations in maintenance, repair, and employment.” The objective of the report was to correct that situation, which contained 211 pages of extensive operational and technical information. Suffice to say it was an invaluable resource that now provides fascinating look at military and industry responses to UDT’s craving for submersibles.
During the post-World War II period, the UDTs on the east coast were under the leadership of Commander Francis Douglas “Red Dog” Fane. It was Fane that worked with Dr. Chris Lambertsen to bring about combat-diving capabilities to the UDTs. This began in 1947 with introduction of the Lambertsen Amphibious Respiratory Unit (LARU), a closed-circuit, pure-oxygen rebreathing diving apparatus, and the British submersible canoe “Sleeping Beauty.” These capabilities were derived from Office of Strategic Services Maritime Unit (OSS MU) use during World War II. Dr. Lambertsen was inventor of the LARU and served as the OSS MU medical officer and combat swimmer-diver trainer.
The LARU and “Sleeping Beauty” began an intense and long-standing effort by the UDTs to develop improved combatant capabilities focused on submersibles. During the 1950s, many design, development, and experimental activities were undertaken. Most were miserable failures, but all played a major role expanding the knowledge base, and eventually acquiring an operationally worthy Swimmer (later SEAL) Delivery Vehicle (SDV) during the mid-1960s as will be seen.
Testing with the Convair Model 14 SDV began my long-term relationship with SDVs. In the summer of 1967, I took a detachment of men from UDT-21, UDT-22, and SEAL Team TWO to Naval Operations Support Group ONE in San Diego for six months to participate as human-test subjects in an SDV diver-performance experimentation program sponsored by the Office of Naval Research. The west coast needed assistance for various reasons; including a paucity of men because of Vietnam. The purpose of our testing was to determine the effects of cold water on diver performance during prolonged expose during SDV missions lasting up to four-hours duration. The results of testing demonstrated that there were no human-performance operational issues encountered.
The average annual water temperature along the coast of San Diego is 63°F. By seasons: Winter 59°F, Spring 61°F, Summer 67°F, and Autumn 66°F. The results of our testing and those conducted by others resulted int the operational fielding of the MK VII SDV, which was the designation given by the Navy to the service-approved version of the Convair Model 14.
UDT Commander Doug “Red Dog” Fane
Dr. Chris Lambertsen is seen instructing use of the LARU
UDT men during LARU training at St. Thomas, USVI in 1947
UDT men diving the LARU with “Sleeping Beauty” during 1947 submarine operations at St. Thomas
Italian SLC “Pig” (1939-1943). The Italian SLC (initials of “slow-speed torpedo” in Italian) was a two-man submersible capable of making 2.2 knots with an operating range of 10 miles. It was also highlighted in the Part I story. The “Pig,” was used operationally and successfully during World War II. The submersible was brought to the United States for trials with the UDTs in the mid-1950s. This photograph of the SLC was taken at the Naval Amphibious Base, Little Creek, Virginia during UDT trials in the Chesapeake Bay.
Aerojet Experimental Pedal-Powered SPU (1952). A pioneering petal-powered attempt by Aerojet General Corporation in the field of swimmer propulsion. The weight and dimensions of the Swimmer Propulsion Unit (SPU) are not known, but the photo provides a perspective. The vehicle had no instrumentation. At 100 rpm, the device was capable of about three knots speed. The maximum practical range was estimated to be about three NM. Adding payload would have been problematic.
Aerojet Mark I SPU (1952). A one-man, pedal-powered SPU. It was a cleaned-up version of the previously built experimental version. The Mark I designation was given by Aerojet. A final development in 1952 resulted in the SPU being fitted with a body fairing to reduce drag.
Aerojet Mark I SPU (1952). A one-man, pedal-powered SPU. It was a cleaned-up version of the previously built experimental version. The Mark I designation was given by Aerojet. A final development in 1952 resulted in the SPU being fitted with a body fairing to reduce drag.
Aerojet Mini-Sub Mark II (1952). The Aerojet Mini-Sub Mark II was a further improvement of the Aerojet Mark I SPU through the addition of a CO2 propulsion system. This was in addition to the pedal-drive system. It was a one-man submersible. A steady-state speed of three knots for three miles could be achieved with the pedal-drive system. Using C02, the SPU was capable of four knots for 15 minutes.
Aerojet Aquaped SPU (1952-1953). A simple SPU capable of surface or submerged operation, with or without a breathing apparatus. It was simply a pole and saddle connected to counter-rotating propellers driven by bicycle pedals and gears. A fixed speed and efficiency for the vehicle of four times that obtainable with swim fins was claimed. The operator could cruise comfortably at 1- 1 ½ knots (without payload).
Aerojet Mini-Sub Mark III (1952-1953). This one-man vehicle was the next step in Aerojet’s SDV development program. The hull was constructed of plastic laminated glass cloth. The operator rode in an upright and seated position. Propulsion consisted of counter-rotating propellers on a single shaft driven by a battery-powered motor or bicycle pedal system.
Daystrom Waterboy (1953). Originally designed to satisfy a UDT requirement for a swimmer-towed explosive container that was to be a simple design and expendable. The design, however, evolved into a somewhat complicated device; a towable container with a system to control buoyancy automatically or manually and trim so that the device could be towed underwater.
Aquamotor (1954). Designed as a commercial SPU for sport divers. The swimmer strapped the unit to his chest using a canvas harness assembly. The unit consisted of three streamlined aluminum ally cylinders mounted on a sheet of aluminum alloy chassis. Two outer cylinders contained silver-cell batteries that powered a small motor contained in a middle cylinder. None were purchased for service use.
Aerojet Mini-Sub Mark VI (1954). Designed with space to carry another operator or cargo. The hull and fins were made of Plexiglas reinforced plastic. Two models were made. Model F was a foot-pedal powered and Model P was powered by an electric motor. Swimmers sat erect back-to-back with their heads in transparent domes. It was tested by members of UDT-13 and UDU ONE at the Aerojet plant. As far as could be determined, about seven or eight Mk VI vehicles were built.
Aerojet Mini-Sub Mark VI (1954). Designed with space to carry another operator or cargo. The hull and fins were made of Plexiglas reinforced plastic. Two models were made. Model F was a foot-pedal powered and Model P was powered by an electric motor. Swimmers sat erect back-to-back with their heads in transparent domes. It was tested by members of UDT-13 and UDU ONE at the Aerojet plant. As far as could be determined, about seven or eight Mk VI vehicles were built.
Aerojet Mini-Sub Mark VII (1955). A two-man submersible designed primarily bottom search. Divers’ rode in a prone position. To minimize magnetic signature, the hull and almost all structural components were made of fiberglass-reinforced plastic. The requirement for a low-acoustic signature was accomplished by utilizing large diameter, slow turning, high-efficiency aircraft-type propellers powered by a 1-hp, 24-volt d-c motor. The vehicle had no longitudinal-trim system. Eleven Mk VII submersibles were built.
Aerojet Mini-Sub Mark VII (1955). A two-man submersible designed primarily bottom search. Divers’ rode in a prone position. To minimize magnetic signature, the hull and almost all structural components were made of fiberglass-reinforced plastic. The requirement for a low-acoustic signature was accomplished by utilizing large diameter, slow turning, high-efficiency aircraft-type propellers powered by a 1-hp, 24-volt d-c motor. The vehicle had no longitudinal-trim system. Eleven Mk VII submersibles were built.
Peter Stackpole Swimmer Propulsion Unit (1955). Named after the builder; a well-known Life Magazine photographer. Tested by East Coast UDT personnel, deemed to have no military potential.
Peter Stackpole Swimmer Propulsion Unit (1955). Named after the builder; a well-known Life Magazine photographer. Tested by East Coast UDT personnel, deemed to have no military potential.
Undersea Hot Rod (1955). A one-man submersible sled built as a private venture by the P.L. DeLuca Co. of Los Angeles. It was demonstrated to UDU ONE personnel, who recommended no further evaluation. The hull was constructed with balsa wood covered with fiberglass.
Sea Bat (1955). A towed sled-like vehicle equipped with stern and bow planes and a rudder. The diver rode prone behind a partially enclosed plastic water screen and maneuvered the vessel as it was towed by a surface craft. The vehicle was designed for mine hunting and bottom search. It was tested by UDT personnel on both coasts and determined not satisfactory for UDT use.
USNUSL Sea Sled (1955). Only one vehicle was built by the Underwater Sound Laboratory, New London, Conn. It was a battery powered, pressurized, aluminum ally hull that could be exited through a submarine torpedo tube. It could accommodate one or two prone divers and had controlled buoyancy that could be flooded to a very heavy condition and bottomed. Trim was achieved by movement of a 100-pound lead weight.
USNUSL Sea Sled (1955). Only one vehicle was built by the Underwater Sound Laboratory, New London, Conn. It was a battery powered, pressurized, aluminum ally hull that could be exited through a submarine torpedo tube. It could accommodate one or two prone divers and had controlled buoyancy that could be flooded to a very heavy condition and bottomed. Trim was achieved by movement of a 100-pound lead weight.
USS X-1 Submarine (1955). A dry miniature submarine originally conceived in 1953 for the UDTs. It was launched in September 1955 and commissioned at New London, Connecticut in January 1956 as USS X-1. Originally intended for the Amphibious Force, instead, the Navy transferred responsibility to the Submarine Force. As a result, many of the original design concepts were modified or dropped. USS X-1 was designed to carry two submarine crew members and six UDT operators with equipment. (Note the two Swimmer Propulsion Units (SPUs) mounted near the man standing in the B&W photo.)
USS X-1 Submarine (1955). A dry miniature submarine originally conceived in 1953 for the UDTs. It was launched in September 1955 and commissioned at New London, Connecticut in January 1956 as USS X-1. Originally intended for the Amphibious Force, instead, the Navy transferred responsibility to the Submarine Force. As a result, many of the original design concepts were modified or dropped. USS X-1 was designed to carry two submarine crew members and six UDT operators with equipment. (Note the two Swimmer Propulsion Units (SPUs) mounted near the man standing in the B&W photo.)
BUSHIPs/Aerojet Mark 1, Mod O SPU (1957). Designed primarily as a reconnaissance vehicle for use from a submarine; it could be carried in the ship’s torpedo tubes. The swimmer lay in a prone position on the after-body and was towed by curved shoulder hooks. A second swimmer could be towed by gripping the heels of the forward swimmer. The operator maneuvered the vehicle by means of body English and swim fins.
Underwater Demolition Unit ONE Swimmer Propulsion Unit DRUT (1960). Conceived, designed, and built by UDT men at NAB, Coronado. Two divers rode astride and semi-prone on the body of the torpedo-like vehicle. The submersible was built from scrap parts drawn mostly from the NAS, North Island salvage yard. The name, spelled backwards, was a play on words.
Italian SEA HORSE II (1960). A two-man submersible built by Costruzione Motoscafi Sottomarini (COS.MO.S) Industries of Livrorno, Italy. It was constructed entirely of fiberglass. For UDT use, a clear plastic water shield was later installed. This SDV was designed as a sports vehicle and had minimal instrumentation. UDT-21 Lieutenant Chris Bent is seen standing beside a Sea Horse. The larger Italian TRASS vehicle can be seen in the background.
Italian SEA HORSE II (1960). A two-man submersible built by Costruzione Motoscafi Sottomarini (COS.MO.S) Industries of Livrorno, Italy. It was constructed entirely of fiberglass. For UDT use, a clear plastic water shield was later installed. This SDV was designed as a sports vehicle and had minimal instrumentation. UDT-21 Lieutenant Chris Bent is seen standing beside a Sea Horse. The larger Italian TRASS vehicle can be seen in the background.
Italian SEA HORSE II (1960). A two-man submersible built by Costruzione Motoscafi Sottomarini (COS.MO.S) Industries of Livrorno, Italy. It was constructed entirely of fiberglass. For UDT use, a clear plastic water shield was later installed. This SDV was designed as a sports vehicle and had minimal instrumentation. UDT-21 Lieutenant Chris Bent is seen standing beside a Sea Horse. The larger Italian TRASS vehicle can be seen in the background.
Italian TRASS III (1960). A four-man submersible also built by COS.MO.S. Four were purchased by the U.S. Navy and substantially modified. TRASS had the same construction characteristics as the SEA HORSE. The picture taken at UDT-22 at Little Creek shows a highly modified TRASS. It resembles the Convair Model 14 / MK VII SDV, which can be seen in the background. TRASS operations with a submarine were conducted in Puerto Rico during early 1967.
Italian TRASS III (1960). A four-man submersible also built by COS.MO.S. Four were purchased by the U.S. Navy and substantially modified. TRASS had the same construction characteristics as the SEA HORSE. The picture taken at UDT-22 at Little Creek shows a highly modified TRASS. It resembles the Convair Model 14 / MK VII SDV, which can be seen in the background. TRASS operations with a submarine were conducted in Puerto Rico during early 1967.
Italian TRASS III (1960). A four-man submersible also built by COS.MO.S. Four were purchased by the U.S. Navy and substantially modified. TRASS had the same construction characteristics as the SEA HORSE. The picture taken at UDT-22 at Little Creek shows a highly modified TRASS. It resembles the Convair Model 14 / MK VII SDV, which can be seen in the background. TRASS operations with a submarine were conducted in Puerto Rico during early 1967.
Loral T-14 / Pegasus (1961-1962). Developed by French engineer Dr. Dimitri Rebikoff in the late 1950’s. It was described as a winged torpedo, a single diver rode astride the vehicle in a prone position. A diver is being towed in the background. The Navy purchased six of these vehicles for evaluation. This SPU had bow planes, which were called “diving fins.”
Loral T-14 / Pegasus (1961-1962). Developed by French engineer Dr. Dimitri Rebikoff in the late 1950’s. It was described as a winged torpedo, a single diver rode astride the vehicle in a prone position. A diver is being towed in the background. The Navy purchased six of these vehicles for evaluation. This SPU had bow planes, which were called “diving fins.”
Italian CE2F (1962). A two-man submersible built by COS.MO.S. It was purpose built for military application by the same company that made the TRASS and SEA HORSE. A sliding Plexiglas canopy protected the crewmembers. Maximum speed was claimed to be 4.5 knots, and cruising speed 3.3 knots for 60 nautical miles.
Italian CT2F (1962). A two-man COS.MO.S. submersible. Similar in general to the CE2F configuration but had a dual propulsion system powered by gasoline or an electric battery and motor. It carried compressed air for buoyancy tank control. Surface full speed claimed was 6.5 knots for 100 miles and submerged speed 3.5 knots for 20 miles. (Photos from Naval Analyses).
Italian CT2F (1962). A two-man COS.MO.S. submersible. Similar in general to the CE2F configuration but had a dual propulsion system powered by gasoline or an electric battery and motor. It carried compressed air for buoyancy tank control. Surface full speed claimed was 6.5 knots for 100 miles and submerged speed 3.5 knots for 20 miles. (Photos from Naval Analyses).
BUSHIPS / AeroJet TOWCAR X-1 (1962). Designed using a flexible-hull construction principal to carry four or more swimmers towed behind an SDV. The hull was made of nylon-reinforced plastic with large, transparent, plastic windows. Water inflated ribs gave the craft “shape” during tow. It had no variable ballast or trim control and was unstable under tow.
BUSHIPS / AeroJet / General Electric Mark II (1962). A two-man, free-flooding vehicle constructed of reinforced Plexiglas and designed for 1000 feet so that it could be carried on the deck of a submarine. Onboard compressed air provided life support and ballast. It was powered by Yardney LR-220 silver-zinc batteries.
BUSHIPS / AeroJet / General Electric Mark II (1962). A two-man, free-flooding vehicle constructed of reinforced Plexiglas and designed for 1000 feet so that it could be carried on the deck of a submarine. Onboard compressed air provided life support and ballast. It was powered by Yardney LR-220 silver-zinc batteries.
BUSIPS/AEROJET Mark 1, Mod 1 Swimmer Propulsion Unit (SPU). An improved Mod 0 version. Four units were delivered. Mod 1 changes included: redesign of the electrical system, speed selector, dead-man switch, installation of a remote compass, a reliable depth gauge and tachometer, and redesigned ballast system.
BUSIPS/AEROJET Mark 1, Mod 1 Swimmer Propulsion Unit (SPU). An improved Mod 0 version. Four units were delivered. Mod 1 changes included: redesign of the electrical system, speed selector, dead-man switch, installation of a remote compass, a reliable depth gauge and tachometer, and redesigned ballast system.
Italian Sea Horse II, Mod 1 (1964). Modified at the Navy Laboratory in Panama City, Florida, major modifications included: a cable control system, Plexiglass canopies, Silver Zinc vs. Lead Acid Batteries, enlarged rudder and stern planes, new instrumentation, new buoyancy system, and new air system for ballast and breathing.
French PR-77 (1964). The PR-77 was a two-man SDV designed and built by Bronzsvis of Paris. Only one of these vehicles was built, and it was purchased by the U.S. Navy as a test platform. Note the minimal control systems. It had compressed air for breathing and could reach a submerged speed of 8.7 knots (French claim, never verified).
French PR-77 (1964). The PR-77 was a two-man SDV designed and built by Bronzsvis of Paris. Only one of these vehicles was built, and it was purchased by the U.S. Navy as a test platform. Note the minimal control systems. It had compressed air for breathing and could reach a submerged speed of 8.7 knots (French claim, never verified).
French PR-77 hull with American electronics.
Mine Defense Laboratory Two-Man SDV (1964). Only one of these vehicles was ever fabricated. It was influenced by the French PR-77 design. The hull was constructed of stainless-steel tubing covered by fiberglass panels. As an experimental platform (EXP), the SDV went through several significant design changes. It was a testbed for development of advanced-technology submersibles. It was eventually given the designation MK VI SDV.
General Dynamics/Convair Model 14 SDV (1966-1967). Five of these SDVs were built under a BUSHIPS six-month contract and delivered to Naval Operations Support Group, Pacific for test and evaluation. They exceeded contractual operational and technical requirements. This four-man SDV set the baseline for six additional modifications and remained in the inventory until 1983.
General Dynamics/Convair Model 14 SDV (1966-1967). Five of these SDVs were built under a BUSHIPS six-month contract and delivered to Naval Operations Support Group, Pacific for test and evaluation. They exceeded contractual operational and technical requirements. This four-man SDV set the baseline for six additional modifications and remained in the inventory until 1983.
1967: East Coast SDV Test Detachment. Front (l-r): Tom Winters (UDT-21), Jack Lynch (ST-2), Dr. Bill Vaughan (ONR Project Investigator), John Hunt (UDT-22), and Detachment CPO Don Blackwell (NOSG-1 RDT&E, Detachment CPO). Back (l-r): Tom McCutchen (ST-2), Rex Davis (UDT-22), Tom Hawkins (OIC, UDT-21), and Dan McEvoy (UDT-21).