Combatant Submersibles – Part III

By CDR (SEAL) Tom Hawkins, USN (Ret.)

No documentation has been discovered about the forethought and promulgation of the Navy’s Technical Development Plan 38-02, which was entitled “The Swimmer Support System.” It was very simple and very visionary view of future UDT and SEAL Team capabilities development. TDPs were the Navy’s bureaucratic methodology for planning, programming, and budgeting its advanced technology research and development programs during the 1960s and 1970s.

A somewhat stained and preserved U.S. Navy recruiting poster displayed an artist’s conception of future UDT-SEAL capabilities and caption that reads: “Project SURAC (Swimmer Underwater Reconnaissance and Clearance) and the “Seeing Eye,” the newest addition in underwater detection, add increased capabilities to one of the most challenging and demanding missions in the world—the UDT and SEAL Teams.” The poster is dated 1965. Presumably, the “Seeing Eye” is the hand-held sonar with the diver at the bottom center of the poster’s rendering.

“Project SURAC” was apparently a name of the development program fashioned before promulgation of TDP 38-02. The TDP was a very ambitious program to develop advanced-technology Class I and Class II SDVs (six-man and two-man capabilities), Class I and Class II Underwater Breathing Apparatus (UBAs: closed-circuit mixed gas and closed-circuit pure oxygen versions), and a host of ancillary equipment (hand-held sonar, diver’s decompression computer, underwater communications, etc.). The TDP also called for conversion of two former Reguleus missile-carrying submarines to transport SEALs and SDVs. They were to be USS Grayback (SSG-574) and USS Growler (SSG-577), which required close coordination with the Navy’s submarine community.

Under Naval Sea Systems Command (NAVSEA) direction, the Navy’s research and development laboratory in Panama City, Florida was tasked to develop specifications for acquisition of the SDVs. UBA specifications were developed by the Navy Experimental Diving Unit in Washington, DC. These specifications intended to go through a commercial competitive bidding process. The NAVSEA office of the Supervisor of Diving and Salvage directed and supervised preparation of these contract specifications, oversaw the awarding of contracts, and participated in design reviews once awarded. The Navy’s aim was to develop Performance Specifications vs. Design Specifications and let industry compete for the designs.

General specifications for the SDVs and UBAs were somewhat simple: the Class I SDV would be a six-man SDV and operate at six knots for six hours. The Class II SDV was to be a low-profile, two-man reconnaissance vehicle with the same operational attributes. The Navy would provide USS Grayback and USS Growler, on which their two Regulus-missile hangers would be converted to floodable diving chambers that could house one SDV each or be used for mass-swimmer lock-outs.

TDP 38-02 developments were considered “long-range” programs; which, in the eyes of the Navy, could take seven years or longer to complete. Because SEALs were increasingly deployed for operations in Vietnam during this period; Naval Operations Support Group, Pacific (today Naval Special Warfare Group ONE), became involved in a cooperative-program with the Electric Boat Division of the General Dynamics Corporation in San Diego to accelerate and build a “Modified TRASS” SDV. Since GD’s build capability was in San Diego, they were readily available to NOSG-1 for close coordination. “Modified TRASS” was a play on words to acquire funding.

Italian TRASS
The TRASS submersible was an Italian design obtained by the U.S. Navy and substantially modified for UDT operations. No matter how hard attempted, the TRASS had very limited and unreliable operating characteristics. Most likely a total waste of money, but certainly enhanced the SDV capability learning curve.

Italian SEAHORSE
The Navy acquired the SEAHORSE, an Italian two-man submersible, designed for the commercial market and somewhat worthless; although it too provided an excellent learning curve for the UDTs. TRASS and SEAHORSE were never seriously considered “operational.” Both were maintenance intensive and quite limited in any capability, save being able to submerge and follow a basic compass course during day-time operations.

French PR-77
In 1964, the Navy acquired the French designed Loral PR-77 submersible for the Navy’s Panama City lab to serve as a test bed for development of Class I and Class II SDV procurement specifications. The PR-77 was a teardrop shaped, two-man submersible, with an expansive Plexiglas viewing area in the forward cockpit area. The PR-77’s design was replicated, and electronics were replaced with experimental navigation sonars and other modernized subsystems. The Panama City submersible was simply called the EXP – Experimental Platform. Although never actually becoming operational, the EXP was later given the designation MK VI SDV.

Convair Model 14
In 1967, five General Dynamics/Convair Model 14 SDVs (“Modified TRASS”) were built under a NAVSEA contract and delivered to the Navy for test and evaluation. This was a four-man submersible capable of sustained speeds up to four knots. Sea trials were accomplished in the Pacific Ocean area along the Coronado, California coast. During sea trials, the SDV exceeded specified operational and technical requirements, and was declared operational. It was later given the Navy designation Mark VII, Model 0 (MK VII, Mod 0). A hull of this SDV is on display at the Museum.

Because of west coast UDT and SEAL Team manpower struggles in 1967, resulting from demands in Vietnam, the east coast was requested to provide a detachment of operators to serve as human-test subjects in support of an Office of Naval Research (ONR) bio-medical study using the Convair Model 14 as a test bed. The study was designed and investigated by Dr. Bill Vaughan. Its major premise was to determine the medical effects of prolonged diver exposure to cold water during SDV operations.

For operational planning, no one really knew the medical and human-performance aspects of men exposed to cold water for up to four or more hours’ time. Divers in an SDV accomplish what’s essentially called a “non-working dive,” which actually means they are literally setting motionless for several hours’ time – thinking about being wet and cold, i.e., the men are positioned in a confined space with little room for movement to generate body heat. The study permitted accumulation of critical performance attributes to optimized SDV operational-performance parameters. The average water temperature in San Diego was 55 degrees.

Thermal protection was obviously required, and the west coast UDTs worked with San Diego Diver’s, a local dive shop, to design and acquire what the men called the “Farmer John” wet suit. Basically, it was a precisely measured, custom-built, neoprene-wet suit having two layers. The undergarment was a full-body, one-piece design akin to bib overalls. The second layer was a protective jacket that provided a double the amount of upper-body thermal protection for the core area, including a wet-suit hood.

To collect the essential elements of data needed, a portable water-and-pressure-proof depth recorder was secured inside the SDV for each test event. The data collected would display SDV pilot control and stability throughout the test event (flying completely level was the goal). Also, during pre-mission preparation, the men were outfitted with an anal probe, which recorded core temperature throughout the test mission. SDV test event began at one-hour duration underway; expanding eventually to four hours or longer. The experimentation concluded that thermally protected UDT-SEAL divers could perform SDV operations accurately and safely in 55-degree water for four-hours duration.

38-02 SDVs
After Class I and Class II SDV specifications were completed, a competitive contract for development was awarded to the AeroJet General Corporation in Azusa, California. There is a larger-longer story here, but simply to say now that the SDV effort with Aerojet floundered badly and the company wanted out of the contract. The Navy didn’t want to cancel that contract, since NSW had already invested a lot of money in the effort. Instead, AeroJet established a spin-off company in San Diego called Ocean Products, Inc. (OPI), which also failed. OPI did, however, actually “field” a Class II SDV test article. It sank at a NAS, North Island pier while being launched and never got underway. After that, NSW transitioned the project into Government control, and established a SDV design and build program at the Naval Weapons Center, China Lake, California.

Taking the SDV program to China Lake ended up being a salient move. The SDV group amassed there designed, developed, and tested the first MK VIII and MK IX SDV prototypes; and an SDV build program was established. All of the in-water testing was accomplished in fresh-water at Lake Haiwee Reservoir, which was some distance north of China Lake. Fascinating, that the SEAL Team’s modern-day SDV capability was developed in the California high desert. MK VIII and MK IX SDV hulls are on display at the Museum.

Other activities occurring at the SDV program in China Lake were improvements and modernizations to the in-service MK VII SDV, and coordinating with the Applied Research Lab in Austin, Texas on an ahead-looking “obstacle-avoidance sonar” or OAS system. There were also several follow-on human-performance studies conducted in a temperature-controlled building and pool built for this testing. Notable projects included testing diver performance in cold-water during six-hour SDV full-mission profiles (including pool-side land-simulated activities), and a study to assess diver perceptions in low-turbidity water. These projects were sponsored by the Office of Naval Research, and Dr. Bill Vaughan was again the ONR investigator.

MK VIII and MK IX SDVs
The MK VIII and MK IX SDVs were approved for service use around 1978, and began phase replacing the MK VIIs. Primarily for budget and manning considerations, the MK XI SDV was eventually removed from Fleet service. The MK VIII SDV went through six continuous improvement enhancement- modernization programs. It was phase replaced by MK 11 SDV, with delivery to the SDV Teams beginning in 2018.