Deep Submergence Vehicle

There are many kinds of deep submergence vehicles (DSV). Some are built to carry scientists and pilots while others operate as robots controlled by computer systems or manual control. Some sources reference these craft as deep submergence research vehicles (DSRV) but this appelation is depecrated since it invites confusion with Deep Submergence Rescue Vehicle [DSRV] The Naval Vessel Register recognizes five Deep Submergence Vehicles of a single class. These five vessels are all phyiscally dis-similar, though treated here as a single class. In addition, there are several other Deep Research Vessels, that are kindred to the five DSVs recognized by the NVR, but not included in the NVR's class listing. All deep-submergence systems owned or operated by the Navy are certified in accordance with Naval Sea Systems Command SS800-AG-MAN-010/P-9290, System Certification Procedures and Criteria Manual for Deep Submergence Systems.

The Navy's Submarine Development Squadron 5 [formerly Submarine Development Group 1] operates several Deep Submergence Vehicles capable of deep ocean floor salvage work, and retrieval and emplacement of material of interest to the intelligence community. These vessels are all part of the single DSV class, although there are substantial differences in configuration between individual submersibles. Although there had been attempts since antiquity to work underwater, humans had never been able to penetrate very far into the depths until the 1930s, when William Beebe, an American ichthyologist, succeeded in reaching a depth of 1,000 meters in his "bathysphere" ("bathy" = deep).

The bathyscaphe ("bathy" = deep, "scaphe" = ship) Trieste was built in 1953 at Naples, Italy, by the Swiss scientist Auguste Piccard. The Trieste, essentially a steel sphere attached to large float filled with aviation petrol for buoyancy, lacked manipulators or samplers, and was quite large and not very maneuverable. But it allowed unprecedented observations from the water surface down to the benthos (organisms that live on or in the ocean bottom) and provided a tantalizing glimpse of future discoveries.

The subsequent development of occupied research submersibles focused on systems allowing access to undersea depths of up to 6,000 meters (20,000 ft). The ambient pressure at these depths is over 4 tons per square inch, of order the same pressure that structural engineers must deal with in designing mechanical support systems for skyscrapers. Although the design of a simple structural items may be straightforward in principle, in practice they may fail due to changes in tolerance or material deformation due to such ambient pressures. Most submersibles have much shallower diving capabilities (300 meters to 3,000 meters). In 1964, the US Navy launched Deep Jeep at the Naval Ordnance Test Station, China Lake, California. Deep Jeep could dive 2,000 feet and hold a 2 crew of two. It was built to do oceanographic research and as a general underwater work submersible. Other US Navy submersibles built for the same purposes include Nemo, Makakai, Hikino, and Deep View. Of the vehicles in the Navy inventory (or operated by academic contractors for the Navy), the nuclear-powered NR-1 was rated at only 3,000 feet, and the DSRVs (Deep Submergence Rescue Vehicles) Mystic (DSRV-1) and Avalon (DSRV-2) were rated to only 5,000 feet.

The art of submersible design was in a state of rapid change and sophistication, but it had a long way to go. Submersibles remained expensive; difficult to transport, handle, and control; and short on visibility, endurance, and depth. The immense effort already undertaken with such well-known designs as Aluminaut, Alvin, Trieste, and Deepstar had shown both the problem and the promise. The promise was that the inconvenience of pioneer equipment can be eliminated, that submersible transport systems will give the investigator the freedom to go deep without restraint, and that once there he will have the option of traveling as far as he wishes.

But with the advent of remotely operated and autonomous vehicles in the 1990s, the crewed submersible's utility declined, and Turtle and Sea Cliff and other DSVs were retired.

Deep Submergence Vehicle Design Considerations

For centuries, man has attempted to descend into the oceans for scientific observation, salvage and rescue operations, animal and mineral harvesting, and attacking enemy ships in times of war. Often, such activities require vessels capable of submerging to great depths. Thus, the foremost concern in designing and fabricating the hull of a deep submergence vessel is that the hull be strong enough to resist the large crushing forces resulting from hydrostatic pressure. For this reason, submarines have been typically constructed of welded steel that is several inches thick. However, there are many disadvantages of such construction. The thickness of the hull makes rolling and welding operations extremely difficult. Also, the resulting weight of the welded steel structure is immense and it impacts buoyancy and maneuverability. Furthermore, the substantially tubular, elongated structure of a typical submarine hull is impossible to shape without specialized components.

Submarine design follows the basic pattern of an inner hull designed to withstand the pressure of extreme depths and a partial or complete outer hull designed to provide the optimum in hydrodynamic performance. The volume between the two hulls is called the free-flooding areas. Fleet submarines have free flooding volumes between hulls. These "volumes" or tanks are designed to be completely water or air filled depending on whether the submarine is to be submerged or surfaced. Additional hard ballast tanks (auxilliary or trim) are used to maintain a specific submergence depth and angle.

Deep submersibles also have hard tanks which take on water to achieve a specific submergence depth. The ISRV, Deep Submergence Rescue Vehicle, and Deep Quest can achieve a specific buoyant level by pumping water into and out of its variable ballast tanks. Certain deep submersibles such as the Trieste are designed to release iron shot to control their descent. Gasoline can be released by the Trieste to control buoyancy when near the bottom. Surfacing is achieved by release of additional iron shot. The DSRV and Deep Quest surface by pumping sea water from the variable ballast tank.

The design and use of cable cutters to be operated in the ocean environment has become of great importance in the field of marine engineering. Cable cutters have been of extreme interest to the US Navy. Operation of cable cutters is presently being extended to all depths of the world's oceans. The design and construction of cable cutters cover an extensive area of the engineering fields. The general method used for cutting is a mechanical technique usually involving a cutter impinging on an anvil to cut the cable or wire. In some cases scissor-like devices have been used. Operation of the cable cutter has included the manipulation of the cutter at the cable by a diver, either remote or hands-on operation of a cutter which is actuated by the force of contact with the cable, and by remote means using electrical wires to actuate an explosive firing mechanism. Generally, such cable cutters have been designed as expendable in that they can only be used to cut once and are either lost or destroyed by that operation. Originally, cable cutters were designed mostly for cutting simple wire ropes and electrical cables. Modern state-of-the-art for electrical cable construction has resulted in the use of KEVLAR as a strength member. KEVLAR is a tough synthetic fiber and cannot easily be cut by scissor mechanisms. Consequently, many new designs for various types of cable cutters have been presented during the recent years. These have generally incorporated powerful anvil/cutter blade mechanisms.

Modern cable cutting technique is also being applied to underwater deep submergence vehicles. Cutters have been designed which mount to such vehicles and can be manipulated by an operator located inside the vehicle. Cable cutters designed for use at great ocean depths have been required to be heavy and bulky in order for certain pressure sensitive components to withstand and high hydrostatic pressures. This is particularly true where hydraulic systems have been used to provide a powerful cutting force. The essence of the present invention is the presentation of an improved hydraulic cable cutter which is designed to be lightweight and to operate from, and mate with, the manipulators of a deep submergence vehicle.