In 1971 a u.s. patent was issued on an Underwater Support Vessel, in the names of William Kumm and Harley Smith. It can be thought of as an oceanographic or “science submarine”, or in the case of the polar seas, as the preferred form for a polar research vessel. This submarine concept responded to a 1966 President’s Commission (the Stratton Commission) whose Report in 1969, inspired the book The Ocean Quest. It recommended development of an oceanographic research vessel -a submarine of 1000-foot depth capability, with its own divers, small submersibles and unmanned probes. Now, with the Arctic Research and Policy Act of 1984 calling for a five-year Arctic research plan, the Arctic Research Commission -thus formed to “assess our· national needs for Arctic research” — has highlighted that “the u.s. is the only nation with substantial interests in the Arctic that does not have a dedicated polar research vessel.” This suggests a renewed interest in the oceanographic submarine patented by Kumm and Smith.
Figures 1 and 2 show the physical configuration of the science submarine concept: the twin screw, twin hull, beamy configuration with the flat working deck in between providing excellent roll stability. Present day naval submarines, in contrast, have body of revolution hulls with little flat deck space and provide poorer roll stability. The point is, the “science submarine” configuration starts from a different set of missions and therefore functional requirements than those of an SSN or SSBN.
View full article for table data
A recent study under a grant rrom the National Science Foundation notes that “in the case of research vessels, it is the science requirements which define the type of ship, along with its size, speed, endurance, arrangements and overall capability.” Although six surface ship types are addressed for consideration, no mission requirements for an Arctic-capable science submarine appear. However, in specifying the requirements for “new oceanographic ships” which would include polar research vessels, the study lists “Endurance: sixty days, providing the ability to transit to most areas and work 3-4 weeks on station, 15,000 mile range at cruising speed.” And then later in the study, there are additional requirements under Seakeeping, “Maintain science operations at the following speeds and Sea States: 15 knots cruising through Sea State 4 . . . . 6 knots cruising through Sea State 7.”
In the latter case, the words used include not only functional requirements i.e. “maintain science operations at following speeds ···”,but also words which actually describe the inherent limitations of surface ships i.e. “6 knots cruising through Sea State 7.” A “science submarine” transiting at 6, or at 15 knots submerged would have ~ Sea State limitation, because it is by definition not at the sea surrace, subject to these external forces.
Other requirements call for 60-ton loads, which are spec1ried for stern-mounted A frames. Such heavy oceanographic objects put over the stern of an oceanographic ship and lowered into the seaway should, in all probability, be very close to neutrally buoyant in seawater — weighing little, if anything, in water. For the oceanographic submarine the functional requirement definition for the capability to deploy such oceanographic objects needs more precise definition. Would the deployment cable tension be relative to the object’s dry weight or its drag, if in tow at a stated submarine transit speed? Or is there on-station vertical lift tension to be also considered for something such as a largediameter piston corer stuck in the bottom. One method that the submarine could use for such a case, which a surface ship moving in a seaway could not, is to apply positive submarine buoyancy over a period of time to gradually overcome the bottom sediment suction force. It is thus very important to define the operating environment as well as the functional requirement in each instance, recogni zing that surface ships have many inherent limitations.
Consider now, some of the inherent advantages that a science submarine platform would have over a surface ship as a sensor platform, or as a support system for deployed sensor platforms:
- Adeauate Size. For multibeam high resolution bottom mapping or hydrographic sonars, the hull must be of sufficient length to bold all of the transducers necessary to achieve the highest possible resolution on the bottom. This is true for downward looking keel-mounted arrays for use in deep water as well as for sidelooking multibeam sonars mounted to port and starboard along the sides of the bull, as used in shallow waters such as continental shelves.
- Motion StabilitY. A submerged submarine hull, unlike a surface ship in a seaway, will not pitch, heave or roll in random fashion. Thus there is no requirement for additional transducers to compensate for platform random motions during the round trip time of the sonar signal to and from the ocean floor. The motion stability also contributes to the resolving power of the system because the return signal from a given bottom resolution cell is not affected by the platform-induced random angular noise.
- Terrain Following. In the shallower portions or the offshore Exclusive 200-mile Economic Zone, for example, the science submarine would be able to use hull-mounted focused sensors such as multibeam side-looking sonars in an altitudefollowing mode, down to the maximum depth of the submarine’s design; say 1000 feet. Such bull-mounted focussed sonar use is not possible with a surface ship because the altitude over the bottom is a variable over which the surface ship has no control.
- Reduced Towed Body Motion. When a submarine is used in deep water to tow a bottom-terrain following focused sonar or optical sensor vehicle, the random motions imparted to the top end of the tow cable are dramatically reduced, compared to a surface oceanographic ship tow. The surface ship will be subject to weather, currents and other yaw-producing effects, which will almost always be from a bearing other than in the direction or the tow. It is worth remembering that the tow direction is set by the requirements of moving the sensors at the end of the tow cable across the ocean floor in the altitude-following mode, depending upon the local terrain. The random surface ship motions imparted to its tow cable cannot be fully decoupled, with the result that the accuracy of terrain-following for low alti~ tude focussed sensors is thereby reduced. The science submarine, on the other band, operating below the random motions of the surface seaway, imparts none of these motions to the tow cable and hence to the towed platform.
- Operation in Homogeneous peep Water. The portion of the water column in the first few hundred feet of water near the surface is less homogeneous than the water below the thermocline. The science submarine. on the other hand, is capable of operating below the thermocline and can take full advantage of the homogeneous water column to further improve the resolution of hydrographic sonar systems as well as seismic sensor arrays. This is another fundamental advantage that the submarine platform has over any surface oceanographic ship.
- Noise Reduction. Present day U.S. oceanographic ships, (including the KNORR and the MELVILLE,) are acoustically noisy platforms with gear-driven diesel propulsion plants and propeller cavitation adding to the background noise. A fuel cell powered. electric drive science submarine would dramatically reduce the cavitation noise because it can operate at depths where the ambient pressure will reduce the cavitation to the lowest level possible. This advantage is particularly important for low-level, high sensitivity seismic studies which are of increasing interest to the ocean and geophysical science communities. The beamy science submarine configuration described, with its twin-screw electric drive, would also provide locations art for streaming seismic arrays and deploying active sound sources. as appropriate.
- A Clean. Motionless Laboratory. Except for the fact that the submarine may occasionally accelerate, decelerate or make beading changes, the laboratory spaces are as close to motion free as is possible underway. On station, these motions are likely to be minimized. The laboratory spaces will also be clean and free of atmospheric contaminants. as the submarine’s life support system should be of a much higher caliber than that of a surface ship. The addition of a hyperbaric section to the submarine permits saturated diving on station at depths of 300 to 500 feet, permitting marine biological studies to be carried out inside and outside the submarine, with the ability to keep the living samples at the ambient pressure of the sea, in the water.
- Submerged Suoport for Submersibles. Deployment of one-atmosphere, manned, deep diving submersibles of the ALVIN type will be made much safer. They would be totally weather and surface independent. It therefore will become possible to operate under the Arctic and Antarctic icefields. Submerged support, for example servicing external equipment fitted to the submersibles, would be performed by saturated divers — part of the crew of the science submarine. Small vehicles and oceanographic instruments would be brought into the submarine pressure hull for one-atmosphere servicing through the use of suitable equipment “air locks.”
These are some of the first-order advantages that the science submarine will offer over any surface oceanographic ship. Many other secondorder advantages will no doubt occur to the readers of the REVIEW, and are limited only by one’s imagination. This paper makes the case for the science submarine, not yet part of the u.s. submarine inventory, but producible with will and appropriate funding.
The science submarine need not be nuclear powered, and the use of “Solid State” fuel cell electric propulsion would permit it full civilian port access around the world. Once operational, the ocean science community will look back and wonder how they ever got along without it. In that respect it is akin to the science revolution occasioned by the availability of spacecraft for space science as compared to traditional terrestrial and atmospherically limited telescopic astronomy of the past.
Bill kumm
