Fear Not VOD

To demonstrate one manufacturer’s approach to meeting the constraints and requirements of submersible diving, Lockheed Missiles and Space Corporation’s DEEP QUEST system will be examined (Fig. 2.4a). DEEP QUEST is not necessarily the most successful approach, but its 8,000-ft operational depth capability and support systems confront and offer solutions to the majority of problems encountered. (The following data was attained from refs. 7 through 11.)

Fig. 2.4 a) The submersible system DEEP QUEST (LMSC)

Environmental Constraints

Pressure

The manned compartment (pressure hull of DEEP QUEST ) consists of two intersecting spheres welded together with a 20-inch-diameter opening between the two and a 20-inch- diameter opening (hatch) atop the aft sphere. The spheres are 7 feet in outside diameter (OD), 0.895 inch thick, and are composed of 18 percent nickel, 200-KSI-grade maraging steel. A weldment of four hemi-heads and interconnecting “Y” rings form the basic structure. A collapse depth of 13,000 feet (5,772 psi) provides a safety factor of 1.6 at its operating depth of 8,000 feet (3,554 psi). DEEP QUEST has been designed to incorporate a diver lock-out compartment and a transfer bell as shown in Figure 2.4b, but these are not affixed to the submersible at present.

Seawater (Corrosion Protection)

To protect the fairings and foundations, piping, variable ballast tanks, high pressure air tanks, and electrical inverter/controllers, a multi-coat polyurethane Laminar X-500 finish has been applied. The pressure hull is isolated from contact with the aluminum outer hull by mounting it on rubber pads and clamping it down with a phenolic collar. It is further protected by a mild steel anode system. Whenever possible, dissimilar metals are electrically isolated by non-conductive mountings. Small zone anodes are utilized freely to protect against electrolysis.

Fig 2.4 b) Schematic of DEEP QUEST as designed with potential diver lockout compartment and transfer bell. (LMSC)

Temperature

To control the pressure hull’s internal temperature there are two temperature sensors in each of the two spheres which activate an electrical damping system to apportion air through three heat exchangers. Excess heat (from personnel and operation of electrical equipment) is conducted through the hull wall. Electrically powered heating strips supply additional heat if that produced by equipment operation is insufficient. Toughness (crack arrest) of the pressure hull’s maraging steel was improved by careful modification of the chemical composition of the steel.

Light

To provide external lighting at depth, DEEP QUEST has nine fixed lights ranging in power from 500 to 2,500 watts; these may be individually controlled. On each of the two television pan and tilt mechanisms is a 500-watt flood light for trainable illumination.

Currents

To counter adverse currents, in addition to maneuvering, DEEP QUEST may employ two 7.5-hp, stern-mounted axial thrusters and one 7.5-hp lateral water-jet bow thrusters.

Density

A steel shot (1,900 lb dry weight) releasable ballast system is used to adjust for minor seawater density changes. DEEP QUEST normally operates submerged in a slightly heavy (negative buoyancy) condition, taking advantage of her lifting body outer hull configuration and vertical thrusters.

Acoustics

To minimize the effects of sound refraction, the submersible’s support ship TRANSQUEST attempts to maintain a position nearly above DEEP QUEST during the dive. Two 27-kHz acoustic pingers are affixed to the submersible; one is omnidirectional and one is vertically oriented by a parabolic reflector. A directional hydroplane antenna on TRANSQUEST provides the relative bearing to DEEP QUEST and a modification to the submersible’s underwater telephone (UQC) provides range information on a digital readout.

Sea State

TRANSQUEST’s launch/retrieval system, a hydraulically-powered elevator platform mounted in the open-stern-well, is marginally effective at sea state 4 in short period waves, optimizing at longer period swells.

Bottom Conditions

DEEP QUEST’s outer hull is streamlined and rugged. Two skids on the bottom of the vehicle protect it against damage and hold it high enough off the bottom to inhibit the possibility of accidentally taking aboard sediment. Object avoidance/search sonar provides for full-scale range indications from 15 to 1,500 yards.

Vehicle Performance

Viewing

For direct viewing, DEEP QUEST incorporates two viewports: one in the forward hull looks down and forward; one in the aft hull looks directly down through a hatch located on the bottom of the aft hull. The aft viewport is equipped with an optical remote viewing system incorporating an external “fish-eye” lens. Augmenting the viewports are two (port/starboard) pan- and tilt-mounted TV cameras; one bow-mounted TV camera, and one sail-mounted, 360-degree-vision, periscope-scanning, TV camera, and a fifth camera mounted as desired to observe a particular area or equipment for the specific dive.

Buoyancy

Four ballasting/buoyancy components are incorporated in DEEP QUEST (Fig. 2.5): 1) A Main Ballast System, consisting of two forward and two after tanks (port/starboard), provides 12 percent reserve buoyancy on the surface and is blown free of water by compressed air; 2) a Shot Ballast System, consisting of 1,900 pounds (wet) of steel shot in two cylindrical hoppers mounted outboard in the longitudinal C.G. plane provides “fail safe” ballast which is electromagnetically held and dropped in the event of a total power loss or metered out as desired; 3) 34,000 pounds of syntactic foam (36-pcf ave. density) neutralizes negative buoyancy of fixed structure and equipment; and 4) movable lead ballast (26-lb bricks), up to 3,000 pounds, provides the means of adjusting trim and weight as calculated prior to each dive.

Trim

The longitudinal moment (trim) of DEEP QUEST can be changed 30 degrees up or down during the dive by pumping oil from one to another of two, 18-inch-diameter, pressure-compensated, spherical tanks located fore and aft; each tank is initially half filled with 720 pounds of mercury which are separated from the oil by a rubber diaphragm and forced forward or aft by the pumped oil. A further refinement on DEEP QUEST is a port/starboard list tank system which changes the roll or transverse moment (+ or – 10 degrees) of the vehicle in a fashion similar to the trim system.

Stability

The surfaced metacentric height (GM) of DEEP QUEST is 12 inches; the submerged metacentric height (BG) is 3 inches. The short BG requires that careful consideration be given to attachment location and weight

Power

Main power is supplied by two, 120-VDC, pressure-compensated, lead-acid batteries supplying a total of 230 kWh which enable the vehicle to cruise at a speed of 2 knots for 18 hours. For scientific or other work instruments the following is available:

Fig. 2.5a. DEEP QUEST’s dynamic maneuvering ability.

Fig. 2.5b. DEEP QUEST’s static maneuvering ability.

120 VDC (nominal)

29 VDC + or – 2%

115 VAC rms + or – 2.5V, 60 Hz, single phase

115 VAC rms + or – 2% , 400 Hz, single phase

Two independent 28-VDC, silver-zinc batteries within the pressure hull provide 3.6 kWh of emergency power.

Maneuverability

The axial, vertical, and lateral propulsive units, as described in Figure 2.5, in conjunction with stern planes and a rudder, provide five degrees of freedom (pitch, roll, heave, yaw, surge) and a dynamic maneuvering capability through the speed range of 0 to 3.5 knots. Static roll and pitch rotational moments are applied by weight transfer in the trim and list systems. An automatic pilot (course, speed and pitch angle) and an automatic depth control are additional control adjuncts.

External Attachments

DEEP QUEST offers several areas for attachment of instruments, and a jettisonable, steel framework or “brow” may be attached on the bow to carry a variety of instruments including a 700-pound coring device or a 1,500-pound reel of line. Abaft the pressure hull is an enclosed area within the fairing of approximately 385 cubic feet; this area may be used to accommodate instruments or tools of widely varying dimensions and weights. In the event that these areas are not desirable or usable, it is possible to attach instruments to the top of the vehicle by bolting down “Unistrut” configurations as desired. (Fig. 2.6). Within the after pressure sphere two 19-inch-wide, 59-inch-high, standard electronics racks are available for installation of equipment; within the entire pressure hull approximately 20 cubic feet of space are available for additional equipment. Electrical penetrations through the pressure hull are provided for additional equipment; these consist of twenty-six, 2-wire (No. 18) AWG circuits and four, 2-wire (No. 16) AWG circuits. Extra leads can be made available by alternate substitution means.

Fig. 2.6. “Unistrut” instrument attachment to DEEP QUEST’s fairing. (NAVOCEANC)

Lock-out/Lock-in

A 25-inch-diameter door on the after pressure sphere is configured to join with a “man-in-sea” module to provide diver lock-out/lock-in facilities for at least two divers. The module, when installed, will occupy the enclosed area now available for additional instrumentation. A transfer bell may be attached to the bottom hatch of the pressure sphere for transferring personnel to or from manned undersea stations at atmospheric pressure or to rescue personnel from disabled submarines configured to accommodate the transfer bell.

Payload

In excess of 2,000 pounds (wet weight) may be carried within the diver module area. A total of 7,000 pounds may be accommodated by relocation of buoyancy (syntactic foam) material.

Human Considerations

Respiration

Oxygen is carried within the pressure hull in four bottles (0.37 ft ? each at 2,250 psi), two of which are spares. Oxygen is automatically bled into the cabin by a solenoid-actuated differential pressure control switch maintaining cabin pressure at 2 inches of water above a 1-atmosphere reference chamber. Carbon dioxide and other contaminants are removed by blowing a portion of the circulated air through lithium hydroxide/activated charcoal cannisters. An emergency blower is available for backup contaminant removal. Cabin pressure is monitored and displayed on a gage in the forward sphere. Oxygen and carbon dioxide partial pressures are detected by sensors and displayed; a red light alarm is activated when these pressures are beyond allowable limits (02: 140 to 180 mm Hg; CO2: 8 mm Hg max.). A Mine Safety Appliance universal kit is carried to identify trace contaminants.

Temperature/Humidity

With seawater temperature between 28 degrees and 55 degrees, cabin temperature is controlled, as explained previously, at 70 degrees + or – 10 degrees F. Relative humidity is maintained at 60% + or – 20% by condensation of moisture in the heat exchangers. All parts of the pressure hull’s interior, with the exceptions of the heat exchange portion and hatches, are covered with 5/8-inch-thick polyvinyl chloride (Ensolite) insulation.

Food/Water

Normal diving food rations consist of sandwiches and other foods prepared daily prior to each dive. Emergency dehydrated food is carried to sustain four people for 48 hours. Water is carried in plastic containers.

Waste-Management

Wide-mouth plastic jars enclosing vinyl bags are carried for collection and storage of liquid and solid wastes. Wescodyne germicide is used as a stabilizing agent and activated charcoal for odor control. A folding camp-type toilet seat with plastic waste bag is carried.

Fatigue

Pilot and co-pilot are provided with cushioned seats in the forward sphere. No permanent facilities are provided for the two observers other than a foam-rubber cushion located on the deck between the pilot and co-pilot upon which the observer may lie to use the forward-looking viewport. The dimensions of the pressure hull are sufficient to provide headroom for standing and stretching.

Emergency Procedures

Entanglement

DEEP QUEST’s streamlined fairings present minimal entanglement potential. Its manipulators, pan and tilt mechanisms and forward instrument brow are jettisonable. All propellers are shrouded and screened to prevent entanglement with rope or wire.

Power Loss

An emergency power source is carried inside the pressure hull on each dive. In the event of a total power (normal and emergency) loss the steel shot is automatically dumped. Emergency power can be used to operate jettisoning circuits, underwater telephone, radio, and life support equipment.

Fire and Noxious Gasses

An emergency breathing system for four people is carried which consists of four full-face masks coupled to a common rechargeable LiOH/charcoal cannister and oxygen supply with a breathing bag which acts as an accumulator. A pressure of 1.5 inches of water above cabin ambient pressure is maintained in the emergency system to prevent contaminated air from entering. The system provides a total of 3 hours for each person. Two 2.5-pound CO2 fire extinguishers are carried at all times. When a fifth person is carried, an OBA (Oxygen Breathing Apparatus) is added.

Deballasting Loss

In the event that normal ballasting methods and power are lost, the following may be dropped to gain positive buoyancy as indicated:

Fig. 2.7 DEEP QUEST’s jettisonable components.

Not included above are the jettisonable mechanical arms and brow and breakaway pan and tilt mechanisms (Fig. 2.7).

Tracking Loss

If DEEP QUEST becomes separated from TRANSQUEST, it has several options while on the surface for communication and location. A radio direction finder on the support ship may home in on a 2182-kHz voice transmitter, or a Coast Guard aircraft may home on a 121.5-MHz signal transmitted from a self-powered, omnidirectional emergency beacon aboard the submersible. A transducer affixed to the bottom of the submersible allows for UQC communication when surfaced. A floodable sail over DEEP QUEST’s top hatch allows for opening of the hatch in inclement weather to flush out cabin air if required. Surface viewing capability without opening the hatch is obtained through use of the sail-mounted television periscope. DEEP QUEST’s international orange sail and rudder provide excellent contrast against all spectrums of water color. A pressure-switch actuated, sail-mounted, flashing xenon light is provided for nighttime visual location.

Support Requirements

Transportation

As it is one of the larger deep submersibles, DEEP QUEST is normally considered only sea transportable. However, with the sail and stern planes removed, DEEP QUEST could be air (C-141) and land (tractor, trailer, rail) transportable. At its home port, San Diego, a marine railway is available to transport it in and out of its shop.

Support Platform

The Motor Vessel TRANSQUEST (see Table 12.2 for specifications) was specifically designed to support DEEP QUEST in extended open-sea operations, but it is somewhat limited by its size (108 ft) and speed (6.2 knots max.).

Launch/Retrieval Apparatus

(See sea state above.)

Tracking and Navigation

Tracking of DEEP QUEST was outlined under Acoustics above and is utilized to vector DEEP QUEST to desired locations as well as to track her movements. Three systems are available aboard DEEP QUEST for navigation independent of the surface (Fig. 2.8). The first system consists of a gyrocompass (providing heading azimuth which is further corrected to true heading by a vertical reference gyro and the navigation computer), a Doppler sonar log (provides vehicle speed relative to the bottom), and an analog computer which processes the direction and speed information and plots the vehicle’s course on an x-y plotter, as well as presenting the information to a data recorder. The second system uses gyrocompass or remote reading magnetic compass (Magnesyn) heading and flowmeter speed (or odometer distance) through the water to obtain a manual navigational track. A third system utilizes the laterally-trainable Straza Model 500 CTFM sonar mounted on the sail which transmits and receives sonar signals and generates both audio and visual outputs in the pressure hull and, in addition, provides a cathode ray tube with digital readout of range to a target. Using fixed bottom objects as landmarks or range and bearing of transponders placed on the sea floor, DEEP QUEST can employ the CTFM to obtain a plot of its progress relative to them. By using a down-looking depth sounder/strip chart recorder and upward-looking depth sounder in conjunction with the CTFM and transponders, accurate post-dive navigational charts may be constructed.

Fig. 2.8a DEEP QUEST’s navigational components. Underside View

Fig. 2.8 DEEP QUEST’s navigational components.

The DEEP QUEST submersible system is one of the most sophisticated in existence and was designed to accomplish such diverse tasks as research, surveying, engineering, search and retrieval, diver support and rescue. Relative to the shallower diving submersibles, it may appear unduly complex. Undoubtedly, one can do without a great number of DEEP QUEST’s capabilities if the operational tasks are merely for viewing and simple work functions. The trade-offs are obvious: The simpler the submersible, the simpler the tasks it may perform. Nonetheless, the basic design and operational aspects outlined above must be confronted and solved by all submersibles to varying degrees; where one or several of these functions have been slighted and no submersible is without fault the weakness is apparent.

A common weakness, undoubtedly the most crucial obstacle to wide-scale submersible employment, resides in the operational concepts. Possibly influenced by independently-operating, self-sufficient military submarines, submersible architects have tended to overlook or underestimate the critical role played by surface craft in supporting extended open-sea operations. In the formative years, the many technical problems of deep submergence overshadowed this surface dependency, but, once they were solved and submersibles routinely dived without crippling malfunctions, inadequacies of surface support came into proper perspective and still plague vehicle owners. Future submersible designers must, if they hope to achieve more effective diving records, be cognizant of the fact that small, maneuverable, battery-powered vehicles are inextricably bound to their surface support platform for safety, sustenance and operational efficiency.

REFERENCES

1. King, D. A. 1969 Basic hydrodynamics. in Handbook of Ocean and Underwater Engineering, McGraw-Hill Book Co., New York, p. 2-1 thru 2-32.

2. Warren, W. F. 1961 Seawater Density in the Ocean as a Function of Depth and a Method of Utilizing this Information in the Design of Pressure Vessels Which Will Remain in a Constant Depth Range Between the Surface and Bottom. Naval Ord. Lab. NOLTR 61-179, AD 273634.

3. McQuaid, R. W. and Brown, C. L. 1972 Handbook of Fluids and Lubricants for Deep Ocean Applications. Naval Ship Research and Development Lab., Annapolis, Md., Rept. MATLAB 360, 249 pp.

4. Busby, R. F. 1967 Undersea penetration by ambient light and visibility. Science, v. 158, n. 3805, p. 1178-1180.

5. Encyclopedia of Oceanography 1966 Encyclopedia of Earth Science Series, v. 1, edited by R. W. Fairbridge, Reinhold Pub. Corp., New York.

6. Personal Communication with A. Markel, Reynolds Submarine Services, Inc., Miami, Florida.

7. Lockheed Missiles and Space Corp. 1967 DEEP QUEST Summary Description. LMSC No. 5-13-67-3, Sunnyvale, California.

8. ________, 1968 Lockheed DEEP QUEST Submersible System. LMSC/DO80197, Revision B, Sunnyvale, California.

9. ________, DEEP QUEST Research Submarine. LMSC/DO15168 (unpub. Manuscript).

10. ________, DEEP QUEST – The Versatile Submarine. Ocean System Marketing (Sales Brochure), Sunnyvale, California.

11. Shumaker, L. A. 1972 New Developments in Deep Submersible Operations (unpub. manuscript).

TRANSPORTATION

Weight and size are the factors controlling a submersible’s transport and, hence, mobility. Land, sea and air transportation are possible; but, for some vehicles, this means dismantling major components. Deployment at the site of embarkation requires lift and possible rail facilities not available at many ports.

SUPPORT PLATFORM

There are few, if any, occasions when a submersible will not require a support platform. At the very least, this platform will be required to tow the vehicle to the dive site and track it while submerged. In open-sea operations, the platform will act to maintain the vehicle, house its support and scientific crew, and perform work tasks in conjunction with the submersible. Proper selection of such a platform is critical to the effectiveness of the submersible system.

LAUNCH/RETRIEVAL APPARATUS

Unless the submersible is too large for launch/retrieval at sea, an apparatus is required to deploy and retrieve it after each dive. Four basic methods may be utilized. One is a device to attach to and lift the vehicle out of the water, such as a crane. The second involves deballasting a submersible platform onto which the submersible is maneuvered. Third is the mechanical hoisting of an elevator platform attached to a surface vessel. A fourth approach involves the mother submarine concept in which the submersible is launched or retrieved and transported by a completely submerged platform. In the event of external repairs or maintenance to the submersible, the mother submarine may be required to surface.

May be an in situ navigation network by which the vehicle itself maintains a real-time display and record of its underwater position.

ENTANGLEMENT

To minimize the fouling potential with foreign objects such as wreckage, cables, or ropes, submersibles should have smooth, streamlined exterior surfaces, and objects extending beyond the fairing should be kept to a minimum. When possible, objects that offer a potential for fouling should be jettisonable.

Power Loss

In the event of a complete electrical power loss, the vehicle should have mechanical means of surfacing either by jettisoning components, dropping extra ballast, or blowing water ballast. An emergency power supply to operate critical emergency components should be considered.

FIRE AND NOXIOUS GASES

Emergency breathing apparatus and fire extinguishers within the pressure hull are required in the event of fire and release of noxious or toxic gases. Noninflammable wiring insulation should be used for all power cables and control wiring. Only insulation, paint, plastics, and other materials free of detrimental outgassing should be used inside manned spaces.

DEBALLASTING LOSS

A number of vehicles contain backup deballasting procedures in the event that the normal deballasting does not function or is insufficient. These include jettisoning of batteries, instruments, manipulators, or trim liquids (mercury). Where depth allows, many vehicles may be flooded by ambient seawater or pressurized by compressed air to open the hatch for emergency exit. In a few cases, the entire positively buoyant pressure hull can be manually released from the remainder of the vehicle, whence it will free float to the surface.

TRACKING LOSS

Owing to inaccuracies in tracking procedures or accidental loss of acoustic contact, a submersible may surface out of contact with its support ship and be completely on its own. Emergency signaling devices and radios are required. Some vehicles have such low freeboard that to open the hatch in anything higher than sea state 1 could swamp the pressure hull. In this case, emergency flares might be impossible to employ, and if a long period of time must be spent with the hatch closed awaiting outside assistance, the endurance of the emergency life support system to sustain the passengers could be exceeded. The color of the submersible might also be critical to visual sighting. A white submersible, with only 1 or 2 feet of its conning tower or sail protruding above the surface and posed against a background of whitecaps, is extremely difficult to see. Furthermore, radar may be ineffective owing to the sail being masked by sea return.

RESPIRATION

Oxygen must be supplied, and carbon dioxide must be removed for the duration (6-12hr) of a normal dive and for an extended period in the event of an emergency. Monitoring devices must be included to maintain proper levels and to check for the presence of contaminants. In the event of diver support, storage and supply of air or mixed gas (e.g., helium/oxygen) must be accommodated.

TEMPERATURE/HUMIDITY

In shallow tropical dives, temperatures (F) and relative humidity (%) reach into the 90’s; with depth, or in the high latitudes, the temperature can fall into the 40’s with a corresponding humidity decrease. Both these extremes bear heavily on human performance and must be dealt with successfully. Deep diving in the tropics can combine both extremes and includes condensation on the interior walls of the hull with consequent drippage; this can be detrimental to equipment as well as to human occupants.

FOOD/WATER

Normal and emergency food and water rations must be carried; limited power or the possibility of its entire loss restricts the type of food and preparation possible.

WASTE MANAGEMENT

Means must be provided to accommodate metabolic wastes and to treat and store such wastes for the duration of the dive.

FATIGUE

The internal arrangements for pilot and passenger(s) must be such that the efficiency of both is not decreased by uncomfortable or awkward layout of instruments and controls. Similarly, long periods at the viewports can be extremely taxing and detrimental to the mission if pilot or observer is forced into awkward positions to view or work

No one submersible is designed to perform all the underwater tasks that may arise, but there is a commonality of vehicle performance requirements which may be found by analyzing past dives; these requirements are listed below.

VIEWING

Some means for external viewing is required. Viewports (windows) provide the easiest and most reliable solution, but their location and quantity are arbitrary and frequently dictated by other characteristics of the hull configuration. Acrylic plastic pressure hulls are available which can provide panoramic viewing. Television cameras are an adjunct to direct viewing and, with low light level amplification, may provide greater range and resolution. Optical viewing systems, e.g., periscope-type, have also been employed.

BUOYANCY

Archimedes’ principle defines the magnitude of upward buoyant force: any object immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced. Three states of submersible buoyancy are desired: Positive, negative, and neutral. Displacement volume (D) determines the buoyant force, and buoyancy is expressed by the ratio W/D, i.e., weight of vehicle (W) to weight of displaced water. Buoyancy regulation under different vehicle load and water density conditions requires variable ballast systems which may include one or more of the following: Water ballast tanks, steel shot, gasoline filled tanks, or interconnected hard and soft containers.

TRIM

To correct unequal weight distribution along the longitudinal axis which might cause the vehicle to have an up and down angle from the horizontal, or to intentionally obtain such an up and down angle for the dive mission, a trim system is required. This system, through a variety of methods, acts to transfer weight or ballast forward or aft.

STABILITY

Stability is that property of a body that causes it, when disturbed from a conditional equilibrium, to develop forces that tend to restore it to its original condition. Equilibrium is a state of balance between opposing forces which may exists in three states: Stable, neutral, and unstable. For example, if when an angle is put on a ship forces are set up which act to reduce the angle, the ship is stable. Neutral equilibrium exists when a body remains in its displaced position after a force that displaced it is removed; unstable equilibrium exists when a body continues movement after a slight displacement. Stability in a submersible is intimately related to center of buoyancy and center of gravity. The center of buoyancy is the geometric center of volume of the displaced water. The center of gravity is the effective center of mass. These two centers are indicated as B and G, respectively, in Figure 2.3a. When a floating body is in a state of equilibrium, its center of buoyancy and center of gravity are in the same vertical line.

Fig. 2.3. Change of center of buoyancy metacenter during submergence.

Of a vertical line through the center of buoyancy of a body floating upright and a vertical line through the new center of buoyancy when it is inclined a small amount as indicated by the letter M in Figure 2.3b.

When a surfaced submersible is tipped as shown in Figure 2.3b, the center of buoyancy moves from B to B1 because the volume of displaced water at the left of G has been decreased while the volume of displaced water to the right is increased. The center of buoyancy, being at the center of gravity of the displaced water, moves to point B1 and a vertical line through this point passes G and intersects the original vertical at M. The distance GM is known as the metacentric height. This illustrates a fundamental law of stability. When M is above G, the metacentric height is positive and the vessel is stable because a moment arm, GZ, has been set up which tends to return the vessel to its original position. It is obvious that if M is located below G, the moment arm would tend to increase the inclination. In this case, the metacentric height is negative and the vessel is unstable.

When on the surface, a submarine presents much the same problem in stability as a surface ship. However, differences are apparent as may be seen in the diagrams in Figure 2.3c, where the three points B, G, and M, though in the same relative position, are much closer together than is the case with surface ships.

As noted above, when a ship on the surface heels over, there is a shift in the position of the buoyancy center because of the volume shape change below the waterline. In the case of a submerged submarine, no such change takes place because all the volume of the submarine is below the surface of the water. Thus, for submerged stability, the center of gravity must be below the center of buoyancy.

During the process of going from the surfaced condition to the submerged condition, the center of gravity of the submarine, G, remains fixed slightly below the centerline of the boat while B and M approach each other. At complete submergence, G is below B, and M and B are at common point. These changes are shown diagrammatically in Figure 2.3c.

As the ballast tanks fill, the displacement becomes less with the consequent rising of B and lowering of M. There is a point during submergence when B coincides with G. Due to the configuration of the upper part of the hull, B would only move a short distance from G if a list were taken at this point. In this condition, the stability is least; and the time spent at this low-righting stage must be minimal. When the ballast tanks are fully flooded, B rises to the normal center of buoyancy of the pressure hull, and stability is attained with G below B.

To keep the center of gravity low, batteries and other heavy items are carried as low as possible where they have the greatest effects on stability. Submersible transverse metacentric heights (submerged) are quite small and range from 3 to 12 inches.

POWER

Electric power is compatible with all propulsion, lighting, hotel, and virtually all instrument requirements and is the exclusive ultimate power source in all deep submersibles. Long duration power can be supplied from the surface through a cable, but at the expense of maneuverability; conversely, maneuverability is retained using self-contained batteries, with a corresponding limitation in operating time. Two power options predominate in shallow (less than 1,000-ft) submersibles: Manual power through the pressure hull

can be by direct mechanical linkage (limited to shallow depths owing to compression on the hull with consequent size reduction of thru-hull penetrations) or by hydraulics.

MANEUVERABILITY

The requirements for maneuverability vary considerably in speed and degree, but generally the vehicle is expected to be capable of controlled movement in the vertical and horizontal. For many if not all missions, the vehicle must be able to “hover” (dynamically or statically) at a given depth or distance above the bottom.

EXTERNAL ATTACHMENTS

Fro maximum mission adaptability, the vehicle should have external attachment points for installation of various instruments or devices to conduct undersea tasks. Since few, if any, of these instruments are standard in weight, size, shape, or mode of operation, a degree of flexibility in such attachment points is desirable. In the probable event that such devices will require electrical power and/or control, provisions must be made to spare electrical connectors and thru-hull penetrators..

LOCK-OUT/LOCK-IN

If the submersible is designed for transporting and supporting divers, provisions must be made for ballasting the vehicle when they leave (to restrain it from ascending) and deballasting when they return. Hatches and viewports in the diver’s compartment must be double-acting to resist not only external pressures, but internal pressures as well. Communications must be arranged between the diving compartment and the unpressurized part of the pressure hull; and, when surfaced, a means of providing food or medical aid must be incorporated in the design if decompression is required. Whereas the egress/ingress hatch will be on the keel of the submersible, and the vehicle might be bottomed during diver operations, space between the hatch and bottom must be sufficient to allow easy access to the hatch. Consideration must likewise be given to personnel transfer to a decompression chamber.

WEIGHT AND SIZE

The submersible’s dry-weight (in air) and physical dimensions will govern the methods of launch and retrieval as will as the size of its support ship and the methods available to it for land and air transport.

PAYLOAD

There are no minimum or maximum, payload standards, and they range from less than 100 pounds to several tons. The larger the payload requirements, the larger the vehicle size and, correspondingly, the greater the necessary support efforts become, with resultant lowered mobility. Trade-offs are possible whereby a non-essential manipulator, for example, might be replaced with another instrument or5a lock-out chamber replaced with a different module for a particular dive. Distribution of payload weight and balance must be considered to assure that vehicle trim and control are not jeopardized.

PRESSURE

A fundamental consideration in the design of any vehicle transporting man or equipment underwater is pressure. Pressure may be resisted, as it is by the submersible’s hull, or it may be compensated, as is the case with many battery packs, propulsion motors, etc. Once the submersible’s operating depth has been established, the pressure at that depth will determine the dimensional and compositional characteristics of the vehicle and its components.

Pressure in the ocean is a function of depth, and for routine oceanographic calculations the 33-foot depth is equal to about 1 atmosphere (14.7 psi). To moderate depths, say to several thousand feet, seawater may be considered incompressible and the following expression is used:

• p = pa + wh

where p is pressure in pounds per square inch (psi), pa is atmosphere pressure (psi), w is a 1.0-ft head of standard salt water equal to a pressure of 0.4447 psi and his depth in feet; then

• p = 14.7 + 0.444h psi

At greater depths, the compressibility of water must be considered and, to obtain a more accurate value, the density of seawater may be taken as varying linearly from 64 pcf at the surface to 66.6 pcf at 30,000 feet (Fig. 2.1). Neglecting atmosphere pressure, the pressure at depth h then is approximately

p = 0.444h + 0.3 (   h   )² psi (ref.1)
                                1,000

Hence, at 6,000 feet, the pressure on the surface of a body is 2,674.8 psi acting normal to every exposed surface.

SEAWATER CONDUCTIVITY

Various devices in submersibles, e.g., motors, batteries, pumps, are immersed in a protective liquid which serves as an ambient pressure compensator and an insulator against loss of power to seawater. The intrinsic dielectric conductivity of seawater is approximately 4 mhos/m (milliohms/meter) or 4,000 times greater than that of fresh water; and, it increases with temperature, salinity, frequency of the propagating wave and pressure (1). A common cause of failure in electrical systems is contamination of the compensating/insulating fluid by seawater, where as little as 0.1 percent contamination reduces the resistivity of some fluids below recommended limits (3). Various forms of corrosion (pit, crevice, stress, layer, etc.) Attack metals in seawater. Protective coatings and/or sacrificial anodes should be considered in the initial design stage.

TEMPERATURE

The temperature of seawater (Fig. 2.1) has, among others, two important effects on submersible diving: 1) The occupants must deal with extremes of temperature caused mainly by loss or gain of heat through the pressure hull; and 2) the pressure hull material must be capable of retaining its desirable characteristics (crack arrest) under cold temperatures encountered above and below the surface.

LIGHT

Sunlight has been observed to penetrate the ocean to depths as great as 2,300 feet (4), but usable sunlight for detailed external viewing generally terminates at 1,000 feet even under the very best conditions. Consequently, the submersible user must rely on artificial light sources for external illumination. Because of the lateral and vertical variability of light transmission properties and the frequent blinding effects of backscatter throughout the oceans, lighting for each diving mission is approached on a case-by-case basis.

Fig. 2.1 Seawater density, salinity, and temperature as function of ocean depth. {From Ref. (2)}

CURRENT

Currents in the ocean and contiguous waters range in horizontal speeds from less than 0.05 knot (Pacific deep water) to 15.5 knots (Skjerstadt Fjord, Norway), and they fluctuate rapidly both spatially and temporally (5). Where currents are strong, the submersibles must be able to maintain control and headway to conduct its task and maneuver safely.

DENSITY

Since seawater density varies not only with depth (Fig. 2.1), but with temperature and salinity as well, vehicle buoyancy calculations must be based on the specific diving location. In some instances, underwater discharge of fresh or brackish water near the bottom has caused significant loss of positive buoyancy on a submersible working close to the bottom (6).

ACOUSTICS

Light and radio waves attenuate rapidly in the ocean. Depending on the frequency of the signal and oceanographic conditions, sound waves may travel for thousands of miles. Sound, therefore, is used for communications between ship and submersible, for tracking of the submersible from the surface and for a variety of data collection instruments. The velocity of sound in seawater varies from 4,775 to 5,150 feet/second and increases with increasing temperature, salinity and pressure (5). If sound is traveling vertically downward, the effect of refraction (bending) is relatively slight; as the beam direction approaches the horizontal, refraction may become quite great. The usual situation (Fig. 2.2) is for sound speed to decrease initially with depth as the temperature decreases; hence, the upper part of the sound beam travels faster than the lower part and a shadow zone, into which the sound beam does not penetrate, is left near the surface. Such refraction may occur at any depth in the ocean; its effects can control the ranges from which a submersible can be tracked from its surface support and still maintain voice contact.

SEA STATE

The operational limits of submersibles’ launch/retrieval devices are determined by wave height (the vertical distance from wave trough to crest) and period (the time interval between successive crests passing a stationary point); the condition is generally termed Sea State, and its boundaries are presented in Table 2.1. Sea state, as defined in the accompanying table, is misleading as a measure of the ability of a launch/retrieval apparatus, for it does not take into account wave period. For example, launch/retrieval may be ruled out in low sea states if the period is on the order of 8 to 10 seconds, but, if the period is doubled or greater, the frequency of the wave crest’s passage is less and time may be sufficient to complete the hook-up of lift lines between successive crests. One must be aware that the sea surface is rarely calm and is in a constant state of change. If a submersible system is to

SPEED OF SOUND, (FT/SEC)

Fig. 2.2 Typical variation of speed of sound with depth in the ocean.

be economically practicable, the ability to deploy and recover the vehicle safely under average weather conditions is just as important as pressure hull integrity.

BOTTOM CONDITIONS

The ocean floor ranges in composition from soft, fine muds to hard rock cliffs; a submersible can be expected to operate within these ranges. During operations requiring a vehicle to transit near the bottom, search missions for example, the pilot generally prefers to “fly” just off the bottom, a few pounds negatively buoyant. This procedure makes vertical control of the submersible much easier. Over a rough, hard bottom, rugged skegs or other devices (wheels, skids,) are used to protect the pressure hull and other components. On a soft bottom the submersible may accumulate sediment, the weight of which can become great enough to restrain the vehicle from surfacing. ALUMINAUT, for example, accumulated approximately 4,000 pounds of sediment in this manner during an operation off the coast of Spain.

To accomplish its passenger-carrying and work functions economically, a submersible must be transportable, easily maintainable, and amenable to launch/retrieval from a rolling vessel. A review of submersibles in Chapter 4 reveals the varied approaches to these requirements. No matter what the approach, there are laws of physics and human biology which all successful vehicles must obey. There are also logistical and operational considerations which, because of their importance, are an integral part of the submersible diving system; these are its support platforms, and its launch/retrieval apparatus.

Five categories have been defined and include the design and operational factors with which the successful submersible operator must contend; these categories are:

1. Environmental Constraints
2. Vehicle Considerations
3. Human Considerations
4. Emergency Procedures
5. Support Requirements

The factors within these categories are drawn from the history of submersible operations and deal with the submersible system instead of the submersible as an independent operator. Inclusion of support requirements may seem outside the scope of submersible diving principles; but submersibles are not military submarines, and none routinely operates in the open sea without surface support and in the final analysis, shore support.

The most significant omission of submersible components in the the following chapters in the human component. The Deep Submersible Pilot Association and the Navy’s Submarine Development Group One have defined the minimal requirements for an operator or pilot. Chapter 12, herein, tabulates the number and types of operating and support personnel for selected vehicles. Unfortunately, all of these fall quite quite short in actually defining the nature and qualityies of the people who keep the system running efficiently and safely. Indeed, if one were to list the desirable attributes of a submersible crewman – and the crew includes support as well as operating personnel – the final product would seem unattainable.First, for the most part submersibles work far out at sea or in other isolated places where public admiration is not the rule. Secondly, photographers, press agents and media representatives are generally unaware of submersible activities until there is an emergency, and these are quite rare. Thirdly, working at sea in arduous, frustrating, continuous and, in the submersible business, calls for the skill of a seaman, an engineer, a diver and a master mariner. The point is that the personnel must be highly-skilled, dedicated individuals who are willing to spend a good portion of their life on a pitching, rolling, benevolent prison. The pay in not fantastic and residuals for television advertisements are unknown. One hundered percent successful missions are rare, and frustrating compromise is generally the rule.

So one might ask, where do you find such people and what do you offer? Quite frankly (and somewhat mysteriously), the find you and surmounting the challenge seems to be reward in itself. Commonality of background, such as education, technical training and the like, is not readily apparent. Most however, have spent a major portion of their adult life working with the sea, either in the Navy or with commercial enterprsies. Many, through various channels, simply drift into the submersible area, others specifically seek out the field. In either case, all have a capacity for hard work and seem to possess an unusually wide-ranging knowledge of seasmanship, diving, electronics and other skills related to submersibles. Admittedly it would be quite helpful to state the desirable background of characteristics to llok for in a submersible operator and the support crew, but, in the author’s experience, all are quite individualistic and, like submersibles themselves, defy categorization. Yet each seems to have a particular skill that contributes to a successful operation.

In this respect, an incident comes to mind of a lost current meter array retrieved by ALUMINAUT in 1967 off St. Croix, Virgin Islands. ALUMINAUT, at that time was the ultimate in deep submergence technology, it represented the best efforts of the best scientific and engineering expertise industry and academia could offer. In the course of retrieval it dived, made the necessary hookup and performed perfectly. The final step, however to reel the retrieving line onto the support ship. To complicate matters, when the array line began appearing at the surface it was a snarled and tangled mass of nylon rope, wire and current meters. At this point the knot-tying and load-handling talents of an ex-navy bosun, Mr. Doug Farrow, were required for several hours to successfully bring the spaghetti-like mess aboard.

The “manned” component, therefore, requires skills which range from those traceable to the Phoenicians to those developed in the scape age. Man’s ancestors, it is said, left the ocean in primordial times, since recorded history it is evident that he has tried, with some success, to return. In earluer days it was in wood and leather diving bells and suits; now it is in stell and plastic shells. Whatever the means, it has always been man; never machines, against the sea. The instruments, be they submersibles, submarines, towed devices or whatever, are inanimate, inert and functionless without the intervention of a human being. Regardless of its duration, if the return to the sea is to be successful, an arsenal of human talents must be drawn from pages of ancient and recent history. The know tier, the navigator, the mariner, the engineer and the theoretical scientist all share equal responsibilites and all can be found somewhere in the successful submersible system.

Conspicuous by its absence is any discussion of Soviet Bloc submersible design. The reason is quite simple: There is no easy way to authenticate what information is available. Mr. Lee Boylan of Informatics Inc., Rockville, Maryland summarized Soviet-bloc submersible development in a 1969 monograph for the Marine Technology Society Journal (v. 3, n .2) and updated this report in 1972 in the same Journal (v. 6, n. 5). Mr. Boylan’s original work was based on 206 acticles and reports from the Soviet Union and elsewhere. It is most comprehensive, but Boylan himself admits that his 45-year history does not comprise the entire Soiet Bloc. There are a few other articles which serve to reinforce Boylan’s tabulation, but the picture is still confusing.From those details that are available, Soviet submersible development and use have been primarily aimed at fisheries investigations. In 1957 the Soviets converted a fleet-type submarine into the fisheries research vehicle SEVERYANKA. Seven research cruise were conducted by this vehicle during the next few years. Then it appears to have been decommissioned in the early sixties.

At present, Russian, according to Boyland, has or has had four submersibles which followed SEVERYANKA; these are: The 6,562-ft SEVER 2, the 810-ft GVIDON, the 984-ft TINRO, and the DOREA for which no operating depth is state. International Hydrodynamaics of Canada is constructing a PISCES-class submersible (6,500-ft depth) and the lock-out vehicle ARIES (1,200-ft depth) for the Soviet Union for delivery sometime in 1974.

Admiittedly, this is making very short shrift of Soviet Bloc undersea efforts. Although they seem quite active in habitats and swimmer delivery (wet) vehicles, there is little information available on the actual submersible field. A report by V.S. Yastrebov, Head of the Laboratory of Underwater Research Technique, Academy of Sciences, USSR, tends to confirm that there is really very lettle to report is Soviet submersible activities. Yastrebov’s report (presented at the Brighton Oceanology International Conferences, 1972) compares the efficiency of divers and underwater devices. He speaks of an unmanned Soviet bottom crawler, CRAB, and of manipulator experiments at the Academy of Sciences, but every example of submersible performance he cites is of a U.S. vehicle. Furthermore, of 14 references in Yastrebov’s report, 11 are from U.S. sources. In another paper given at the Brighton Conferences, V.G. Azhazha of the Central Research Institute of Fisheries Information and Economics analyzed the efficiency of submersibles in fishery investigations. Here again, except for a brief mention of SEVERYANKA, all of the submersibles mentioned are U.S., English or Canadian. One is left to conclude, therefore, that Soviet-bloc at-sea submersible experience is quite limited, of a confidential nature, or both.

Throughout the text reference is made to a variety of books, articles and reports dealing with specific design aspects or operations of submersibles. For the reader who might be interested in only one vehicle or particular components of submersibles, the following books or reports, though referenced later, are noted:

GENERAL LISTINGS AND DESCRIPTIONS OF MANNED SUBMERSIBLES

• Terry, R.D. 1966 The Deep Submersible. Western Periodicals Co., North Hollywood, Caiif., 456 pp.
• Shenton, E.H. 1972 Diving for Science. W.W. Norton & Co., New York (describes the major components of submersibles in non-technical terms)

SPECIFIC SUBMERSIBLE DIVING HISTORY AND DESIGN

Beebe, W. 1934 Half Mile Down. Harcourt, Brace & Co., New York (contruction and diving history of the bathysphere)

• Piccard, A. 1954 In Balloon and Bathyscaphe. Cassell & Co. Ltd., London (FNRS-2 and TRIESTE 1)
• Houot, G.S. and Willhm, P.H. 1955 2,000 Fathoms Down. E.P. Dutton & Co., New York (FNRS-3)
• Cousteau, J.Y. 1956 The Living Sea. Harper & Row, New York (early history of SP-350)
• Piccard, J. and Dietz, R.S. 1960 Seven Miles Down. G.P. Putname’s Sons, New York (TRI-ESTE 1 and the events leading to its record dive)
• Shenton, E.H. 1968 Exploring the Ocean Depths. W.W. Norton & Co., New York (Scientific diving of SP-350)
• Piccard, J. 1971 The Sun Beneath the Sea. Charles Scribners’s Sons, New York (AUGUSTE PICCARD, BEN FRANKLIN, and the Gulf Stream Drift Mission)
• Link, M.C. 1973 Windows in the Sea. Smithsonian Instriution Press DEEP DIVER, JOHNSON-SEA-LINK, and other undersea activities of Mr. Edwin Link

The Woods Hole Oceanogrwaphic Institution beginning in 1960 issued yearly reports on the design, construction, operations and modifications to ALVIN. The first 2 years deal with ALUMINANT, which at that time was a cooperative venture between the Navy and Reynolds International, but from 1963 on through 1970 they deal only with ALVIN. These reports are entitled Deep Submergence Research and each covers a calendar year during the above period. Unfortunately they are not widely disseminated, but are available atat WHOI and may be found in university libraries where oceanographic courses are offered.. Careful reading of these is literally a course in deep submergence components and the painful progress of making a manned submersible a useful scientific tool. One of the deficiencies with most reports describing modifications to submersibles is that the author tells what has been changed but not why it was changed or what was the problem. The WHOI reports, on the other hand, provide all such details, and they explain each change in detail: Why each was made, what the component or system was lacking and how the new approach is intended to improve the vehicle, its support platform and its launch/retrieval system. They constitute, in substance, a technological stroll through deep submergence problems and developments of the sixties.

Another series of reports, also not readily available, are the handbooks issued by the U.S. Navy’s Deep Ocean Technology (DOT) Program. Recognizing the severe problems in various electrical and mechanical components in manned deep submersibles, the Navy began this program in the late sixties, and the results are profitable reading for both present and future submersibles operators and designers. The various components investigated can be seen in the list below. Each handbook summarizes the problems with available components, solutions to some problems and recommendations for surmounting others. The reports are limited in distribtuion to those who have a legitimate need for such data, and requests should be address to:

• Defense Documentation Center
  Cameron Station
  Alexandra, VA, 22314

As of 1974 the following handbooks have been issued which pertain manned submersibles.

• Handbook of Electric Cable Technology for Deep Ocean Application. NSRDL (A), 6-54/70, Nov. 1970. AD 877-774
• Rotary Shaft-Seal Selection Handbook for Pressure Equalized, Deep Ocean Equipment. NSRDC(A), 7-753, Oct. 1971. AD 889-330(L.)
• Handbook of Vehicle Electric Penetrators, Connectors and Harnesses for Deep Ocean Applications. NAVSEC, July 1971. AD 888-281.
• Handbook of Fluids and Lubricants for Deep Ocean Applications. NSRDC(A) MAT-LAB 360, Rev. 1972. AD AD 893-990.
• Handbook of Fluid Filled, Depth/Pressure Compensating Systems for Deep Ocean Applications. NSRDV(A) 27-8, April 1972. AD 894-795.
• Handbook of Electrical and Electronic Circuit-Interrupting and Protective Devices for Deep Ocean Applications. NSRDC(A), 6-67, Nov. 1971. AD 889-829.
• Handbook of Underwater Imaging System Design. NUC TP 303, July 1972 AD 904-472(L).

SUBMERSIBLE WORK AND INSTRUMENTSÂ

Excluding the DOT handbooks, all of the publications listed above contain accounts of various work performed by the particular submersibles. Additionally, the references in Chapter 11 relate specific work accomplishments by a variety of submersibles. Noteworthy, is reference (1) of Chapter 11, which summarized all of the published scientific accounts of submersible work through 1970. A popularized version of submersibles and their accomplishments is contained in:

• Soule, G. 1968 Undersea Frontiers.Rand McNally & Company, New York

The references in Chapter 11 also describe, to varying degrees, the instruments used to perform certain tasks. The best single reference for work tools is Winget’s report (ref. 6 Chap. 11) which not only describes a wide array of work tools, but also provides the manufacturer’s name and address for each component used in each device described. This report can only be described as a goldmine for the builder or designer of submersible work equipment.

Since the seventies most of the literature describing submersible work is relatively sparse. Perhaps because the work is no longer mainly scientific and may be considered proprietary information by the user. Virtually all recent accounts merely describe the job as pipeline inspection, cable burial, or the like, with details of the why, how and performance of the vehicle and tools omitted. Likewise, are accounts of submersible scientific endeavors sparse regarding performance of vehicles and instruments. Reports of the National Oceanic and Atmospheric Administration’s Manned Undersea Science and Technology Program relate what work was done, why and, when possible, its scientific implications, but nothing regarding the performance, problems or solution is including. Such omissions, though clearly a prerogative of the user, are unfortunately, because identifying and making known the problem areas of submersibles is the only means of providing direction or goals to the designer of future vehicles.