Fig 1.2 Shipwreck Central’s Underwater Video Archive (Click to view)

Eco-Nova Productions dive teams have been traveling the planet searching for and filming shipwreck sites for over a decade. Such documentaries for shipwreck investigations that you might otherwise not see are exclusively seen on National Geographic, and History Televison.

Working with world renowned author, Clive Cussler, marine archaeologist and author, James Delgado, the Sea Hunters dive team, headed up by Mike and Warren Fletcher, take viewers on searches for some of the worlds most famous shipwrecks.

Shipwreck Central’s Web Interactive archive allows you travel to the ocean’s depths as the Sea Hunters build their shipwreck record.

Water resorts are nothing new. Cruise ships carry thousands of people to exotic destinations aboard their luxurious decks. Countless hotels and resorts have been built on the shores of some of the most beautiful beaches in the world. But now travelers can take it a step further, or more accurately a step deeper. Poseidon Undersea Resort will allow guests to enjoy incredible accommodations between 35 and 60 feet under the water’s surface.

Such an ambitious undertaking has been years in the making and now construction is set to begin mid-year off the shores of a 235-acre private island in Fiji. “It’s never been done before, which is sort of amazing,” says Poseidon Undersea Resorts president L. Bruce Jones. “There hasn’t been a single one-atmosphere undersea resort built.” He and the design, construction and installation branch Poseidon Engineering are eager to change that. The revolutionary resort will consist of two parts: one is underwater and the other is along the shoreline. The twenty underwater suites will be opulent and incredible, using only the finest fixtures, wood, and fabrics. Guests can enjoy rooms ranging from 550 to 1,600 square feet, in which they can lounge and watch fish swim by the transparent acrylic walls and even feed them using an external fish feeder installed outside each suite. The panoramic views are breathtaking, but privacy is protected using a reflective film to prevent others from seeing into the suite through the day, and at night guests can choose to opaque sections of the viewports to increase privacy.

For those guests looking for an even more spectacular stay, the Poseidon’s Lair will make for an unforgettable vacation. This private suite brings luxury and extravagance to a new level, with this two-bedroom underwater bungalow accessed only by a submersible. This $20,000 feature includes a private submarine captain and butler. The rest of the resort consists of a library-conference room as well as a revolving restaurant and bar that will boast five-star cuisine and unbeatable ambience.

While underwater living is fascinating and exciting, guests are not restricted in the least. They can take the elevator to a pier and walk to shore to enjoy the amenities available on land. Underwater rooms are likely to run about $1800 per night, but guests can pepper their stay with fantastic on-shore accommodations to make their vacation more affordable. The shore resort, which is currently 80 percent complete, features twenty individual bungalows with private splash pools, ponds in the entrance area, outdoor showers, and Jacuzzi tubs. “It’s five-star-plus accommodations,” says Jones. In addition, guests can make use of the posh restaurant and bar, health club, and high-end spa facilities along with the executive nine-hole golf course. Resort guests onshore can also access the restaurant and other underwater facilities.

The resort is incredible but the natural splendour of the area is appealing as well. “The island is surrounded by a magnificent lagoon, which is about 7.8 square miles,” says Jones. Guests can enjoy the underwater life via deep submersible tours to nearby coral reefs and walls as well as SCUBA explorations around the resort. To ensure this will always be the case, the developers have taken pains to guarantee the resort doesn’t have a negative affect on the coral reefs and marine life in the area.

Fig 1.1 Poseidon Undersea Resorts (Click to view)

Originally trained in these system in the Royal Navy, United Kingdom I was equally amazed at how rapidly my peers to visualize the environment around them… while seemingly “best guess” such guesses were almost alway accurate. Since I firmly believe, “We are what we repeatedly do. Excellence, therefore, is not an act, but a habit”, I put to habit that which my peers possessed.

On returning to Canada, I had the privilege of working with an experimental towed array system called Experiemental Submarine Integrated Sonar System (ESISS) that was to be be trialed first on the Acoustic Research Ship CFAV (Canadian Forces Auxiliary Vessel) Quest, and then HMCS/m Onondaga. While only an experimental system it was (in my honest opinion) a truly revolutionary approach to passive acoustics.

Fig 1.1 Towed Array Passive Acoustics – Towed Integrated Active-Passive Sonar

Today, TIAPS is the “new thing”.

Under the ocean’s waves there is 5 times the biodiversity as above it… and with three quarters of the earth covered by water — there is little mystery why we are all fascinated by the subsea world.

Whether naturally forming by maritime disasters or intentional sinking mankind assists in the creating artificial reefs that attract prey and predator making life out of death… in the depths of darkness comes flashes of brilliance ans wonder.

From the dry security of a subsea vessel — vivid imagination!Â

Fig 1.1 Submarine tours throughout the world.

As both Humpback and Right Whales routinely populate Nova Scotian waters – I became accustom to hearing their songs whether close in or from hundreds of miles away.

While I don’t get much of a chance anymore to listen to any marine life in real life – WhaleSounds.com has numerous short recordings and a few 5-10 minute songs.

Fig 1.1 Whale Sounds (Click to listen).
Image Copyright © Andrew Woodburn

Fig 1.1 Map of shipwrecks surrounding Sable Island (Click to view).

For many sailors, this sandy island hidden by waves, storms and fog meant death and destruction. Since 1583 there have been over 400 recorded shipwrecks on Sable Island. While the number of shipwrecks has decreased with the development of modern navigational aids, but the island and it’s shoals continues to provide a hazard to shipping. The last vessel wrecked on the island was on July 27, 1999, the small yacht Merrimac.

Until recently, sextants were the instruments used to figure out a ship’s position. Sextants are accurate, but they worked by taking a sighting from the sun or stars. They were useless in dense fog or under cloudy skies.

In bad weather, the Captain navigated by “dead reckoning”- using ship speed and direction to estimate his position. But even in good conditions this was educated guessing. Currents and storms confused the calculations of the best skippers.

Many accounts of ships wrecked on Sable report that the Captain simply lost his way – he had misjudged his ship’s position and bumped into Sable Island by mistake.

After World War II radar and other advanced navigation equipment became widely used on merchant and fishing ships. Sable ceased to be a major threat to shipping.

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).

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.

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.

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