Fathom’s Insight

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.