164
The Last Resource
involved in such experimental dives go beyond the kind of supply
which can be sensibly carried on the back. Add to this the com—
plexity of maintaining safe ratios of oxygen to helium (which
change with depth) and one begins to appreciate that the deep diver
needs some form of technical support. The Royal Navy technique
is to descend as rapidly as possible in a submersible diving chamber
which also carries the necessary gas supplies. For safety’s sake each
diver also carries an emergency supply of breathing mixture, but if
all goes well his supply comes via an ‘umbilical’ from the gas
cylinders on board the chamber even while he is working out in the
sea. To return to the surface, the diver re—enters the chamber which
now becomes a submersible decompression chamber (SDC). Once
at the surface the SDC still under pressure is locked on to a deck
decompression chamber (DDC), which is much larger and more
comfortable. The divers transfer to the DDC to complete their
lengthy decompression. This transfer involves little effort; in earlier
systems the divers had to open and close doors and operate pressure
looks, but the whole system was automated when navy doctors
found that this activity during decompression could cause gas
bubbles to form in the tissues and hence bring on decompression
sickness.
The Cachalot system of the Westinghouse Underseas Division
works on very similar principles (sec gure 21). First used in 196 5
for work in fresh water at Smith Mountain Dam in Virginia, it
_
enables divers to work at depths of up to 600 feet or more. In a
typical assignment, four divers enter the DDC to begin a week’s
work under pressure. They work alternate two—man shifts and are
carried to and from their underwater location in the SDC, which
serves as both an underwater elevator and a haven. An umbilical
line from the chamber supplies the divers with breathing mixture,
warm
water to
heat specially—designed diving suits, and com—
munications. Generally they work from two to six hours before
clambering back into the SDC, which is usually kept less than
50 feet from the work area, for the return journey to the surface
chamber.
When divers are kept under pressure for longer than twenty—four
hours as in the Westinghouse system, their blood and body tissues
become saturated with inert gas. But this is no problem; the time
taken to decompress is based on the degree of saturation of the
tissues and once they are completely saturated there is no further
The Last Resource
involved in such experimental dives go beyond the kind of supply
which can be sensibly carried on the back. Add to this the com—
plexity of maintaining safe ratios of oxygen to helium (which
change with depth) and one begins to appreciate that the deep diver
needs some form of technical support. The Royal Navy technique
is to descend as rapidly as possible in a submersible diving chamber
which also carries the necessary gas supplies. For safety’s sake each
diver also carries an emergency supply of breathing mixture, but if
all goes well his supply comes via an ‘umbilical’ from the gas
cylinders on board the chamber even while he is working out in the
sea. To return to the surface, the diver re—enters the chamber which
now becomes a submersible decompression chamber (SDC). Once
at the surface the SDC still under pressure is locked on to a deck
decompression chamber (DDC), which is much larger and more
comfortable. The divers transfer to the DDC to complete their
lengthy decompression. This transfer involves little effort; in earlier
systems the divers had to open and close doors and operate pressure
looks, but the whole system was automated when navy doctors
found that this activity during decompression could cause gas
bubbles to form in the tissues and hence bring on decompression
sickness.
The Cachalot system of the Westinghouse Underseas Division
works on very similar principles (sec gure 21). First used in 196 5
for work in fresh water at Smith Mountain Dam in Virginia, it
_
enables divers to work at depths of up to 600 feet or more. In a
typical assignment, four divers enter the DDC to begin a week’s
work under pressure. They work alternate two—man shifts and are
carried to and from their underwater location in the SDC, which
serves as both an underwater elevator and a haven. An umbilical
line from the chamber supplies the divers with breathing mixture,
warm
water to
heat specially—designed diving suits, and com—
munications. Generally they work from two to six hours before
clambering back into the SDC, which is usually kept less than
50 feet from the work area, for the return journey to the surface
chamber.
When divers are kept under pressure for longer than twenty—four
hours as in the Westinghouse system, their blood and body tissues
become saturated with inert gas. But this is no problem; the time
taken to decompress is based on the degree of saturation of the
tissues and once they are completely saturated there is no further