new water heated garment consists of a modified 
neoprene wet suit supplied with hot water by a 
hose from the surface or from a diving chamber. 
The hot water enters a simple hose distribution 
system from a control block at the waist and flows 
to the hands and feet. From the extremities, water 
flows back over the diver’s skin and exits from the 
suit to the ocean at the face and neck openings. 
Another diver undergarment contains tubes 
stitched to the fabric, an adaptation from a 
cooling garment used in outer space. Water enters 
at the waist, is piped back again to the waist, and 
returns thence to the heating unit. The tubes 
extend to hands, feet, and fingers. 
The bulk of a suit relying only on the insulating 
value of its material limits diver mobility and 
dexterity. In water below 45°F., insulation will 
not protect fingers inside a glove. When manual 
dexterity is required, mission duration is limited to 
about one hour. However, a diver can be sustained 
indefinitely in near-freezing water by hot water or 
electrical energy readily supplied. Present technol- 
ogy would require about 500 pounds of silver-zinc 
batteries for the energy necessary for a six-hour 
mission. For this reason, such advanced concepts 
as isotope heat sources are being investigated. 
b. Future Needs The most critical problem with 
exposure suits is development of a light, compact, 
selfcontained energy pack for a free swimming 
diver. The most promising systems rely on silver- 
zinc batteries to supply electrical energy, a pyro- 
technic cartridge to supply heat, or an isotopic 
power source to supply both. Suits produced for 
the astronauts may be adaptable for underwater 
use. Because of the high cost of development, the 
initial versions are likely to be tailored for military 
needs. 
Diving with a selfcontained underwater breath- 
ing apparatus is restricted by the compressibility, 
solubility, and narcotic effects of gases. Increased 
volumes of gases can be made available by cryo- 
genic technology. Another solution would be to 
use breathing mixtures that are not compressible. 
Liquids such as physiologic saline solution are 
likely to behave as biologically inert respiratory 
gas dilutants at great depths, in contrast to 
compressed inert gases. 
No excessive amounts of inert gas can dissolve 
in the blood and tissues of a diver with liquid filled 
lungs regardless of depth. Hence, the diver could 
VI-60 
return to the surface regardless of the time spent 
underwater and as rapidly as desired. 
Medical technology has produced artificial kid- 
neys and artificial lungs. It may be possible that 
suitable extracorporeal gas exchangers modeled 
after the gills of fish could be constructed. An 
artificial gill, enabling a diver to obtain oxygen by 
diffusion from the sea rather than from stores 
carried in cylinders, would have obvious logistic 
advantages. Even more important, a diver equip- 
ped with an artificial gill, extracting oxygen like a 
fish from the water, could never be exposed to 
toxic oxygen partial pressures (Figure 21). 
aa) 
i oe i 
Rae 
om 
Figure 21. Artist's concept of future diver 
wearing gill-pack. 
The possibility of man exchanging respiratory 
gases directly with an aquatic environment have 
not been explored seriously until the present 
decade, and it is difficult to predict the outcome 
of such research. 
Underwater breathing systems during the next 
few decades will be dictated by the need for 
breathing support related to man existing under 
high pressure. More people will spend appreciable 
time in wet environments operating untethered 
from a habitat or diving system. Therefore, they 
will need compact, reliable systems and the ability 
to eliminate or reduce manyfold the present 
decompression time penalties. The technique of 
liquid breathing, anticipated as a revolutionary 
