Assault on the Wet Continent

Abstract

Earth's continental shelves, defined as that land sloping down beneath the ocean to a depth of 600 feet, amount to a continent in themselves. Together they cover some 11.5 million square miles-equal to the area of Africa. Exploring and exploiting them is a major oceanographic goal, held up by the limitations imposed by extreme depths. In October, at least 40 men will join in what will be the first true attempt to live and work at the deepest limit of the continental shelf. Their home will be Sealab III, an elaborate dwelling anchored in 620 feet of water near San Clemente Island off the California coast. There five consecutive eight-man teams of aquanauts will live for 12 days each, opening wider the gateway to man's exploration and use of the wet continent. The technique that makes this possible, the key to the assault on the deeps, is called saturation diving. The U.S. Navy's depth limit for hard-hat divers spending half an hour on the bottom is 380 feet; at that depth, decompression from a 30-minute dive takes more than three hours, or six times the available working time. By the time a diver has been at a given depth for about 24 hours, however, all the tissues in his body become saturated with the compressed gases in his breathing supply. can stay at that depth as long as he wants without increasing his decompression time. It thus becomes much more economical for divers to refrain from commuting to the surface. The first diver to reach saturation at significant depth in open water was Robert Stenuit, a young Belgian who spent 24 hours at a depth of 200 feet in a submersible decompression chamber designed by Edwin A. Link, inventor of the Link flight trainer. In June, 1964, Stenuit and another diver made what is still the deepest saturation dive, when they spent 49 hours in a new Link-designed capsule, 432 feet down in the Atlantic, off the Bahama Islands. One of the leading pioneers in the field, however, Navy Capt. George F. Bond of the Naval Medical Research Lab. at New London, Conn., began working in 1957 with animals in depth-simulating compression chambers. Besides investigating helium instead of intoxicating nitrogen as the inert component in the breathing mixture, he envisioned development of both mobile and fixed underwater habitations from which scientists, engineers and military personnel could be routinely deployed. At first, the use of human subjects in saturation diving was turned down. Soon afterward, however, the Navy's fledgling interest in manned space flight created some interest in research into helium-oxygen atmospheres, and the idea began to grow. In simulation chambers, three Navy divers first spent three days at 200 feet, then 300, and finally 400 feet. Finally, in July 1964, Capt. Bond got his first sealab. About the only way Sealab I could have been more of a personal triumph would have been if Bond had paid for it himself. He practically got it going by the skin of his teeth, says another Navy diving doctor. By comparison to its successors, Sealab I was a simple affair, made of two old mine floats, sectioned and welded together into a 40-foot cigar, 10 feet in diameter. Four aquanauts lived there for 11 days, placing ultrasonic beacons on the sea floor (the site was also a Navy sonar test area), installing current meters, rigging spot-