National Geographic : 1964 Jun
Sonic boomer lets scientists "see" through the bottom. Every ten seconds two circular metal plates spring violently apart, forming a vacuum that creates a "smoke ring" of bubbles. At the same time a sound pulse is sent out. It penetrates water, then sediments, rebounds off underlying rock, and returns to shipboard, giving a continuous profile of both bottom and sub-bottom. Through the viewing port, Dr. Harold his invention under test in a tank in Boston. the backs of our minds, we turned first to the military, as is proper for a Navy group. Early in our work, after briefings from officers directing the Thresher search, we became aware of how badly the development of the seas had been neglected. Deep diving, salvage, and rescue techniques had scarcely changed in 25 years. Nuclear subs were rou tinely using depths far beyond our abilities in search and rescue. New Methods Will Find Subs If Thresher had sunk in less water than would crush her, her crewmen could have lived on inside the hull for months-in a world unable to save them from a prolonged and hopeless end. But even before rescue could be considered, there was the immense problem of locating the lost sub, as told in the two preceding arti cles. If Thresher had been equipped with a "sonar transponder" which would answer a search craft's sonar with a sound pulse of its own, it would have been simpler to locate her. A distress buoy that would rise to the surface and send an SOS would have brought help in a hurry. Our group recommends that in the future all submarines carry both. 786 E. Edgerton watches We deliberated long about the relative merits of towing search instruments from sur face ships (which had proved so frustrating in the Thresher search) or sending down an untethered vehicle, manned or unmanned, which could be accurately maneuvered at the bottom. It would need much greater range than any existing bathyscaph. Although some group members still incline to towed instru ments, the majority decided on the manned vehicle. No adequate model of one exists at the moment, although there are some ap proaches to it under construction. Finding a hull is one thing, rescuing men from it quite another. The best device we have now is an eight-man diving bell called the McCann cylinder, which winches itself down from the surface on a cable to the dis abled sub. It must be sealed to the sub's es cape hatch-a feat that often requires diver assistance. Since about 500 feet is the emer gency limit for Navy divers, this depth is the limit for the McCann when divers are used. So for rescue as well as search, we decided a deep-diving submersible is needed. We plan a small, multipurpose vehicle that can work to 6,000 feet-and we hope to see it in the water within two years.