National Geographic : 1961 Nov
"The bottom of the San Diego Trough lies 3,100 feet under us. If we can drill here-if a few things work-we'll try next in 12,000 foot depths, south of San Diego between the Mexican coast and Guadalupe Island." Bascom's "few things" included holding the ungainly CUSS I* within a few hundred feet of a precise position, hour after hour and day after day. Anchor cables could not do this at such great depths. From a free-floating platform drillers had to lower thousands of feet of flexible drill pipe and, without snap ping it, drive it through the ancient ooze of the sea bottom into unknown layers of rock. "Our drill string is no more rigid," Bascom continued, "than a wire one-sixteenth of an inch thick lowered from a twelfth-story office window to the sidewalk. With it we have to bore into rock harder than concrete." Invisible Signals Guide CUSS I Exploring that incredible ship, I soon dis covered how Mohole engineers had solved their first problem. CUSS I stayed on station by an unlikely combination of radar, sonar, and outboard motors. In the pilothouse, a lone man was maneu vering the ship with a small joy stick and control wheel. Sonar echo-ranging signals from beneath the keel bounced off tautly anchored underwater buoys that ringed the ship; the returning "pings" indicated ship to-buoy distances. Meanwhile, radar pulses tirelessly scanned special reflectors bobbing on surface buoys, giving still another check on position. The joy stick and wheel controlled four huge diesel outboard motors mounted on CUSS I's flanks. A touch jockeyed the ship to compensate for a shift of position shown by reflection from the buoys (photograph and diagram at right). Another innovation, a 38-foot guide shoe, jutted into the sea beneath the derrick (upper diagram). Flaring like a trumpet pointed to the deep, this collar encased the drill pipe at a crucial point, cushioning it against any sharp bend-and possible break- should the ship roll severely or drift off position. At the other end a flexible casing cushioned bend ing where the pipe entered the sea floor. But, you may ask, why drill the Mohole at sea at all? Haven't oil wells already gone miles deep on solid land? *CUSS I is named for Continental, Union, Shell, and Superior oil companies, which converted an ex-Navy freight barge to an offshore. drill rig. Global Marine Ex ploration Company of Los Angeles now operates the ship. 690 HS EKTACHROME) N.G .S.