Science: Underwater Radar

All Seattle Engineer Wayne M. Ross planned to do was build a simplified sonar* device for finding sunken outboard motors, lost fishing gear and other salvage. When he thought he had solved the problem, he mounted his invention on a fishing boat and tested it off the coast of Alaska. It worked so well that he could not only spot schools of fish, he could usually tell what kind they were (by the size of the school and the depth at which it swam). Even more important, in narrow, rock-lined Alaskan channels his underwater signals bounced back from shoals and shore line, allowed him to navigate in dense fog when even craft equipped with radar (which cannot operate under water) stayed at the dock.

test Run. Last week, in a run through the Lake Washington ship canal and across placid Lake Union, Inventor Ross put on a demonstration of his “underwater radar” that left Navy sonar experts stuttering with excitement. On his cathode-ray screen the observers could easily locate a submerged steel drum 1,200 ft. away, a garbage can at 900 ft., sand bars, dock pilings, fish nets and ropes.

It was a performance that the Navy could not come near matching with its present equipment. The target data was presented on an easy-to-read radar-like screen, and the new sonar rig also operated best just where the Navy’s bulky, complicated equipment is weakest—the tricky, close-range job of picking up mines and submarine nets, or charting underwater obstructions.

Returning Echoes. The heart of Ross’s compact (150 Ib.) machine is a crystal of Rochelle salt† that converts electrical energy into pulses of “ultrasonic sound” (unlike radar, which uses radio frequencies). Focused into a narrow beam, the sound pulses are shot out through an underwater transmitter that can turn through 360°. Echoes from underwater objects come back to the transmitter and are displayed on one cathode-ray screen as part of a glowing map that measures distance and direction from the ship. Moving targets can be tracked across the scope as on an ordinary radar screen. Another cathode-ray tube, which measures distance, also helps to identify the nature and exact position of the target.

Ross’s device also records its information in two other ways. The returning echoes are translated into audible sounds which a trained operator, listening to the loudspeaker, can easily identify. Solid objects, for example, like the Lake Washington canal wall, give a hard, clipped ping. Signals from a smooth beach or hidden sand bar are drawn out, sound for all the world like someone scratching granite with his fingernails. And as if all this were not enough, an automatic pen-and-ink recording is made of all the signals that shine in the scopes and sing their peculiar modulations from the loudspeaker.

“You Have No Idea.” Inventor Ross, 31, who got his technical training as a radar expert after volunteering for the British Army in World War II, made most of his new device himself from spare parts and equipment he dug up at Seattle’s Intervox Corp. (electronic products), where he is chief engineer. Last week he seemed a little surprised at all the excitement he had caused in the Navy.

“My God, man,” said a startled sonar expert, “you have no idea what can be done with this finder.” “Oh, I don’t know,” replied Ross, who is already planning a longer-range set. “I’ll probably be playing around with it when I’ve got a long white beard.”

* A system of undersea detection. High frequency sound waves, near the upper edge of the audible range, bounce off targets and return to the transmitter. Target distance is measured by timing the echo.

† A crystal which can be ground to control ultrasonic signals at a desired frequency.