Ahoy?

South of the Rat Islands, beneath the grey-green greasy Pacific swells off Alaska and close to the international date line that keeps Thursday from being Friday, an American submersible is missing. Shrouded in a fog bank, the S.S. Robert Louis Stevenson started on her first--and presumably last--underwater cruise on Aug. 10. Ever since, the U.S. Navy and Coast Guard have kept five search vessels and a gaggle of aircraft looking for the R.L.S. -- to the intense interest of Russian trawlers in the area.

It is not that the Navy wants the R.L.S. back. It was trying its best to sink her when she escaped. A superannuated World War II Liberty ship taken from the mothball fleet, she had been ballasted with concrete and topped off with a cargo of 2,000 tons of overage torpedo warheads, mines and other obsolete ammunition, becoming in effect a floating bomb. Then she was fitted with six Sofar charges with hydrostatic fuses set to shiver her bulkheads automatically under the pressure of 4,000 ft. of water. One purpose of the planned undersea blast was to help the Pentagon's Advanced Research Projects Agency sharpen scientific techniques for detection of bootleg underground atomic tests. It was also a convenient way to dispose of munitions that become unpredictable with age.

But Sofar proved not so good. When a demolition crew opened her sea cocks, the unmanned R.L.S. drifted out of sight before a brisk sou'easter and lingered for 16 hours instead of disappearing from radar screens in four hours, according to schedule. Where she finally came to rest, nobody is quite sure, and the waterlogged hulk of the R.L.S. is almost "transparent" to sonar blips used to locate submarines. But it seems likely that she lies in about 3,500 ft. of water--not deep enough to activate the fuses. Because the added pressure of a vessel passing overhead might detonate her, all shipping was ordered to keep clear. But early attempts to explode the lost ammo ship with bombs dropped by Navy Invader jets were in vain. The special fuses fitted to three 1,000-lb. bombs did not go off.

Late last week a magnetometer towed by the U.S.N.S. Silas Bent, a 285-ft.-long floating oceanographic laboratory, transmitted a suspect blip. But more than a score of wrecks litter the ocean floor off the Rat Islands; until a special camera synchronized to a high-powered strobe light can be lowered over the spot, the sea is guarding its secret.

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