The Nation: How the Underwater Mines Work

MOST people envision underwater mines as the sort of studded black balls that Gary Grant dodged in Destination Tokyo. But the delayed-action mines used to seal off North Vietnamese ports last week are considerably more complex. Sown by low-flying Navy planes, some of them were dropped to the surface by parachute; others, equipped with tail fins, plunged straight to the water. Then they were programmed to settle at various depths in patterns designed to frustrate enemy minesweepers. Some were probably sent to the bottom while others were moored by cables. The mines used last week were not the most sophisticated the...

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