National Geographic : 1959 Jan
Opening a Submerged Northwest Passage for the Atomic Cargo Fleets of the Future darkened attack center. We keep the center lighted only by red lights between sunset and sunrise, so that our eyes are always adapted for night vision should we have to come up during darkness and use the periscope. Down the ladder in control, the diving of ficer reported to me that depth and course held well, the compasses checked with each other, and the sounding showed 300 feet. I relieved the watch and made another careful check of positions plotted on the chart. While doing so, I reflected on the naviga tional complications we would face when we were under the ice pack. Beneath that mas sive canopy we could not confirm our position by observational fixes or by radar. Success or failure would hinge upon how well we used five sensitive navigational aids. Nautilus carried two magnetic compasses. Errors would creep into their readings, of course, for this type of compass is not wholly reliable so near the North Magnetic Pole. It tends to wander and finally, at the Magnetic Pole itself, to spin erratically. We also had on board two fine gyrocom passes, one of them the master. You can point a gyrocompass at north and it will cling there, provided you compensate periodically for changes in the speed of the earth's rota tion. This speed lessens as you journey north. Our ace in the hole, however, was an amaz ing instrument called an inertial navigator, an aid we had lacked in 1957. Its stable plat form points always at earth's center. Two instruments on the platform sense changes in acceleration, and hence changes in direction and speed, somewhat as a blindfolded person in a car can interpret movement by sensing how his body reacts against the seat as the car speeds up, brakes, or turns. A computer records the machine's signals and disgorges information for us. In effect, this brainy navigator shows where it is by remembering where it has been.