The Hunt for Red October - Tom Clancy [36]
At first it had not been all that dangerous. Submarines had highly accurate inertial navigation systems able to fix their positions to within a few hundred yards from one second to another. But the Victor was skirting cliffs as though her skipper could see them, like a fighter dodging down a canyon to avoid surface-to-air missile fire. The Los Angeles could not keep track of the cliffs. At any speed over twenty knots both her passive and active sonar, including the echofathometer, became almost useless. The Los Angeles thus found herself navigating completely blind. It was, the skipper later reported, like driving a car with the windows painted over, steering with a map and a stopwatch. This was theoretically possible, but the captain quickly realized that the inertial navigation system had a built-in error factor of several hundred yards; this was aggravated by gravitational disturbances, which affected the "local vertical," which in turn affected the inertial fix. Worst of all, his charts were made for surface ships. Objects below a few hundred feet had been known to be misplaced by miles—something that mattered to no one until recently. The interval between mountains had quickly become less than his cumulative navigational error—sooner or later his submarine would drive into a mountainside at over thirty knots. The captain backed off. The Victor got away.
Initially it was theorized that the Soviets had somehow staked out one particular route, that their submarines were able to follow it at high speed. Russian skippers were known to pull some crazy stunts, and perhaps they were trusting to a combination of inertial systems, magnetic and gyro compasses attuned to a specific track. This theory had never developed much of a following, and in a few weeks it was known for certain that the Soviet submarines speeding through the ridge were following a multiplicity of tracks. The only thing American and British subs could do was stop periodically to get a sonar fix of their positions, then race to catch up. But the Soviet subs never slowed, and the 688s and Trafalgars kept falling behind.
The Dallas was on Toll Booth station to monitor passing Russian subs, to watch the entrance to the passage the U.S. Navy was now calling Red Route One, and to listen for any external evidence of a new gadget that might enable the Soviets to run the ridge so boldly. Until the Americans could copy it, there were three unsavory alternatives: they could continue losing contact with the Russians; they could station valuable attack subs at the known exits from the route; or they could set up a whole new SOSUS line.
Jones' trance lasted ten minutes—longer than usual. He ordinarily had a contact figured out in far less time. The sailor leaned back and lit a cigarette.
"Got something, Mr. Thompson."
"What is it?" Thompson leaned against the bulkhead.
"I don't know." Jones picked up a spare set of phones and handed them to his officer. "Listen up, sir."
Thompson himself was a masters candidate in electrical engineering, an expert in sonar system design. His eyes screwed shut as he concentrated on the sound. It was a very faint low-frequency rumble—or swish. He couldn't decide. He listened for several minutes before setting the headphones down, then shook his head.
"I got it a half hour ago on the lateral array," Jones said. He referred to a subsystem of the BQQ-5 multifunction submarine sonar. Its main component was an eighteen-foot-diameter dome located in the bow. The dome was used for both active and passive operations. A new part of the system was a gang of passive sensors which extended two hundred feet down both sides of the hull. This was a mechanical analog