SSN - Tom Clancy [125]
CTF 74 agreed with Mack's assessment, but he had a further question: If the crews were so inexperienced, how did they detect Pasadena and Portsmouth! And in an aspect that allowed passive torpedoes to home undetected, for a while at least, on what must have been a reasonably good solution.
"I hate to suggest it, Admiral," Mack said, "but maybe someone needs to go back and re-evaluate our position on non-acoustic ASW. Were their any unusual Chinese or Russian aircraft in the area around that time?"
It was a sobering thought for every officer in the room, and the CTF 74 admiral promised to get right on it. He would see what he could iearn, and hoped to have an answer before any of his SSNs put to sea.
Mack hoped the admiral could turn something up. He knew that the submarines would not wait for an answer before returning to their patrols. There was a threat out there, and Cheyenne and her sister ships would have to deal with it, whether they could put a name to it or not.
While Mack was at his debriefing, discussing Cheyenne's recent patrols and learning what little information was available about this new threat, his officers and crew were overseeing Cheyenne's refit.
The sonar men on Pasadena and Portsmouth brought their last sonar tapes leading up to and following the torpedo explosions. These tapes were fed to Cheyenne's sonar consoles and her BSY-1 computer consoles, while the sounds were played over both the sonar room and control room speakers. This was not virtual reality. It was in situ reality, stark reality of a new foe-a chilling new foe.
Cheyenne's sonar operators and BSY-1 operators put seven different computer consoles, four in sonar and the three in control, to work analyzing the sparse data. They played the tapes over and over again, enhancing them with the computers each time and then starting the cycle again. They were even able to merge the tapes from both SSNs, a feat made possible by the accurate timekeeping systems on U.S. submarines, but they weren't able to leam anything useful.
Then they slowed the tapes, and got their first break. When the tapes were slowed enough to produce sub-harmonics of the main electrical frequency line, the chief sonar man noted a warbling that could not be attributed to slowed tapes, or even merged tapes. The chief sonar man had never heard that particular sound before, but he knew what it was: the sound of a previously unknown submarine. More than that, he knew that it had to be an anomaly of the new submarine's signature, which was masked at higher frequencies, even at the base frequency.
In order to be certain, the chief sonar man, along with Cheyenne's executive officer and the sonar men from Pasadena and Portsmouth, applied this same technique to previous Cheyenne recordings of other Chinese and Russian submarines. They found no matches. This anomaly was new, and it was unique. Even better, it was a low, low frequency, something the TB-23 thin line array would thrive on if they let it search that low.
When Mack was informed of the anomaly, he immediately dubbed it, "a slowly varying constant." He'd picked up that term in a "pure math" class, and it seemed more than appropriate for this war with the Chinese.
It was several days before the McKee captain notified Mack that the next war patrol briefing would again be at the naval base headquarters. Mack had expected that. He had been alerted earlier that Cheyenne had been selected as the obvious choice for this next-and hopefully last- mission: to move President Jiang into Zhanjiang Naval Base.
Prior to the briefing, Cheyenne was moved next to McKee as planned, except that she didn't actually swap locations with Portsmouth. CTF 74 had decided to move Portsmouth outboard of Pasadena on the other side so that there would be one less move when Cheyenne was finally loaded and ready to sail for southern China with President Jiang aboard.
With all Cheyenne's preparations completed prior to this briefing. Mack decided to make it a nearly *'all hands" evolution.