David Weber - Storm From the Shadows

It was physically impossible for any ship to cross the hyper wall without radiating a hyper footprint, but the strength of that footprint was—to a large extent, at least—a factor of the base velocity the ship in question wanted to carry across the wall. The alpha translation's bleed factor was roughly ninety-two percent, and all of that energy had to go somewhere. There was also an unavoidable gravitic spike or echo along the interface between the alpha bands of hyper-space and normal-space that was effectively independent of a ship's speed. Reducing velocity couldn't do anything about that, but a slow, "gentle" translation along a shallow gradient produced a much weaker spike, as well.

No translation, however slow and gentle, could render a hyper footprint too weak to be detected by the sort of arrays covering the Manticore Binary System. Yet arrays like that, because of their very sensitivity, were notorious for throwing up occasional "false positives," ghost translations that the filters were supposed to strain out before they ever reached a human operator's attention. And the most common ghosts of all normally appeared as a hyper footprint and an echo, which was precisely what Topolev's maneuver was supposed to counterfeit.

Under normal circumstances, there would have been very little point to deceiving the arrays where a simple hyper footprint was concerned, given the fact that those same arrays would almost certainly have picked up the impeller wedge of any ship headed towards the system. Even the best stealth systems were unreliable, at best, against a sensor array which could measure eight or nine thousand kilometers on a side, and Manticore's long-range sensors were even larger—and more sensitive—than that. Closer in, where the gradient of the stellar gravity well provided background interference and there were dozens of other gravity sources to clutter the landscape and turn the master arrays' very sensitivity against them, yes. The really big arrays were all but useless once you got within a light-hour or so of a system primary or a wormhole junction. That was where the shorter-ranged sensors aboard warships and recon platforms took over, and with good reason. But this far out was another matter entirely. Really good first-line stealth systems might manage to defeat the big arrays at this range, but no betting man would care to risk his money on the probability.

Fortunately, Frederick Topolev had no need to do anything of the sort.

It seemed to take much longer to complete the maneuver than it had in any of the training exercises, although the time displays insisted it really hadn't. Personally, Topolev suspected the damned clocks were broken.

"Translation completed, Sir," Lieutenant Commander Vivienne Henning, his staff astrogator, announced. "Preliminary checks indicate we're right on the money: one light-month out on almost exactly the right bearing."

"Good work," Topolev complemented her, and she smiled with pleasure at the sincerity in his voice. He smiled back, then cleared his throat. "And now that we're here, let's go someplace else."

"Yes, Sir."

The twenty Shark -class ships, each about midway between an old-fashioned battleship and a dreadnought for size, deactivated the tractors which had held them together. Reaction thrusters flared, pushing them apart, although they didn't seek the same amount of separation most starships their size would have. Then again, they didn't need that much separation.

A few moments later, they were underway at a steady seventy-five gravities. At that absurdly low acceleration rate it would take them a full ninety hours—almost four T-days—to reach the eighty percent of light-speed that represented the maximum safe normal-space velocity permitted by available particle shielding, and it would take them another three T-weeks, by the clocks of the rest of the universe, to reach their destination, although the subjective time would be only seventeen days for them. Another ship of their size could have attained the same velocity in a little more than thirteen hours, but that was all right with Admiral Topolev. The total difference in transit time would still be under six days—less than four, subjective—and unlike the units of his own command, that hypothetical other ship would have been radiating an impeller signature . . . which his ships weren't.

"What've you got for me, Clint?"

Lieutenant Clinton McCormick looked up from his display as his supervisor, Lieutenant Commander Jessica Epstein, appeared at his shoulder. McCormick liked Epstein, but he sometimes wondered why in the world she'd ever decided to pursue a naval career. Born and bred on Gryphon, the dark-haired lieutenant commander was an avid backpacker, camper, and birdwatcher. She also liked cross-country running and marathons, for God's sake! None of those hobbies were particularly well-suited to the constrained dimensions found on the insides of spacecraft.

At least her assignment to Hephaestus meant she spent her time someplace big enough that there were actually personnel tubes, not just treadmills, set aside for the use of people who wanted to jog or run, but she clearly still had a lot of excess energy to burn off. Most other supervisors would simply have requested that McCormick shunt his data to their console, but not Epstein. She wanted any excuse to get out of her command chair and move around, which explained why he found her peering over his shoulder at his display in the big, cool, dimly lit compartment.

"Probably nothing, Ma'am," he told her now. "Looks like a ghost to me, but it popped through the filters. Right here."

He used a cursor to indicate the faint, almost invisible light splotch, then zoomed in. At maximum zoom, it was evident that there were actually two light splotches, each tagged with the time it had appeared, and Epstein grimaced at the telltale sign of a ghost footprint.

"I take it that this thing was strong enough the computers classified it as a genuine possible?" she said.

"That's what happened, all right, Ma'am," McCormick agreed.

"Well, better safe than sorry." Epstein sighed, then flicked her head in a sort of shorthand shrug. "I'll kick it upstairs, and they'll roust out some poor cruiser or destroyer division to go take a look."

"Hey, they ought to be grateful for us for finding them something to do instead of just sitting around in orbit," McCormick replied, and Epstein chuckled.

"If you think that's the way they're going to react, should I go ahead and tell them who spotted this in the first place?"

"Actually, now that I've thought about it, Ma'am, I think I'd prefer to remain anonymous," he said very seriously, and her chuckle turned into a laugh.

"That's what I thought," she said, then patted him on the shoulder and turned to walk back to her own command station.

Given the range on the possible footprint, the datum was over twelve hours old. Footprints, like gravitic pulses, were detectable by the fluctuations they imposed on the alpha wall interface with normal-space, which meant they propagated at roughly sixty-four times the speed of light. For most practical purposes, that equated to real-time, or very near to real-time, but when you started talking about the detection ranges possible to Perimeter Security Command's huge arrays, even that speed left room for considerable delays.

It seemed like an awfully long way to go for very little return. There'd been no sign of an impeller wedge, which meant no one was out there accelerating towards the star system. If there'd been an actual hyper footprint in the first place—which Epstein frankly doubted was the case—it had to have been some merchantship coming in with appallingly bad astrogation. Whoever it was had popped out of hyper a full light-month short of his intended destination, and then promptly (and sensibly) popped right back into hyper rather than spending the endless weeks which would have been required to reach anyplace worthwhile under impeller drive. And when she did arrive in the star system, or at the Junction, she wasn't going to tell a single solitary soul about her little misadventure. That kind of astrogation error went beyond simply embarrassing to downright humiliating. In fact, if Astro Control had hard evidence of a Manticoran astrogator who'd been that far off, they would undoubtedly call her back in for testing and recertification!