Starfall

Starfall minus 1 year

Sol System

In Pella's Virtual tank, the invasion fleet showed as a scatter of bright red sparks against the background of the stars of the Centaurus constellation, labelled with distance, velocity and acceleration vectors. Stillich studied the display gloomily, as Pella and her team worked patiently, gathering data and updating their displays.

They were in a bunker, a node of the Navy's command and control system. This new facility had been emplaced deep beneath the ancient sewers and tube-train tunnels of London, in compliance with Shira's order to use the cities and their populations as shields. Stillich had spent some time up in London itself; it was a beautiful city, with relics even more ancient than New York. And nobody among the old, old-young and true-young who walked the parks of this bright northern-hemisphere summer knew anything about the looming threat from the sky—or that far beneath their feet Navy analysts worked in fearful huddles.

"I still can't believe what I'm seeing," Stillich said. "I mean, I know I predicted this. But even a month after we detected them—"

Pella smiled. "Maybe four years of Admiral Kale's scepticism has infected you, sir."

"Maybe. Anyhow it's just as well you can't hide a GUTship, isn't it, Number One?"

"Yes, sir. We're seeing them by the gamma radiation and neutrino flux from their GUTdrives and exhaust plumes, and also by the sparkle where the interstellar medium is impacting their erosional shields, or is being destroyed or ionised by X-ray laser ... "

You could see a GUTship coming, even across light years. But Pella's detection system had had to be improvised, a net of sensors hastily thrown into place. It had surprised, even shocked Stillich that the empire had had no way of tracking a hostile GUTship. The implicit assumption had been that no GUTship would ever be turned against Earth, so there was no need to look.

Pella said now, "The incomers are actually separating into two groups, as we analyse them further." The field of ships was further labelled by pink and grey rings—eight pink, four grey. "The pink ones are ahead of the greys, and are decelerating. They're following what we'd recognise as a standard trajectory, more or less. Constant acceleration at about one G, to a flip-over at half way and then a one-G deceleration run-in."

"So what's their ETA?"

"It's hard to say. They are imposing random changes—small deltas, but at such large distances, small changes make for large uncertainty as to the destination."

"Smart tactic."

"Yes. But it does look as if they are coming in fast, and heading for a close approach to the sun."

"That makes sense." Admiral Kale walked into the room. He was wearing a vest, sweating, panting, and he looked a few years younger than he once had. Since the rebel threat had been actualised by such observations as these, many in the military had been upping their AS treatments and taking physical training. "They'll enter the system as fast as possible to evade interception. And they will head for the sun. Perihelion is the most efficient place to dump your excess kinetic energy."

"That's a bottleneck, then, if they get that far," Stillich said. "And maybe we can find a way to hit them when they pass through that neck. Pella, prepare a briefing on options, would you?"

"Yes, sir. But that won't help us with these others." She pointed to the pink sparks, four of them, clustered close together.

Kale walked into the Virtual tank and peered closely at the pink markers, which were like insects before his face. "These bastards aren't decelerating."

"No, sir."

"Why? Are they going to bypass Sol system altogether?"

"I don't think so, sir," Pella said. "Right now their best-guess trajectory takes them straight to Earth—although they're moving so fast they're hard to track, even harder than the decelerators. By the time they reach Sol system they'll be running at only two per cent under lightspeed. So when we see an image like this, light-months old, it's not necessarily a good projection of where the ships are right now."

"What can their purpose be, if they don't stop?"

Pella took a breath; Stillich nodded to her, having already been briefed on this. "They may be relativistic missiles."

Kale stared at her. "Are these ships manned?"

"As far as we can tell," Stillich said.

"A suicide mission, then. Do we have any defence?"

"We're working on it, sir— "

"There has to be a way to stop these fuckers before they get here. Throw a screen in their way—overwhelm their erosion shields, their laser defences. How about that? You could blow up a Kuiper object."

"Sir, they're coming from out of the ecliptic," Pella said. "The plane of Sol system where most of the mass—"

"I know what the ecliptic is, Commander," Kale said coldly. "Well, find a way." He peered at the images, pretty emblems behind which lay the capacity for huge destruction. "I never conceived anybody would launch such a weapon. I should have listened to you earlier, Stillich; you're thoroughly vindicated. What worries me now is what else we haven't thought of. The difficulty we have is that we've all been trained to serve a Navy that has for centuries acted in a policing role. We're no experience in fighting pitched battles—we aren't used to thinking this way. What about a second echelon? Is there a second fleet on the way after this dozen?"

"We don't think so," Stillich said. "There simply can't be more serviceable GUTships out there. We think they've thrown at us everything they've got."

"Well, that's something. Beat this lot and the war is won." He glared at Pella. "So what else have you got?"

Pella tapped hastily at her data desk. "The results of the latest echo bomb." The Virtual tank cleared, to be replaced by a ghostly outline of Sol system out to the Kuiper belt, with the orbits of the inner planets traced concentrically at its tight heart.

An echo bomb was a powerful detonation that sent an X-ray pulse out in all directions. Echoes indicated the location of any artefact in Sol system more than a metre across, out to dozens of astronomical units. The objective was, by screening out all known objects, to detect the coming of the unknown. The three-dimensional field filled up with markers, but Pella cleared most of them away, leaving the field empty save for a curtain of needle shapes at one side of the Virtual tank, and a misty sphere the size of a pea, out beyond the orbit of Pluto.

"No new intruders, sir," Pella said. "It's taken a few iterations of this exercise to complete the labelling of all friendly items, and—"

"I understand the principle." Kale pointed to the needles. "These are our ships."

"Yes, sir," Stillich said, "mostly Navy interstellar cruisers—everything we have, save for those too remote from Sol to recall—and some commercial vessels, requisitioned and adapted. You can see that we have twenty-five ships, more than twice the aggressors' fleet. And you can see that we've deployed them as a screen, covering the geodetic between Sol and Alpha."

"Hmm."

Stillich said, "Sir, if we can keep them out of the system altogether—"

"The trouble is, Captain, if the Alphans break through this defensive crust of yours, our GUTships once bypassed are going to be quite useless." Kale shook his head, black hair speckling the grizzle of grey. "I'd suggest you explore alternative deployments—deeper defence strategies. Let them come all the way into the heart of Sol system if they like. As you said, we may be able to dream up ways to hit them when they round the sun. It won't matter as long as we down them in the end."

Pella coughed. "I don't think the Empress Shira will like that idea, sir."

Kale said, "The Empress has delegated the fighting of this battle to us." He pointed to the pea-sized ball. "And what's this?"

"Just a routine long-period comet," Pella said. "We can see from the radar reflections that its surface hasn't been modified by previous interactions with the sun. We've been tracking it since it started its fall in from the Oort cloud. It's inert." She smiled. "It ought to make a pretty show later in the year. Morale booster. "

"'Just a comet'," Stillich said. "And yet it arrives just as the first interstellar invasion of Sol system ever attempted is showing up in our sensors. Let's assign a GUTship to track it."

Pella glanced at Kale. "Captain, we only have twenty-five ships. To pull one out of the line for a comet—I told you, it shows no threat signatures at all—"

Kale clapped a heavy hand on Stillich's shoulder. "For once I agree with your Number One. We don't have the resources to go shadowing inert blocks of ice. Forget it." He turned to leave. "Call me if anything else shows up."

"Sir." Stillich stared at the comet, still unsure. But surely the Admiral was right in his general judgement that you had to devote your limited resources to tackling verifiable threats. "Get rid of it, Pella."

Pella touched the Virtual of the comet with a fingertip, thus labelling it as a 'recognised' object, and it winked out of existence.

"So, Number One," Stillich said. "What's next?"