Pushing Ice

by Alastair Reynolds

  “How… how big?” asked Regis, hesitantly, as if the question were a kind of heresy that could only be voiced in the most trusted company.

  “Big,” Bella said. “Really, really big. The structure appears to be floating somewhere close to the Lagrange point between the two stars, where their gravity fields cancel each other out. If that’s the case then the object is truly enormous: seventeen or eighteen light-seconds wide, and nearly three light-minutes long. If you placed the Earth at one end of that tube, the other end would reach to the orbit of Venus.”

  “Agreed on big,” Regis said.

  “You’ll notice that the long axis of the tube isn’t aligned with the vector joining the stars” centres of gravity. Even if that were the case, there’d still be unthinkable tidal stresses working to stretch the tube, but with the tube tilted like that, the two stars are trying to snap it like a dry twig. And yet there isn’t a hint of deflection: to the limit of our observational abilities, it appears completely oblivious to the gravitational gradient across it. It’s absurdly rigid. It can’t possibly be made of any material exploiting ordinary inter-atomic forces.“

  “One more question,” Svetlana said, raising her hand, “and possibly a stupid one: what is it?”

  “We don’t know. We’ll probably never know, unless something at Janus gives us a clue. But we can guess. Spica is where Janus is headed. It must be the place it calls home. This is where they live.”

  Svetlana looked scornful. “In that thing? In a piece of scaffolding?”

  “Just consider one of those longitudinal spars,” Bella said. “If we’re right about the scale of the object, then the spars are half a light-second thick. Now imagine that those spars are hollow cylinders, with habitable living space on the inner surface. Just one of the spars would have an internal surface area equivalent to fifty thousand Earths. And there are twenty of them. That’s a million Earths’ worth of living space — and that’s if they don’t utilise the cross-struts. If they do, you can easily double that figure.” Bella smiled at Svetlana. “Is that enough room for you, or do you need more?”

  Bella had hoped for laughter, but something about the looming Spican structure had touched them all on some disagreeable level. Janus was one thing: it was clearly the product of a culture far in advance of human capabilities. It spoke of a technological gulf that was centuries, even thousands of years wide. But the Spican structure crushed those easy assumptions. This was not the result of a gap that could be measured in the cosy units of historical time.

  This was a geological gap, and it required appropriately geological thinking. It spoke of millions of years of disparity. At the very least.

  FOUR

  The bad thing happened on day eleven. Svetlana was riding a car up the spine from the engine to the hab. She had already passed through the machine shop: it was about a hundred vertical metres beneath her, falling further behind each second as the car climbed higher. She was somewhere else: not exactly daydreaming, because her mind was still on her job, but not remotely focused on her immediate surroundings. A flicker of movement in the corner of her eye was the first hint of wrongness. A brief surge in her own weight was the second.

  A moment later she let out an involuntary gasp.

  High above, not far from where the spine plunged into the underside of the hab, one of the remaining mass drivers had come loose. It hung at an odd angle to the spine, no longer properly coupled. Horrified, Svetlana saw that it was attached by only a single bracket, and that bracket was buckling like toffee, yawning away from the trusswork of the spine. The mass driver was about to break away completely.

  A single thought screamed through her skull: shut down the engine! At worst, the mass driver would detach itself and drift slowly away from the spine. They could send out tugs and haul it back, or abandon it to deep space. She had about a second to process those thoughts before she knew there wasn’t enough time.

  The mass driver fell.

  It was a big object, built to bulldoze comets. At half a gee it fell ponderously at first, gaining speed with a certain reluctance. But it fell dead straight and parallel to the spine, as if in some deft illustration of Newtonian law, accelerating all the while until it hit the mass driver suspended below it on the next coupling down.

  Three hundred metres above her head, the second mass driver sheered off instantly, its vast mass careening into the spine. Svetlana felt the appalling impact, saw the spine flex unnaturally at the impact point. The car jolted from its guidance rail and ran rough until it came to a juddering halt, only partially attached to the line. Above, the two mass drivers fell in unison, the lower one scraping against the spine as it fell, spitting shards of broken metal work. There were no further mass drivers beneath the falling pair, at least above Svetlana. She dared to look down and she saw the bulge in the spine that the falling machines were about to slam into: the machine shop.

  The two falling mass drivers slid by her stalled car, the wake of their passage slamming her into the seat restraints with bruising force. She felt something crack in her chest, but the car stayed intact and retained its tenuous grasp on the line.

  Then the drivers hit the machine shop, and the force of that impact shuddered through her. When she could bring herself to look down again she saw a glittering debris cloud already spuming from the ruins of the shop, sliced clean through on this side of the spine. Yellow robots tumbled out like tiny dried-up spiders. Through the cloud she could just make out the two falling drivers, both tumbling now, but both still intact. The impact with the shop had nudged them away from the spine.

  But they were still going to hit the engine.

  The crash came quickly: almost as soon as she had registered its inevitability. As the two mass drivers interrupted the ship’s smooth acceleration, it juddered in a way it hadn’t when they ghosted through the thin fabric of the machine shop. She narrowed her eyes, anticipating the explosion from an uncontained fusion reaction: the explosion that would almost certainly swallow the entire ship up to this part of the spine, in an eyeblink of numbing whiteness.

  But the ship was still working. The ride felt smooth, normal. A fusion reaction was a delicate, temperamental thing: it either happened or it didn’t. Against all the odds, the engine must have escaped serious damage.

  They’d survived.

  That was when the adrenaline rush hit her. Her hands were trembling as she reached for the car’s communication switch. It hurt to breathe. She flicked the toggle, heard the snap, crackle and pop of cosmic rays.

  “This is Svetlana,” she said, hoping someone could hear her. “We’ve got a situation here.”

  * * *

  With delicate taps of thrust, Parry brought his suit to a halt above the cathedral-like vastness of the fuel tanks.

  Evidence of cautious but urgent human and machine activity was all around him. Suited figures floated around the floodlit engine assembly and moved across it: the plodding, deliberate movement of people using geckoflex pads on their soles and palms. Most of the workers weren’t wearing propulsion packs, but no one was tethered. Years of experience had proved that safety lines were more trouble than they were worth. They got in the way, tangling around obstructions and other tethers. Sometimes they themselves were responsible for bizarre, grisly accidents. A swiftly moving tether was a thing of horror.

  Parry studied the damage, comparing it against the reports he had read. Things could certainly have been worse. Most of the wreckage the workers were clearing away had come from the machine shop; comparatively little of it had originated from the engine or fuel tanks. In the bright foci where the floodlights were trained, people and machines tugged at debris with exquisite caution, mindful of coolant or fuel lines that might have been pierced just beneath the surface. All the workers had three-dimensional blueprints projected onto their faceplates, but it paid not to put too much faith in them.

  “Someone’s going to pay for this,” Bella said over the ship-to-suit channel. “We’ve tracked down
the screw-up to a single incorrect digit in a stress-loading spreadsheet.”

  Parry whistled. “Must be some digit.”

  “Someone back home thought we were hauling type-seven mass drivers, whereas we’re actually carrying type eights, which happen to weigh quite a bit more.”

  Parry tapped the controls and lowered himself towards the fuel tanks. They were arranged like four cylindrical skyscrapers around a narrow central plaza, with the spine of the ship passing between them. The tanks’ foundations were mounted on a huge dish-shaped shield assembly which screened most of the radiation from the Lockheed-Krunichev fusion engine; it also served as the anchoring point for the spine.

  “Is this a show-stopper?” Parry asked.

  “Bob Ungless says we can reinforce the existing driver attachments without too much trouble. We’ll have to run at reduced thrust until it’s done, but it shouldn’t kill us.”

  “I take it Svieta isn’t up and about yet?”

  “I’ve just spoken to Ryan. She’s going to be pretty bruised and battered for a few days.”

  “Is she awake?”

  “Oh yes. Just try tearing that flexy out of her hands.”

  “I might need to speak to her.”

  “You’ve found something outside?”

  Parry made an equivocal sound. “Probably nothing, but I don’t think anyone’s taken a good look between the tanks yet.” He brought the pack to a halt, disengaged from it and used geckoflex to station himself on the inner wall of the tank.

  “We’re not expecting damage there,” Bella said.

  Parry started descending. “All the same, we’ve got a dead cam down there. It happens to be the one that looks up from the shield between the tanks. I’m wondering if something clobbered it.”

  There was a crackle of static. “Okay. Advise you send in a small robot.”

  “There aren’t any. I’m making my way down on foot.”

  “Say again?”

  “We lost all the small robots, Bella.” Parry caught his breath, out of practice with flexwalking. “They were all in the machine shop, so the drivers took them out.”

  “It never rains, does it?”

  “This is beginning to feel uncomfortably like an incident pit,” Parry muttered.

  “Incident pit? Now there’s a phrase I haven’t heard in a long time.” As Bella well knew, incident pits were underwater situations that turned bad in little increments. Each small step — almost inconsequential in themselves — took one ever deeper into a pit with ever-steepening sides. Near the top, there was still time to reverse the situation and get out. Deeper in, options thinned out fast.

  “You know what they say about shit coming in threes, too,” Parry said.

  “Something else the guys used to say,” Bella answered, “anything even smelled like this, we’d call it a serious Charlie Foxtrot.”

  “Charlie Foxtrot?”

  “Clusterfuck, dear boy: CF stands for clusterfuck.”

  “I see,” Parry said. He laughed, grimly. “I suppose you could arrange a clusterfuck in an incident pit, too, if you tried hard enough.”

  “I suppose so,” Bella said. She shuddered involuntarily.

  “That’s something you’d want to keep the hell away from.”

  His torch beam glanced against faint, vague shapes some twenty metres below. Parry called up his helmet overlay, superimposing the wire-frame blueprint over his view. The thin red vector lines matched perfectly against the real-time view, highlighting the tanks and the spinal truss. The shield contained a scrawl of complex arterial machinery, delineated in green and blue, difficult to relate to the shapes picked out by the torch.

  He pushed himself closer, grunting with each metre of hard-won progress. The tank side was smooth above the scratch in the cladding where the debris had hit: he decided he’d risk drifting his way back to the top, rather than repeating the crawl. Then he would make a point of putting in more time in the gym, rehearsing for exactly this kind of job.

  “How’s the viz?” Bella asked.

  “Not great — it’s a Braille dive down here.” Parry tried various combinations of torch, helmet beam and visor filter until he found an uneasy optimum. “There is something down here, though. Actually, lots of somethings.”

  “Talk to me, buddy.”

  Parry crawled lower, then panned the beam around, whistling at what he found. “No wonder the cam was dead: there must be about ten tonnes of crap gathered down here, trapped between the tanks.”

  “What kind of crap?”

  “Highly compacted crap.” Closer now, he was able to identify some of the rubble. Bent, jagged-edged corrugated plates had come from the outer skin of the machine shop. Chunks of red metal had probably broken away from one or both of the mass drivers. Mangled bright-yellow parts were all that remained of several robots, jumbled together like crabs in a bucket. “It’s an unholy mess,” Parry said. “Are you seeing any of this?”

  “I’m getting a very fuzzy feed from your cam,” Bella said, “enough to see that it isn’t good news.”

  “Someone’s going to have to clear this up.”

  “Easier said than done. But you’re right — we can’t risk any of it shifting and damaging the tanks.”

  Parry looked around the bombsite, visualising the cleanup: all of it would have to be carried out by suited workers rather than robots. At least if they worked under weightless conditions they wouldn’t have to lift any of the debris free. Once the pieces had been dislodged from the compacted pile, they could be allowed to drift beyond the tanks. Afterwards, when the area had been cleared, they could reinforce any damage to the tanks with sprayrock.

  Sprayrock, he thought: now that was going to be fun.

  “You still there?” Bella asked.

  “Yeah. Just wondering why I ever thought space operations would be an astute career move.”

  “We all have those days.”

  “With me it’s fast becoming one of those decades.”

  Parry swept the area one more time, making sure his helmet cam obtained good coverage. Then he looked up to where the four tanks framed open space, the hab poised far above, impossibly distant and small, like a child’s balloon bobbing on the end of a string. He judged his angle and kicked off.

  Svetlana sat on the side of the bed and nervously watched the clearance work. Although drugged to the eyeballs, she retained enough focus to feel genuine anxiety about her beautiful, deadly engine.

  “It looks bad,” Parry said, rubbing his forearm; he felt as if he’d pulled a muscle. “But there’s nothing down there they won’t be able to clear, given time.”

  “I don’t want cutting gear near those tanks,” Svetlana said.

  “We thought of that. They’ve taken down powered tools, but nothing that you need worry about. It’s just a question of freeing the pieces.”

  The workers had formed an efficient clear-up chain. Five of them were down at the base of the tanks, using hammer-drills to break up the compacted mass into manageable chunks. Once loose, they nudged the chunks back towards the open end of the tank assembly. Five more workers were poised on geckoflex halfway up the inner wall, ready to shove the debris back on course if it looked as if it would scrape against the tanks or the spine. Another five waited at the top, three on geckoflex and two hovering in propulsion packs. They caught the arriving chunks and made a quick assessment of their value. The booty they tossed into a sticky web of epoxy-coated fibres; the junk they threw overboard, obeying the old and largely pointless tradition of flinging stuff away from the ecliptic plane.

  “The pile’s visibly smaller,” Parry said.

  Svetlana watched on the cam as the workers at the base attacked a piece of debris. “Tell them to take care.”

  “Just because they’re fast doesn’t mean they’re not good. These are the same people I’d trust with the trickiest jobs on a comet.”

  Svetlana forced herself to nod. She could never quite overcome a lingering prejudice against the come
t miners. They were too brave, too courageous. Svetlana thought that the only kind of person you wanted anywhere near any part of a fusion motor was someone with a strong aversion to risk.

  Cowards were exactly the kind of people you wanted around nuclear technology.

  “I’m just saying they need to be careful,” she said. “If there’s a leak —”

  “Nothing we saw down there suggested a leak. Do me a favour and stop worrying. You need to rest.”

  “I’ve broken ribs before now. They mend.”

  “Is there anything I can do for you?”

  “Yes,” she said sweetly. “You can bring me a flexy, please.”

  Parry grimaced. “You’re supposed to be relaxing, babe, not working.”

  “To me relaxing is working. Just do it, okay?”

  Parry gave in and returned a minute later with a flexy. “The little lady won’t be thrilled about this,” he said.

  “I’ll square things with Bella. You just worry about your people.”

  Svetlana held the flexy before her face, allowing the device to identify her via a combination of fingerprint analysis, hand movement, breath chemistry, voice, face and retinal recognition.

  “Anything in particular you’re interested in?” Parry asked.

  “Leakage,” she said.

  “That doesn’t tell me much.”

  “If the fuel tanks really were punctured, and if there was a leak into space, it should show up in the pressure readings.”

  “Even a tiny leak?”

  “There’s a limit, obviously — the pressure gauges won’t be able to detect a few atoms dribbling into space every second. But it’s foolish not to check.”

  “Do you think I should tell my people to stop working until you’ve looked at this?”