Pushing Ice

by Alastair Reynolds

  “What exactly does that mean?” Schrope said, in the voice of a man who had just seen his own ghost. “In terms of the mission objectives, I mean.”

  “I don’t know about the mission objectives, Craig, but I’ll tell you what it means to you personally if we don’t get out of this fast. It means you’re fucked. It means we’re all fucked.”

  Bella flinched, expecting Schrope to react. But nothing came. He just sat there in a slack-jawed stupor, as if he had been tranquillised.

  “If this is confirmed,” Bella said tentatively, “then… what should we do? Can we back out of the slipstream, or whatever it is?”

  “We can try,” said Svetlana. “The free-flier didn’t appear to suffer any damage when it left the slipstream: we only lost contact with it because of the sudden shift in frequencies.”

  “We’ll need to know that for certain before we try anything. I’ll have Pagis and Hinks see if they can widen the reception bandpass and pick up a signal.”

  “We don’t have time for this, Bella. We have to reverse out of this now, before it pulls us any faster than we’re already travelling.”

  “Not until we know that the free-flier survived the transition. It shouldn’t take long.” She reached for her flexy, preparing to give the order. She already regretted not having Pagis and Hinks present in her office.

  “Bella,” Svetlana said urgently, “listen to me. Every minute you sit here thinking about this is an additional three kilometres per second of speed we have to lose if we ever want to get home. There isn’t time to look into all the angles here. You have to move us now.”

  Schrope suddenly came back to life. “The free-flier… how long did it take it to clear the slipstream?”

  Svetlana answered him with a flat absence of emotion. “It was more than half a light-second out. If we push at half a gee now, we might reach the drop-out point in two or three hours, by which time we’ll be moving even faster.”

  Schrope looked at Bella. “Perhaps we should consider a withdrawal —” He said it plaintively, like a child after sweets. Bella saw it plainly: the utter collapse of his neatly ordered corporate world. Until now Schrope had been in control. Now he was at the mercy of something frightening and powerful in equal measure.

  Bella’s flexy chimed with an incoming call from Belinda Pagis. She had a hard number on the aberration problem.

  “This is… not good,” she said, as if Bella had imagined it could be anything else. “To match the star positions as we see them, we need to allow for —” She lowered her eyes, reading data from another flexy. “Four-point-nine-eight per cent of the speed of light.”

  “Good work,” Bella said.

  “We’ve picked up a faint signal from the free-flier,” Pagis said, almost apologetically. “We allowed for the excess in our Doppler shift. It’s… worryingly consistent.”

  “Does the free-flier telemetry look healthy?”

  “No sign of any damage. The accelerometer curve was —”

  “Flat,” Bella finished for her.

  “Um, yes.”

  Bella turned to Svetlana. “Then we could — theoretically — survive exiting the slipstream.”

  “Start the process now,” Svetlana urged. “Full burn at half a gee. We’ll ditch the remaining mass drivers — anything we absolutely don’t need.”

  “We still have to turn the ship around,” Bella said. “That’ll take two hours, if we don’t want to snap in two.”

  Svetlana closed her eyes. “Jesus, I forgot.”

  Rockhopper didn’t take kindly to torsional stresses, any more than a skyscraper took kindly to being tipped on its side. Slewing the ship — bringing the fusion motors around to reverse their thrust — was a delicate operation that could not be hurried.

  Normally there was no need to hurry it.

  “Belinda,” Bella said, “drop whatever you’re doing and prep for a one-hundred-and-eighty-degree turnaround. Emergency slew speed: I don’t care if we blow the warranty on this one.”

  “I’m on it,” Pagis said. “Anything else?”

  “Yes,” Bella said. “While we’re slewing I want a full flight-dynamics update. Do we still have enough fuel left to slow down? Do we have enough to make it home after that?”

  “I’ll get those numbers for you,” Pagis said. “Permission to begin the slew as soon as we’re stowed.”

  “Granted — begin it immediately if you can.”

  When the call was complete, Svetlana said quietly, “We’ll never make it in time.”

  “We’ll try. That’s all we can do.”

  A ship-wide siren alerted the crew of the impending slew, warning everyone to secure bodies, equipment and possessions against the impending kick from the steering thrusters. When it came, the jolt was no worse than a mild fender-bender, but it still felt ominous and wrong: a shove in a direction in which the ship rarely moved.

  The water in Bella’s fish tank sloshed to the lid and the fish looked agitated. The ship’s frame creaked and groaned before settling down again.

  “We’re rotating at three minutes of arc per second,” Pagis told Bella, “which is as fast as I can manage.”

  Bella did the sums. “It’s not fast enough. It’s still going to take us another hour to get the nose turned around at that rate.”

  “The system won’t allow a faster rotation,” Pagis said. “Thruster control is under software override: I can slow the rotation, but not speed it up.”

  “Pass me the flexy,” Svetlana said. Bella slid it to her and indicated that she should speak. “Belinda, listen carefully. There’s a file you need to update. I’ll talk you through it, all right?”

  “Go ahead,” Pagis said.

  “Open a separate window and navigate to dynamics tasks. Make sure you do it under system privilege.”

  Bella heard Pagis’s fingers scratching against the hide of her flexy. After a few moments they heard her say, “I’m there.”

  “You should see two subdirectories. Go into ‘OMS’ underscore ‘tasks’ and look for a file called something like failsafe limits.”

  “Not seeing it… not seeing it…” Pagis said. “Oh, wait, there’s something called ‘struct’ underscore ‘lims’.”

  “That’s probably the one. Open it and scroll down until you see a parameter called ‘slew’ underscore ‘upper limits’, or something similar. It’ll be about twenty lines down.”

  “Got it,” Pagis said quickly.

  “The numeric field gives our maximum permitted slew rate in fractional degrees per second: it should say something like point-oh-five right now.”

  “Yep, got it — you want me to change that?”

  Svetlana glanced at Bella. “That failsafe’s there for a reason. It’s to stop the ship tearing itself apart.”

  “Increase it to point-oh-seven-five,” Bella said. “I’ll take responsibility if she snaps.”

  “Do it,” Svetlana said to Pagis.

  “I’ve made the change,” Pagis said.

  “Close the file, go back to your navigation window and see if the ship accepts the new rate of slew.”

  “I’m on it. Better brace, because if this goes through —”

  Bella flinched, but nothing happened: no shove of motion; no creaking or groaning.

  “Did you get a reaction from the rockets?” Svetlana asked.

  “No dice. She still isn’t accepting an increased rate of slew.”

  Bella saw Svetlana screw her eyes shut in absolute concentration, her face taking on an expression that spoke as much of pain as it did of intense intellectual effort. Svetlana knew Rockhopper’s functional parameters better than anyone alive, but the ship was still too complex for any one person to know with an easy intimacy. “Okay,” she said, her face slackening, “I think I know what the problem is. The slew-management system won’t pick up the changes to the file unless we zero the slew and start again.”

  “Goddamn,” Bella muttered, “who the hell designed this piece of crap?”


  “Engineers,” Svetlana said tersely.

  “All right, do it. Zero the slew and start over.”

  After a few tense moments, the siren sounded again. The shove came from the opposite direction this time, halting the ship’s inching rotation. There was another protestation from the structure, like an old building flexing in a squall.

  “Zero,” Pagis said.

  “Try it again,” Svetlana told her, “and be ready to shut it down fast.”

  Another siren warning sounded. The shove was half as powerful again this time, the difference perceptible. The water in the fish tank found its way through the gap between the top of the tank and the lid, sluicing onto Bella’s carpet. The ship registered its disapproval, but so far it seemed to be holding together.

  “How are we doing?” Bella asked Pagis.

  “We’re in one piece. No reports of pressure breaches or fatigue warnings.”

  But the ship’s nervous system was still in tatters after the mass-driver accident, Bella thought. Only vital command signals were being routed up and down the spine. She did not think it likely that damage reports would have been able to reach her anyway.

  “Belinda, I need one of your team stationed at a viewing port. I want someone keeping an actual eye on the spine and engine assembly.”

  “It’s okay,” Pagis said. “We’re holding.”

  “At the moment we are, but I’m going to zero the slew again. This still isn’t fast enough.”

  “We’re already pushing the envelope here,” Svetlana warned.

  “It can take some more pushing. Belinda: edit that file again and raise our slew rate to one-tenth of a degree per second.”

  Svetlana shook her head in warning. “You’ll have exceeded the failsafe margin by a factor of two.”

  “I thought you were the one keen to get out of here.”

  “I am — but I know what this ship is built to take, and what it definitely isn’t built to take.”

  Timidly, Pagis said, “I’ve updated the file. Shall I —”

  “Zero the slew,” Bella said. “Zero and restart.”

  “I don’t recommend that we do this,” Svetlana said.

  “Duly noted. If the ship breaks up, you can have the satisfaction of telling me you were right.”

  The thrusters killed the slew. More water sloshed from the fish tank, more noises signalled the ship’s displeasure, but Rockhopper held together. Ten or fifteen seconds passed: then came the next warning siren. What, Bella wondered, did the rest of the crew think was going on? If she had been less preoccupied, she might have found time to speak to them. Then again, perhaps not speaking to them was the kinder thing: it was not necessarily good to know that the ship was being tested to its limits. Please let me believe that this ship was designed to take more punishment than the design specifications, Bella prayed. Please let me believe that the engineers were in a generous mood.

  But the ship held. Bella’s fish tank lost more water, but it would all be collected again by the humidity filters, even if it took months for the lost allocation to wind its way back to her cabin.

  “We’re in one piece,” Pagis said, her surprise unconcealed. “Slewing at one degree every ten seconds. We’ll be nose-around in about twenty-seven minutes.”

  Then we’ll have to slow again, Bella thought. But if the ship had withstood this latest jolt it would probably withstand that one as well. She would push it no further. They were inching around no faster than the minute hand of a clock, but it would be insane to push for more.

  “I’m still going to need that flight-dynamics report,” Bella said. “The sooner the better.”

  Thirty minutes until they could fire the engine. Two hours more — at least — until they reached the point where the free-flier had appeared to accelerate away. And all the while Janus was pulling them ever faster, making their homeward journey increasingly difficult.

  If flight dynamics said it could not be done, what then? She needed to have a plan in place for that eventuality, even if that plan consisted of nothing more than trying.

  The best-case scenario was that they had enough fuel left in the tanks to not only slow down to the local solar rest frame, but also to make it back home in a reasonable amount of time. If that wasn’t feasible, then Earth would have to meet them halfway with some kind of resupply operation. And if that wasn’t possible, if all they could do was stop, then Earth would have to come all the way out here to rescue them. Maybe they could endure that long. Rockhopper’s closed-cycle life-support system could sustain them for a good long while. It wouldn’t be comfortable — there would be no luxuries — but it could keep the crew alive. But it would still take power to make that life-support tick. And if they ran out of fuel, they would also lose their main source of power. There were back-up systems, but they were designed to keep the ship warm and habitable for a handful of weeks during reactor downtime; they were not designed for the months — or years — that it would take Earth to implement a rescue operation. That was a pretty bad scenario.

  But there was a worst-case option that she had to consider as well: what if they couldn’t slow down? She was sure they would be able to decelerate a bit, but the amount necessary? If, when the fuel tanks gave their last splutter and ran out, the ship was still moving in the direction of Spica at one or two per cent of the speed of light… Nothing might ever catch them. Not for years, anyway. And by that time — would anyone even bother, just to recover a hundred and forty-five cold, dry corpses?

  Not DeepShaft, at any rate.

  Her flexy chimed. “Yes, Belinda?” she asked, hoping that no one could pick up on the anxiety she felt.

  “I have that flight-dynamics report. It still needs to be double-checked, but —”

  Bella interrupted her. “What’s the verdict?”

  “We can slow down, if we make it out of the slipstream within three hours.”

  “And then?”

  “We’ll have a small margin, just enough fuel to put us on the return trajectory. We won’t have enough to brake at the other end, but shuttles should still be able to reach us.”

  “How long will it take?”

  “Ten months,” Pagis said. “That’s the most optimistic estimate.”

  Bella shot a glance at Svetlana. “And that scenario — it was based on the assumption that our fuel-load reading is accurate?”

  “Yes, of course,” Pagis said.

  “Run it again,” Bella told her. “Assume that the fuel-load reading is fifteen per cent lower than the systems are telling us.”

  Schrope stirred. “We’ve been over this already. There’s no reason to take Barseghian seriously.”

  “We won’t make it,” Svetlana said, addressing Bella as if Schrope was not there. “It’s already marginal. Drop that fuel load by fifteen per cent and we’ll never even slow down.”

  “I’ll wait for flight dynamics to get back to me,” Bella said. “But if — for the sake of argument — you’re right about this, is there anything we can do about it?”

  “The time to do something,” Svetlana said, “would have been two weeks ago.”

  “But I didn’t,” Bella said, “and here we are, so let’s deal with it. Assume the fuel load is marginal. Could we improve our situation by escaping the slipstream sooner?”

  Svetlana’s face glazed over as she thought about it. For all the tension between them, she could not ignore a technical query.

  “Perhaps… but we’re already basing our calculations on a half-gee burn.”

  “I know that,” Bella said, “but could you squeeze more thrust out of the engine? Would it give us a gee? Or more than a gee, if only for the time it takes us to clear the slipstream?”

  “I — I don’t know,” Svetlana said. “I’ve never even considered it before. It’s well outside the design limits.”

  “What about the structural frame of the ship?”

  “If we ditched the remaining mass drivers —”

  “That’s a given.”
>
  “Then if it came to that she might hold. But the engine… I don’t know. I’d need to look into it. We’d be burning fuel at twice our usual rate —”

  “But presumably it’s better to burn fuel now, while we’re still inside the slipstream.”

  “I understand.” Svetlana suddenly seemed distant, as if her body was a shell while her mind was elsewhere, roving the mental architecture of the ship, considering fearful new possibilities.

  “Fifteen minutes to end of slew,” Pagis reported. “Flight dynamics has those numbers. It doesn’t look good for the fifteen-per-cent-less scenario. We’d still have a residual drift in the direction of Spica.”

  “How fast?”

  “Four thousand klicks per second. That’s more than —”

  “One per cent of the speed of light. Thank you, Belinda. Now do me one final favour. Re-run the simulation. Assume the same fuel deficit, but allow for a two-gee burn for the first thirty minutes, or until we’ve cleared the slipstream.” Bella spoke with exaggerated clarity, mindful that a single misunderstanding could cost them dearly. “Oh, and Belinda?”

  “Yes, Bella?”

  “I need an answer on that pretty quickly.”

  * * *

  Bella sat down at her desk and breathed in deeply. Here it was, she thought: that cusp, that moment of maximum crisis she had always known would visit her at some point in her career. From time to time she had wondered what shape it would take, and, more importantly, how she would rise to meet it.

  She had always hoped her reaction would be adequate at the very least.

  What she had never imagined was that when that moment came she would be sitting at her desk with her feet squishing soggy carpet.

  But that was reality: always pissing on the epic moment.

  The flexy shook a little: her hands were trembling. Flight dynamics said that a two-gee burn would compensate for most of the fuel deficit. It would not get them home, but it would bring them to a stop in the local rest frame —”stop” in this case meaning that they would have a residual velocity relative to the Sun of no more than a few tens of kilometres per second. Planetary speed.