Seveneves

by Neal Stephenson

  “What is Camila doing here?” Dinah asked Moira, as they maneuvered down the Stack.

  Moira had obviously been crying and seemed badly shaken up. She and Tekla had become a couple at some point, and Moira was taking the news of her partner’s injury hard.

  “Tekla came for J.B.F.,” Moira said, “and J.B.F. tried to shoot her. Camila reached out and grabbed for the gun, I guess. She was always wearing that gauzy wrap, as a veil. The fabric caught fire from the flash of the gun, and burned her arm before she could get it off.”

  “But she saved Tekla?”

  “Who knows? The bullet struck something else and fragmented, apparently.”

  The holes where shrapnel had struck T1—the first, oldest, and smallest torus—had been patched, and it had been repressurized. They had always considered it a safe place before; they needed to begin thinking of it in that light again, which was why Ivy had insisted they come here. They took seats in the Banana.

  The numbers had come in. Ivy opened the meeting by reciting them.

  At the onset of the Hard Rain, the human population—not counting any who might still be alive on Earth—had been 1,551, or 1,553 if you counted the two late arrivals, Julia and Pete Starling. Starling hadn’t even made it out of his space capsule, so the initial number had been 1,552.

  At the same time there had been 305 occupied, free-flying arklets plus 11 spares that were attached to Izzy but not occupied. The free-flying ones had housed 1,364 people; the remaining 188 humans had lived aboard Izzy as members of the General Population. But at any given time, 10 percent of the Arkies had been rotating through Izzy, bringing its population on a typical day up to 324.

  Prior to today’s disaster, 26 people had been killed in various mishaps, mostly smaller bolide strikes. Another 24 were now aboard the stolen MIV calling itself Red Hope, and if their claims were taken at face value, they would soon be en route to Mars.

  Of the persons who had been aboard Izzy at the time of the disaster, 211 had been killed outright and another two dozen or so remained in critical condition. The number of living people aboard Izzy had therefore been reduced to 113. The General Population—the older, more experienced, highly trained specialists—had been reduced from 188 to 106.

  At the moment of the disaster, 1,178 persons had been living in arklets. The distributed nature of the swarm, combined with the fact that many arklets had flown the coop with Julia, made it difficult to estimate casualties. The best estimate they currently had was that seventeen arklets had fallen victim, with assumed 100 percent loss of life, reducing that population to about 1,100. If that was correct, then the day’s full death toll had been close to 300.

  In terms of arklet count, they’d started the day with 299 surviving, occupied arklets, a figure that had been reduced to 282 by the collision. Ten of them—a heptad and a triad—were attached to Red Hope, leaving 272. Approximately 200 were missing and presumed to have flown the coop with J.B.F. The remaining 70 or so had elected to stay behind and were still reporting in as members in good standing of the Cloud Ark. The 11 spares were still attached to Izzy and would be inspected for damage later.

  The arklets still with them probably had a population of some 300. That plus the survivors aboard Izzy added up to a bit over 400. The population of J.B.F.’s breakaway swarm must then be something like 800 souls. She had taken two-thirds of the human race with her.

  “God forgive me,” Doob said, “but right now I don’t even care about head count. The number I’m after is engines. Arklet engines. Until Dinah showed up with all of that ice, they were useless. Now, we have a way to fuel them. If we get them all pointed in the same direction, all pushing on Izzy, we can go on the Big Ride.” He paused to look at his notes. With his reading glasses down on his nose he suddenly looked a lot older to Dinah. She could only imagine how she looked. “Based on what you just told me, am I right in thinking we have—”

  “About seventy,” Ivy said, “plus the eleven spares. We haven’t checked those yet, but on visual inspection they seem undamaged.”

  “Eighty-one,” Doob said. “I like that number. A perfect square.”

  “A perfect square of perfect squares,” Rhys put in.

  “If we could come up with a structural system for ganging them in clusters of nine—just a three-by-three grid, with shared propellant feeds—and make nine of those clusters, and integrate them into Izzy’s structure somehow—that being the hard part—then we’d have an array of eighty-one engines. If those things all come on at full power when we pass through perigee, it’ll give us enough combined thrust to make a difference. I think we can make the Big Ride work with that level of power.”

  “It’s a lot of structure,” Fyodor pointed out. “A lot, a lot, a lot.”

  “We have a lot of raw materials to work with, don’t we?” Luisa asked. “I’ve seen rolls and rolls of that aluminum ribbon for feeding into the extruder machines.”

  “It is a question of time,” Fyodor said. “Yes, we have a lot of material. But to assemble it with so few people is difficult. Atmosphere is growing, drag is increasing, orbit is decaying.”

  Dinah looked across the table at Rhys. Rhys the biomimetic engineer, the man who had perhaps saved Ymir with his idea of turning robots into little, radiation-resistant Ben Grimms.

  “We’ll build it out of ice,” Dinah said.

  Rhys looked up at her, pondered it for a second, and nodded.

  “Too brittle,” Fyodor said.

  “I don’t think Dinah’s speaking of regular ice,” Rhys said. “She means the pykrete stuff they used on Ymir. Fiber-reinforced ice. It worked to hold the shard together. We can make it work here.”

  Moira spoke up. “Perhaps I’m missing something, but I was under the impression that the ice was our propellant. Aren’t we going to melt it, and consume it, as we go along?”

  “Yes,” Doob said.

  “And doesn’t that mean that we’ll be consuming the structure that’s holding everything together?”

  “Yes,” Doob repeated, “but it’s okay. Because the more of it we use, the lighter we get, and the less thrust we need. So it’s okay to sacrifice some structure as we go along.”

  Sal had been listening intently. “I don’t mean to throw cold water on the idea,” he said. The pun—assuming he meant it as such—elicited a few groans. “But we’ve been hearing about radioactive contamination.”

  “On the outer surface of the shard, yes,” Dinah said. “Microscopic motes of stuff that is super radioactive, stuck to the ice. Beta won’t penetrate our living spaces. We’ll have to be careful, though, not to track it inside. We can program robots to crawl around, look for those hot motes, and get rid of them over time.”

  Sal looked unconvinced.

  “I won’t lie to you,” Dinah said. “People are going to die of it.”

  “But the trade is as follows,” Rhys said. “Izzy already has a massive battering ram of nickel-iron on her snout. Her flanks are vulnerable, as we learned today. Now we have the ability to shroud everything—the entire space station—in reinforced ice. Oh, it will dwindle over time. But through most of the Big Ride we’ll be living deep inside of a gigantic iceberg with a steel nose. I submit that the death toll from possible contamination will be minor compared to what we would experience if we went on the same journey unprotected.”

  “What do you need to make it happen?” Ivy asked.

  “Permission,” Dinah said.

  “When did you ever ask for that before?”

  The joke elicited a high-pitched laugh from the corner of the conference room. Heads turned toward Camila.

  “Camila,” Ivy said, “we’ve hardly heard a word from you since we found you in the Shipyard. One of our witnesses there claims you may have saved Tekla’s life. You had the opportunity to escape with Julia. Instead you stayed behind to free the bound Shipyard workers. You saved their lives. Now you’re here among us. You must know how this looks.”

  The look on Camila’s face ma
de it clear that how it looked had never crossed her mind. She didn’t even get what Ivy was saying.

  “Dear,” Luisa said, “people are going to say you are a spy who volunteered to be left behind.”

  Camila held up a closed fist and opened it to reveal a small white plastic box, loose tape still dangling from it. “Julia’s bug,” she announced. “It was here.”

  No one looked very convinced.

  “She invited me to dinner at the White House,” Camila said. “She helped me pick out a dress. She introduced me to generals, ambassadors, movie stars. She wrote me letters on White House stationery. I was—I was in love with her. You can call me naive if you want. All right. I was naive. Until this morning. And then all of a sudden I saw. I saw what I was dealing with. I hate her now. And I hate myself for having been in love with her.”

  “Best remember that, sweetheart,” Moira said. “Because she made the wrong choice today. And sooner or later, she’ll be coming back.”

  “I’ll be ready,” Camila said.

  Endurance

  SEEN BY HUMAN EYES, THE HOLLOW HULK OF YMIR’S ICE SHARD WAS as dead, brittle, and gleaming as the discarded carapace of a beetle. Captured through the electronic eyes of cameras, then speeded up a hundred-thousandfold, so that the events of one day were compressed into one second of video, it looked like an amoeba pursuing, capturing, and swallowing Izzy. A person with no preconceptions of what they were watching would perceive Izzy as a steel-headed insect, all legs and pods and antennas, twitching and kicking in an effort to defend itself from the slow, relentless, liquid onslaught of the ice monster.

  In truth, of course, the four hundred survivors, moving at lightning speed compared with the slow evolutions of the ice, were reconfiguring the space station in preparation for the Big Ride. The crippled Caboose was cut free and the components of the Shipyard moved forward. The big power reactor was brought in close to the Stack; from now on they would rely on ice to shield the rest of Izzy from its radiation. The eighty-one arklets arranged themselves into nine groups of nine and were tacked into place at the aft end, nozzles aimed backward. The structural works holding them into place at first were flimsy trellises on which spacewalkers could string cables, propellant lines, and hamster tubes. As soon as those were in place, the ice caught up with them, driven forward by the ceaseless operations of a giant Nat swarm, and the arklets were gradually cemented into place within a solid matrix of the fiber-reinforced ice known as pykrete.

  Forward the ice flowed. It was like watching video of a melting iceberg played in reverse. The Nats, blindly following a simple collection of rules, packed it into every vacant space they happened upon. In the few minutes out of each day when the crew could take some rest and eat some rations, they would try to top each other telling funny stories about where they had found a living infestation of ice, and what they had done to beat it back.

  Within a month, the remnants of Ymir had all been consumed, and Izzy had seemingly ceased to exist. The two of them had merged into an orbiting mountain. Its summit was a battered and scarified lump of nickel-iron, hazy with angular scaffolding where antennas and sensors were mounted. Its slopes were a smooth rampart of black ice, interrupted here and there by outcroppings of thrusters or other equipment, observation domes peeking out like hermits’ huts. Its base was a plane decorated with a neat grid of eighty-one small holes from which blue-white fire erupted from time to time as the ship passed through her perigee.

  They couldn’t make out what to call the thing. People tried and failed to combine the words Izzy and Ymir. The closest they came was Izmir, but that had been the name of a city in Turkey. Sentiment was in favor of naming her after the martyrs of the Ymir expedition, but there had been several. In honor of Markus it was likened to the Daubenhorn, later shortened to the Horn. Which was not a bad nickname. But the name that stuck was a continuation of the Shackleton theme that Markus had established with New Caird. Shackleton’s big ship had been called Endurance, and was famous for having gotten stuck in the ice. So Endurance it was, and Fyodor christened her thus by getting into his battered Orlan, climbing out onto the surface of Amalthea, and dashing a bottle of champagne against the metal.

  A more distant camera, looking down on Earth from high above the North Pole and watching the career of Endurance over the next years, would have seen a nail-biter of an opening, followed by endless grinding tedium, slowly building to a dramatic final reel.

  Prior to Ymir’s arrival, the Cloud Ark’s pilots had put no small amount of attention into the problem of keeping Izzy out of the expanding atmosphere. This produced greater drag, which Amalthea, with its high ballistic coefficient, was well made to resist. But the decay of her orbit had to be mended from time to time with burns of the big engine that in those days had lived on the aft end of the Caboose, fueled by the Shipyard’s reactor-powered splitters.

  The Break—as they called the event when the big bolide had smashed into Izzy, and the Swarm and Red Hope had gone their separate ways—had put an end to all that. Between then and the day about a month later when Endurance was christened, she spiraled gradually downward. Had the featherweight arklets tried to keep formation with her, they’d have been pushed back by the wind. They were forced to creep into the lee of Amalthea and ride along within her bow wave, like bicyclists slipstreaming behind a truck, until they could be integrated into the framework of the ship. Down and down she spiraled, and the SI team had to send Grabbs out onto the forward trusswork and remove the fragile antennas and sensors mounted there, lest they be slowly burned off by a rarefied but white-hot windblast. Fyodor’s champagne space walk was a brief one, and when he got back inside he reported that he could see the spraying foam of the champagne being blown backward by the atmosphere.

  Their mission was to move their apogee from where it was now—just a few kilometers higher than the altitude of the perigee—all the way out to the altitude of Cleft, some 378,000 kilometers more distant. It was a reversal of the maneuvers that Markus, Dinah, Jiro, and Vyacheslav had executed in order to bring Ymir into orbital sync with Izzy. The way to achieve it was to burn the engines for brief intervals as Endurance made her regular swings through perigee.

  The first of those burns happened about thirty minutes after she was christened, and yielded a delta vee of four meters per second. The acceleration was so mild that most of the crew could not even sense it. For the combined thrust of eighty-one arklet engines was nearly powerless against the bulk of Endurance, with her roughly equal masses of iron and ice. Nonetheless it was enough to boost her apogee, which occurred some forty-six minutes later, by 14.18 kilometers. And forty-six minutes after that, another burn during another scrape with the atmosphere gained them another four meters per second that, at the ensuing apogee, added 14.21 kilometers on top of that. The result of Endurance’s first day of operations was a boost in apogee altitude of more than one hundred kilometers, enough to get them clear of the expanded atmosphere except during the few minutes each orbit when they swung through perigee.

  After that, however, they had to suspend operations, since they’d used up all the propellant stored in the Shipyard’s ice-buried tanks. They needed to give the reactor and the splitters some time to catch up. Even a nuclear power plant could split water only so fast.

  Not long after, the operation was shut down for a week by problems in feeding clean water to the system. For another month it could only operate at about a quarter of its planned capacity. But over time they worked the bugs out and began to burn the engines more and more at each perigee, gradually extending Endurance’s reach toward Cleft.

  If they could keep it up, that reach would get less gradual over time. The first delta vee had gained them 14.18 kilometers. The second, equivalent delta vee had reaped 14.21 kilometers—an improvement of about thirty meters. These gains were tiny in comparison to the distances of outer space, but from a mathematical standpoint the trend was extremely significant. It meant that the higher they went—the more elongated t
he orbit became—the more leverage they could obtain from each one of those tiny delta vees. That difference of thirty meters would grow and grow until it spanned many kilometers, and each of those improvements would feed back into the equations and amplify the next result a little bit more. It was an exponential sort of phenomenon, and this time humanity was on the right side of it.

  This didn’t even take into account another piece of good mathematical news, which was that Endurance grew a little bit lighter with each one of those burns. She had less mass with which to resist the force of the thrusters, and so it gradually became possible to produce more than a piddling four meters per second of delta vee on each turn around the planet.

  So everything was going to get better, if they could stay alive and keep Endurance working. But these gains accrued painfully slowly at the beginning.

  IT ENDED UP TAKING THREE YEARS.

  They had planned for one. It took longer because things kept breaking and needed to be fixed. The tools and supplies needed to fix them weren’t always available. Sometimes they had to be improvised. Elaborate workarounds had to be devised through the force of human ingenuity, hard work, and, when all else failed, the risking and the sacrifice of lives.

  The human capital of Endurance dwindled. They were always short on food. Arklets were designed to grow their own food supplies in their translucent outer hulls. But Endurance’s arklets were buried in ice to protect them from the Hard Rain. The ones near the outside got enough sunlight to produce some food, but not enough compared to the mouths that had to be fed. She began her journey well stocked with emergency provisions, which were rationed out on a schedule that assumed a mission length of one year. As it became clear that the journey would go on much longer, the rations were cut back. Endurance also had abundant stockpiles of vitamins, most of which had survived the Break. These were sought after by the people of the Swarm, who had flown the coop without stockpiling enough of them. Trade began to happen between Endurance and the Swarm, but it wasn’t the free market that the Swarmamentalists had once envisioned. Deals were negotiated over the radio and consummated by exchanges between MIVs and arklets, difficult to arrange because of the need to match orbits that had now become very different.