Seveneves

by Neal Stephenson

  Ivy and Dinah didn’t have to worry too much about cosmic rays during the intermission, because they had so arranged it that the Kupol was on Endurance’s nadir side, facing toward Earth. And Earth was close enough to fill their view. Useless as the planet might be for the support of life, it still acted as a very effective cosmic ray absorber. Nothing was getting through that, short of another mysterious Agent that could pass all the way through a planet and keep on going. So, Dinah and Ivy hovered in the middle of the sphere, arms linked so that they wouldn’t drift apart, and sucked bourbon from plastic bags, and looked at their old planet for the last time. In their six years of hurtling around this world, they’d grown accustomed to the steep angle that Izzy’s orbital plane made with the equator, and the views it afforded them of the high latitudes. Because of the changes they had lately been making to Endurance’s plane, however, they were now confined to a belt around the tropics.

  Not that it mattered a hell of a lot with Earth in its current state. The sky was still on fire, streaked with the bluish-white incandescence of the Hard Rain. The ground, where they could see it through smoke and steam, was a mottled terrain of dully glowing lava: some of it the hot impact craters of recent big meteorites, some of it spewing up out of the Earth’s fractured crust. Oceans were dark at night, hazed with steam in daylight, their coasts difficult to make out, but clearly shallower than they had been. Florida was reaching out toward the Keys but being battered down and chipped away by bolides, and washed away by tsunamis, even as it did so. A year and a half ago, a big rock had torn the lid off the long-dormant Yellowstone supervolcano. That had been cloaking most of North America with ash ever since then; glimmers of yellow light in the northern extreme of their view hinted at a vast outpouring of magma. A long-suppressed habit told Dinah, absurdly, that she should go and turn on her radio in case Rufus was transmitting. This made the tears come, and that in turn made Ivy’s tears come, and so they spent the last half of the intermission, from perigee onward, gazing at Earth through water. It didn’t really affect the view much. But Dinah tried to register the memories as best she could. Humans would not again look on Earth from such a close vantage point for thousands of years.

  The burning planet started to drop away from them. It would only ever get smaller from now. They needed to get back to work. But they found it difficult to let go of each other. Back in the old days, before Zero, they’d had the occasional heart-to-heart about their shared, secret fear that they weren’t qualified to carry out the missions for which they’d been sent up, at vast taxpayer expense. That they’d screw it up, fall on their faces, and embarrass a lot of people on the ground. By now, of course, they had long since put those fears to rest, or at least seen them overwhelmed and buried by much greater fears. Ever since the beginning of the Cloud Ark project, however, and especially since they had made the irrevocable decision to build Endurance and go on the Big Ride, it had frequently come back to them in a bigger and more dreaded form. What if they were completely getting it wrong? They could scarcely remember, now, the great civilization that had once spread across the planet below them. But the contrast between it and its orbiting residue was painful. The dirty, beat-up kludge that was Endurance was an embarrassment to the human race. Could they really have done no better than this? And now, after a voyage of three years—three years that had been an unrelieved spiral of decline, punctuated by catastrophes—they were reduced to a maneuver, coming up in five days’ time, that seemed more and more desperate the more they thought about it.

  If they screwed it up, it would be their fault, more than anyone else’s.

  Of course, no one would be left to blame them for it.

  They went through these crises of confidence frequently, but usually at different times, so that one could pull the other out of despair. Right now they were both feeling it together, and so they had to pull themselves out.

  Dinah was thinking about Rufus’s last transmission:

  BYE HONEY DO US PROUD

  “Okay,” she said. “Come on, sweetie. Let’s get to work.”

  WORK GAVE THEM SOMETHING TO DO DURING THE FINAL ORBIT OF the Big Ride besides worry about what was going to happen at the end of it. The huge burn that they would make at apogee, combining a final plane change with an acceleration into the “fast lane” where Cleft rolled around the world like a ball bearing in a tire, contained so many unfathomable chances that it beggared prediction. The new wrinkle, however, was this: since they would be moving into a stream of rocks moving faster than they were, the rocks would be coming at them from behind, where Amalthea had no power to protect them.

  Early in the mission Doob had dreamed of reconfiguring Endurance at the last minute, moving the vulnerable stuff around to the asteroid’s other side. With the manpower they’d had in those days, it might have been possible. As it was, reduced to a crew of twenty-eight starvelings, it was out of the question. It took all the people they had to make accommodations for the Swarm’s heptad. They would dock it in the middle of the Stack, lock it in place with a few cables, and hope it stayed attached during the subsequent maneuvers. They would keep the hatch closed. The eleven members of Aïda’s group would simply stay in their arklets until it was all over. The justification was that they’d be safer there. The true reason was that no one wanted cannibals in the shared spaces of Endurance.

  The big project for Dinah, and for the small remnant crew of robot jockeys who tended to work with her, was getting ready to dump Amalthea itself.

  On one level the idea seemed nearly unthinkable. They had, however, been planning to do it for a long time. Endurance’s final series of maneuvers would have to be accomplished quickly, deftly, in an environment where the rocks tended to be much larger than the ones that made up the Hard Rain. In a sense, the boulders up there were the mothers of the tiny fragments that had destroyed the surface of Earth. Every time two of them collided, a few chips exploded outward from the impact, and a fraction of those ended up falling into Earth’s atmosphere. The Hard Rain would continue until all of them had been reduced to sand and organized themselves into a neat system of rings. In any case, Amalthea’s ability to protect Endurance from the impacts of baseball- or even basketball-sized rocks was of little interest in a place where a rock the size of Ireland would be considered unremarkable. The entire ship, Amalthea and all, would be a bug on the windshield of such a thing. Their only way to stay alive, once they had entered the slipstream of the main debris cloud, was to maneuver around the big rocks and hope that they didn’t get hit by too many little ones during their dash to Cleft. And that sort of maneuvering was impossible as long as Amalthea—which weighed a hundred times as much as the rest of Endurance—was attached to her.

  In addition to Amalthea, Endurance was still burdened by a considerable mass of ice, which they had hoarded both as shielding and as propellant. It weighed a significant fraction of what Amalthea weighed. But unlike Amalthea, they could burn it. The basic plan was to split most of that ice into hydrogen and oxygen, then burn it during the final speed-up at apogee. Over the course of a few hectic minutes, Endurance would expend most of her water weight by using it as propellant. Between that and the ditching of Amalthea, her total weight would drop by a factor of more than a hundred in the course of an hour. After that, she truly would be like a bug flitting around in heavy traffic, dodging big rocks and taking hits from little ones until she made her way to Cleft.

  In any case, they had anticipated all of this long ago. Dinah and the other surviving members of the Mining Colony had had three years in which to reshape Amalthea from the inside. Seen from the forward end, the asteroid looked the same as ever. Internally, however, most of it had systematically been whittled loose. In a sense the process had begun around Day 14, when Dinah had set one of her Grabbs to work carving out a niche in which she could stash her electronic parts. Since then it had proceeded in fits and starts. They’d moved a lot of metal in order to make a storage bay for Moira Crewe’s genetic equipment, whi
ch in a sense was the raison d’être of everything else they had done in the last three years. Once that was safe they had begun tidying up, enlarging the pockets of protected space, breaking down walls, and joining them together into a cylindrical capsule scooped out of Amalthea’s back, called the Hammerhead for the way it lay athwart the top of the Stack.

  Thanks to a lot of ticklish work by robots in the last couple of years, the Hammerhead was now separated from the rest of Amalthea—99 percent of the asteroid’s bulk and mass—by walls of nickel-iron that were only about as thick as the palm of a person’s hand. This still made them extremely massive by the standards of space architecture—more than strong enough to hold in atmospheric pressure and to stop small bolides. But the additional tens of meters’ thickness of metal beyond those walls was now physically detached from the hand-thick walls, and could be pushed away by a puff of compressed air.

  Or rather, given the disparity in masses, Endurance could be pushed away from it. Most of Amalthea would stay where it was, and the radically lightened Endurance would back away from it like a grasshopper springing off a bowling ball.

  When the time came, they would have to shatter the remaining structural links with demolition charges. One of Dinah’s duties on the last lap, as they soared back up out of Earth’s gravity well toward their rendezvous with Cleft, was to go out in a space suit and inspect those charges, make sure they were packed in where they needed to be and wired up correctly. She was the only person remaining who knew much about explosives, and so she was the only person who could be sure. Just another of those duties that would have left her half paralyzed six years ago and now seemed routine.

  “I KNOW THAT WE DON’T NEED ANY MORE BAD NEWS,” DOOB ANNOUNCED to the 25 percent of the human race seated around the conference table in the Banana, “but here’s some for y’all.”

  No one said anything. Nothing could make much of an impression on them at this point.

  Forty-eight hours remained before apogee, the final burn, the ditching of Amalthea, the dash to Cleft. If Aïda’s transmission of half an hour ago was to be believed, the remnants of the Swarm would rendezvous with them shortly before all of those things happened.

  “Let’s have it,” Ivy said.

  “I’ve been keeping an eye on a certain sunspot,” Doob said. “Kind of angry looking. Well, about twenty minutes ago it kicked out a huge flare. Not the biggest we’ve ever seen, but pretty big.”

  “So, we’re expecting a CME?” Ivy asked.

  “Yeah. Somewhere between one and three days from now. I’ll provide better estimates as soon as I have more data.”

  They all considered it. Until recently, coronal mass ejections had been of little concern to them except insofar as they made them wonder how the people of the Swarm were getting along. As for the tiny faction that had split away on Red Hope, it was assumed that they had long since been wiped out by one or more of the hazards and calamities that had inflicted such a death toll on the Swarm. For the crew of Endurance, Amalthea and ice had provided plenty of shielding. Even the comparatively thin walls of the Hammerhead would protect anyone inside of it against the kind of radiation that would envelop them in a CME. But Endurance’s flanks were now exposed. Grabbs had been at work carrying away the last of the ice and feeding it to the splitters to be made into rocket fuel. They were storing the cryogenic gases anywhere they could now, pumping them into empty arklet hulls and disused modules. Parts of the Stack were seeing the light of day for the first time since the Break.

  “It’ll affect our operations,” Ivy concluded. “But this is a drill we know pretty well. Take amifostine. Get your space walks finished before it hits. We should make arrangements to accommodate all nonessential personnel in the Hammerhead. Some of us will have to be down farther in the Stack, but we’ll have storm shelters ready.”

  “What about . . . them?” Michael Park asked.

  “They are a problem,” Ivy admitted. “They’re in plastic arklets. They’re gonna get cooked. Even if they have any amifostine left, even if they have enough water to fill their storm shelters, they’re going to take damage. Ethically, we need to bring those eleven aboard Endurance and get them to safer places.”

  “The original plan was to send three people out on an EVA to lock down their heptad, make it fast to the stack, so that we could maneuver,” said Zeke Petersen. Of all the crew of Endurance he looked the most similar to his pre-Break appearance. He was skinnier, of course, with a bit of gray around his temples, but his health was still good, and he’d managed to keep his electric shaver working, so he was beardless. After the deaths of Fyodor, from an accident, and Ulrika, from a stroke, Ivy had designated him Endurance’s second in command.

  He referred to the fact that Endurance was about to shed 99 percent of her mass, which meant that the same complement of engines, producing the same thrust, could make her accelerate a hundred times faster. The gee forces still would not be extreme—well within the range that humans could tolerate—but the maneuver would impose stresses on the ship’s frame the likes of which it had never experienced before. This was another of those eventualities that they had foreseen long ago and built into Endurance before covering her with ice.

  So most of Endurance came prerigged for higher acceleration. Provided that nothing had broken during the last three years, she’d hold together, albeit with a lot of loose junk sliding around her interior spaces the first time they hit the throttle.

  They hadn’t planned, though, for the last-minute addition of the heptad from the Swarm. This was awkward. It would be connected to the Stack by a docking port, which wasn’t designed to take a lot of mechanical strain. It was heavy, because Aïda and her crew had crammed it full of supplies and strapped even more to the outside of it. For the same reason, Ivy didn’t want to just ditch it—they could use those supplies. So the plan had been for three spacewalkers to greet the heptad and lash it into place with cables as soon as it arrived.

  “We’ll just have to see what we can do with robots,” Ivy said, looking toward Dinah and Bo. “Just about everything we have out there is Grimmed, correct? So it can operate even in heavy radiation.”

  “We’ll get ready for that,” Dinah agreed.

  “As soon as the heptad docks, the robots get to work,” Ivy said, “locking it down as best we can. We open the hatch and get the eleven down through the hamster tubes as fast as possible—they’ll have no protection whatsoever while they’re moving through those tubes. We’ll have storm shelters waiting for them. They can climb into those and ride out the rest of the journey. The flight crew will operate out of the Hammerhead.”

  THE NEXT TWO DAYS REMINDED DINAH OF THE NEW CAIRD EXPEDITION, in that there was a lot to do but no way to affect the schedule. They were at the mercy of astronomical events. Part of her wanted to pull all-nighters until this thing was finished, but she knew she had to be well rested and fed when it counted, and so she forced herself to eat and sleep on the usual schedule. When awake, she worked on preparations for the arrival of the heptad, pre-positioning Grabbs near the docking port that it would use, connecting cables to suitable anchor points, tuning up the programs that the robots would execute when it came time to snap the other ends of those cables onto the heptad, rehearsing them to check for places where the cables might snag.

  The timeline gradually came into clearer focus. Aïda sent out a sharp request for amifostine and water to fill their storm shelters. Of course, it was impossible for Endurance to comply. They had plenty of both, but they had long since cannibalized all of their MIV parts and so they had no way to transport them.

  Aïda decided to roll the dice by committing all the water she had left to a large burn that would bring them to the rendezvous with Endurance a little earlier than they’d originally planned. Meanwhile Doob’s space weather forecast was becoming more precise; he had a better idea now of when the radiation storm would break over them and thought that the timing was looking favorable. The heptad might arrive before things g
ot bad. It might be okay after all to have some spacewalkers out there to cooperate with Dinah’s robots.

  Dinah didn’t know how to feel about that. The schedule had been accelerated, and now she had to take into account the vagaries of human spacewalkers. If Aïda’s heptad docked soon enough, Doob pointed out, they might be able to transfer many of her heavy supplies through the docking port into the Stack and thereby reduce the awkward strains that all of Dinah’s cables were meant to take up.

  Meanwhile Ivy and Zeke, the pilots, were addressing similar last-minute convolutions in their mission plan. As they got nearer, they got better information about the part of the debris cloud that they’d be maneuvering through. They could clearly make out Cleft’s radar signature, as well as those of many other big rocks that traveled in its vicinity. A clutter of faint noise and clouds on the optical telescope gave them data about the density of objects too small and numerous to resolve. All of it fed into the plan.

  Doob looked tired, and nodded off frequently, and hadn’t eaten a square meal since the last perigee, but he pulled himself together when he was needed and fed any new information into a statistical model, prepared long in advance, that would enable them to maximize their chances by ditching Amalthea and doing the big final burn at just the right times. But as he kept warning Ivy and Zeke, the time was coming soon when they would become so embroiled in the particulars of which rock was coming from which direction that it wouldn’t be a statistical exercise anymore. It would be a video game, and its objective would be to build up speed while merging into a stream of large and small rocks that would be overtaking them with the speed of artillery shells.

  The details, the sudden distractions and improvisations, piled up and thickened in a way that made Dinah think of a sonic boom on Old Earth: the onrushing stream of air thickening and solidifying in the path of the airplane, turning into a barrier that must be broken through or succumbed to. They seemed to break through it at the point when Michael and two other spacewalkers pulled on their cooling garments, much patched and mended, and donned their space suits. Doob had the incoming heptad on radar, then on optical, and verified that it was on course to rendezvous with them. This meant, of course, that the heptad was on a collision course with Endurance; the difference between a collision and a rendezvous was the final burn of the heptad’s thrusters that would slow it down at the last minute and bring its params into nearly perfect synchronization with the larger ship’s. Endurance herself, still burdened with Amalthea and with many tons of stored propellant, had next to no maneuverability, and so it would all be up to Aïda, or whoever was at the controls of her heptad.