Seveneves. Neal Stephenson

smart chain.”

      This little digression into nineteenth-century physics turned out to be one of those “one step back, five steps forward” sorts of trades. It was the work of a few minutes to concatenate four more Siwis onto the existing chain, then turn off all the motors except a few that she used to fashion a U-shaped bend. Applying tension to one end of it caused the Knickstelle to propagate just as in Rhys’s demonstration, so that the end of the chain whipped lazily around the entire circumference of the Luk. Several attempts were required before the grappler at the end of the chain was able to snag a handhold on the far side, but then the Luk was securely captured in the chain’s embrace. Grabbs could scuttle along it carrying the ends of cables anchored to other parts of Amalthea, or Izzy, and thus the Luk was gradually ensnared in a loose web of hardware that Dinah used to draw it away from the position where it had been anchored, and pull it up snug against the module containing Dinah’s shop. As it came closer, the vague nimbus of white light thrown against the Luk by the LED in the airlock narrowed and sharpened, and was finally all but snuffed out as the big balloon enveloped the protruding stub of the airlock chamber. The airlock was now poking into the nested layers of the Luk like a finger prodding a balloon.

      Even after the success of the whip-cracking gambit, this took most of a day. Rhys drifted off, as was his habit. Bo, the Mongolian cosmonaut, slipped into Dinah’s shop, observed silently for a couple of hours, and then began finding ways to make herself useful. She learned how to use the data glove and the mouse-and-keyboard interface just by watching Dinah, and by the end of the day was piloting Grabbs around, and manipulating Siwis, like an old hand.

      Margie Coghlan showed up to watch the final preparations. She was an Australian physiologist who had been sent up to Izzy a few months ago to study the effects of spaceflight on human health. Dinah had always found her a little brusque, but maybe that was just an Australian thing. She brought with her a box of medical supplies and surgical equipment. All the astronauts on the ISS had medical training. Dinah and Ivy had done their time working in Houston emergency rooms stitching up trauma victims and setting bones. But Margie was the best.

      “Not exactly what you signed on for,” Dinah said.

      “None of us is getting what we signed on for,” Margie observed.

      “With the possible exception of Tekla,” said another voice. Ivy’s. She was not in Dinah’s shop—that was full now with Dinah, Bo, and Margie—but she was in the adjacent SCRUM.

      “Ivy, you ready to set another record?” Dinah asked.

      “Ready to try,” Ivy said.

      This was Q code for the number of women on the space station at one time. The old record had been four, set in 2010. They had tied it months ago when Margie and Lina had come up to Izzy, joining Ivy and Dinah. They had broken it when Bo had turned up in the Soyuz launch three weeks ago. Tekla would make six, if they could only get her through the airlock.

      Or the number might drop back if this went wrong.

      “Bo, thanks for helping. You should probably go out with Ivy.”

      “Good luck,” Bo said, and, pushing off from the inner hatch of the airlock, drifted across Dinah’s shop and out through the hatch into the SCRUM, where Ivy hovered, waiting.

      “Everything sealed up behind you?” Dinah asked, more out of nervousness than anything else. It was out of the question that Ivy would get that wrong. Since the breakup of the moon, they’d intensified their precautions anyway, keeping the various modules of Izzy separated by airtight hatches wherever possible so that the perforation of one module by a bolide wouldn’t lead to the destruction of the whole complex.

      Ivy didn’t answer.

      “You know what to do with that hatch if this all goes sideways,” Dinah went on.

      “You talk a lot when you’re nervous,” Ivy said.

      “I concur,” Margie said. “Are we going to do this or not? That woman might be asphyxiating out there.”

      “Okay. Giving her the signal now,” Dinah said.

      In the space program that she had dreamed of when she’d been a little girl with a “Snoopy the Astronaut” poster on the ceiling of her shack in the hinterlands of South Africa, or watching live feeds from the space station on satellite TV in western Australia, the signal would have been a terse utterance into a microphone, or a message struck out on a keyboard. But what she actually did was drift over to her little window and peer through fourteen layers of milky translucent plastic at Tekla, almost close enough to reach out and touch, and give a thumbs-up.

      Tekla nodded and held up a small object next to her head. It was a folding knife with a belt clip and a lanyard, which she had prudently wrapped around her wrist. Using one thumb she snapped its serrated blade open.

      Dinah nodded.

      Tekla nodded back, then drifted out of view, headed toward the airlock.

      “Here she comes,” Dinah said.

      She had already sized Margie up as a woman of some physical strength. She was stocky, but in a powerful rather than a flabby way.

      Dinah got a grip on the mechanical linkage that would swing the outer hatch of the airlock closed. “Brace me,” she said.

      She was worried about all that plastic. Shreds of it were certain to get caught in the hatch’s delicate seal.

      The principle was simple enough. She’d run through it in her head a hundred times. If Tekla cut a slit, a few inches long, through the innermost layer of the Luk, air would rush out into the space between it and the next layer, which was at a lower pressure. If Tekla put her head and shoulder into that slit, she’d become like a cork in a champagne bottle, and the pressure would try to force her out. If she then cut a slit through the next layer, and the next, and the next, a wave of pressure would build up behind her and spit her out like a watermelon seed. And as long as she kept aiming for the white LED on the airlock’s inner hatch, she would be projected into that airlock.

      At that point she’d be naked and unprotected in the middle of a jet of air that would be exploding away from her into the vacuum. And at that point—

      There was a whoosh and a meaty thunking impact.

      “Jesus Christ, I think that was it,” Margie said.

      “She is out,” Bo confirmed. Bo, out in the next compartment, had a tablet on which she was watching a video feed from a nearby Grabb. “I mean she is in the airlock.”

      Dinah hauled on the handle, swinging the outer hatch closed. Her body, in accordance with Newton’s Third Law, moved in the opposite direction, stealing her force, but Margie’s arms caught her in a bear hug and pushed back—Margie had found a way to brace herself.

      Bo gasped. “You are smashing her foot!”

      “Oh, shit.”

      “Her foot is sticking out.”

      “Dinah,” Ivy said, “you have to open the hatch a little, her foot’s caught.”

      Dinah relaxed her arms. What if Tekla was unconscious? What if she was unable to draw herself up into the fetal position they’d shown her in that photograph?

      The change in Bo’s and Ivy’s tone told her otherwise. “She’s in!” Ivy exclaimed.

      “Close the hatch, close it!” Bo was shouting.

      Dinah swung the handle all the way around and snapped it into its locked position. It didn’t feel quite right, but at least it was closed.

      Meanwhile Margie was actuating the valve that let air into the airlock. This was supposed to be a gradual process, but she just let it go explosively, with a sudden movement of the air that tugged at their diaphragms and popped their ears.

      “Blood is coming out,” Bo said dully. “Leaking out of the hatch.”

      “Fuck!” Dinah said. Because that meant