Seveneves - Страница 90

She went “up” into the common room and found Jiro, as usual, lost in contemplation of arcane plots on his computer screen, reflected in miniature on the lenses of his bifocals. During the year he had been in space, his prescription had changed, and so he had been the first consumer of the optical lens-grinding machine that had been sent up and installed in Izzy. Without it, much of the Cloud Ark’s population would gradually have been rendered nonproductive as their eyeglasses were broken or wore out. It was a military machine capable of making glasses in one style, and one style only. At some point a few years down the road, everyone who needed glasses would be wearing this style. It was interesting to contemplate how many decades or centuries would have to go by before the population had grown, and the economy developed, to the point where it could support an eyewear industry with different styles.

He looked up at her through the milky reflections. “I let you sleep,” he said. “Your robots seem to be working fine. There is nothing to do until I finish these calculations.”

“And then what?”

“We have to eliminate the last of the tumbling,” Jiro said, “before we make the final braking burns.”

For Dinah, that was all clear. Ymir was in a safe orbit now and would not fall into the atmosphere anytime soon. But she was still going much too fast, and way too high, to rendezvous with Izzy. They needed to finish the execution of the same plan they’d had all along, which was to make one or two more braking burns as Ymir passed through her perigee, slowing her down to the point where a rendezvous with Izzy was feasible. This required getting the nozzle pointed forward again, and keeping it that way.

“How much damage was done to the—”

“They were destroyed,” Jiro said. “We have two remaining.” They were both referring to the thruster packages, embedded in the ice, that would normally have been used to manage the shard’s attitude. “It is fine. It was necessary,” Jiro added, almost as if worried that Dinah would think poorly of him for criticizing the decisions made by a dead commander.

“Can more be sent out from—”

Jiro nodded. “It is possible to assemble a MIV that could rendezvous with us and assist with the problem. Just in case my idea does not succeed. But since our radio link was lost with New Caird, we cannot coordinate this.”

“And what is your idea?”

“We can use your robots to alter the shape of the nozzle exit,” Jiro said. He held up one hand like a blade, pointed toward the ceiling, and then flexed his knuckles slightly, indicating a shallow bend. “Make it asymmetrical.”

“Like a scarfed nozzle?”

“Exactly. When we fire the main propulsion it will give us an off-axis thrust. If the scarf is oriented correctly, it will have tremendous control authority.”

“Maybe too much,” Dinah said. “We’ll end up overcorrecting.”

“One thing at a time,” Jiro said. “We scarf the nozzle, we do a little correction, we scarf it the other way, we kill the rotation. It might take several repetitions. It can be done. I have been modeling it.”

Dinah pulled herself into position before her triptych of flat-panels, and began opening windows, checking on the activities of her menagerie of robots: some sunning themselves on the outside to soak up power, others sipping juice from the reactors, some mining propellant for the next burn, others mending the nozzle. The latter group, mostly Nats, would be responsible for the nozzle-sculpting program. Until now, having an asymmetrical nozzle, delivering thrust at an off angle, had been a problem to be avoided, not a feature to be encouraged. Jiro had emailed her some diagrams of what the nozzle bell would need to look like. The alterations were surprisingly minor. In an engine that produced that much power, a little bit of off-axis thrust went a long way. “When’s our next perigee?” she asked.

“We just went through one. So, about eight hours from now.”

THE PARAMOUNT DUTY OF THE CLOUD ARK’S COMMANDER — SO IMPORTANT that Markus had broken character and described it to Ivy as “sacred”—was to stay on top of the Bolide Scan, which was a feed of information synthesized out of all of Izzy’s long-range radars and optical telescopes. A disproportionate number of GPop members devoted their lives to managing this, or to maintaining the equipment used to produce it. Because the stream of data was continuous, it needed to be broken down, for the consumption of someone like Markus or Ivy, into reports that showed up on their screens at regular intervals. A Triurnal Bolide Scan was issued at the top of each shift: dot 0, dot 8, and dot 16. Ivy read one of them when she woke up, another in the middle of her “afternoon,” and the third just before going to sleep. Each of these summarized what was known about bolides that might come near them during the next eight hours, and made recommendations as to what maneuvers the Cloud Ark should execute in order to avoid them. Typically they made small burns several times a day for this purpose. The policy was “default go,” which meant that the maneuver would be promulgated to the Cloud Ark via Parambulator, and carried out automatically, unless the commander vetoed it. The only reason this was ever likely to happen was in cases where two dangerous rocks were headed their way at about the same time and they needed to make a decision. Such events had occurred twice during the Hard Rain so far, but they had been simulated and war-gamed hundreds of times before that. The name of the game was to avoid getting cornered.

To be detected eight hours in advance, a bolide had to be pretty big. Smaller ones came along all the time, and weren’t picked up on the radars until minutes or even seconds before collision. Accordingly, smaller reports were issued at the top of each hour, listing all noteworthy rocks that had been detected during the last sixty minutes. This covered most of them, so the commander — or whoever covered for her while she was sleeping — could discharge most of her responsibilities in re the Bolide Scan by dropping everything else she was doing at the top of each hour and reading it. From time to time, however, they would become aware of a “hot rock” or “streaker” that had surprised them by coming in from a weird angle, or at unusually high speed, and then the commander would be notified immediately so that an alert could be issued and evasive action could be seen to. The Streaker Alerts combined elements of the small-town midwestern tornado siren with the red alert from Star Trek. All sleeping people were awakened, all nonessential personnel were evacuated from the larger tori, which were considered most vulnerable, and hatches were closed between different sections, in case of a breach. Similar precautions were taken by the Arkies. Arklets were, of course, more vulnerable to bolide strikes, but they were also more maneuverable. As the hot rock drew closer and its orbital parameters were determined more precisely, the data would be fed to Parambulator. Any arklets in danger of being hit would be identified, and a collective solution would be calculated that would enable them to move into safer trajectories without banging into anyone else. These events happened, on average, between one and two times a day, but as always the devil was in the statistical details. They had once gone three days without a single streaker. On another occasion they’d had five of them within a twelve-hour period. The first of these events had caused an upwelling of chatter on Spacebook to the effect that the powers that be were overstating the threat in order to cow the Arkies into submission, and the second had generated a hard-hitting blog post from Tav Prowse calling the GPop on the carpet for systematic incompetence.

It was in the wake of such an alert, while cleaning up her desktop of postaction chatter, that Ivy’s attention was drawn to a post that had just come up on Tav’s blog: an interview with Ulrika Ek.

“Ulrika has a lot to learn about bloggers” was Ivy’s verdict, after she’d finished reading it. She shook her head. “You’d think she of all people would know — she’s been through PR training.”

These remarks were delivered to a Banana that had been slowly repopulating itself, during the last few minutes, with people who had been called away on other duties during the Streaker Alert. Tekla was the last to arrive, bringing Tom Van Meter and other members of Markus’s security detail in her wake. Luisa and Sal were already present in the room. Doob had just texted his regrets, explaining that he needed to crunch some numbers about what had just happened.

“She probably dropped her guard,” Luisa suggested, “thinking she was just chatting informally.”

“You’ve read it then?”

“I scanned it.”

“Referring to what?” Tekla asked.

“Ulrika made a few off-the-cuff remarks about swarm theory, and which strategies we might wish to pursue in the future, and Tav is blowing them up into a cause célèbre,” Ivy said.

“What if anything would you like to do about it?” Sal asked.

“Nothing,” Ivy said. “Look, the longer this thing with Ymir continues, the more anxiety people have about the Big Ride. Every time a hot rock comes in it juices up that anxiety for a little while. Well, either it’ll work or it won’t. If it doesn’t work then we have very little choice anyway — we have to Dump and Run.”

Sal nodded. “But if it does work, it’ll change everything about the way people think.”