“All of the arklets?”
Zeke swallowed. “No. She doesn’t make a big enough bow wave to shield all of the arklets. Unless they fly so close together that Parambulator goes nuts.”
“This is the part of Markus’s plan that I can’t understand,” Julia said. “What is to happen to all of the arklets that are not afforded the privilege of nestling into Amalthea’s wake?”
“I don’t know all the details of the plan,” Zeke said. “It is fluid.”
“Meaning, it’s not really a plan,” Julia said.
“It depends on when Ymir gets back. What kind of condition she’s in. How much ice she has. Then we’ll make a plan.”
“And is that to be a dictatorial process? Under the, whatever it’s called—the martial law thing?”
“PSAPS,” Camila said.
Zeke shrugged. “I don’t think Markus is going to put it up for a vote. He’ll get together with his brain trust and they’ll decide.”
“Why bother consulting the brain trust?” Julia asked, as if the idea were a fascinating novelty.
“To bring in different perspectives . . . make sure they’re not missing anything.”
“Are there any Arkies in this brain trust, or are we expected to meekly accept its verdict?”
Zeke was flummoxed. Had he been given the ability to rewind and replay the conversation, he would see that he’d been outmaneuvered. Lacking that perspective, he was tongue-tied for now.
Julia wasn’t. “I ask only because I’ve been getting to know a lot of Arkies. I have nothing else to do. No duties. No applicable skills. I find that many of them crave a bit of society. It’s a natural human need, just as much as sleep and exercise. So I talk to them—in person here on our little heptad, or through the channels you mentioned, the Spacebook and the Scape. These young people find it at least a novelty to have a conversation with a lonely and bored ex-president. My point being, Major Petersen, that our system worked. The Casting of Lots and the training camps produced the brightest collection of young talent it has ever been my privilege to encounter. They are brimming over with energy and ideas. These are the scarcest resources in our universe right now—scarcer than water, scarcer than living space. And as such I’d consider it a shame if their energy was wasted and their ideas were not taken into account by whatever smoke-filled room Markus assembles to make his plan—assuming he even survives what sounds to me like a somewhat harebrained endeavor.”
THE CREW OF THE ORIGINAL JAMES CAIRD HAD USED CELESTIAL NAVIGATION to find their way across hundreds of leagues of stormy seas to the coast of South Georgia Island. The crew of the New Caird would have to do something similar. It was easier for them. The navigator on James Caird had had no choice but to await breaks in the ever-present cloud cover and snatch observations when he could, comparing them against a mechanical chronometer that he hoped was still telling true time. New Caird had better timepieces and a better view of the sky. In place of a sextant, they had a device consisting of a wide-angle lens and a high-resolution image sensor that could tell what direction it was aimed in just by comparing what it saw to an astronomical database stored in its memory. So they knew precisely how they were oriented in space, and how that orientation was shifting as the giant shard of ice to which they were attached progressed through the inexorable mathematics of its long ellipse. That, combined with direct measurements of Earth’s position, enabled Markus to calculate the parameters of their orbit and to reckon, with precision that grew each time he rechecked the figures, exactly how low they were going to go. Whenever Izzy was on their side of the planet, which was about half the time, they were able to get the latest figures from Doob concerning the expansion of the atmosphere.
It was in combining those two sets of figures that pure Newtonian mechanics began to break down. For, in a traditional calculation of a space vehicle’s trajectory, one assumed no atmosphere and no extraneous forces resulting from it. But there was now no denying that Ymir would be going low enough to scrape the air. At a minimum, this meant it would experience some drag that would throw it off the course that Sean Probst had laid in. As these things went, drag wasn’t that difficult to calculate. Its effect on their course could be estimated. But because the ice shard wasn’t a symmetrical body, coming in straight, it was also going to generate some lift. Not a lot of lift—nothing like an airplane wing—but some. If that lift got aimed in the wrong direction it would make Ymir veer downward, like a stricken airplane going into its death spiral. But if they aimed it up, it would ease their passage by pushing them away from the Earth into an altitude where air was thinner. They would lose the benefit of lift then and drift back downward, but as the air got thicker, the lift would resume and push them back up. They might skip off the atmosphere several times during the hectic half hour when they were slingshotting around the world. The results would have been difficult to predict even if Ymir had been a traditional vehicle with a fixed and regular shape. But the shard was irregular. They didn’t have time to measure it and to feed the data into an aerodynamics simulator, so they could only guess how much lift it was going to produce. And when its leading edge and its underside began to plow through the air—even though the air might be so thin as to be indistinguishable, for most purposes, from a vacuum—it was going to heat up. Steam would rise from it, producing some amount of upward thrust, and its shape would change. So even if they had been able to simulate the shard’s aerodynamics, its lift and its drag, those numbers would quickly have become wrong during its first encounter with the upper air.
Compared with all of those complexities, the fact that Ymir would be flying backward while operating a damaged, experimental nuclear propulsion system at maximum power seemed like a mere detail.
Faced with so many imponderables, a well-managed aerospace engineering project would have called a halt to all further work and devoted several years to analyzing the problem down to its minutest detail, exposing pieces of ice to the blast of hypersonic wind tunnels, building simulations, and war-gaming possible alternative strategies. But by the time Markus understood the general shape of the problem, they had twenty-four hours remaining to perigee. The tangerine Earth had grown to the size of an orange. No power wielded by humans could prevent Ymir from passing around it and scraping the atmosphere. They couldn’t even ditch. New Caird, detached from Ymir, didn’t have enough propellant in her tanks to materially change her course and would end up going on the same ride anyway. So Markus made a reasonable guess as to what would be a good angle of attack—the orientation that Ymir would adopt vis-à-vis the atmosphere—and initiated a program of thruster firings that, over the course of half a day, swung the ponderous shard around into the position he deemed best.
Ymir’s “stern” was now aimed in the direction of movement, the huge mouth of the nozzle aimed forward so that it could make the all-important braking burn. But she was now twisted about her long axis in such a way that New Caird, still docked up near the “bow,” and projecting from the side of the shard at approximately a right angle, was on the zenith. This meant that during the passage of the high atmosphere her view of the Earth below would be blocked by Ymir, the nozzle of her engine pointed “up” toward the stars. Firing that engine would therefore tend to rotate the bow downward and the stern up, an attitude likely to produce more lift and help get Ymir out of trouble. Were the shard to tumble the other direction, it could end up in a position that would yield much more drag and much less lift, pulling the whole contraption deep into the atmosphere. In effect New Caird had been reduced to the status of a small attitude control thruster. It was a thruster that could only push in one direction, and so Markus had picked out the direction most likely to be useful if things began to go sideways. Vyacheslav would ride it out in New Caird’s pilot’s seat, from which he would enjoy an arm’s length, tunnel-vision view of some dirty, five-billion-year-old ice. He would wait for a verbal command from Markus, ensconced in Ymir’s common room, to fire New Caird’s main propulsion if needed.