Seveneves. Neal Stephenson

Чтение книги онлайн.

СКАЧАТЬ as far as Sean is concerned. Izzy’s orbit is angled with respect to the equator. It has to be that way so Baikonur can launch to it—Baikonur is as far north as Seattle. But when you are doing interplanetary stuff, which is what Sean has in mind—basically, whenever you want to get out of low Earth orbit—you want to be in an orbit that’s closer to the equator. Because that’s pretty much where the rest of the solar system is—including the big chunk of ice that Sean wants to grab and bring back here.”

      “Ymir,” Luisa said, pronouncing it as she’d heard Sean do: ee-meer. A word from Norse mythology referring to primordial ice giants. Sean’s code name for a particular hunk of ice that his project had identified, and that he meant to bring back.

      “Yeah. Not an official name. Sean doesn’t divulge much.”

      “And how do you get from one to the other?” Luisa asked. “From a geocentric orbit—that’s what we’re in now, right?”

      “Yes.”

      “To a heliocentric one?”

      “Well, first he’s going to have to do a plane change—from the angled Izzy orbit we’re in now, to one closer to the equator. He’ll rendezvous with the rest of his gear.”

      “Why didn’t they just send everything up here?”

      “Plane-change maneuvers are expensive. It’s not too bad if the only thing plane-changing is Sean and Larz and a Drop Top, but it would be ridiculously wasteful to send the whole expedition package up here only to plane-change later.” Dinah didn’t mention the other reason, which was that the biggest part of Sean’s package was so screamingly radioactive that it couldn’t be allowed anywhere near Izzy.

      “Okay. But we’re still talking geocentric, right?”

      “Correct, we’re still just a few hundred miles high.”

      “So, how do they get from the rendezvous point to a heliocentric situation?”

      “There’s a bunch of different ways to do it,” Dinah said, “but if I know Sean he’ll go through the L1 gateway.”

      “I have no idea what that is,” Luisa said, then finally lost a fight to suppress a giggle. “But once again I feel that I have been dumped into a sci-fi movie when I hear people around me talking like that.”

      “Doc Dubois probably covers it in that video,” Dinah said, nodding at Luisa’s tablet, “but the gist of it is really straightforward.” Looking around, she spied a mesh bag stuffed with clothing. She pulled it out of its niche and let it drift in the center of the cabin. “The sun,” she said. Now patting herself down, she found in her pocket a small plastic bottle of pills—antinausea medication she had fetched for one of the new arrivals. She opened it up and pulled out the ball of cotton stuffed into its top, then let the cotton drift in the air a little closer to Luisa. “The Earth, in its heliocentric orbit.” The sick crew member would have to wait for a few minutes. Dinah carefully tapped a few pills free from the bottle’s open neck and let them float for a moment while she pocketed the bottle. Then she began to arrange the pills in the space already staked out by the “sun” and the “Earth.”

      “Asteroids?” Luisa guessed.

      “These are more like abstract mathematical points,” Dinah said. “They’re called the Lagrange points, or the libration points, and there’s five of them around every two-body system. Always in the same basic geometry. Two of them, L4 and L5, are way off to the sides. I’m not going to try to show you those because we don’t have room. But the other three are all along the line running between the sun and the Earth.” She pushed off and glided to the far side of the “sun” and stationed a pill there, exactly on the opposite side from where the “Earth” was. “This is L3, very far away, invisible to us because the sun’s always in the way, not that useful.”

      Gliding back toward the hovering cotton ball, she stopped herself against a bulkhead and placed a second pill out beyond it. “This is L2, outside of Earth’s orbit.” Finally, she put a pill in between the “sun” and the “Earth” but much closer to the latter. “And this is—”

      “L1, by process of elimination,” Luisa said drily, and laughed. “You space people love to count down, I know your ways.”

      “It’s where the gravity of the sun and the Earth balance,” Dinah said, “and people sometimes call it a gateway because it’s an easy place to effect a switchover between a geocentric and a heliocentric orbit. This even happens naturally sometimes: an asteroid in a heliocentric orbit will wander close to L1 and get captured by the Earth. Or, going the other way, there’s a case where an Apollo upper stage orbiting around the Earth passed near L1 and got ejected into a heliocentric orbit for a number of years. Later it came back through the same gateway—only to get ejected again.”

      Luisa nodded. “Like changing from the D to the A train at Columbus Circle, in New York terms.”

      “A lot of people have used the analogy of a switching yard or a train station to describe it, yeah,” Dinah said.

      “So you think Sean and his crew are headed that way.”

      “Once they get all their—” Dinah paused.

      “Their shit together?” Luisa suggested.

      “Thank you, yes,” Dinah said with a smile. “They need to get to a higher orbit than we are in now if they are going to reach L1. That means burning their engines, expending a lot of fuel in just a few minutes, and then coasting for a few weeks. They’ll have to pass through the Van Allen belts and soak up a lot of radiation. No avoiding it, unfortunately. L1 is four times farther away than the moon.”

      “Or what used to be the moon,” Luisa said under her breath.

      “Yeah, which means that in a few days Sean and his crew are going to be farther away from Earth than any humans who have ever lived. When they get to L1—which will take five weeks—they’ll have to execute another burn that will switch them from the D to the A train—place them into a heliocentric orbit. And from there they can plot whatever course is going to get them to the comet.”

      Luisa had gotten a bit sidetracked by the first part of what Dinah had said. “Farther away from Earth than anyone in history,” she repeated. “I wonder if there might be a certain feeling of jealousy at work in Fyodor’s reaction, knowing that after all the time he has spent in space—”

      “Some rich whippersnapper is going to show up and make his accomplishments look minor,” Dinah said, nodding. “Could be. Fyodor’s got the Russian granite face, you can’t tell what’s going on inside.”

      “Anyway,” Luisa said, “they go and fetch the big ball of ice and then reverse all of those steps to come back to what by that point will hopefully be the Cloud Ark.”

      “Not exactly,” Dinah said. “And that’s where things get interesting.”

      “Oh, I thought they were already pretty interesting!” Luisa said.

      Dinah was limited, here, in what she was allowed to say. “Maneuvering a space vehicle—which is designed and engineered to be what it is—around the solar system is one thing. Moving a huge raggedy-ass ball of ice is another.”

      “It’s СКАЧАТЬ