“The principle is simple,” Bud said. “It’s a cannon driven by electromagnetism. You wrap your cargo in a blanket of iron—which we can reuse, by the way. You put your cargo pellet on the rail. The magnetic field, generated from that blockhouse over there”—he pointed at a nondescript dome—“then pulses through the solenoid, and your pellet is pushed along the track.” The changing magnetic field induced electric currents in the iron blanket, and the currents then pushed against the magnetism: “It’s just the principle of the electric motor,” Bud said.
As he spoke he pressed his hand against the small of her back with a pleasing familiarity.
She prompted, “And after thirty kilometers of accelerating—”
“You have escape velocity, without the need for any of that messy business of rockets and launch pads and countdowns. And then you can go wherever you want—fall all the way down to Earth, even.”
“It’s really a fantastic conception,” she said.
“Yeah. But like most of what we do on the Moon, people figured it all out long before they had a chance to get here to build it. The idea of an electromagnetic launcher dates back to the 1950s, I think. A science fiction writer. Famous in his day …”
“Couldn’t you build a mass driver on Earth?”
“Yeah. In principle. But the air would be a problem. You would be flying at interplanetary speeds a meter above the ground. On Earth, at escape velocity, Mach 20 or 25, you’d burn up. But up here there’s no air, so no air resistance. Then we have our famous low gravity, so the speeds we need to acquire are much less than on Earth: down there you’d need a launcher twenty times as long as this one—maybe six hundred kilometers. As for power, all that lovely sunlight falls down from the sky for free. But the real economy comes from the fact that unlike with rocket technology, all our launch equipment stays bolted to the ground, where it belongs. With the Sling, we can get off this rock for pennies per kilogram.”
He started to wax enthusiastically about the opportunities the Sling and its more sophisticated successors would one day give to the Moon. “From here we can send heavy-lift components to the Lagrange points, or Earth orbit, or to the planets and beyond, for a fraction of the effort and cost of launching from Earth. Once people dreamed that the Moon would be the stepping-stone to opening up the solar system. Those dreams died when it was found that the Moon has only a trace of water. But this is how the dream will live again.”
She touched his arm a little wistfully. She relished his passion, his energy. But he was oddly like Eugene Mangles, in a way: as Eugene’s obsession was his work, so Bud’s was evidently the Moon and its future—to the exclusion of herself, she thought. “Bud,” she said. “You sold me. But for now, all I want the Moon to do is to save the Earth.”
“We’re working on it. Even though we all know it won’t be enough.”
The shield couldn’t provide perfect cover. It had had to be designed to block the sunstorm’s peak-energy bombardment in the visible light spectrum, but could do nothing about an anticipated accompaniment of X-rays, gamma rays, and other nasties, peripheral in terms of the storm’s total output, but potentially devastating for the Earth. “We couldn’t do it all,” she said.
“I know. I keep telling my folk that. But even so it doesn’t feel enough, whatever we do … Look. I think they’re ready for a test.”
The cargo pellet was in place on the gleaming track. The crane withdrew. She saw the pellet start to move: slowly at first, a ponderous start that told of its mass, and then more rapidly. That was all there was to it. There were no special effects: no flaring fire, no billowing smoke. But as the generators poured their energies into the launcher she felt a tingle in her gut, perhaps some biochemical response to the mighty currents flowing just a few hundred meters away.
The pellet, still accelerating, shot out of sight.
Bud clenched a fist. “Today all we can do is dig another hole in Clavius’s floor. But in six months tops we’ll be firing to orbit. Imagine riding that thing, riding the lightning across the face of the Moon!”
On the Moon’s surface, rovers were already racing to retrieve the cargo pellet, spraying up rooster tails of dust behind them. And the crane was moving back into its position, ready for another run.
20: Human Resources
Eugene sat in his room, hands folded on a small table. The room was without decoration or personalization—minimal even by the standards of the Moon, where everything was filtered through the huge expense of being shipped up from Earth. He didn’t even have a closet, just the packing carton that must have brought his clothes to the Moon in the first place.
Eugene remained an enigma to Siobhan. He was a big, handsome boy. If you knocked him cold and rearranged his limbs a bit he’d have made a great fashion model. But his posture was slumped, his face creased up with concern and shyness. Siobhan thought she had never met anybody with a greater contrast between his inner and outer selves.
“So how are you feeling, Eugene?”
“Busy,” he snapped back. “Questions, questions, questions. It’s all I get, day and night.”
“But you understand why,” she said. “We’ve already started building the shield, and on Earth they are making other preparations. All on the basis of your predictions: it’s really quite a responsibility. And unfortunately, Eugene, right now it’s only you who can do that for us.” She forced a smile. “If you’re building a shield thirteen thousand kilometers across, a mistake in the sixth decimal place means a mismatch of a meter or more—”
“It gets in the way of the work,” he said.
She stopped herself from snapping back, I amthe Astronomer Royal. I’ve done the odd bit of science myself. I do understand what it takes. But we’re talking about the safety of the world here. For God’s sake stop being such a prima donna … But she glimpsed real misery in his downcast face.
After all, she reflected, it wasn’t likely somebody as unworldly as this would be any use at prioritization or time management. Eugene surely had no mental equipment for handling conflicting demands—and probably no tact in dealing with those making such demands, from Prime Ministers and Presidents on down.
And then there was his public notoriety.
Siobhan had the feeling that even now, despite all the grave scientific pronouncements and political pontificating and arguing, most people didn’t really believe, in their guts, that the sunstorm was going to happen. Alvarez’s initial announcement had triggered a wave of alarm, flurries of speculation on the stock markets, flights into gold, and a sudden surge of interest in properties in Iceland, Greenland, the Falklands, and other extreme-latitude locations wrongly imagined to be relatively safe from the storm. But for most people, as the world kept turning and the sun kept shining, the sense of crisis quickly faded. Vast defensive programs, like the shield, were being mobilized, but even they weren’t visible yet to most people. It was still a phony war, the analysts said, and most people had forgotten about it and just got on with their lives. Even Siobhan found herself fretting about the long-term cosmological projects she’d been forced to abandon.
But in a world of billions there was a fraction of a percent imaginative enough, or crazy enough, to take the threat to heart—and a fraction of them looked for somebody to blame. As the man who had figured out the sunstorm, there were plenty prepared to dump their fear on Eugene. There had even been death threats. It had been a mercy he had stayed on the Moon, she thought, where his safety was relatively easy to assure. But even so he must have felt as if he were being flayed alive.
She got out her softscreen and began making notes. “Let me help you,” she said. “You need an office. A secretary …” She saw panic in his eyes. “Okay, not a secretary. But I’ll set up somebody to filter your calls for you. To report to me, not you.” But I think you will need somebody here on the Moon to hold your hand, she thought. An idea struck her. “How’s Mikhail?”
He shrugged. “Haven’t seen him.”
“I kno
w he has his own priorities.” The Space Weather Service, which had suddenly grown from an obscure near joke to one of the most high-profile agencies in the solar system, was almost as inundated as Eugene himself. But she had seen Mikhail work with Eugene; she had a sense the solar astronomer would be able to get the best out of the boy. And, given the way Mikhail looked at Eugene, it would be a task Mikhail would perform with competence and affection. “I’ll ask him to spend more time with you. Maybe he could move back here to Clavius; he doesn’t have to be physically at the pole station.”
Eugene showed no notable enthusiasm for the idea. But he didn’t reject it outright, so Siobhan decided she had made some progress.
“What else?” She bent forward so she could see his face more clearly. “How are you feeling, Eugene? Is there anything you need? You must know how important your welfare is, to all of us.”
“Nothing.” He sounded sullen, even sulky.
“What you found is so important, Eugene. You could save billions of lives. They’ll build statues to you. And believe me, your work, especially your classic paper on the solar core, is going to be read forever.”
That provoked a weak smile. “I miss the farm,” he said suddenly.
The non sequitur took her aback. “The farm?”
“Selene. I understand why they had to clear it all out. But I miss it.” He had grown up in a rural area in Massachusetts, she remembered now. “I used to go work in there,” he said. “The doctor said I needed exercise. It was that or the treadmill.”
“But now the farm’s been shut down. How typical that in trying to save the world we kill off the one bit of green on the Moon!”
And how psychologically damaging that might be. In trying to figure out these spacebound folk she had read stories of cosmonauts on the first, crude, tin-can space stations, patiently growing little pea plants in experimental pots. They had loved those plants, those small living things sharing their shelter in the desolation of space. Now Eugene had shown the same impulse. He was human after all.
“I’ll fix it,” she said. “A farm’s out of the question for now. But how about a garden? I’m sure there’s room here in Hecate. And if there isn’t we’ll make room. You lunar folk need reminding of what you’re fighting to save.”
He looked up and met her gaze for the first time. “Thank you.” He glanced at the softscreen before him. “But if you don’t mind—”
“I know, I know. The work.” She pushed back her chair and stood up.
***
That night she went to Bud’s room.
He whispered, “I wasn’t sure if you’d come.”
She snorted. “I knew for sure you wouldn’t walk down the corridor.”
“Am I so transparent?”
“As long as the journey got made by one of us,” she said.
“I told you we’d be a good team.”
She unzipped her jumpsuit. “Prove it, hero.”
Their lovemaking was wonderful. Bud was a lot more athletic than she was used to, but he was more focused on her than most of her lovers ever had been.
And he was ingenious in his use of the Moon’s gentle gravity. “One-sixth G is the gravity of choice,” he gasped at one point. “On Earth you’re crushed. In zero G you’re floundering around like a beached salmon. In one-sixth, you’ve enough weight to give you a little traction, and yet you’re still as light as a kid’s balloon. Why, I’m told that even on Mars—”
“Shut up and get on with it,” she whispered.
Afterward she stayed awake for a long time, just relishing the strong warmth of his arms around her. Here they were, two humans in this bubble of light and air and warmth on the lethal surface of the Moon. Like the cosmonauts and their pea plants, she thought: all they had, in the end, was each other.
Even when the sun betrayed them, they had each other.
21: Showstoppers
“So there it is,” Rose Delea said flatly. “You have two problems you can’t get over. Without the Chinese heavy-lift capability, you can’t finish the shield infrastructure on time. And even if you could, you don’t have a way to manufacture all the smartskin you need.” She sat back and stared out of her softscreen at Siobhan. “You’re fucked.”
Siobhan pressed the balls of her thumbs to her eyes, and tried to keep her temper. It was January 2039—six months after she had seen those first shield components stacking up on the Moon, already eighteen months since the June 9 event. Another Christmas had come and gone, a bleak and joyless festival, and little more than three years remained before the sunstorm was due to hit.
Save for Toby Pitt and the talking heads from space on the softscreens, Siobhan was alone here in the Royal Society Council Rooms, the location that had come to serve as her communications base. Toby’s job as the Society’s events manager had gradually evolved into his becoming her PA, amanuensis, and shoulder-to-cry-on. And she certainly felt like crying now.
“We’re fucked, Rose,” she said.
“What?”
“Rose, sometimes you sound like my plumber. You’re fucked is wrong. Language is crucial. It’s not my problem, it’s ours. We’re fucked.”
Bud Tooke, peering from another softscreen, laughed gently.
Rose glared. “Fucked is fucked, you stuck-up pom. I need a coffee.” And she pushed herself out of her chair and drifted out of shot.
“Here we go again,” Mikhail said grimly.
***
Despite her usual intrinsic anxiety about the schedule, before she had come into work this morning Siobhan had actually felt optimistic about the way things were going.
On the Moon, after months of stupendous effort by Bud and his people, the Sling was completed and operational. Even the construction of a second mass driver was under way. Not only that, but the glass manufacturing operations were proceeding apace: plants had been set up all over the bare soil of Clavius Crater, so that streams of components poured into the Sling’s launching bay by lunar day and night. Rose Delea, seconded from her helium-3 processing work, had proven a more than capable manager for that end of the project, despite her dour attitude.
Meanwhile Aurora2 had been safely brought back from Mars and was lodged at L1, the crucial Lagrangian point suspended between Earth and sun. With the Sling fully operational the first loads of lunar-glass buttresses and struts had been fired up to the assembly site, and construction of the shield itself had started. Bud Tooke was now in nominal charge of all the subprojects at L1, and, as Siobhan had always known he would, he was delivering quietly and efficiently. Soon, it was said, the proto-shield would be big enough to see with the naked eye from Earth—or would have been, were it not forever lost in the glare of the sun.
Even Siobhan’s personal life had been looking up, to general astonishment among friends and family. She hadn’t expected that her affair with Bud would deepen so smoothly and so quickly, especially since they spent almost all their time on separate worlds. In the toughest days of her life, the relationship had been a source of comfort and strength to her.
But now, in what should have been a routine weekly progress meeting, two showstopper problems had come looming out of nowhere.
On her screen Rose Delea reappeared with coffee that sloshed in a languid low-G way. The conversation resumed, and Siobhan tried to focus on the issues.
Mathematically, the positioning of an object at a Lagrangian point was simple. If the shield had been a point mass, it could have been poised neatly on the sweeping line joining Earth to sun at L1. But this project was no longer mathematics; it was engineering.
For one thing the L1 point wasn’t really stable at all, but only semi-stable: if you knocked that point mass out of position it would tend to drift back to its place along the line of the Earth—sun radius, but would happily float away from the line in any other direction. So you needed to add station-keeping mechanisms, such as rocket thrusters, to hold the shield in place.
And then, of course, the shield was not a point mass, but an exte
nded object large enough eventually to shadow the whole Earth. Only the shield’s geometric center, intersecting the Earth—sun line, could be properly balanced at the L1 point. All other points were drawn toward the center, and given time the shield would have crumpled in on itself. Making it rigid would have raised the mass unfeasibly. The problem was to be overcome by giving the shield a slow rotation. The spinning was stately, at only four revolutions per year—“as if God is twirling His parasol,” as Mikhail described it—but enough to keep the shield rigid.
But the rotation created other problems. Docking with a spinning object in space, even one as slow moving as the shield, was a lot more tricky than with a stationary object. More seriously, by being spun up, the shield would become a huge gyroscope. As it followed its orbit between Earth and sun it would tend to keep the same orientation in space—and so, over a year, it would tip its face away from the sun—Earth line, making it useless as a parasol.
Meanwhile there were other forces to consider besides gravity. Sunlight itself, a rain of photons, exerts a pressure on every object it touches. It is too gentle a force for human senses to detect on an upraised hand, but it would be enough to drive a yacht with filmy kilometer-wide sails from world to world—and it was certainly enough to exert a significant force on an object as large as the shield. There were other complications too, such as perturbation by the gravity fields of the Moon and the other planets, and a tweaking by Earth’s own magnetic field.
To cope with all this, the shield’s surface was to be made adjustable. Panels could be opened and closed in careful patterns, so that the gentle pressure of sunlight could be harnessed to turn the shield. It was an elegant solution: sunlight itself would be used to keep the shield properly positioned.
But to maintain its station in this environment of multiple and constantly changing forces, the shield itself had to be smart enough to be aware of its position in space, and able to adjust itself dynamically. Ideally every square centimeter of the shield would know all about the forces acting on it and on the shield as a whole, and would be able to compute how it should position itself in response.
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