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Later he took her out of Clavius Base to see Davids Sling.
As they approached the site of the Sling, Siobhan stood up in the surface tractors bubble-dome pressure compartment to see better. Only three kilometers of the launcher had been completed, of a projected thirty. Even so, it was an astonishing sight: in the low sunlight, under a pitch-black sky and against a gray-brown backdrop of Moon dust, the launcher shone like a sword.
The engineers called it a mass driver, or an electromagnetic launcheror, more simply, a space gun. The heart of it was an aluminum track standing on trestle legs, thin and light like all lunar constructions. Wrapped around the track was a coil of iron, a vast spiral that Bud called the solenoid. At the loading end spacesuited figures moved cautiously around a crane, which was hoisting a glistening pellet up onto the track. The track stretched away across the level floor of Clavius, soon passing out of sight beyond the Moons close horizon.
The principle is simple, Bud said. Its a cannon driven by electromagnetism. You wrap your cargo in a blanket of ironwhich we can reuse, by the way. You put your cargo pellet on the rail. The magnetic field, generated from that blockhouse over therehe pointed at a nondescript domethen 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: Its 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 wantfall all the way down to Earth, even.
Its 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
Couldnt 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, youd burn up. But up here theres 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 youd need a launcher twenty times as long as this onemaybe 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 Eugenes obsession was his work, so Buds was evidently the Moon and its futureto 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.
Were working on it. Even though we all know it wont be enough.
The shield couldnt provide perfect cover. It had had to be designed to block the sunstorms 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 storms total output, but potentially devastating for the Earth. We couldnt do it all, she said.
I know. I keep telling my folk that. But even so it doesnt feel enough, whatever we do Look. I think theyre 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 Claviuss floor. But in six months tops well be firing to orbit. Imagine riding that thing, riding the lightning across the face of the Moon!
On the Moons 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 personalizationminimal even by the standards of the Moon, where everything was filtered through the huge expense of being shipped up from Earth. He didnt 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 hed 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. Its all I get, day and night.
But you understand why, she said. Weve already started building the shield, and on Earth they are making other preparations. All on the basis of your predictions: its really quite a responsibility. And unfortunately, Eugene, right now its only you who can do that for us. She forced a smile. If youre 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. Ive done the odd bit of science myself. I do understand what it takes. But were talking about the safety of the world here. For Gods sake stop being such a prima donna But she glimpsed real misery in his downcast face.
After all, she reflected, it wasnt likely somebody as unworldly as this would be any use at prioritization or time management. Eugene surely had no mental equipment for handling conflicting demandsand 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 didnt really believe, in their guts, that the sunstorm was going to happen. Alvarezs 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 werent 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 shed been forced to abandon.