Green Mars. Kim Stanley Robinson

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       Asteroids with elliptical orbits that cross inside the orbit of Mars are called Amor asteroids. (If they cross inside the orbit of Earth they are called Trojans.) In 2088 the Amor asteroid known as 2034 B crossed the path of Mars some eighteen million kilometres behind the planet, and a clutch of robotic landing vehicles originating from Luna docked with it shortly thereafter. 2034 B was a rough ball about five kilometres in diameter, with a mass of about fifteen billion tons. As the rockets touched down, the asteroid became New Clarke.

       Quickly the change became obvious. Some landers sank to the dusty surface of the asteroid and began drilling, excavating, stamping, sorting, conveying. A nuclear reactor power plant switched on, and fuel rods moved into position. Elsewhere ovens fired, and robot stokers prepared to shovel. On other landers payload bays opened, and robot mechanisms spidered out onto the surface and anchored themselves to the irregular planes of rock. Tunnellers bored in. Dust flew off into the space around the asteroid, and fell back down or escaped forever. Landers extended pipes and tubes into each other. The asteroid’s rock was carbonaceous chrondrite, with a good percentage of water-ice shot through it in veins and bubbles. Soon the linked collection of factories in the landers began to produce a variety of carbon-based materials, and some composites. Heavy water, one part in every six thousand of the water-ice in the asteroid, was separated out. Deuterium was made from the heavy water. Parts were made from the carbon composites, and other parts, brought along in another payload, were brought together with the new ones in factories. New robots appeared, made mostly of Clarke itself. And so the number of machines grew, as computers on the landers directed the creation of an entire industrial complex.

       After that the process was quite simple, for many years. The principal factory on New Clarke made a cable of carbon nanotube filaments. The nanotubes were made of carbon atoms linked in chains so that the bonds holding them together were as strong as any that humans could manufacture. The filaments were only a few score metres long, but were bundled in clusters with their ends overlapping, and then the bundles were bundled, until the cable was nine metres in diameter. The factories could create the filaments and bundle them at speeds that allowed them to extrude the cable at a rate of about four hundred metres an hour, ten kilometres a day, for hour after hour, day after day, year after year.

       While this thin strand of bundled carbon spun out into space, robots on another facet of the asteroid were constructing a mass driver, an engine that would use the deuterium from the indigenous water to fire crushed rock away from the asteroid at speeds of two hundred kilometres a second. Around the asteroid smaller engines and conventional rockets were also being constructed and stocked with fuels, waiting for the time when they would fire, and perform the work of attitude jets. Other factories constructed long-wheeled vehicles capable of running back and forth on the growing cable, and as the cable continued to appear out of the planet, small rocket jets and other machinery were attached to it.

       The mass driver fired. The asteroid began to move into a new orbit.

       Years passed. The asteroid’s new orbit intersected the orbit of Mars such that the asteroid came within ten thousand kilometres of Mars, and the collection of rockets on the asteroid fired in a way that allowed the gravity of Mars to capture it, in an orbit at first highly elliptical. The jets continued to fire off and on, regularising the orbit. The cable continued to extrude. More years passed.

       A little over a decade after the landers had first touched down, the cable was approximately thirty thousand kilometres long. The asteroid’s mass was about eight billion tons, the cable’s mass was about seven billion. The asteroid was in an elliptical orbit with a periapsis of around fifty thousand kilometres. But now all the rockets and mass drivers on both New Clarke and the cable itself began to fire, some continuously but most in spurts. One of the most powerful computers ever made sat in one of the payload bays, co-ordinating the data from sensors and determining which rockets should fire when. The cable, at this time pointing away from Mars, began to swing around toward it, as in the pivoting of some delicate part of a timepiece. The asteroid’s orbit became smaller and more regular.

      More rockets landed on New Clarke for the first time since that first touchdown, and robots in them began the construction of a spaceport. The tip of the cable began to descend toward Mars. Here the calculus employed by the computer soared off into an almost metaphysical complexity, and the gravitational dance of asteroid and cable with the planet became ever more precise, moving to a music that was in a permanent ritard, so that as the great cable grew closer to its proper position, its movements became slower and slower. If anyone had been able to see the full extent of this spectacle, it might have seemed like some spectacular physical demonstration of Zeno’s paradox, in which the racer gets closer to the finish line by halving distances … but no one ever saw the full spectacle, for no witnesses had the senses necessary. Proportionally the cable was far thinner than a human hair—if it had been reduced to a hair’s diameter, it would still have been hundreds of kilometres long—and so it was only visible for short portions of its entire length. Perhaps one might say that the computer guiding it in had the fullest sensation of it. For observers down on the surface of Mars, in the town of Sheffield, on the volcano Pavonis Mons (Peacock Mountain), the cable made its first appearance as a very small rocket descending with a very thin leader line attached to it; something like a bright lure and a thin fishing line, being trawled by some gods in the next universe up. From this ocean bottom perspective the cable itself followed its leader line down into the massive concrete bunker east of Sheffield with an aching slowness, until most humans simply stopped paying attention to the vertical black stroke in the upper atmosphere.

       But the day came when the bottom of the cable, firing jets to hold its position in the gusty winds, dropped down into the hole in the roof of the concrete bunker, and settled into its collar. Now the cable below the areosynchronous point was being pulled down by Mars’s gravity; the part above the areosynchronous point was trying to follow New Clarke in centrifugal flight away from the planet; and the carbon filaments of the cable held the tension, and the whole apparatus rotated at the same speed as the planet, standing above Pavonis Mons in an oscillating vibration which allowed it to dodge Deimos, controlled still by the computer on New Clarke, and the long battery of rockets deployed on the carbon strand.

       The elevator was back. Cars were lifted up one side of the cable from Pavonis, and other cars were let down from New Clarke, providing a counterweight so that the energy needed for both operations was greatly lessened. Spaceships made their approach to the New Clarke spaceport, and when they left they were given a slingshot departure. Mars’s gravity well was therefore СКАЧАТЬ