feel like a slow blind takeoff into space.
The crater of Pavonis, as the Afrikaaners had reminded him, was amazingly equatorial; the round O of its caldera sat like a ball placed right on the equator line. This apparently made the south rim of Pavonis the perfect tethering point for a space elevator, as it was both directly on the equator, and twenty-seven kilometers above the datum. Phyllis had already arranged for the construction of a preliminary habitat on the south rim; she had thrown herself into work on the elevator, and was one of its chief organizers.
Her habitat was dug into the rim wall of the caldera, in Echus Overlook style, so that windows in several stories of rooms looked out over the caldera, or would when the dust cleared. Photos blown up and stuck on the walls showed that the caldera itself would eventually be revealed as a simple circular depression, with walls 5,000 meters deep, slightly terraced near the bottom; the caldera had slumped often in earlier days, but always in nearly the same place. It was the only one of the great volcanoes to have been so regular; the other three had calderas that were like sets of overlapping circles, with each circle set at a different depth.
The new habitat, nameless at this point, had been built by UNOMA, but the equipment and personnel had been provided by the transnational Praxis, one of the biggest of them all. Currently the rooms that were finished were crowded with Praxis executives, or executives of some of the other transnationals who had subcontracts on the elevator project, among them were representatives of Amex, Oroco, Subarashii, and Mitsubishi. And all their efforts were being coordinated by Phyllis, who was now apparently Helmut Bronski’s assistant in charge of the operation.
Helmut too was there, and after John had greeted him and Phyllis, and been introduced to some of the visiting consultants, John was led into a big high room with a window wall. Outside the window swirled clouds of dark orange dust dropping down into the caldera, so that it seemed that the room ascended, uncertainly, in a dim fluctuating light.
The room’s only furnishing was a globe of Mars one meter in diameter, resting waist-high on a blue plastic stand. Extending from the globe, specifically from the little bump that represented Pavonis Mons, was a silver wire about five meters long. At the end of the thread was a small black dot. The globe was rotating on the stand at about one rpm, and the silver wire and its terminating black dot rotated with it, always remaining above Pavonis.
A group of about eight people ringed this display. “Everything is to scale,” Phyllis said. “The areosynchronous satellite distance is 20,435 kilometers from the center of mass, and the equatorial radius is 3,386 kilometers, so the distance from the surface to the areosynchronous point is 17,049 kilometers; double that and add the radius, and you have 37,484 kilometers. We’ll have a ballast rock at the far end, so the actual cable won’t have to be as long as it would be without it. The diameter of the cable will be about ten meters, and will weigh about six billion tons. The material for it will have been mined from its terminal ballast point, which will be an asteroid that starts at around thirteen-and-a-half billion tons, and ends up when the cable is finished at the proper ballast weight of around seven-and-a-half billion tons. That’s not a very big asteroid, about two kilometers in radius to begin with; there are six Amor asteroids crossing Mars’s orbit that have been identified as candidates for the job. The cable will be manufactured by robots mining and processing the carbon in the asteroid’s chondrites. Then, in the last stages of construction, the cable will be maneuvered to its tethering point, here.” She pointed at the floor of the room in dramatic fashion. “At that point, the cable will be in areosynchronous orbit itself, barely touching down here, its weight suspended between the pull of the planet’s gravity and the centrifugal force of the upper part of the cable, and the terminal ballast rock.”
“What about Phobos?” John asked.
“Phobos is way down there, of course. The cable will be vibrating to avoid it, in what the designers call a Clarke oscillation. It won’t be a problem. Deimos will also have to be avoided by oscillation, but because its orbit is more inclined this won’t be such a frequent problem.”
“And when it’s