She stood up and led the way out of the main cabin and through the lock. The rotation rate of Atlantis was low, barely enough to give a feeling of weight. The ship had docked at the exterior surface of the asteroid, on the “equator” farthest from the axis of rotation of the sphere. A flexible umbilical led to the entry shaft. It had been attached automatically as the ship docked. As they passed into the main shaft, baffles sealed it behind them. Within thirty seconds the atmosphere in the interior was up to half a standard atmosphere, oxygen-rich and matched to that of the ship they had just left. Rob followed Corrie as she pulled herself easily along the broad, dark tunnel that led to the central metal sphere. About halfway along they halted at a second lock and removed their suits. Once they were ready to go on, Corrie led Rob to the side of the tube.
“I think I can show you something to match your Coal Moles,” she said. “You know, Morel and Regulo built a complete water-world here, and this is one of the viewing ports. You’ll find the same sort of thing all over the inner sphere. Take a look through there.”
She pointed to a transparent panel about two meters across set into the side of the lock chamber. Rob went to it and looked out. It took a few seconds to become accustomed to the scale and distance of what he was seeing. Then he grunted with surprise and leaned closer to the panel.
The water that filled the interior of Atlantis was very clear. He could see for at least a hundred meters into a green, shady interior, filled with huge and abundant plant growth. It clustered around a complex supporting grid in the form of a symmetrical series of spherical frames, like concentric shells. Between the spheres of vegetation, far away into the dim light, moving shapes were faintly visible. In rainbow colors, they turned, darted, or cruised lazily among the curtains of floating plant life. At the limit of vision, Rob fancied that he could see the phantom outline of something much bigger, a dark irregular shape outlined against the lighter green-blue background. As he watched, it drifted farther off and merged into the fronded luxuriant weeds.
He turned back to Corrie. “That looks like a fresh-water ecology out there, but I could swear that I’m seeing forms that only live in salt water back on Earth. Is it fresh, salt, or what?”
“It’s all fresh water. There was no easy way to find a mass of salt where and when they wanted it. They discovered salt deposits later on some of the asteroids, but by that time they were committed to most of the biological forms.” Corrie again began to lead the way toward the central structure. “You’re quite right about the mixture of life-forms. That has been one of Morel’s interests. Over the past twenty-five years he has been developing marine animals that can stand the transition from salt water to fresh. You’ll see how successful he has been when you have an opportunity to examine the aquasphere. It wasn’t an easy problem. Morel had to do a good deal of genetic engineering before he was satisfied with most of them.”
They had reached the final hatch that marked the end of the entry shaft. She led the way through.
“I’ll take you as far as Regulo’s office, then I’m supposed to go and meet Morel in the bio section. I’ll see you later on, when we eat. It’s a good bet that Regulo will have an elaborate meal planned. He likes to show off the latest from the sea-farms. It can’t compete with Way Down, but I think you’ll be impressed.”
She continued along the curving corridor that followed the outer wall of the central living sphere. Rob followed, noting that there was scarcely enough gravity to give his feet useful contact with the smooth floor. He copied her example, using his hands on the ridged side walls to propel himself along.
At a big sliding door set into the left-hand wall of the passage, Corrie paused. “Here you are. He’s inside. Have fun with your boy toys, and I’ll see the two of you at dinner.”
She went on her way along the corridor. After a moment’s hesitation, Rob reached out and touched his hand to the door control.
CHAPTER 7: How to Build a Beanstalk
Either Regulo had somehow furnished the study with exactly the fittings that Rob had seen in the room where Rob first met him, or he took the whole thing with him from place to place. There was no mistaking the curious pink-topped desk, with its flanking wall displays, video cameras and output terminals. The dark red carpet was the same, and the internal lighting was held to its familiar subdued level. Only the gravity was noticeably different, lower here than at the station in Earth orbit. Atlantis could not tolerate the rotation rate that significant centrifugal gravity would require.
Regulo was seated behind the big desk. He watched while Rob stared around him, reading his reaction.
“You see, now, I’m no better than a tortoise,” he said. “I carry my house about on my back. Costs a little, but it’s worth it for the convenience. Old dogs don’t like new kennels. Come on in and sit down, Merlin. Welcome to Atlantis.”
Rob moved to the chair that the old man indicated. His weight on the seat was barely perceptible, no more than a fraction of a kilogram. He looked at Regulo, shocked again by the sight of the ravaged face with its seamed and corroded features. Then he pushed that thought to the back of his mind. Regulo had a big pile of documents sitting in front of him, and a curious expression of suppressed glee shone in his bright eyes.
“Got your work on the beanstalk design,” he said gruffly. “Ready to talk about it, or do you need time to settle down?”
Apparently Regulo didn’t intend to indulge in social patter about the length of the trip from Earth. That suited Rob. He wanted to get to the real meeting as much as Regulo. He nodded. “I’m ready.”
“Good.” Regulo patted the stack of materials in front of him. “I pulled my old work out of the files. All done a long time ago, back before we could even mass-produce high-load graphite whiskers, never mind the doped silicon stuff that we’ve got now. You’ll see it soon enough” — Rob was leaning forward in the seat — “but first I’d like to hear what you have to say. Do you think you could build me a beanstalk?”
“I can build it.” Rob’s voice was confident as he pulled out his own design notes. “That’s the least of my worries. First of all, I can speed up the Spider. Two hundred kilometers a day of extruded cable will be no problem; maybe we can do a bit more than that. I can make it work with doped silicon instead of graphite, that’s a minor change. That gives us a load-bearing cable that can take over two hundred million newtons per square centimeter. I used a design diameter of two meters for the bottom end, but you can make that any value you choose. There will be a little bit of a taper as you go up, but it’s very small. The cable is only five percent thicker at geosynchronous altitude than it is at the ground tether.”
Regulo was nodding, his eyes fixed on Rob’s. “What load will it take with that diameter?”
“More than I ever see us needing. About two-thirds of a billion tons at the bottom end. I wouldn’t expect that you’d ever want to haul anything more than a few hundred thousand tons up to orbit at one time, or bring it down to Earth. Actually, I can’t see us needing even a tenth of that, but I’m following your advice and thinking big.”
Darius Regulo was nodding happily, drinking in Rob’s words and numbers. He was in his element. “I started out my design with a one-meter base diameter when I did it. Either way, it ought to give us more capacity than we’ll expect to use; but I’ve found that whenever you build in a capacity, you somehow get to use it.” His eyes seemed to capture and focus the dim light of the room, shining cat-like at Rob through the gloom. “So far, our thinking matches. What problems have you found?”