"This is the seventh time I've done this," Barney complained. She looped a thick soft rope around her waist, tied the other end around Rick under his armpits, and motioned for him to start down. "Make me an old woman before my time, it will. Go on, start down. I'll be right behind you. And go slow. You use both hands and both feet, and three of those must work to support your weight at all times. Did you ever go rock climbing back on Earth?"
"No. No rocks where I lived."
"That figures."
"I did a few night climbs, though. Up and down the outside of buildings." Rick still shivered when he remembered the jump from the roof of the Lafferty apartments to a balcony on the building next door. Only eight feet, but when you stood in the dark waiting, ten stories up, eight seemed more like eighty.
"Dumb ass." Barney sniffed, a few feet above him. "Risking your neck for nothing. Trying to impress some girl, I bet."
"No." Rick was climbing down the shaft, slowly and carefully, a boulder strapped to each arm and to his back. If he fell, Barney was supposed to hold him until he could grab another handhold. But could she do it? She'd have to hold up four times her own weight. "I was just trying to prove I was brave," he panted.
"And did you?"
"I don't think so. I proved I was scared." Rick had no more breath for talking. He could see now why Barney had been struggling for breath when she came into his cabin. But he was almost there, reaching the solid floor of the little dining area.
"Take your time," said Barney. "You won't need to do much of this unless we have an emergency, but you have to know how ahead of time—just in case."
Rick nodded a head made of solid lead. He turned, making sure that his feet landed in the correct place—and found himself staring into Deedee's anxious face. Goggles Landau was next to her.
"Message from the flight deck," said Goggles at once. He was talking not to Rick but to Barney French, now on the last step of her own descent. "Pilots Garcia and Kotite want you there as soon as possible. They have more news."
"Shoot. I've got one more still to do. Anybody know where Teazle's cabin is?"
"I do," said Rick and Deedee simultaneously. They stared at each other. Her cheeks darkened with a blush, and she glared defiantly at Rick.
"Good." If Barney noticed, she did not care. "Landau, you come with me. I have a job for you. Mao and Luban, I showed you how to climb. Now you go and show Teazle—I want all three of you roped together when you do it. Understand?"
"Yes, sir."
"I'm putting a lot of trust in all of you, more than I should in an apprentice. Don't let me down."
"We won't." Rick and Deedee stared at each other as Barney and Goggles left the dining area for the lower level between passenger quarters and drive units, where the flight deck was located.
"What do you think happened on CM-31?" Deedee asked.
Rick jumped at the chance of a neutral subject. He was forced to put his arms around her to tie the rope, and it was the closest they had been since the night of the dance. He couldn't help brushing against her.
"I'll make a guess," he said. "They were using new mining methods. Something went wrong while they were melting and separating the different metals. CM-31 is mostly metal, iron and nickel and platinum."
She didn't ask how he knew, merely nodded and started to climb. He followed close behind. Going up was harder work than going down, but it was also easier. You could see just where your hands had to go, instead of groping around with your feet.
"Do you know what centrifuge melting is?" he asked, after they had climbed about five meters.
"Sure." She was breathing heavily, but moving up steadily. "It's a confusing term—two different things in one. It means melting, plus centrifuge separation. You take a cylinder filled with different materials, and you melt them. At the same time you spin the cylinder around on its axis. That gives you like a gravity gradient, but of course it's not gravity, its centrifugal force. The denser liquids go to the outside, farthest from the axis. The light ones stay close to the middle, sort of floating on the heavy ones. So you've separated them out from each other. The dross floats at the very center."
"Dross?"
"Scum. You know, the light useless stuff."
The long speech had taken all her breath, and she paused in her climb. Rick, focused on the placement of his own hands and feet, took an upward step and ran the top of his head into something soft.
"Oof! Do you mind?" Deedee sounded exasperated. "That's my rear end you're poking. It's off limits."
"Sorry. Not the first time you've called me a butt-head, though." Rick waited, until she began to move upward again. "What happens if you don't have a cylinder available?"
"Then you can't do centrifuge melting, can you? Why are you asking?"
"The data bank says CM-31 was testing centrifuge melting methods. That's why I said I guessed that something went wrong when they were trying to do it."
They had finally reached Chick Teazle's cabin, tucked away up near the very front of the Vantage. Deedee knocked and went in without pausing.
"Hey there!" Rick heard Chick, loud and self-confident as usual. "This is an unexpected treat. Let's get"—Chick saw Rick at the door, and his voice changed on the final word—"friendly."
"Barney French sent us." Deedee sounded abrupt and unnatural. "Get up from your bunk. We have to show you how to climb down to lower ship levels."
"Why you two?" Chick stared at Rick.
"We happened to be there with Barney." Rick held up the thick rope. "We have to be all tied together, just in case."
"I don't need no damn rope." But Chick took the end that Rick handed him, looped the rope around under his arms, and tied a deft knot. "All right, go ahead. I'll follow you down."
"No." Rick put his arm on Deedee's, just as she was about to start the descent. "You go first, Chick. That way if you fall, we'll be above you and have a chance to brace ourselves. If you were above us you could knock us with you."
"I'm not going to fall, you dummy." Chick glared at Rick, but he moved forward. "What happens if you fall on me?"
"You cushion my landing." Rick watched as Chick started down. He was long-limbed and powerful, and he moved with a speed and confidence that Rick envied. Deedee followed, saying what Rick was thinking: "Slow down a bit, Chick, or you'll pull us off-balance."
Chick grunted, but he did as she asked. The three descended steadily, to find Barney French waiting for them back at the dining level.
"Good," she said. "Everyone has been through the drill. Now you do it without the rope. I want each of you back in your own cabin, and on your own bunk until we get to CM-31."
It seemed such an anticlimax that they all stared at her instead of jumping at once to do what she said.
"Can't you tell us more about what happened?" asked Deedee.
"I propose to do exactly that. But I'm not going to go round telling you one at a time. Get to your bunk, or you'll miss the beginning."
It was incentive enough. Chick went swinging away up the vertical passage like a monkey, while Deedee started downward.
Rick, about to follow right behind Chick, felt Barney's hand on his arm.
"Give him a few seconds," she said. "If he does goof, I assume you don't want two hundred pounds plummeting down on you under two gees."
Rick waited impatiently, staring up but ready to jump out of the way, until Chick vanished into his cabin. Then he made his own ascent, trying to strike the balance between speed and caution. Barney was right. Practice made all the difference. Already it felt easier than the first time.
He lay down on his bunk, fixed the straps into position, and waited impatiently for something to happen. What had Chick meant when he said, "Let's get friendly"? And why had Deedee suddenly turned all stiff and weird?
Rick could guess, but before he had time to brood on it Barney's image was again projected on the ceiling.
"I told you during our very first session that when you came aboard the Vanta
ge all the babying ended," she said. "Well, I lied. This phase of your training is supposed to place you in what we call a Level Three environment. Unfortunately, the situation at CM-31 represents a Level Five environment—the highest level of danger and uncertainty that fully-trained staff ever expect to meet. You are not ready for that, but needless to say this was not from choice. Headquarters have again confirmed that every other ship in the fleet will need at least thirty-six hours more than the Vantage to reach Company Mine 31. That time could be the difference between life and death. Therefore you, the apprentices, must assist in operations. When we reach CM-31 you will supplement six experienced staff members: myself, Tait, and Styan; Garcia and Kotite, our pilots; and Skipios, our engineer.
"Meanwhile, in the nine hours remaining until our arrival at CM-31, you are all to remain in your bunks. If you can sleep, do so. First, however, I am going to give you background on where we are going and what we will find there."
It was far into the usual rest cycle and Rick was tired out, but the idea of sleep while in a two-gee field sounded like pure fantasy. The slightest movement made you aware of your body. Even breathing was an effort.
"Here is CM-31," Barney went on, "as it was when our original prospecting team arrived and confirmed the nature of the find." Her face vanished, and was replaced by the image of an irregular and pock-marked lump of rock. Rick knew that the Belt held billions of similar mountain-sized boulders. Without knowing this one's composition there was no hint that it might have unusual value.
"Now for a few basics," went on Barney. "Gravity is the force that defines the whole shape and movement of the solar system—the galaxy, too, if it comes to that—but for objects the size of the one you are looking at now, gravity is a very weak force. It is just strong enough to pull small particles of material into contact with each other, but if gravity was all that held CM-31 together, you'd be able to mine it and the other asteroids with a spoon. But when the dust and grains of sand and pebbles meet, a different form of bonding takes over. The little particles sinter, which means that they all stick together to form a single mass. And that mass doesn't come apart easily. You can think of CM-31 as we discovered it as a ball of iron, with some rock and small fractions of other metals. It's solid, and it's hard, and if you want to break a bit off you have to do it with a chisel.
"It's strong enough that it would still hold together if you started to rotate it around its principal axis of inertia, which is the most stable way to make it spin."
The lumpy surface of CM-31 now showed dozens of bright points of light all around it. They were drive units. Rick could not tell if this was a simulation or the real thing, but the body began to turn, slowly at first and then gradually faster.
"You can rotate it pretty fast, and the body will still hold in one piece," Barney's voice said. "But that's not true if you also heat it. We use electric induction, which will produce internal currents to heat the body all the way through. If you did that until CM-31 melted, and it was also spinning, it would just fly apart."
The image on the screen showed the dark planetoid beginning to glow a dull red. It slowly deformed to the shape of a thick plastic disk, then suddenly disintegrated and was gone, parts flying away in all directions.
"Obviously, that's no way to mine an asteroid. You'd lose the asteroid itself, and you'd lose valuable drive units. It's also not what people imagine, when they think of the word 'mining.' You might ask, what's the point of heating and spinning a body, when you could just as well mine CM-31 the way most of the mines, like CM-2, were done? Remember the tunnels in CM-2? Mining machines made those, dug ore, and brought it out from the interior.
"The answer to my question, in one word, is economics. It's far less expensive if you can melt and refine and process a whole asteroid, in one swoop.
"And you can. Here's how.
"First, you place a cylinder in position around the whole body."
CM-31 reappeared, just as it had been at the time of discovery. Now a huge silvery cylinder appeared from nowhere and gradually swallowed the whole asteroid into its open end. When the body was totally engulfed, the open end of the cylinder irised shut.
"There's a couple of things to notice about that cylinder," said Barney. "First, if you look very closely you'll see drive units spaced at intervals around the curved part. On the cylinder, not on the asteroid. They will make it spin around its central axis. Second, you can't see them but there are also hundreds of induction field generators on the cylinder. They will heat anything inside by induced eddy currents. They will also, if the cylinder is rotating, make the asteroid inside start to rotate through an electromagnetic dragging effect. Keep that up long enough, and the material inside will melt. When it melts, it will be thrown outward to the wall of the cylinder.
"One other thing, and this you can't see: the cylinder is made of the strongest material we know, dislocation-free carbon filaments. It remains strong at high temperatures. It will contain the materials inside it, even when everything is spinning around the cylinder main axis at high speed."
Rick could see what was coming next, he had known it the moment that the cylinder appeared. The fact that he really owed his knowledge to Deedee did nothing to lessen his pleasure. He could imagine her, tucked away in her own bunk, hugging herself in satisfaction. She had got it exactly right.
"I assume you can all see what's coming next," said Barney's voice, taking away Rick's sense of superiority. "As everything rotates, the liquid metals press outward on the cylinder wall, the heavier ones toward the outside and forcing the lighter ones closer to the axis of rotation. Actually, it's not quite as simple as that, because some metals form eutectic alloys that don't separate by centrifuging, but the general principle is valid. The heaviest metals are tapped first, from spigots on the outer circle of the circular ends of the cylinder. Then we run out the lighter ones. Finally all that's left behind is a low-density layer of melted rock and sand. With a really high metal content asteroid, that's not much more than a froth. We empty that, too, and leave it behind in space, all that remains of the original asteroid. At that point, the empty cylinder—after a bit of scrubbing and servicing—is ready to move on and tackle the next mine.
"I'm sure you're asking, what went wrong in processing CM-31 ? If I could answer that, I would tell you. But I don't know. We're moving closer as fast as we can, and a few hours from now we'll be able to take a look. Until then I suggest that you all rest, even if you don't think you can sleep."
Barney French stopped speaking. The projection unit remained alive, throwing onto the ceiling an image of the cylinder, drive units flaring, spinning hypnotically. Rick watched and watched, until at last he slipped into a half-trance. He was neither asleep nor fully awake. He was aware of a time of freefall, when the Vantage turned end-over-end and began its deceleration, but he could not have given an estimate as to how long it lasted. It seemed long after that when the thought came into his head that it should not be necessary to watch a simulation. By now it might be possible to see the real CM-31.
He roused himself and tapped the code for Barney French's cabin. There was a risk that she was sleeping, but somehow he doubted it.
"Yes?" The answer came at once.
"This is Luban."
"I know. I can see your call ID. Why aren't you sleeping?"
"I can't. I want to ask your permission to climb up to the front of the ship and use the scope there to look for CM-31."
"You may not be sleeping, but your brain is turned off. We passed turnover a while ago, so we are now decelerating—which means that the front of the Vantage is pointed directly away from our destination. You'd see nothing." And, while Rick was feeling like a prize buffoon, "You are the fourth person to call and ask me that, so I suppose it's a general concern. There is no observation port down toward the stern, but there are imaging sensors. Stay where you are. I'm going to hook the output of the rear-pointing sensors into the terminal display. You'll have a chance to see CM-31 at the
same moment as the pilots. Don't expect anything for a while."
The projection on the ceiling above Rick flickered through a kaleidoscope of random color swirls, then settled to show a stationary star field. A blue icon at the upper left of the image blinked "target zoom." There was an impression of impossibly fast motion as stars moved toward the scene edge and disappeared. The image became increasingly grainy, until at last the words "maximum magnification" replaced the first icon.
Rick peered, and saw nothing but fuzzy points of starlight. The scene was steady now, but as minute followed minute he noticed that one point of light at the outside edge of the image area was creeping slowly across the screen. That was not a zoom effect. The moving point had to be a substantial asteroid. It was close to the Vantage compared with everything else, but it could not be CM-31. The ship's telescope would surely be aimed to place the mine at the center of the field of view.
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