Tales of the Flying Mountains by Poul Anderson

Belt’s going to grow!” He aimed his words at Ellen. “This is the real frontier. The planets will never amount to much. It’s actually harder to maintain human-type conditions on so big a mass, with a useless atmosphere around you, than on a lump in space like this. And the gravity wells are so deep. Even given nuclear power, the energy cost of really exploiting a planet is prohibitive. Besides which, the choice minerals are buried under kilometers of rock. On a metallic asteroid, you can find almost everything you want directly under your feet. No limit to what you can do.”
    â€œBut your own energy expenditure—” Gilbertson objected.
    â€œThat’s no problem.” As if on cue, the worldlet’s spin brought the sun into sight. Tiny but intolerably brilliant, it flooded the dome with harsh radiance. Blades lowered the blinds on that side. He pointed in the opposite direction, toward several sparks of equal brightness that had manifested themselves.
    â€œHundred-meter parabolic mirrors,” he said. “Easy to make; you spray a thin metallic coat on a plastic backing. They’re in orbit around us, each with a small geegee unit to control drift and keep it aimed directly at the sun. The focused radiation charges heavy-duty accumulators, which we then collect and use for our power source in all our mobile work.”
    â€œDo you mean you haven’t any nuclear generator?” asked Warburton.
    He seemed curiously intent about it. Blades wondered why, but nodded. “That’s correct. We don’t want one. Too dangerous for us. Nor is it necessary. Even at this distance from the sun, and allowing for assorted inefficiencies, a mirror supplies better than five hundred kilowatts, twenty-four hours a day, year after year, absolutely free.”
    â€œHm-m-m. Yes.” Warburton’s lean head turned slowly about, to rake Blades with a look of calculation. “I understand that’s the normal power system in stations of this type. But we didn’t know if it was used in your case, too.”
    Why should you care ? Blades thought.
    He shoved aside his faint unease and urged Ellen toward the dome railing. “Maybe we can spot your ship, Lieutenant, uh, Miss Ziska. Here’s a telescope. Let me see, her orbit ought to run about so.…”
    He hunted until the Altair swam into the view-field. At this distance the spheroid looked like a tiny crescent moon, dully painted; but he could make out the sinister shapes of a rifle turret and a couple of missile launchers. “Have a look,” he invited. Her hair tickled his nose, brushing past him. It had a delightful sunny odor.
    â€œHow small she seems,” the girl said, with the same note of wonder as before. “And how huge when you’re aboard.”
    Big, all right, Blades knew, and loaded to the hatches with nuclear hellfire. But not massive. A civilian spaceship carried meteor plating, but since that was about as useful as wet cardboard against modern weapons, warcraft sacrificed it for the sake of mobility. The self-sealing hull was thin magnesium, the outer shell periodically renewed as cosmic sand eroded it.
    â€œI’m not surprised we orbited, instead of docking,” Ellen remarked. “We’d have butted against your radar and bellied into your control tower.”
    â€œWell, actually, no,” said Blades. “Even half finished, our dock’s big enough to accommodate you, as you’ll see today. Don’t forget, we anticipate a lot of traffic in the future. I’m puzzled why you didn’t accept our invitation to use it.”
    â€œDoctrine!” Warburton clipped.
    The sun came past the blind and touched the officers’ faces with incandescence. Did some look startled, one or two open their mouths as if to protest and then snap them shut again at a warning look? Blades’s spine tingled. I never heard of any such doctrine , he thought, least of