Launch Pad Read Online Free PDF Page B

his feet shot out from under him.
    It was like trying to stand on ice. He worked at it, and eventually found his balance. It was a lot like snow-boarding on the hills of Callisto, he realized, or skiing the polar caps of Mars, something he’d tried once on shore leave. The carbon dioxide snow of Mars was nearly frictionless, too, but if you stayed loose and alert, you could stay vertical. The trick was to keep his center of gravity above his feet. It was a matter of holding his arms out, keeping his knees bent, and making continuous sliding adjustments. The low gravity worked in his favor, giving him time to correct.
    He stood, surfing down the slope. If only his brother could see him now!
    It did nothing to help his situation, but just being able to stand gave him a tremendous feeling of accomplishment, as if he were now in control of his environment. He imagined himself an Olympic ski champion, gliding down the run of artificial-snow on the slopes of Olympus Mons. He checked his display: almost to the bottom and heading uphill again, he was racing at 150 meters per second. That must certainly be breaking all ski records! He raised his hands in triumph to the imagined cheers of thousands—and skittered backwards, landing on his butt.
    In a tenth gee, falling down was no big deal. Lee twisted around and tried again, and with practice found he could stand almost without conscious effort.
    As if being able to stand up would do him any good.
    Or would it? Wait, if he could stand, couldn’t he jump? In a tenth gee, he ought to be able to jump pretty high. Wouldn’t there be some way he could just jump that tiny distance from the top of his trajectory to the rim?
    With a little practice, he discovered that indeed, he could push himself off the ice hard enough to get momentarily airborne. It took concentration and a lot of coordination to actually jump, instead of just having his limbs all flail out in all directions across the ice. (Not ice, he thought. Mirror. It’s not really ice.)
    But as quickly as his elation rose in him at the sudden hope, it drained away. Being able to jump didn’t do him any good, because he could only jump straight up. No, not even straight up—he had no traction at all, so he could only jump in a direction exactly perpendicular to the surface of the mirror. He called up the picture of his trajectory across the mirror in the heads up display, and stared at it, trying to see a flaw in his reasoning. Suppose he jumped right at the moment he reached his highest point. But the slope of the mirror was the wrong direction; he’d actually be jumping away from the rim. No help. If he jumped a little early? No, still no good; he’d always be jumping the wrong direction.
    He drew himself a little diagram in the heads-up display, and put an icon of a man in a space-suit on it. Any way he studied it, though, he couldn’t see a way that jumping was going to help him. In fact, it even hurt him—if he could add just a little bit to his velocity toward the rim, he could make it, but his jumping added velocity away from it.
    Or, wait, was that right? His jumping would actually be perpendicular to the way he was moving. So it wouldn’t change his velocity along the mirror. Or would it? He wished he understood the physics a little more. The mirror was curved. It sure looked like there ought to be a way to make this work. His jump was a vector, and there had to be some way to make that vector work in his favor. But he couldn’t see it. It was too complicated for him
    Appraise resources available, and apply them to solving your problem. His resources were himself, the child on the world’s biggest swingset … and a databot tutorial about physics.
    He flicked back to the tutorial, searching through screen after screen explaining simple harmonic motion. That was his situation, he saw; sliding in a parabolic potential well. But nothing in the tutorial discussed pushing off in the third dimension. It explained that