"Well," explained the gravital engineer, "it would have to be someone living here, and he wouldn't like it if he suddenly got double or triple gravity or maybe none at all. But there's another reason. Now take a gravital unit. Any gravital unit. Most people think of it as just that—a unit. It isn't really that at all. It has three parts.
"One part is a power source that can be anything as long as it's big enough. Our power source is a nuclear pile, buried deep in the asteroid. You'd have to take Handicap Haven apart to get to it. Part two is the gravital coil, which actually produces the gravity and is simple and just about indestructible. Part three is the gravital control. It calculates the relationship between the amount of power flowing through the gravital coil and the strength of the created gravity field in any one microsecond. It uses the computed relationship to alter the power flowing through in the next microsecond to get the same gravity. No change of power, no gravity. I guess you could call the control unit a computer, as good a one as is made for any purpose."
The engineer rubbed his chin. "Fatigue," he continued. "The gravital control is an intricate computer that's subject to fatigue. That's why it has to rest an hour and a half to do forty-five minutes of work. Naturally they don't want anyone tinkering with it. It's non-repairable. Crack the case open and it won't work. But first you have to open it. Mind you, that can be done. But I wouldn't want to try it without a high-powered lab setup."
If it didn't seem completely foolproof, neither did it seem a likely source of trouble. "Then we can forget about the gravital units," said Cameron, arising. "But what about hand weapons? Are there any available?"
"You mean toasters?"
"Anything that's lethal."
"Nothing. No knives even. Maybe a stray bar or so of metal." Vogel scratched his head. "There is something dangerous, though. Dangerous if you know how to take hold of it."
Instantly Cameron was alert. "What's that?"
"Why, the asteroid itself. You can't physically touch any part of the gravital unit. But if you could somehow sneak an impulse into the computer and change the direction of the field...." Vogel was very grave. "You could pick up Handicap Haven and throw it anywhere you wanted. At the Earth, say. Thirty miles in diameter is a big hunk of rock."
It was this kind of information Cameron was looking for, though the engineer seemed to regard the occasion as merely a social call. "Is there any possibility of that occurring?" he asked quietly.