re darned useful in emergencies.
What do you think, Arcot?"

"I favor the torpedo shape. Okay, now we've got a hull. How about some
engines to run it? Let's get those, too. I'll name the general things
first; facts and figures can come later.

"First: We must have a powerful mass-energy converter. We could use the
cavity radiator and use cosmic rays to warm it, and drive the individual
power units that way, or we can have a main electrical power unit and
warm them all electrically. Now, which one would be the better?"

Morey frowned. "I think we'd be safer if we didn't depend on any one
plant, but had each as separate as possible. I'm for the individual
cavity radiators."

"Question," interjected Fuller. "How do these cavity radiators work?"

"They're built like a thermos bottle," Arcot explained. "The inner shell
will be of rough relux, which will absorb the heat efficiently, while
the outer one will be of polished relux to keep the radiation inside.
Between the two we'll run a flow of helium at two tons per square inch
pressure to carry the heat to the molecular motion apparatus. The neck
of the bottle will contain the atomic generator."

Fuller still looked puzzled. "See here; with this new space strain
drive, why do we have to have the molecular drive at all?"

"To move around near a heavy mass--in the presence of a strong
gravitational field," Arcot said. "A gravitational field tends to warp
space in such a way that the velocity of light is lower in its presence.
Our drive tries to warp or strain space in the opposite manner. The two
would simply cancel each other out and we'd waste a lot of power going
nowhere. As a matter of fact, the gravitational field of the sun is so
intense that we'll have to go out beyond the orbit of Pluto before we
can use the space strain drive effectively."

"I catch," said Fuller. "Now to get back to the generators. I think the
power units would be simpler if they were controlled from one electrical
power source, and just as reliable. Anyway, the molecular motion power
is controlled, of necessity, from a single generator, so if one is apt
to go bad, the other is, too."

"Very good reasoning," smiled Morey, "but I'm still strong for
decentralization. I suggest a compromise. We can have the main power
unit and the main verticals, which will be the largest, controlled by
individual cosmic ray heaters, and the rest run by electric power units.
They'd be just heating coils surroun