"To begin with," said Fuller, "let's decide what shape we want to use. As designer, I'd like to point out that a sphere is the strongest, a cube easiest to build, and a torpedo shape the most efficient aerodynamically. However, we intend to use it in space, not air. "And remember, we'll need it more as a home than as a ship during the greater part of the trip." "We might need an aerodynamically stable hull," Wade interjected. "It came in mighty handy on Venus. They'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 surrounded by the field."