f the
pieces weren't brought together rapidly enough, the mass would fission
in a slow chain reaction with no explosion.

Rip was trained in scientific analysis. He tackled the problem logically,
considering the design of a nuclear bomb and the reasons for it.

Atomic bombs had to be carried. That meant an outer casing was necessary.
The casing had a lot to do with the design. Suppose no casing were
required? What would be needed?

He took the stylus and computation board from Koa and jotted down the
parts required. First, two or more pieces of plutonium large enough to
form a critical mass. Second, a neutron source--the type of radioactivity
that produced neutrons--to accelerate the reaction. Third, some kind of
neutron reflector. And fourth, explosive to drive the pieces together.

Did they have all those items? He checked them off. Their single five KT
bomb contained at least enough plutonium for two critical masses, if
brought together inside a good neutron reflector. Each mass should give
about a two kiloton explosion. And they did have a good neutron
reflector--nuclite. There wasn't anything better.

"What have we got for a neutron source?" he asked aloud. He was really
asking himself, but he got a quick answer from Koa.

"Sir, some of the stuff left in the craters from the other explosions
gives off neutrons."

"You're right," Rip agreed instantly. A small piece from one of the
craters, when combined with half of the neutron source in the bomb,
should be enough. As for the explosive, they had exploding heads on their
attack rockets.

In other words, he had what he needed--except for a method of putting all
the pieces together to create a bomb.

If only they had a tube of some sort that would withstand the chemical
explosion--the one that brought the critical mass together!

He told the Planeteers what he had been thinking, then asked, "Any ideas
for a tube?"

"How about a tube from the snapper-boat?" Santos suggested.

Rip shook his head. "Not strong enough. They're designed to withstand the
slow push of rocket fuel, not the fast rap of an explosion. When I say
slow, I mean slow-burning when compared with explosive. Any more ideas?"

Kemp, the expert torchman, said, "Sir, I can burn you a tube into the
asteroid."

Rip grabbed the Planeteer so hard they both floated upward. "Kemp, that's
wonderful! That's it!" The details took form in his mind even as he
called orders. "Dominico, tear down that bo