one of
them would have an idea. But no useful suggestions were forthcoming until
little Dominico spoke up. "Sir, why don't we make two bombs from one?"

[Illustration: "Sir, Why Don't We Make Two Bombs From One?"]

"Sir, Why Don't We Make Two Bombs From One?"

"I wish we could," Rip said. "Do you know how, Dominico?"

"No, Lieutenant. If we had parts, I could put bombs together. I can take
them apart, but I don't know how to make two out of one." The Italian
Planeteer looked accusingly at Rip. "I thought maybe you know, sir."

Rip grunted. If they had parts, he could assemble nuclear bombs, too. Part
of his physics training had been concerned with fission and its various
applications. But no one had taught him how to make two bombs out of one.

The theory of nuclear explosions was simple enough. Two or more correctly
sized pieces of plutonium or uranium isotope, when brought together,
formed what was known as a critical mass, which would fission. The
fissioning released energy and produced the explosion.

But there was a wide gap between theory and practice. A nuclear bomb was
actually pretty complicated. It had to be complicated to keep the pieces
of the fissionable material apart until a chemical explosion drove them
together fast and hard enough to create a fission explosion. If the pieces
weren't brought together rapidly enough, the mass would fission in a slow
chain reaction and no explosion would result.

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.
Probably 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--some material with the type
of radioactivity that produced neutrons--to start 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.