our orders enroute.
They don't say when. I'll decide that. Until I do decide, I have a job for
you and your men. Do you know anything about nuclear physics?"

Rip's eyes narrowed. He said cautiously, "A little, sir."

"I'll assume you know nothing. Foster, the designation SCN means Space
Cruiser, Nuclear. This ship is powered by a nuclear reactor. In other
words, an atomic pile. You've heard of one?"

Rip controlled his voice, but his red hair stood on end with anger.
O'Brine was being deliberately insulting. This was stuff any new Planeteer
recruit knew. "I've heard, sir."

"Fine. It's more than I had expected. Well, Foster, a nuclear reactor
produces heat. Great heat. We use that heat to turn a chemical called
methane into its component parts. Methane is known as marsh gas, Foster. I
wouldn't expect a Planeteer to know that. It is composed of carbon and
hydrogen. When we pump it into the heat coils of the reactor, it breaks
down and creates a gas that burns and drives us through space. But that
isn't all it does."

[Illustration: "You're a Planeteer. I Don't Like Planeteers."]

"You're a Planeteer. I Don't Like Planeteers."

Rip had an idea what was coming, and he didn't like it. Nor did he like
Commander O'Brine. It was not until much later that he learned that
O'Brine had been on his way to Terra to see his family for the first time
in four years when the cruiser's orders were changed. To the commander,
whose assignments had been made necessary by the needs of the Special
Order Squadrons, it was too much. So he took his disappointment out on the
nearest Planeteer, who happened to be Rip.

"The gases go through tubes," O'Brine went on. "A little nuclear material
also leaks into the tubes. The tubes get coated with carbon, Foster. They
also get coated with nuclear fuel. We use thorium. Thorium is radioactive.
I won't give you a lecture on radioactivity, Foster. But thorium mostly
gives off the kind of radiation known as alpha particles. Alpha is not
dangerous unless breathed or eaten. It won't go through clothes or skin.
But when mixed with fine carbon, thorium alpha contamination makes a mess.
It's a dirty mess, Foster. So dirty that I don't want my spacemen to fool
with it.

"I want you to take care of it instead," O'Brine said. "You and your men.
The deputy commander will assign you to a squadroom. Settle in, then draw
equipment from the supply room and get going. When I want to talk