s is Coxine--" The pirate's voice bawled over
the audioceiver again. "You are under my guns. Stand by to receive a
boarding party. If you make any attempt to escape, you will be blasted!"

Tom grabbed the microphone to the audioceiver and replied, "Orders
understood, but you'll have to wait until we can build up air pressure
in the air lock."

"Very well," said Coxine. "We'll give you fifteen minutes."

Tom thought desperately. "You'll have to wait at least a half hour. We
broke a valve and have to replace it!"

Coxine's voice became suspicious. "Hey, what're you trying to pull?"

"Honest, Mister Coxine," whined Tom, "we're not doing anything."

"Fifteen minutes," roared Coxine, "or I blast a hole in your ship!"

"Yes, sir!" answered Tom, fully aware that the pirate captain would
carry out his threat.

Dropping the audioceiver microphone, the young cadet hurried to the
power deck, where Astro waited impatiently.

"Grab a couple of cutting torches, Astro," he said, "and get me a
lead-lined suit. I'm going into the reactant chamber."

"What?" demanded Astro.

"You heard me! I'm going to hide that beacon where they'll never find
it."

"In the reactant chamber?" asked Astro. "Impossible!"

"Remember when we first arrived at the prison asteroid? How thoroughly
we were searched?"

Astro nodded.

"Remember, they even searched the space between the inner and outer
hulls? There's three inches of clearance in there. If I cut into that
space through the reactant chamber and put the beacon inside, the noise
of the jets will keep Coxine from hearing it, and the radioactivity in
the chamber will keep them from picking it up on their detectors!"

Astro's face spread into a wide grin, and without another word, he began
preparing the cutting torches. Ten minutes later Tom emerged from the
chamber and nodded triumphantly. "All set, Astro! Now all we need is the
beacon."

Suddenly the _Polaris_ was rocked by a heavy explosion.

"They're firing!" yelled Astro.

"Roger! Have you finished the beacon?" demanded Tom over the intercom.

"I need another five minutes!" answered Roger. "I have to set the signal
to send out the SOS."

"Will it send out _anything_?" asked Tom.

The _Polaris_ rocked again from a second explosion.

"I don't know, Tom," yelled Roger. "I haven't even tested it!"

A third explosion jarred the rocket cruiser and the curly-haired cadet
knew that the air lock must have been demolished by now.