fter rigid
examinations and tests. Topside, on the radar bridge, was Roger Manning,
cocky and brash, but a specialist in radar and communications. Below, on
the power deck, was Astro, a colonial from Venus, who had been accused
of cutting his teeth on an atomic rocket motor, so great was his skill
with the mighty "thrust buckets," as he lovingly called the atomic
rockets.

Now, returning from a routine training flight that had taken them to the
moons of Jupiter, the three cadets, Corbett, Manning, and Astro, and
their unit skipper, Captain Steve Strong, completed the delicate task of
setting the great ship down on the Academy spaceport.

"Closing in fast, sir," announced Tom, his attention focused on the
meters and dials in front of him. "Five hundred feet to touchdown."

"Full braking thrust!" snapped Strong crisply.

Deep inside the _Polaris_, braking rockets roared with unceasing power,
and the mighty spaceship eased itself to the concrete surface of the
Academy spaceport.

"Touchdown!" yelled Tom. He quickly closed the master control lever,
cutting all power, and sudden silence filled the ship. He stood up and
faced Strong, saluting smartly.

"Rocket cruiser _Polaris_ completes mission"--he glanced at the astral
chronometer on the panel board--"at fifteen thirty-three, sir."

"Very well, Corbett," replied Strong, returning the salute. "Check the
_Polaris_ from radar mast to exhaust ports right away."

"Yes, sir," was Tom's automatic answer, and then he caught himself. "But
I thought--"

Strong interrupted him with a wave of his hand. "I know, Corbett, you
thought the _Polaris_ would be pulled in for a general overhaul and you
three would get liberty."

"Yes, sir," replied Tom.

"I'm not sure you won't get it," said Strong, "but I received a message
last night from Commander Walters. I think the _Polaris_ unit might have
another assignment coming up!"

"By the rings of Saturn," drawled Roger from the open hatch to the radar
bridge, "you might know the old man would have another mission for us!
We haven't had a liberty since we were Earthworms!"

"I'm sorry, Manning," said Strong, "but you know if I had my way, you'd
certainly get the liberty. If anyone deserves it, you three do."

By this time Astro had joined the group on the control deck.

"But, sir," ventured Tom, "we've all made plans, I mean--well, my folks
are expecting me."

"_Us_, you mean," interrupted Roger. "Astro and I are your guests,