mped up so fast that the action shot him to the
ceiling. He kicked down again and leaned over the officer's 'scope. Rip
got there by pulling himself right across the top of the chart table.

The green point of light on the 'scope was bigger than any other he had
seen.

"It's about the right size," O'Brine said. There was excitement in his
voice. "Correct course. Let's take a look at it."

All hands gripped something with which to steady themselves as the cruiser
spun swiftly onto the new course. The control officer called, "I have it
centered, sir. We'll reach it in about an hour at this speed."

"Jack it up," O'Brine ordered. "Heave some neutrons into it. Double speed,
then decelerate to reach it in thirty minutes."

The control officer issued orders to the engine control room. In a moment
acceleration plucked at them. O'Brine motioned to Rip. "Come on, Foster.
Let's see what Analysis makes of this rock."

Rip followed the commander to the deck below where the technical analysts
were located. His heart was pounding a little faster than usual, and not
from acceleration, either. He found himself wetting his lips frequently
and thought, "Get hold of it, boy. You got nothing to worry about but high
vacuum."

He didn't really believe it. There would be plenty to worry about. Like
detonating nuclear bombs and trying to figure their blast reaction. Like
figuring out the course that would take them closest to the sun without
pulling them into it. Like a thousand things--all of them up to him.

The chief analyst greeted them. "We got the orders to change course,
Commander. That gave us the location of the asteroid. We're already
working on it."

"Anything yet?"

"No, sir. We'll have the albedo measurement in a few minutes. It will take
longer to figure the mass."

The asteroid's efficiency in reflecting sunlight was its albedo. The
efficiency depended on the material of which it was made. The albedo of
pure metallic thorium was known. If the asteroid's albedo matched it, that
would be one piece of evidence.

In the same way, the mass of thorium was known. The measurements of the
asteroid were being taken. They would be compared with a chunk of thorium
of the same size. If it worked out, that would be evidence enough.

Commander O'Brine motioned to chairs. "Might as well sit down while we're
waiting, Foster." He took one of the chairs and looked closely at Rip.
Suddenly he grinned. "I thought Planeteers never got