Roger nudged Astro and whispered, "What's the big deal about a D-18 rate
and a D-9 rate? Why is that so important?"

"It has to do with the pumps," replied the power-deck cadet. "They cool
the reactant fuel to keep it from getting too hot and wildcatting. At a
D-9 rate the reactant is hot enough to create power for normal flight.
Feeding at a D-18 rate is fine too, but you need pumps to cool the
motors, and pumps that could do the job would be too big."

"Kit's problem," commented Tom, "is not so much building the reactor,
but a cooling system to keep it under control."

"Will that make a big difference in who wins the race?" asked Roger.

"With that ship of Kit's," said Astro, shaking his head, "I doubt if
he'll be able to come even close to the top speeds in the trials unless
he can use the new reactor."

The room had filled up now and Strong rapped on the desk for attention.
He stared at the faces of the men before him, men who had spent their
lives in space. They were the finest pilots and crew chiefs in the solar
system. They sat quietly and attentively as Strong gave them the details
of the greatest race of spaceships in over a hundred years.

After Strong had outlined the plans for the time trials, he concluded,
"Each of you competing in the time trials will be given a blast-off time
and an orbital course. Only standard, Solar-Guard-approval equipment
will be allowed in the tests. I will monitor the trials, and Space
Cadets Corbett, Manning, and Astro will be in complete charge of all