while the work of take-off could be divided, so that Joe would not be
distracted. Now Joe had to control everything at once.

The roar of the pushpots outside the ship had long since lost the volume
and timbre of normal atmosphere. Not much sound could be transmitted by
the near-vacuum outside. But the jet motors did roar, and the sound
which was not sound at such a height was transmitted by the metal cage
as so much pure vibration. The walls and hull of the spaceship picked up
a crawling, quivering pulsation and turned it into sound. Standing waves
set up and dissolved and moved erratically in the air of the cabin.
Joe's eardrums were strangely affected. Now one ear seemed muted by a
temporary difference of air pressure where a standing wave lingered for
a second or two. Then the other eardrum itched. There were creeping
sensations as of things touching one and quickly moving away.

Joe swung a microphone into place before his mouth.

"All set," he said evenly. "Brief me."

The tinny voice said:

"_You are at 65,000 feet. Your curve of rate-of-climb is flattening out.
You are now rising at near-maximum speed, and not much more forward
velocity can be anticipated. You have an air-speed relative to surface
of six-nine-two miles per hour. The rotational speed of Earth at this
latitude is seven-seven-eight. You have, then, a total orbital speed of
one-four-seven-oh miles per hour, or nearly twelve per cent of your
needed final velocity. Since you will take off laterally and practically
without air resistance, a margin of safety remains. You are authorized
to blast._"