"It's five.... We're at 17,000 feet ...
18,000. We should get some eastward velocity at 32,000 feet. Our height
is now 21,000 feet...."

There was no change in the feel of things inside the ship, of course.
Sealed against the vacuum of space, barometric pressure outside made no
difference. Height had no effect on the air inside the ship.

At 25,000 feet the Chief said suddenly: "We're pointed due east, Joe.
Freeze it?"

"Right," said Joe. "Freeze it."

The Chief threw a lever. The gyros were running at full operating speed.
By engaging them, the Chief had all their stored-up kinetic energy
available to resist any change of direction the pushpots might produce
by minor variations in their thrusts. Haney brooded over the reports
from the individual engines outside. He made minute adjustments to keep
them balanced. Mike uttered curt comments into the communicator from
time to time.

At 33,000 feet there was a momentary sensation as if the ship were
tilted sharply. It wasn't. The instruments denied any change from level
rise. The upward-soaring complex of flying things had simply risen into
a jet-stream, one of those wildly rushing wind-floods of the upper
atmosphere.

"Eastern velocity four hundred," said Mike from the communicator. "Now
four-twenty-five.... Four-forty."

There was a 300-mile-an-hour wind behind them. A tail-wind, west to
east. The pushpots struggled now to get the maximum possible forward
thrust before they rose out of that east-bound hurricane. They added a
fierce push to eastward to their upward thrust. Mike's cracked voice
reported 500 miles an hour. Presently it was 600.

At 40,000 feet they were moving eastward at 680 miles an hour. A
jet-motor cannot be rated except indirectly, but there was over 200,000
horsepower at work to raise the spacecraft and build up the highest
possible forward speed. It couldn't be kept up, of course. The pushpots
couldn't carry enough fuel.

But they reached 55,000 feet, which is where space begins for humankind.
A man exposed to emptiness at that height will die just as quickly as
anywhere between the stars. But it wasn't quite empty space for the
pushpots. There was still a very, very little air. The pushpots could
still thrust upward. Feebly, now, but they still thrust.

Mike said: "Communications says get set to fire jatos, Joe."

"Right!" he replied. "Set yourselves."

Mike flung a switch, and a voice began to chatter behind Joe's head. It
was the vo