f space," said Joe. "This could've been smaller."

"It'll be nine-tenths empty when it goes up," said Sally. "But you know
about that, don't you?"

Joe did know. The reasons for the streamlining of rockets to be fired
from the ground didn't apply to the Platform. Not with the same urgency,
anyhow. Rockets had to burn their fuel fast to get up out of the dense
air near the ground. They had to be streamlined to pierce the thick,
resisting part of the atmosphere. The Platform didn't. It wouldn't climb
by itself. It would be carried necessarily at slow speed up to the point
where jet motors were most efficient, and then it would be carried
higher until they ceased to be efficient. Only when it was up where air
resistance was a very small fraction of ground-level drag would its own
rockets fire. It wouldn't gain much by being shaped to cut thin air, and
it would lose a lot. For one thing, the launching process planned for
the Platform allowed it to be built complete so far as its hull was
concerned. Once it got out into its orbit there would be no more
worries. There wouldn't be any gamble on the practicability of
assembling a great structure in a weightless "world."

The two of them--and the way they both felt, it seemed natural for Joe
to be helping Sally very carefully through the corridors of the
Platform--the two of them came to the engine room. This wasn't the place
where the drive of the Platform was centered. It was where the service
motors and the air-circulation system and the fluid pumps were powered.
Off the engine room the main gyros were already installed. They waited
only for the pilot gyros to control them as a steering engine controls
an Earth ship's rudder. Joe looked very thoughtfully at the gyro
assembly. That was familiar, from the working drawings. But he let Sally
guide him on without trying to stop and look closely.

She showed him the living quarters. They centered in a great open space
sixty feet long and twenty wide and high. There were bookshelves, and
two balconies, and chairs. Private cabins opened from it on different
levels, but there were no steps to them. Yet there were comfortable
chairs with straps so that when a man was weightless he could fasten
himself in them. There were ash trays, ingeniously designed to look like
exactly that and nothing else. But ashes would not fall into them, but
would be drawn into them by suction. There was unpatterned carpet on the
floor _and_ on the ceiling