Gyroscopes and acceleration-measuring instruments determined the actual
trajectory of the ship; the navigation computer compared the actual
trajectory with the trajectory set in before take-off; when a deviation
from the pre-set trajectory occurred, the autopilot steered the ship
back to the proper trajectory. As the computer on the ground obtained
better velocity and position information about the missile from the
ground radar, it sent course corrections to the ship, which were
accepted in the computer as changes to the pre-set trajectory. The
navigation computer hummed and buzzed; lights flickered on and off on
the instrument panel; relays clicked behind the panel. The ship steered
itself toward the correct intercept point. All this automatic operation
was required because no merely human pilot had reflexes fast enough to
carry out an intercept at twenty-six thousand feet per second. And even
had his reflexes been fast enough, he could not have done the precise
piloting required while being pummeled by this acceleration.

As it was, Major Harry Lightfoot, fighter pilot, lay motionless in his
acceleration couch. His face was distorted by the acceleration. His
breathing was labored. Compressed-air bladders in the legs of his
gee-suit alternately expanded and contracted, squeezing him like the
obscene embrace of some giant snake, as the gee-suit tried to keep his
blood from pooling in his legs. Without the gee-suit, he would have
blacked out, and eventually his brain would have been permanently
damaged from the lack of blood to carry oxygen to it.

A red light on the instrument panel blinked balefully at him as it
measured out the oxygen he required. Other instruments on the panel
informed him of the amount of cooling air flowing through his suit to
keep his temperature within the tolerable range, and the amount of
moisture the dehumidifier had to carry away from him so that his suit
didn't become a steam-bath. He was surrounded by hundreds of pounds of
equipment which added nothing to the performance of the ship; which
couldn't be counted as payload; which cut down on the speed and altitude
the ship might have reached without them. Their sole purpose was to keep
this magnificent high-performance, self-steering machine from killing
its load of fragile human flesh.

At one hundred twenty-eight seconds after launch, the acceleration
suddenly dropped to zero. He breathed deeply again, and swallowed
repeatedly to get th