"Back and steady," said the Chief a moment later. "Okay!"
The tinny voice behind Joe now spoke precisely. Mike had listened to it 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."
Joe said:
"Ten seconds. Nine ... eight ... seven ... six ... five ... four ... three ... two ... one...."
He stabbed the master jato switch. And a monstrous jato rocket, built into each and every one of the pushpots outside, flared chemical fumes in a simultaneous, gigantic thrust. A small wire-wound jato for jet-assisted-take-off will weigh a hundred and forty pounds and deliver a thousand pounds of thrust for fourteen seconds. And that is for rockets using nonpoisonous compounds. The jatos of the pushpots used the beryllium-fluorine fuel that had lifted the Platform and that filled the take-off rockets of Joe's ship. These jatos gave the pushpots themselves an acceleration of ten gravities, but it had to be shared with the cage and the ship. Still....