In effect, as the rocket fuel was exhausted, the tubes that contained it dissolved into their own blast and added to the accelerating thrust, even as they diminished the amount of mass to be accelerated. Then the quantity of fuel burned could diminish—the tubes could grow smaller—so the rate of speed gain would remain constant. Under the highly special conditions of this particular occasion, there was a notable gain in efficiency over a liquid-fuel rocket design. For one item, the Platform would certainly have no use for fuel pumps and fuel tanks once it was in its orbit. In this way, it wouldn’t have them. Their equivalent in mass would have been used to gain velocity. And when the Platform finally rode in space, it would have expended every ounce of the driving apparatus used to get it there.
Now the rocket tubes were being lined and loaded. The time to take-off was growing short indeed.
Joe watched a while and turned away. He felt very good because he’d finished his job and lived up to the responsibility he’d had. But he felt very bad because he’d had an outside chance to be one of the first men ever to make a real space journey—and now it was gone. He couldn’t resent the decision against him. If it had been put up to him, he’d probably have made the same hard decision himself. But it hurt to have had even a crazy hope taken away.
Sally said, trying hard to interest him, “These rockets hold an awful lot of fuel, Joe! And it’s better than scientists thought a chemical fuel could ever be!”
“Yes,” said Joe.
“Fluorine-beryllium,” said Sally urgently. “It fits in with the pushpots’ having pressurized cockpits. Rockets like that couldn’t be used on the ground! The fumes would be poisonous!”
But Joe only nodded in agreement. He was apathetic. He was uninterested. He was still thinking of that lost trip in space. He realized that Sally was watching his face.
“Joe,” she said unhappily, “I wish you wouldn’t look like that!”
“I’m all right,” he told her.
“You act as if you didn’t care about anything,” she protested, “and you do!”