He swung the ship from its circling. He aimed it up and up, south-east by a half east. The ship climbed.
There was a logy wallowing when it penetrated the bottom of the jetstream. But it kept on, and presently a clock assured McCauley that he'd been in the stream long enough to gain all the extra speed it could give him. He aimed the ship's nose still higher and gave the ramjets every particle of fuel they could consume.
The sky grew dark. Dark purple. Faint twinklings appeared here and there. They were the stars, visible in daylight. The ramjets' tumult was still thinner now. And little by little the rate of climb grew less.
Presently the ship did not climb at all. It was as high as the ramjets could take it. Now the sunshine on its aluminum body was painfully bright, but the sky was almost black. Had there been time, he could have traced the constellations—the same constellations that people down below would not see for months, until this part of the heavens shone down on Earth's dark side.
In the pressurized cabin, Furness' voice was more nearly audible. But this was the first of two moments of truth. Here and now McCauley had to perform, as the act of a man, what highly complicated machines would later compute he should have done. He had to get the X-21 into a three-dimensional relationship to the gravitational field of Earth. He had to point the ship not only laterally but vertically in the exact direction that the exact timing of rocket thrust would convert into an orbit. An error of half a degree would immediately be fatal. An even smaller error could make the ship's course so eccentric that when he got back into air it would be with a velocity that would burn ship and men together as a meteor some fifty miles high.
He sweated, in absolute absorption in his task. Not only did the ship have to point exactly when he fired the rocket engine, but it had to be stationary, so it would not move past that point. It had to be settled dead center on an imaginary optimum or the rocket thrust would change direction as the ship's nose turned.
He flung his hand against a switch. The ramjets died. There was a vast, furry stillness—the deafness produced by the past din. McCauley spoke and barely heard his own voice. He shouted to Furness:
"Settle back for rocket fire!"
Furness nodded. He looked cadaverous. His eyes seemed filled with a peculiar, tragic despair. But his lips moved. McCauley knew that he was saying:
"Ramjets off. Maneuvering for course prior to rocket firing. Over."