The jatos burned out and dropped off. The ship swept on smoothly, and there were only two gees acceleration. But McCauley had to work swiftly, in spite of feeling that flatirons were attached to his fingers. He shook his head and panted, and swept his eyes around the horizon. It was level. He grasped the stick, unlocked it, and pulled it back. The horizon dipped downward before him and the ship rose tumultuously toward the sky.
He heard Furness' voice as a faint murmur above the overwhelming noise from the ramjets.
"X-21 reporting. Take-off complete. Everything functioning normally. Rate of ascent...."
His voice went on. There was a strange note in it, though. Even in his desperate absorption in the task at hand, McCauley noted it. But he could not spare a look at Furness.
The ship was airborne and already two thousand feet high. McCauley put it into a gigantic climbing sweep around a circle fully twenty miles across. It flew with the grace and precision of a garbage scow. Now and again it tended to wallow in flight, and he balanced it tensely, and then delicately as he confirmed the calculated feel of its controls.
The earth spread out below, wider and wider as the ship rose, and the ramjets thundered a message of the flight to the empty plain and all the rolling ground beyond it.
Furness' voice was barely audible. He talked steadily, reading off instrument indications into a microphone. There were telemeterings of all these data in transmission that were being recorded down at the base, but when the ship reached the limit to which the ramjets could carry it and began its rocket-powered flight, continuous reception of microwaves would be dubious. A longer wave length for a voice broadcast was necessary if the full value of the flight was to be realized.
The X-21 was eighteen thousand feet up when it passed Quartermain Base on its first circle. Half the atmosphere was already beneath it. Furness read off the fuel consumption of the ramjet.... The air speed.... The altitude. His face was as gray as when he entered the cabin. He kept his left hand pressed stiffly against the left side of his abdomen. McCauley was aware of it, but could not spare the time to think about it.
The eastward-flowing jetstream rushed invisibly overhead. That river of racing air, pouring west to east at three hundred miles an hour and better, was lower than ordinary today. The ship should hit it at twenty-eight thousand feet. McCauley had to get into it without risking the sheering stresses the bottom part of it might exert. He had to get into it like a man stepping onto a moving sidewalk. He adjusted the rate of climb. At twenty thousand feet the ramjets were more effective. The ship climbed more steeply. There was a difference in the bellowing of the ramjets. The noise was still monstrous, but it was thinner. It did not have the substance of thunder at ground level. But the sound was still so tremendous that it seemed to fill all of McCauley's consciousness. It required an effort of will to see, when he was so battered and hammered at by sound. It was difficult to think. His hands were heavy, and movements of which he would ordinarily have been unconscious now required almost painful effort.
Twenty-five thousand feet. McCauley glanced at the gyrocompass, computed swiftly in his head, added together his known air speed and the reported wind direction at this height, and deduced an actual course. Then he had to guess at the angle at which to hit the jetstream so that when its direction and speed were added to the ship's, the result of the several forces would be a course around the globe as nearly as possible the right one. It should pass over the most closely placed tracking stations, and it should not be immoderately far from the wide-spaced Navy ships which had been alerted for the flight and a possible unscheduled descent.