Stage three was easy by comparison. It began with the muted roar of thrust chambers almost behind them, a noise spectrum almost solely confined to the interior of the rocket. Outside there was no longer sufficient air molecules to convey even a whisper of sound. Nor was there a pressure build-up. The stage three engine was designed for extremely low thrust extended over a correspondingly longer time. It would drive them through the escape spiral—an orbital path around the earth during which time they would slowly increase both altitude and speed.
Crag's body felt light; not total weightlessness, but extremely light. His instruments told him they were breaching the exosphere, where molecular matter had almost ceased to exist. The atoms of the exosphere were lonely, uncrowded, isolated particles. It was the top of the air ocean where, heretofore, only monkeys, dogs and smaller test animals had gone. It was the realm of Sputniks ... Explorers ... Vanguards—all the test rockets which had made the Aztec possible. They still sped their silent orbits, borne on the space tides of velocity; eternal tombs of dogs and monkeys. And after monkey—man.
The communicator gave a burp. A voice came through the static. Drone Able was aloft. It had blasted off from its blasting pad at Burning Sands just moments after the Aztec. Prochaska bent over the radarscope and fiddled with some knobs. The tube glowed and dimmed, then it was there—a tiny pip.
Alpine came in with more data. They watched its course. Somewhere far below them and hundreds of miles to the west human minds were guiding the drone by telemeter control, vectoring it through space to meet the Aztec. It was, Crag thought, applied mathematics. He marveled at the science which enabled them to do it. One moment the drone was just a pip on the scope, climbing up from the sere earth, riding a firestream to the skies; the next it was tons of metal scorching through space, cutting into their flight path—a giant screaming up from its cradle.
It was Prochaska's turn to sweat. The job of taking it over was his. He bent over his instruments, ears tuned to the communicator fingers nervous on the drone controls. The drone hurtled toward them at a frightening speed.
Crag kept his fingers on the steering controls just in case, his mind following the Chief's hands. They began moving more certainly. Prochaska tossed his head impatiently, bending lower over the instrument console. Crag strained against his harnessing to see out of the side port. The drone was visible now, a silver shaft growing larger with appalling rapidity. A thin skein of vapor trailed from its trail, fluffing into nothingness.
If angle of closure remains constant, you're on collision course. The words from the Flying Safety Manual popped into his mind. He studied the drone.
Angle of closure was constant!
Crag hesitated. Even a touch on the steering rockets could be bad. Very bad. The slightest change in course at their present speed would impose tremendous g forces on their bodies, perhaps greater than they could stand. He looked at the Chief and licked his lips. The man was intent on his instruments, seemingly lost to the world. His fingers had ceased all random movement. Every motion had precise meaning. He was hooked onto Drone Able's steering rockets now, manipulating the controls with extreme precision. He was a concert pianist playing the strident music of space, an overture written in metal and flaming gas. Tiny corrections occurred in the Drone's flight path.