Space Tug. Murray Leinster

far below and far behind. Mike settled himself in the tiny acceleration-chair built for him. The Chief squirmed to comfort in his seat. Haney took his hands from the equalizing adjustments he had to make so that Joe’s use of the controls would be exact, regardless of moment-to-moment differences in the thrust of the various jets.

      “We’ve got a yaw right,” said the Chief sharply. “Hold it, Joe!”

      Joe waited for small quivering needles to return to their proper registrations.

      “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....

      Joe felt himself slammed back into his seat with irresistible, overwhelming force. The vibration from the jets had been bad. Now he didn’t notice it. He didn’t notice much of anything but the horrible sensations of six-gravity acceleration.

      It was not exactly pain. It was a feeling as if a completely intolerable and unbearable pressure pushed at him. Not only on the outside, like a blow, but inside too, like nothing else imaginable. Not only his chest pressed upon his lungs, but his lungs strained toward his backbone. Not only the flesh of his thighs tugged to flatten itself against his acceleration-chair, but the blood in his legs tried to flow into and burst the blood-vessels in the back of his legs.

      The six-gravity acceleration seemed to endure for centuries. Actually, it lasted for fourteen seconds. In that time it increased the speed of the little ship by rather more than half a mile per second, something over 1,800 miles per hour. Before, the ship had possessed an orbital speed of a shade over 1,470 miles an hour. After the jato thrust, it was traveling nearly 3,400 miles per hour. It needed to travel something over 12,000 miles per hour to reach the artificial satellite of Earth.

      The intolerable thrust ended abruptly. Joe gasped. But he could allow himself only a shake of the head to clear his brain. He jammed down the take-off rocket firing button. There was a monstrous noise and a mighty surging, and Haney panted, “Clear of cage....”

      And then they were pressed fiercely against their acceleration chairs again. The ship was no longer in its launching cage. It was no longer upheld by pushpots. It was free, with its take-off rockets flaming. It plunged on up and out. But the acceleration was less. Nobody can stand six gravities for long. Anybody can take three—for a while.

      Joe’s body resisted movement with a weight of four hundred and fifty pounds, instead of a third as much for normal. His heart had to pump against three times the normal resistance of gravity. His chest felt as if it had a leaden weight on it. His tongue tried to crowd the back of his mouth and strangle him. The sensation was that of a nightmare of impossible duration. It was possible to move and possible to see. One could breathe, with difficulty, and with titanic effort one could speak. But there was the same feeling of stifling resistance to every movement that comes in nightmares.

      But Joe managed to keep his eyes focused. The dials of the instruments said that everything was right. The tinny voice behind his head, its timbre changed by the weighting of its diaphragm, said: “All readings check within accuracy of instruments. Good work!”

      Joe moved his eyes to a quartz window. The sky was black. But there were stars. Bright stars against a black background. At the same instant he saw the bright white disks of sunshine that came in the cabin portholes. Stars and sunshine together. And the sunshine was the sunshine of space. Even with the polarizers cutting off some of the glare it was unbearably bright and hot beyond conception. He smelled overheated paint, where the sunlight smote on a metal bulkhead. Stars and super-hot sunshine together....

      It was necessary to pant for breath, and his heart pounded horribly and his eyes tried to go out of focus, but Joe Kenmore strained in his acceleration-chair and managed to laugh a little.

      “We did it!” he panted. “In case you didn’t notice, we’re out of—the atmosphere and—out in space! We’re—headed to join the Space Platform!”

      Chapter 2

      The pressure of three gravities continued. Joe’s chest muscles ached with the exertion of breathing over so long a period. Six gravities for fourteen seconds had been a ghastly ordeal. Three gravities for minutes built up to something nearly as bad. Joe’s heart began to feel fatigue, and a man’s heart normally simply doesn’t ever feel tired. It became more and more difficult to see clearly.

      But he had work to do. Important work. The take-off rockets were solid-fuel jobs, like those which launched the Platform. They were wire-wound steel tubes lined with a very special refractory, with unstable beryllium and fluorine compounds in them. The solid fuel burned at so many inches per second. The refractory crumbled away and was hurled astern at a corresponding rate—save for one small point. The refractory was not all exactly alike. Some parts of it crumbled away faster, leaving a pattern of baffles which acted like a maxim silencer on a rifle, or like an automobile muffler. The baffles set up eddies in the gas stream and produced exactly the effect of a rocket motor’s throat. But the baffles themselves crumbled and were flung astern, so that the solid-fuel rockets had always the efficiency of gas-throated rocket motors; and yet every bit of refractory was reaction-mass to be hurled astern, and even the steel tubes melted and were hurled away with a gain in acceleration to the ship. Every fraction of every ounce of rocket mass was used for drive. No tanks or pumps or burners rode deadhead after they ceased to be useful.

      But solid-fuel rockets simply can’t be made to burn with absolute evenness as a team. Minute differences in burning-rates do tend to cancel out. But now and again they reinforce each other and if uncorrected will throw a ship off course. Gyros can’t handle such effects. So Joe had to watch his instruments and listen to the tinny voice behind him and steer the ship against accidental wobblings as the Earth fell away behind him.

      He battled against the fatigue of continuing to live,