He cut off and made his preparations. His figuring was extremely close. But there had necessarily been a slight margin of fuel. A circular orbit does not require nearly the fuel expenditure that an elliptical one does. But McCauley had made the most efficient possible use of fuel at the beginning. He'd used one long blast, a two-second blast, and a one-second rocket thrust to get into nearly a perfect space trail. He meant to collect for that partly accidental expertness. But he meant to collect much more for an observation. The observation was that a one-second blast was not a thousandth the ordeal that a sixty-second blast was. No man could survive a long-continued twenty-gravity acceleration. But most men could take a one-second push--and not only once, but many times. With time for recovery in between, and a rocket engine that fired infallibly when it was turned on.... He set the rocket timer. "This," he said over his shoulder, "may be our last chance to exchange compliments, Furness. But I think you're the same kind of idiot as I am. I'd have come on this trip with my insides hanging out rather than stay behind. So would you. Very nearly, you did. It's nice to have known you. I hope we survive." Steam-jets spouted at the ends of the X-21's rear fins. In emptiness, the ship spun halfway about until the swiftly moving solidity below ceased to move toward the pointed nose. It fled away. The ship traveled backward where there was no air. "And here we go," said McCauley. The rocket timer was set. He pressed the blast button. A second later he came out of near-unconsciousness and set it again. There was another rocket blast. He almost recovered from the effect of it before he set the timer for a third. Doggedly he set the timer and pressed the button, and allowed himself three full breaths and set it and pressed again. The shocks seemed to become more and more violent and intolerable. They were. With loss of mass, the acceleration of the lightened ship went up to twenty-two gees. He cut the blasts to three-quarters of a second. A rocket cannot be throttled down. It fires full blast or it has no appreciable effect at all. * * * * * Quartermain Base was built on a flat, flat plain that extended miles in every direction. Its buildings, from a reasonable distance, were only toy structures, tiny angular objects in the middle of vastness. Overhead there was a sky of absolute blue. It was empty. Below, there was flatness to the horizon. It contained nothing. There was no motion of any sort anywhere. The base lay still and silent under the baking two-o'clock sun. Nothing happened. Nothing....