120
onds at two gravities acceleration the rocket burned out. The Chief had fired a matching rocket. They were miles apart, but speeding Earthward on very nearly identical courses.
The Platform grew smaller. That was their only proof of motion.
A very, very long time passed. The Chief fired his steering rockets to bring him closer to Joe. It did not work. He had to aim for Joe and fire a blast to move noticeably nearer. Presently he would have to blast again to keep from passing.
Joe made calculations in his head. He worried. He and the Chief were speeding Earthward--away from the Platform--at more than four miles a minute, but it was not enough. The manned rocket was accelerating at a great deal more than that rate. And if the Platform's enemies down on Earth had sent a manned rocket up to destroy the Platform, the man in it would have ways of defending himself. He would expect guided missiles--but he probably wouldn't expect to be attacked by space wagons.
Joe said suddenly:
"Chief! I'm going to burn a twelve-two. We've got to match velocities coming back. Join me? Three--two--one."
He fired a twelve-two. Twelve seconds burning, two gravities acceleration. It built up his speed away from the Platform to a rate which would have been breathless, on Earth. But here there was no sensation of motion, and the distances were enormous. Things which happen in space happen with insensate violence and incredible swiftness. But long, long, long intervals elapse between events. The twelve-two rocket burned out. The Chief had matched that also.
Brown's voice in the headphones said, "The rocket's cut acceleration. It's floating up, now. It should reach our orbit fifty miles behind us. But our missile should hit it in forty seconds."
"I wouldn't bet on that," said Joe coldly. "Figure interception data for the Chief and me. Make it fast!"
He spotted the Chief, a dozen miles away an