It was simple. Speeding toward the rising assassin, and with his missiles rushing toward them, the relative speeds of the wagons and the missiles were added together. If the space wagons dodged, the missile operator had less time to swing his guided rockets to match the change of target course. And besides, the attacker hadn't made a single turn in space. Not yet. He might know that a rocket doesn't go where it's pointed, as a matter of theory. He might even know intellectually that the final speed and course of a rocket is the sum of all its previous speeds and courses. But he hadn't used the knowledge Joe and the Chief had. Something rushed at them. They went into evasive action. And they didn't merely turn the noses of their space wagons. They flung them about end-for-end, and blasted. They used wholly different accelerations at odd angles. Joe shot away from Earth on steering rocket thrust, and touched off a four-three while he faced toward Earth's north pole, and halfway along that four-second rush he flipped his craft in a somersault and the result was nearly a right-angled turn. When the four-three burned out he set off a twelve-two, and halfway through its burning fired a three-two with it, so that at the beginning he had two gravities acceleration, then four gravities for three seconds, and then two again. With long practice, a man might learn marksmanship in space. But all a man's judgment of speeds is learned on Earth, where things always, always, always move steadily. Nobody making his first space-flight could possibly hit such targets as Joe and the Chief made of themselves. The man in the enemy rocket was making his first flight. Also, Joe and the Chief had an initial velocity of 200 miles a minute toward him. The marksman in the rising rocket hadn't a chance. He fired four more missiles and tried desperately to home them in. But---- They flashed past his rising course. And then they were quite safe from his fire, because it would take a very long time indeed for anything he shot after them to catch up. But their missiles had still to pass him--and Joe and the Chief could steer them without any concern about their own safety or anything else but a hit. They made a hit. Two of the eight little missiles flashed luridly, almost together, where the radar-pips showed the rocket to be. Then there were two parts to the rocket, separating. One was small and one was fairly large. Another demolition-missile hit the larger section. Still another exploded as that was going to pieces. The smaller fragment ceased to be important. The explosions weren't atomic bombs, of course. They were only demolition-charges. But they demolished the manned rocket admirably. Brown's voice came in the headphones, still tense. "_You got it! How about the others?_"