9
But even at ten gravities' drive it takes time to travel 4,000 miles. At three, and coasting a great deal of the way, it takes much longer. The Platform circled Earth in four hours and a little more. Anything intending interception and rising straight up needed to start skyward long before the Platform was overhead. A three-g rocket would start while the Platform was still below the western horizon from its launching-spot. Especially if it planned to coast part of its journey—and a three-gravity rocket would have to coast most of the way.
So there was time. Coasting, the rising manned rocket would be losing speed. If it planned to go no higher than the Platform's orbit, its upward velocity would be zero there. If it were intercepted 500 miles down, it would be rising at an almost leisurely rate, and Joe and the Chief could check their Earthward plunge and match its rising rate.
This they did. But what they couldn't do was match its orbital velocity, which was zero. They had the Platform's eastward speed to start with—over 200 miles a minute. No matter how desperately they fired braking-rockets, they couldn't stop and maneuver around the rising control-ship. Inevitably they would simply flash past it in the fraction of an instant. To fire their tiny guided missiles on ahead would be almost to assure that they would miss. Also, the enemy ship was manned. It could fight back.
But Joe had been on the receiving end of one attack in space. It wasn't much experience, but it was more than anybody but he and his own crew possessed.
"Chief," said Joe softly into his helmet-mike, as if by speaking softly he could keep from being overheard, "get close enough to me to see what I do, and do it too. I can't tell you more. Whoever's running this rocket might know English."
There was a flaring of vapor in space. The Chief was using his steering-rockets to draw near.
Joe spun his little space wagon about, so that it pointed back in the direction from which he had come. He had four guided missiles, demolition type. Very deliberately, he fired the four of them astern—away from the rising rocket. They were relatively low-speed missiles, intended to blow up a robot ship that couldn't be hooked onto, because it was traveling too much faster or slower than the Platform it was intended to reach. The missiles went away. Then Joe faced about again in the direction of his prospective target. The Chief fumed—Joe heard him—but he duplicated Joe's maneuver. He faced his own eccentric vessel in the direction of its line of flight.
Then his fuming suddenly ceased. Joe's headphones brought his explosive grunt when he suddenly saw the idea.