To move the asteroid into a new orbit, they were going to fire nuclear bombs. Most of the highly radioactive fission products would be blown into space, but some would be drawn back by the asteroid's slight gravity. The craters would be highly radioactive and some radioactive debris would be scattered around, too. Every particle would add to the problem.
"Is there anything we can do, sir?" Koa asked.
Rip shook his head inside the transparent bubble. "If you have a good luck charm in your pocket, you might talk to it. That's about all."
Nuclear physics had been part of his training. He read the gamma meter again and did some quick mental calculations. They would be exposed to radiation for the entire trip, at a daily dosage of—
Koa interrupted his train of thought. Evidently the sergeant-major had been doing some calculations of his own. "How long will we be on this rock, sir?[pg 090] You've never told us how long the trip will take."
Rip said quietly, "With luck, it will take us a little more than three weeks."
He could see their faces faintly in the dim sunlight. They were shocked. Space ships blasted through space between the inner planets in a matter of hours. The nuclear drive cruisers, which could approach almost half the speed of light, had brought even distant Pluto within easy reach. The inner planets could be covered in a matter of minutes on a straight speed run, although to take off from one and land on the other meant considerable time used in acceleration and deceleration.
The Planeteers were used to such speed. Hearing that it would take over three weeks to reach earth had jarred them.
"This piece of metal isn't a space ship," Rip reminded them. "At the moment, our speed around the sun is just slightly more than ten miles a second. If we just shifted orbits and kept the same speed, it would take us months to reach Terra. But we'll use two bombs to kick the asteroid into the orbit, then fire one to increase speed. The estimate is that we'll push up to about forty miles a second."
Koa spoke up. "That's not bad when you think that Mercury is the fastest planet and it only makes about thirty miles a second."