There was something else that Rip didn't add, although he knew the Planeteers would realize it in a few minutes. Probably some of them already had thought of it.

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 was certain to 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 calculations. They would be exposed 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? You've never told us just 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. Spaceships 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 spaceship," 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 one bomb for retrothrust, then fire two 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."

"Right," Rip agreed. "After the asteroid is kicked out of orbit, it will fall toward the sun. At our closest approach to the sun, we'll have enough velocity to carry us past safely. Then we'll lose speed constantly until we come into Earth's gravitational field and have to brake."

It was just space luck that Terra was on the other side of the sun from the asteroid's present position. By the time they approached, it would be in a good place, just far enough from the line to the sun to avoid changing course. Of course, Rip's planned orbit was not aiming the asteroid at Earth, but at where Earth would be at the end of the trip.

"That means more than three weeks of radiation, then," Corporal Santos observed. "Can we take it, sir?"

Rip shrugged, but the gesture couldn't be seen inside his space suit. "At the rate we're getting radiation now, plus what I estimate we'll get from the nuclear explosions, we'll get the maximum safety limit in just three weeks. That leaves us no margin, even if we risk getting radiation sickness. So we have to get shielding pretty soon. If we do, we can last the trip."

Private Dominico saluted and moved forward. "Sir, may I ask a question?"

Rip turned to face the Planeteer, still worrying over the problem. He nodded and said, "What is it, Dominico?"

"Sir, I think we can't worry too much about this radiation, eh? You will think of some way to take care of it. What I want to ask, sir, is when do we let go the bombs? I do not know much about radiation, but I can set those bombs like you want them."

Rip was touched by the Planeteer's faith in his ability to solve the radiation problem. That was why being an officer in the Special Order Squadrons was so challenging. The men knew the kind of training their officers had, and they expected them to come up with technical solutions as the situation required.

"You'll have a chance to set the bombs in just a short while," he said crisply. "Let's get busy. Koa, load all bombs but one ten KT on the landing boat. Stake the rest of the equipment down. While you're doing that, I'll find the spots where we plant the charges. I'll need two men now and more later."

He went back to his instrument, putting the radiation problem out of his mind—a rather hard thing to do with the colorimeter glowing pink next to his shoulder. Koa detailed men to load the nuclear bombs into the landing craft, left Pederson to supervise, and then brought Santos with him to help Rip.

"The bombs are being put on the boat, sir," Koa reported.

"Fine. There isn't too much chance of the blasts setting them off, but we'll take no chances at all. Koa, I'm going to shoot a line straight out toward Alpha Centauri. You walk that way and turn on your belt light. I'll tell you which way to move."

He adjusted his sighting rings while the sergeant major glided away. Moving around on a no-weight world was more like skating than walking. A regular walk would have lifted Koa into space with every step. Of course, the asteroid had some gravity, but so little that it hardly mattered.

Rip centered the top of the instrument's vertical hairline on Alpha Centauri, then waited until Koa was almost out of sight over the asteroid's horizon, which was only a few hundred yards away.

He turned up the volume on his helmet communicator. "Koa, move about ten feet to your left."

Koa did so. Rip sighted past the vertical hairline at the belt light. "That's a little too far. Take a small step to the right. That's good ... just a few inches more ... hold it. You're right in position. Stand where you are."

"Yessir."

Rip turned to Santos. "Stand here, Corporal. Take a sight at Koa to get your bearings, then hold position."

Santos did so. Now the two lights gave Rip one of the lines he needed. He called for two more men, and Trudeau and Nunez joined him. "Follow me," he directed.

Rip picked up the instrument and carried it to a point ninety degrees from the line represented by Koa and Santos. He put the instrument down and zeroed it on Messier 44, the Beehive star cluster in the constellation Cancer. For the second sighting star he chose Beta Pyxis as being closest to the line he wanted, made the slight adjustments necessary to set the line of sight, since Pyxis wasn't exactly on it, then directed Trudeau into position as he had Koa. Nunez took position behind the instrument, and Rip had his cross fix.

He called for Dowst, then carried the instrument to the center of the cross formed by the four men. Using the instrument, he rechecked the lines from the center out. They were within a hair or two of being exactly on, and a slight error wouldn't hurt, anyway. He knew he would have to correct with rocket blasts once the asteroid was in the new orbit.

"X marks the spot," he told Dowst. He put his toe on the place where the crosslines met.

Dowst used a spike to make an X in the metal ground.

"All set," Rip announced. "You four men can move now. Let's have the cutting equipment over here, Koa."

The Planeteers were all waiting for instructions now. In a few moments the equipment was ready, fuel and oxygen bottles attached.

"Who's the champion torchman?" Rip asked.

Koa replied, "Kemp is, sir."

Kemp, one of the two American privates, took the torch and waited for orders. "We need a hole six feet across and twenty feet deep," Rip told him. "Go to it."

"How about direction, sir?" Kemp asked.

"Straight down. We'll take a bearing on an overhead star when you're in a few feet."

Dowst inscribed a circle around the X he had made and stood back. Kemp pushed the striker button and the torch flared. "Watch your eyes," he warned. The Planeteers reached for belt controls and turned the rheostats that darkened the clear bubbles electronically. Kemp adjusted his flame until it was blue-white, a knife of fire brighter by far than the light of the sun at this distance.

Koa stepped behind Kemp and leaned against his back, because the flame of the torch was like an exhaust, driving Kemp backward. Kemp bent down, and the torch sliced into the metal of the asteroid like a hot knife into ice. The metal splintered a little as the heat raised it instantly from almost absolute zero to many thousands of degrees.

When the circle was completed, Kemp adjusted his torch again, and the flame lengthened. He moved inside the circle and cut at an angle toward the perimeter. His control was quick and certain. In a moment he stood aside, and Koa lifted out a perfect ring of thorium. It varied from a knife edge on the inner side to eighteen inches on the outer side.

In the middle of the circle there was now a cone of metal. Kemp cut around it, the torch angling toward the center. A piece shaped like two cones set base to base came free. Since the metal cooled in the bitter chill of space almost as fast as Kemp could cut it, there was no heat to worry about.

Alternately cutting from the outside and the center of the hole, Kemp worked his way downward until his head was below ground level. Rip called a halt. Kemp gave a little jump and floated straight upward. Koa caught him and swung him to one side. Rip stepped into the hole, and Santos gave him a slight push to send him to the bottom. Rip knelt and sighted upward. Kemp had done a good job. The star Rip had chosen as a guide was straight overhead.

He bounced out of the hole, and, as Koa caught him, he told Kemp to go ahead. "Dominico, here's your chance. Get tools and wire. Find a timer and connect up the ten-kiloton bomb. Nunez, bring it here while Dominico gets what he needs."

Kemp was burning his way into the asteroid at a good rate. Every few moments he pushed another circle or spindle of thorium out of the hole. Rip directed some of the men to carry them away, to the other side of the asteroid. He didn't want chunks of thorium flying around from the blast.

The sergeant major had a sudden thought. He cut off his communicator, motioned to Rip to do the same, then put his helmet against Rip's for direct communication. He didn't want the others to hear what he had to say. His voice came like a roar from the bottom of a well. "Lieutenant, do you suppose there's any chance the blast might break up the asteroid? Maybe split it in two?"

The same thought had occurred to Rip on the Scorpius. His calculations had showed that the metal would do little more than compress, except where it melted from the terrific heat of the bomb. That would be only in and around the shaft. He was sure the men at Terra base had figured it out before they decided that A-bombs would be necessary to throw the asteroid into a new orbit. He wasn't worried. Cracks in the asteroid would be dangerous, but he hadn't seen any.

"This rock will take more nuclear blasts than we have," he assured Koa. He turned his communicator back on and went to the edge of the hole for a look at Kemp's progress. He was far down now. Pederson was holding one end of a measuring tape. The other end was fastened to Kemp's shoulder strap.

The Swedish corporal showed Rip that he had only about eight feet of tape left. Kemp was almost down. Rip called, "Kemp, when you reach bottom, cut toward the center. Leave an inverted cone."

"Got it, sir. Be up in two more cuts."

Dominico had connected cable to the bomb terminals and was attaching a timer to the other end. Without the wooden case, the bomb was like a fat, oversized can. It had been shipped without a combat casing.

"Koa, make a final check. You can untie the landing boat, except for one line. We'll be taking off in a few minutes."

"Right, sir." Koa glided toward the landing boat, which was moored out of sight beyond the horizon.

It was nearly time. Rip had a moment's misgiving. Had his figures or his sightings been off? His scalp prickled at the thought. But the ship's computer had done the work, and it was not capable of making a mistake.

Kemp tossed up the last section of thorium and then came out of the hole himself, carrying his torch.

Rip inspected the hole, saw with satisfaction that it was in almost perfect alignment, and ordered the bomb placed. He bent over the edge of the hole and watched Trudeau pay out wire while Dominico pushed the bomb to the bottom. The Italian made a last-minute check, then called to Rip. "Ready, sir."

Rip dropped into the hole and inspected the connections himself, then personally pulled the safety lever. The bomb was armed. When the timer acted, it would go off.

Back at ground level, he turned up his communicator. "Koa, is everything ready at the boat?"

"Ready, sir."

The Planeteers had already carried away the torch and its fuel and oxygen supplies. The area was clear of pieces of thorium.

Rip announced, "We're setting the explosion for ten minutes." He leaned over the timer, which rested near the lip of the hole, took the dial control in his glove, and turned it to position ten. He held it long enough to glance at his chronometer and say, "Starting now!" Then he let it go.

Wasting no time, but not hurrying, he and Dominico returned to the landing boat. The Planeteers were already aboard, except for Koa, who stood by to cast off the remaining tie line. Rip stepped inside and counted the men. All present. He ordered, "Cast off." As Koa did so and stepped aboard, Rip added, "Pilot, take off. Straight up."

The landing boat rose from the asteroid. Rip counted the men again, just to be sure. The boat seemed a little crowded, but that was because the rear compartment took up quite a bit of room.

Rip watched his chronometer. They had plenty of time. When the boat reached a point about ten miles above the asteroid, he ordered, "Stern tube." The boat moved at an angle. He let it go until a sight at the stars showed they were in about the right position, ninety degrees from the line of blast and where they would be behind the asteroid as it moved toward the new course.

He looked at his chronometer again. "Two minutes. Line up at the side if you want to watch, but darken your helmets to full protection. This thing will light up like nothing you've ever seen before."

It was a good thing space cruisers depended on their radar and not on sight, he thought. Usually spacemen opened up visual ports only when landing or taking a star sight for an astroplot. The clear plastic of the domes had to be shielded from chance meteors. Besides, radar screens were more dependable than eyes, even though they could pick up only solid objects. If the Consops cruiser happened to be searching visually, it would see this blast. But the chance had to be taken. It wasn't really much of a chance.

"One minute," he said. He faced the asteroid, then darkened his helmet, counting to himself.

The minute ticked off rapidly, though his count was a little slow. When he reached five, brilliant, incandescent light lit up the interior of the boat. Rip saw it even though his helmet was dark. The light faded slowly, and as it did, he gradually put his helmet back on full transparent.

A mighty column of fire now reached out from the asteroid into space. Rip held his breath until he saw that the little planet was sheering off its course under the great blast. Then he sighed with relief. All was well so far.

Someone muttered, "By Gemini! I'm glad we're out here instead of down there!"

The column of fire lengthened, thinned out, grew fainter, until there was only a glow behind the asteroid. Rip took his astrogation instruments and made a number of sights. They looked good. The first blast had worked about as predicted, although he wouldn't be able to tell how much correction was needed until he had taken star sights over a period of five or six days.

"Let's go home," he ordered.

Back on the asteroid, a pit that glowed with radioactivity marked the site of the first blast. Rip ordered the men to stay as far from it as possible, to avoid increasing their radiation doses. He plotted the lines for the second blast, found the spot, and put Kemp back to work on a new hole.

Two hours later the second blast threw fire into space. In another three hours, with the asteroid now speeding on its new course, Rip set off the explosion that blasted straight back and gave extra speed.

Three radioactive craters marked the asteroid. Rip checked the radiation level and didn't like it a bit. He decided to set up the landing boat and their supplies as far away from the craters as possible, which was on the sun side. They could move to the dark side as they approached the orbit of Earth. By then the radioactivity from the blasts would have died down considerably.

He was selecting the location for a base when Dowst suddenly called, "Lieutenant Foster!"

There was urgency in the Planeteer's voice. "What is it, Dowst?"

"Sir, take a look, about two degrees south of Rigel!"

Rip found the constellation Orion and looked at bright Rigel. For a moment he saw nothing; then, south of the star, he saw a thin, orange line.

Nuclear drive cruisers didn't have exhausts of that color, and there was only one rocket-drive ship around, so far as they knew.

Rip said softly, "Let's get our house in order, gang. Looks as if we're going to get a visit from the Connies!"