Moving around on a no-weight world was more like skating than walking. A regular walk would have lifted Koa into s.p.a.ce with every step. Of course the asteroid had some gravity, but it was so slight that it didn't count.

Rip centered the top of the instrument's vertical hair line 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. 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 through the instrument 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 90 degrees from the line represented by Koa and Santos. He put the instrument down and zeroed it on Messier 44, the Beehive star cl.u.s.ter 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 the cross-fix he wanted.

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 cross lines met.

Dowst took a spike from his belt and made 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 b.u.t.ton 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 sun.

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 18 inches thick on the outer edge.

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 s.p.a.ce 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 an overhead guide was straight up.

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 a.s.sured 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 out of sight over the horizon.

It was nearly time. Rip had a moment's misgiving. Had his figures or his sightings been off? His red hair p.r.i.c.kled 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 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."

He 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, he 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 about in the right position, 90 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 s.p.a.ce cruisers depended on their radar and not on sight, he thought. Usually s.p.a.cemen opened up visual ports only when landing or taking a star sight for an astro-plot. 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 the blast. But the chance had to be taken. It wasn't really much of a chance.