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 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 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.