A pair of snapper-boats flashed overhead, and vanished below the horizon. Two more swept past from another direction. Rip watched, curious. What were they up to? Another pair quartered past them at high speed, then two more. The dozen boats seemed to be criss-crossing the asteroid in a definite pattern. Why? A pair streaked past, and something sped downward from one of them, trailing yellow flame. It exploded in a ball of molten fire that licked across the asteroid in waves. Rip tensed, then saw that the chemical would burn out before it reached them. "Fire bomb," Koa muttered. Rip nodded. He had recognized it. The Planeteers were trained in the use of fire bombs, tanks of chemicals that burned even in an airless world. They were equipped with simple jets for use in space. The snapper-boats drew off, back toward the _Scorpius_. Rip watched, searching for some reason for their actions. Then one of the boats pulled away from the others. It returned to the asteroid with stern jet burning fitfully. "Is he landing?" Koa asked. Rip didn’t know. The snapper-boat was moving slowly enough to make a landing. Directly over the asteroid it changed direction, circled, and returned over their heads. Rip could almost have picked it off with a pistol shot. Santos could have blasted it into space dust with one rocket. The snapper-boat changed direction, and for a fraction of a second stern and side tubes "fought" each other, making the boat yaw wildly, then it straightened out on a new course. [Illustration: "They’re Using Fire Bombs," Muttered Koa.] "They’re Using Fire Bombs," Muttered Koa. Koa exclaimed, "That’s a drone!" Rip got it then. A pilotless snapper-boat! That’s why its actions were a little uneven. Only one thing could explain its deliberate slowness. It was bait. The _Scorpius_ had sent piloted snapper-boats over the asteroid at high speed, criss-crossing in order to cover the thorium world completely, expecting to have the unknown rocketeer fire at them. Then a fire bomb had been dropped as a further means of getting the asteroid to fire. But no rockets had been fired from the asteroid, so the pilot in control of the drone had sent it at low speed, a perfect target. That meant O’Brine wasn’t sure of what was going on. He must have seen the blip on his screen as the Connie cruiser flamed off, Rip reasoned. But the commander probably suspected that the Connies had overcome the Planeteers and were in control of the asteroid. He had sent the snapper-boats to try and draw fire in an attempt to find out more surely whether Planeteers or Connies had the thorium rock. "The _Scorpius_ doesn’t know what’s going on," Rip told his Planeteers. "O’Brine didn’t know the cruiser was waiting to ambush him, so the rocket we fired made him think the Connies had taken us over."