O'Brine was not in. Rip searched and found him in the astroplot room, watching a 'scope. Green streaks called "blips" marked the panel, each one indicating an asteroid. "All too small," O'Brine said. "We've only seen two large ones, and they were too large." "Space is certainly full of junk," Rip commented. "At least this corner of it is pretty full." A junior space officer overheard him. "This is nothing. We're on the edge of the asteroid belt. Closer to the middle, there's so much stuff a ship has to crawl through it." Rip wandered over to the main control desk. A senior space officer was seated before a simple panel on which there were only a dozen small levers, a visiphone, and a radar screen. The screen was circular, with numbers around the rim like those on an Earth clock. In the center of the screen was a tiny circle. The central circle represented the _Scorpius_. The rest of the screen was the area dead ahead. Rip watched and saw several blips on it that indicated asteroids. They were all small. He watched, interested, as the _Scorpius_ overtook them. Once, according to the screen, the cruiser passed under an asteroid, with a clearance of only a few hundred feet. "You didn't miss that one by much," Rip told the space officer. "Don't have to miss by much," he retorted. "A few feet are as good as a mile in space. Our blast might kick them around a little, and maybe there's a little mutual mass attraction, but we don't worry about it." He pointed to a blip that was just swimming into view, a sharp green point against the screen. "We do have to worry about that one." He selected a lever and pulled it toward him. Rip felt sudden weight against his feet. The green point on the screen moved downward, below center. The feeling of weight ceased. He knew what had happened, of course. Around the hull of the ship, set in evenly spaced lines, were a series of blast holes through which steam was fired. The steam was produced instantly by running water through the heat coils of the nuclear engine. By using groups or combinations of steam tubes, the control officer could move the ship in any direction, set it rolling, spin it end over end, or whirl it in an eccentric pattern. "How do you decide which tubes to use?" Rip asked. "Depends on what's happening. If we were ducking missiles from an enemy, I'd get orders from the commander. But to duck asteroids, there's no problem. I go over them by firing the steam tubes along the bottom of the ship. That way, you feel the acceleration on your feet. If I fired the top tubes, the ship would drop out from under those who were standing. They'd all end up on the overhead."