Starfire Read Online Free PDF Page B

and overall position to prevent that. The computational problem was continuous and complex. The shield had to maintain a fixed shape and position in the presence of time-varying forces: Earth attraction, lunar, solar, and planetary perturbations; solar wind and radiation pressure. And, of course, it must deal with the variable but steadily increasing sleet of charged particles that provided the shield's whole reason for existing.
    John looked down past his feet. For reasons of personal comfort, suits usually accelerated you headfirst. Until turnover time that meant Cusp Station lay directly below him, at the apex of the cone, while Sky City was above his head.
    Sky City, which for the past seven months had been prowled by an insane—
    No. Not that. Those thoughts were the effects of the second Neirling boost on his nervous system. He had to get his attention fixed on something tangible.
    Cusp Station was still visible below, a bright cluster of green and orange lights. No word from Will and the others. Presumably they were still chewing on the technical problems.
    But Cusp Station was not what he wanted to see. He added an apodizing disk to the suit's optical sensor, removing the unwanted glare of the station, and scanned the area close to it. After a few seconds he located his target and locked on.
    And there it was. An undistinguished second-magnitude star, one of hundreds of that brightness in the sky. Yet a star like no other.
    For all of recorded history Alpha Centauri had been the third brightest star in the heavens: Rigel Kentaurus, a splendid visual binary with a third and faint companion, Proxima Centauri.
    Thirty-one years ago, the Alpha Centauri system had exploded as a mighty supernova. But because Alpha Centauri was about four and a third light-years from the Sun, no one on Earth knew what had happened until twenty-seven years ago, when early in 2026 a torrent of light reached the solar system. For several months Alpha Centauri blazed down on Earth like a second Sun.
    The cascade of light had created freak weather and global devastation. The flux of high-energy gamma rays, a few weeks later, knocked out all microcircuits and everything that depended on them. Civilization shuddered, gasped, staggered—and thought it had survived.
    Until it realized that the Alpha Centauri supernova, unpredicted by all scientists and proclaimed impossible by most, had not finished with the Earth. The star had waned, until the faint remnant provided a poor object for visual observation. But most of the energy of a supernova is not given off as light or gamma rays. It resides in the sleet of electrically charged subatomic particles thrown out during the stellar explosion. That particle storm, fast-moving as it is, travels much more slowly than light. In the case of Alpha Centauri, the densest cloud was calculated to move at about nine percent of light speed. Travel time from Alpha Centauri: about forty-eight years. Arrival date for the storm center: forty-four years after the first blaze. Say, in 2070.
    Earth would need protection. But there were further complications, introduced by the particle velocity distribution. To find when a particle storm has its biggest effect, you must look not at simple particle density but at the product of particle flux density and particle kinetic energy. The most energetic and destructive particles are the ones that travel fastest. Hence the worst time would be earlier than 2070. It was predicted as 2061.
    No. The worst time is here and now, with murder most foul on Sky City . . .
    The suit's acceleration ended abruptly. The skyscape swirled dizzily, bringing John shuddering back to reality.
    Turnover time. Halfway to Sky City. Still an hour to go. An awful situation. The Neirling boost was designed for when you were desperately busy with more work than you could handle. Employ it when you had nothing to do, you were like a motor running against zero load. Your brain spun faster and faster until it