The Sails of Tau Ceti Read Online Free PDF Page A

course.”
    “But you can’t!”
    “Why not?”
    “ Starhopper is the only interstellar probe we’ve got. We can’t waste it. No telling when we will be able to scrape together the resources to build another. Send another ship to look over the light sail. Leave Starhopper for the job it was designed to do.”
    “I’m afraid that is impossible,” Hunsacker said. He touched the cube control. The starfield vanished, to be replaced by a graph in which two brightly colored lines were suspended in a three dimensional gridwork. One line sloped sharply upward, while a second followed a curve with much gentler slope.
    “The red line plots the increase in the observed strength of the Tau Ceti nova over the first two weeks after the explosion. Five days after the initial explosion, Tau Ceti’s output had increased by 100,000 times. The blue line shows the calculated velocity of a hypothetical light sail caught in such an explosion.”
    “Proving what?” Tory asked as she eyed the holocube.
    “That the light sail’s velocity is the result of its having been ejected by the nova. Had it launched while Tau Ceti was a normal star, its velocity would be less than one percent that of light. What that means is that the light pressure from the sun is insufficient to slow it much. It will arrive in the inner system in 40 months time, zip from one side of the system within a few days, and then head back out into interstellar space. If we are to have any opportunity of examining it, we must meet it as far out as possible. Starhopper is the only vessel in the system with the delta velocity capability to make rendezvous.”
    Tory thought about it for a moment and was forced to concede his point. A spacecraft’s performance is measured by its ability to change velocity, its delta V capability. The alien light sail was falling toward the sun at 15,000 kilometers per second. In theory, a vessel able to accelerate to that speed could rendezvous with it. In practice, things were not nearly that simple.
    A human spacecraft must race away from the sun to intercept the light sail before it entered the system. Once well beyond the orbit of Pluto, the explorer craft would turn end for end and begin decelerating. It would shed all of its outbound velocity and then begin accelerating back toward the sun with the light sail in pursuit. If properly done, it would match velocities with the light sail just as the alien derelict overtook it. Humanity would then be able to use the Starhopper probe’s instruments to learn what they could about the alien intruder.
    All of this maneuvering required a prodigious velocity change. To match orbits with the light sail in time to do any good was the equivalent of accelerating to 15% of light speed. As Hunsacker had said, only Starhopper came anywhere close to having the necessary delta V capability.
    “All right, Starhopper is the only spacecraft in the Solar System that can catch this light sail. That does not mean we have to send it out. How do we know we’ll learn anything worthwhile?”
    “Damn it, we’re talking about a vessel built by alien sapients,” an exasperated Hunsacker muttered. “How can we not learn from it?”
    “No sense getting upset, Boris,” Pierce said calmly. “Tory’s questions deserve an answer. What do we know about this light sail?”
    Hunsacker put up the hologram showing Tau Ceti, its light ring, and the sail just beyond the ring’s milk-white boundary. “From its infrared spectrum, we estimate the sail temperature to be 50°K. That is a bit high for that distance from Sol, but not excessively so. We can also estimate its size.”
    “Surely it isn’t close enough to show a disk,” Groschenko said.
    Hunsacker laughed. “No, not anywhere near close enough. We can put an upper bound on its size from the fact that we did not detect it before now. To have escaped our notice, the sail cannot be larger than 1000 kilometers in diameter. It may be smaller.”
    Pierce looked