Arthur Clarke - The Last Theorem

And that was the end of it, except for the good-bye hugs and kisses before the pilots and their handlers moved toward the Skyhook loading platform. Ranjit observed, not with displeasure, that this Ronaldinho Olsos from Brazil was boarding the first capsule, while Natasha was among those going in the third.

When they had kissed Natasha good-bye for the fourth or fifth time, and had at last successfully untangled Robert from her arms, the remainder of the Subramanian family, like everyone else, began to head for the buses.

There, squarely in their way, was Joris Vorhulst, standing by himself and talking agitatedly into his pocket screen. “So, Joris,” Myra said as they came up to him, “what are you worrying about now? Did they find another supernova?”

Her tone was jocular. Vorhulst’s expression was not. He folded his screen shut and shook his head. “Not exactly. What they saw may not be a supernova at all, now that the space telescopes are lining up to get a good look at it. And it’s a lot closer than any supernova should be. It may even be right in the Oort cloud.”

Myra stopped, her hand to her breast. “It isn’t going to bother the racers—?”

Vorhulst shook his head. “Oh, there’s no danger of that. No. The solar sailers will be in low earth orbit. This thing, whatever it is, is a long, long way from there. But I wish I knew what it was.”

Up where the solar sailers were nearly completely assembled, their riggers were not alone.

No one saw the tiny spacecraft of the Nine-Limbeds, because they had restored their photon-shifters long since. But their Nine-Limbed crews were nearly as puzzled as Joris Vorhulst, though about an entirely different matter. These seven nearly completed sail ships—what were they for? They bore no sign of any kind of weaponry. That relieved the Nine-Limbeds of one sort of worry, but another kind remained. None among the Nine-Limbeds had any idea of what these spacecraft were up to. And that was not a fact that the Nine-Limbeds wanted to report to their Grand Galactic masters.

Her ship’s name was Diana, chosen by Natasha Subramanian herself. It had never flown. Now it was ready. It lay moored to its mother ship with its enormous disk of sail straining at the rigging, already filled with the great, silent wind that blew between the worlds. The race was ready to begin.

“T minus two minutes,” said her cabin radio. “Cross-check to confirm readiness.”

One by one the other skippers answered. Natasha recognized every voice—some tense, some almost inhumanly calm—for they were the voices of her friends and rivals. In all of the places where humanity dwelt there were scarcely a score of men and women who owned the skills needed to sail a sun yacht. Every one of them was here, at the starting line like Natasha or aboard the escort vessels, orbiting thirty-six thousand kilometers above Earth’s equator.

“Number One, Gossamer. Ready to go!”

“Number Two, Woomera, all okay.”

“Number Three, Sunbeam. Okay!”

“Number Four, Santa Maria, all systems go.” Natasha smiled. That one was Ron Olsos, of course, whom she liked, though perhaps not as much as he seemed to like her. The Brazilian’s reply had been an ancient echo from the early days of astronautics, typical of Ron’s tendency toward the theatrical.

“Number Five, Lebedev. We’re ready.” That was the Russian, Efremy.

“Number Six, Arachne. Also okay.” Hsi Liang, the young woman from some village north of Chengdu, in the shadow of the Himalayas. And then, at the end of the line, it was Natasha’s turn to say the words that would be heard around the world and in every human outpost:

“Number Seven, Diana. Ready to win!”

And let old Ronaldinho take that, she thought as she turned to make one last check of the tensions in her rigging.

To Natasha, floating weightless in her tiny cabin, Diana ’s sail seemed to fill the sky. Well it might. Out there, ready to take her free of Earth’s gravitational bonds, were more than five million square meters of sail, webbed to her command capsule by almost a hundred kilometers of bucky-cord rigging. Those square kilometers of aluminized plastic sail, though only a few millionths of a centimeter thick, would exert enough force—she hoped!—to put her first across the lunar-orbit finish line.

The wall speaker again: “T minus ten seconds. All recording instruments on!”

Eyes still fixed on the vast billow of sail, Natasha touched the switch that turned on all Diana ’s cameras and instrument recorders. It was the sail that held her imagination. Something that was at once so huge and so frail was difficult for the mind to grasp. Harder still was to believe that this mirrored wisp could tow her ever faster through space by nothing more than the power of the sunlight it would trap.

“…five, four, three, two, one. Detach!”

Seven diamond-edged computer-controlled knife blades sliced through seven thin tethers at once. Then the yachts were free. Until this moment yachts and servicing vessels had circled the Earth as a single unit, firmly held together. Now the yachts would begin to disperse like dandelion seeds drifting before a breeze.

And the one that first drifted past the orbit of the moon would be the winner.

Aboard Diana nothing among the senses of Natasha’s body registered a change. She had not expected anything would; the only thing that showed that any thrust at all was being exerted was the dial on her instrument board, now registering an acceleration that was almost one one-thousandth of one Earth gravity.

That was, of course, almost ludicrously tiny. Yet it was more than any manned solar-sail vessel had ever managed before, just as Diana ’s designers and builders had promised it would be. Such accelerations had never been achieved in any but toy-size rigs, but there it was now. At this rate—she calculated quickly, smiled as the result appeared on her board—she would need only two circuits of Earth to build up enough velocity to leave low earth orbit and head for the moon. And then the full force of the sun’s radiation would be behind her.

The full force of the sun’s radiation…

Natasha’s smile persisted as she thought of all the attempts she had made to explain solar sailing to audiences of potential backers and the merely curious on Earth. “Hold your hand to the sun, palm up,” she would tell them. “What do you feel?” And then, when there was no answer beyond, perhaps, “a little heat,” she would spring the rationale for solar sailing on them. “But there is something else. There’s pressure. Not much of it, no. In fact so little that you can’t possibly feel it, far less than a milligram’s thrust on your palms. But see what that tiny pressure can do!”

And then she would pull out a few square meters of sail material and toss it toward her audience. The silvery film would coil and twist like smoke, and then drift toward the ceiling on the rising plume of warm air the human bodies made. And Natasha would continue:

“You can see how light the sail is. The whole square kilometer my yacht will deploy weighs less than a ton. That’s all we need. It’s enough to collect two kilograms of radiation pressure, so the sail will start to move…and the rigging will pull my Diana right along with it. Of course, the acceleration will be tiny—less than a thousandth of a G—but let’s see what that pitiful little thrust can do.

“In the first second, Diana will move about half a centimeter. Not even that much, really, because the rigging will stretch enough so that that first move can’t even be measured.”