June 9, 2015
LightSail captured this image of its deployed solar sails in Earth orbit on June 8, 2015. (Credit: The Planetary Society)
With the LightSail’s successful deployment yesterday, it brings to mind Sir Arthur’s 1964 short story “Sunjammer” (NASA’s Solar Sail Demonstrator was given that name, but was later cancelled). The Planetary Society mission is entitled LightSail-A.
Reprinted below is Sir Arthur’s “Sunjammer,” which appeared in Boy’s Life in 1964.
By Arthur C. Clarke
“T minus two minutes,” said the cabin radio. “Please confirm your readiness.”
One by one, the other skippers answered. Merton recognized all the voices—some tense, some calm—for they were the voices of his friends and rivals. On the four inhabited worlds, there were scarcely twenty men who could sail a sun yacht; and they were all here, on the starting line or aboard the escort vessels, orbiting twenty-two thousand miles above the equator.
“Number One, Gossamer—ready to go.”
“Number Two, Santa Maria—all O.K.”
“Number Three, Sunbeam—O.K.”
“Number Four, Woomera—all systems go.”
Merton smiled at that last echo from the early, primitive days of astronautics. But it had become part of the tradition of space; and there were times when a man needed to evoke the shades of those who had gone before him to the stars.
“Number Five, Lebedev—we’re ready.”
“Number Six, Arachne—O.K.”
Now it was his turn, at the end of the line; strange to think that the words he was speaking in this tiny cabin were being heard by at least five billion people.
“Number Seven, Diana—ready to start.”
“One through Seven acknowledged.” The voice from the judge’s launch was impersonal. “Now T minus one minute.”
Merton scarcely heard it; for the last time, he was checking the tension in the rigging. The needles of all the dynamometers were steady; the immense sail was taut, its mirror surface sparkling and glittering gloriously in the sun.
To Merton, floating weightless at the periscope, it seemed to fill the sky. As it well might—for out there were fifty million square feet of sail, linked to his capsule by almost a hundred miles of rigging. All the canvas of all the tea-clippers that had once raced like clouds across the China seas, sewn into one gigantic sheet, could not match the single sail that Diana had spread beneath the sun. Yet it was little more substantial than a soap bubble; that two square miles of aluminized plastic was only a few millionths of an inch thick.
“T minus ten seconds. All recording cameras on.”
Something so huge, yet so frail, was hard for the mind to grasp. And it was harder still to realize that this fragile mirror could tow them free of Earth, merely by the power of the sunlight it would trap.
“. . . five, four, three, two, one, cut!”
Seven knife blades sliced through the seven thin lines tethering the yachts to the mother ships that had assembled and serviced them.
Until this moment, all had been circling Earth together in a rigidly held formation, but now the yachts would begin to disperse, like dandelion seeds drifting before the breeze. And the winner would be the one that first drifted past the moon.
# # #
Aboard Diana, nothing seemed to be happening. But Merton knew better; though his body would feel no thrust, the instrument board told him he was now accelerating at almost one-thousandth of a gravity. For a rocket, that figure would have been ludicrous—but this was the first time any solar yacht had attained it. Diana’s design was sound; the vast sail was living up to his calculations. At this rate, two circuits of Earth would build up his speed to escape velocity—then he would head out for the moon, with the full force of the sun behind him. Continue Reading →