Project Solar Sail
Page 1
Table of Contents
Foreword: The Winds of Space
Introduction: Sailing the Void
The Wind from the Sun
To Sail Beyond the Sun (A Luminous Collage)
The Canvas of the Night
Ice Pilot
A Solar Privateer
Sunjammer
A Rebel Technology Comes Alive
Argosies of Magic Sails—Excerpts from “Locksley Hall”
Ion Propulsion: The Solar Sail’s Competition for Access to the Solar System
Grand Tour
Lightsail
Rescue at L-5
Lightsails to the Stars
The Fourth Profession
Goodnight, Children
Solar Sails in an Interplanetary Economy
Afterword
PROJECT SOLAR SAIL
Edited by: Arthur C. Clarke & David Brin
SAILING TO DISTANT STARS
It’s a dream that began with the publication of Arthur C. Clarke’s classic short story "Sunjammer," in which he introduced the concept of space vehicles powered by sunlight. Scientists were so fired by the idea that their research led to the creation of such a machine.
In this intriguing anthology such noted authors as Larry Niven, David Brin, Poul Anderson, Joe Clifford Faust, Ray Bradbury, Charles Sheffield, and Arthur C. Clarke himself contribute their future visions of solar sailing in a fascinating mix of stories, essays, and illustrations.
ROC
Published by the Penguin Group Penguin Books USA Inc., 375 Hudson Street, New York, New York 10014, U.S.A.
Penguin Books Ltd, 27 Wrights Lane, London W8 5TZ, England
Penguin Books Australia Ltd, Ringwood, Victoria, Australia
Penguin Books Canada Ltd, 2801 John Street, Markham, Ontario, Canada L3R 1B4
Penguin Books (N.Z.) Ltd, 182-190 Wairau Road, Auckland 10, New Zealand
Penguin Books Ltd, Registered Offices: Harmondsworth, Middlesex, England
First Published by Roc, an imprint of Penguin Books USA Inc.
First Printing, April, 1990
10 9 8 7 6 5 4 3 2
Copyright © World Space Foundation, 1990
All rights reserved.
“The Winds of Space” copyright © Arthur C. Clarke, 1990
“Sailing the Void” copyright © Isaac Asimov, 1990
“The Wind from the Sun” copyright © Boy Scouts of America, 1963. Reprinted by permission of the author.
“To Sail Beyond the Sun” copyright © Ray Bradbury and Jonathan Post, 1990
“The Canvas of the Night” copyright © K. Eric Drexler, 1990
“Ice Pilot” copyright © David Brin, 1990
“Solar Sailing” copyright © World Space Foundation, 1990
“A Solar Privateer” copyright © Jonathan Eberhart, 1981. Reprinted by permission of the author.
“Sunjammer” copyright © Condé Nast Publications, Inc., 1964. Reprinted by permission of the author.
“Solar Sails in an Interplanetary Economy” copyright © Louis Friedman and Robert Staehle, 1990.
“Friendly Competitors” copyright © Bryan Palaszewski, 1990
“Grand Tour” copyright © Davis Publications, 1987. Reprinted by permission of the author.
“Light Sail” copyright © Scott Green, 1990
“Rescue at L-5” copyright © Kevin J. Anderson and Doug Beason, 1990
“Lightsails to the Stars” copyright © Robert L. Forward and Joel David, 1990
“The Fourth Profession” copyright © Coronet Communications, Inc., 1971. Reprinted by permission of the author.
“Goodnight, Children” copyright © Joe Clifford Faust, 1990
Roc is a trademark of Penguin Books USA Inc.
Printed in Canada
Without limiting the rights under copyright reserved above, no part of this publication may be reproduced, stored in or introduced into a retrieval system, or transmitted, in any form, or by any means (electronic, mechanical, photocopying, recording, or otherwise), without the prior written permission of both the copyright owner and the above publisher of this book.
Electronic version by Baen Books
eISBN: 978-1-62579-211-2
To Konstantin Tsiolkovsky, Fridrikh Tsander, and Carl Wiley, and those who came before them.
Contents
Foreword: The Winds of Space by Arthur C. Clarke
Introduction: Sailing the Void by Isaac Asimov
The Wind From the Sun by Arthur C. Clarke
To Sail Beyond the Sun (A Luminous Collage) by Ray Bradbury and Jonathan V. Post
The Canvas of the Night by K. Eric Drexler
Ice Pilot by David Brin
Solar Privateers by Jonathan Eberhart
Sunjammer by Poul Anderson
A Rebel Technology Comes Alive by Chauncey Uphoff and Jonathan V. Post
Argosies of Magic Sails by Alfred Lord Tennyson
Ion Propulsion: The Solar Sail’s Competition for Access to the Solar System by Bryan Palaszewski
Grand Tour by Charles Sheffield
Lightsail by Scott E. Green
Rescue at L-5 by Kevin J. Anderson and Doug Beason
Lightsails to the Stars by Robert L. Forward and Joel Davis
The Fourth Profession by Larry Niven
Goodnight, Children by Joe Clifford Faust
Solar Sails in an Interplanetary Economy by Robert L. Staehle and Louis Friedman
Afterword by Arthur C. Clarke
Foreword: The Winds of Space
by Arthur C. Clarke
Two very different kinds of wind blow forever from the sun. One is the gale of charged particles that shapes the tails of comets, whipping them across hundreds of mega-miles like pennants in a breeze. It is as inconstant and unpredictable as the hurricanes of Earth; sometimes it is a gentle zephyr, but it may rage with cyclonic violence during the peaks of the solar cycle. Then the ghostly aurora folds its curtains around Earth’s magnetic field, and torrents of incoming electrons paint flickering images as the ionosphere becomes a gigantic cathode ray tube in the sky.
The other wind is a far gentler one, scarcely varying from eon to eon. It is a wind not of particles, but of pure radiation—light itself. Feeble though it is, we may one day learn to harness it, as since the beginning of history we have enslaved the winds of Earth.
The great sailing ships of the past—tea-clippers like Cutty Sark, and the splendid windjammers of the New England master builders—were among the most beautiful achievements of human engineering. They reached one level of perfection just before the advent of steam and oil swept them from the seas—but they may return in a new, environmentally conscious age, with technologies based on composite materials, computer control, and satellite navigation.
This book is about a closely related idea whose time has yet to come. What a delightful irony it will be if the real age of sail has yet to dawn—not only on the oceans of Earth, but also in the far wider seas of space.
What is especially nice is that you’ve helped bring the age of interplanetary sailing closer, just by buying this book! I’ll come back in the final pages to tell you about an exciting opportunity to participate even more dramatically. But right now I’ll pass you on to some colleagues of mine, who volunteered their time and creativity to contribute to this unique volume about the adventure awaiting us tomorrow.
—Arthur C. Clarke
London
October 12, 1989
Introduction: Sailing the Void
by Isaac Asimov
In the early days of civilization, human beings discovered the use of sails. Woven sheets or rough textile caught the wind, and the momentum of that moving air was transferred to the floating ship, whi
ch then moved without a water current, and even against one. It was a wondrous advance. Until this innovation, ships could move upstream only by the unending application of human muscle. Of course, the wind might not always blow, or if it did, it might not blow in the right direction. Nevertheless, sail technology advanced steadily, so that feebler and feebler gusts could be used, even gusts that were in the wrong direction.
By the 1850s, Yankee clippers were the speediest and most beautiful vessels the world had ever seen. The steamships that replaced them were larger and, eventually, faster, but they were also uglier, dirtier, and noisier and always greedy for a steady stream of fuel. Sailing ships (except for pleasure vessels) have now disappeared from the world’s oceans, but humanity faces another ocean today, an infinitely vaster and emptier one. Our water ocean spans tens of thousands of miles, but the ocean of outer space stretches for billions of trillions of miles.
Now, with fossil fuels growing scarce, there is new interest in cutting this umbilical again. Research into renewable power includes experiments in ultramodern sails for cargo ships and even cruise liners at sea.
We’ve begun the navigation of outer space with the equivalent of steamship races—the use of raw power, incredibly noisy power. Rockets. Nothing else will do, perhaps, to break through Earth’s atmosphere and the lower reaches of its gravitational field.
Once a ship is in space, however, and is moving through a vacuum in orbit about Earth, is there anything quieter? Gentler? Better? More important, is there a way to move out there without being tied forever to an earthly supply of fuel? A wind would fit the bill, certainly, but outer space is a vacuum. What is there in space that can form a wind?
Two things, actually—at least in the neighborhood of a star like our sun. As my esteemed friend Arthur has told you, the sun emits two types of radiation: high-energy charged particles—mostly protons and electrons—and, of course, light. The first of these flows, the stream of high-speed particles, is what’s referred to as the “solar wind.” The name may be misleading, especially for the purposes of this book, as this is not the wind that drives a solar sail. The charged protons of the solar wind do possess momentum, and this momentum can be transferred to other charged objects in space. But we won’t be discussing it much here.
The second “wind” in space is the sun’s torrential output of light, which also possesses momentum, and which exerts a minuscule pressure on anything it strikes. Like the solar wind, it grows weaker with increasing distance from the sun. As it turns out, sunlight itself is more than a thousand times stronger than the solar wind from our sun.
A good example of these two streams at work can be seen during the active phase of a comet. A comet, as it approaches the sun, is partially vaporized. The rocky dust frozen in its outer layer then rises to surround the still-frozen nucleus in a haze. The tiny grains have large surface area per mass and so get swept away by light pressure alone. This dust is swept outward from the sun by sunlight to form the long “dust tail.” There is a second comet tail as well, the ion tail, which consists of charged particles interacting with the protons and electrons of the solar wind, shining like neon lamps across millions of miles.
Scientists have long known about these two outward forces from the sun. However, they seemed so weak that it was long before serious consideration was given to how they might somehow prove useful. Except for the predictions of a few visionaries, it wasn’t until the advent of spaceflight that plans began to be made to use these winds of space.
So far, of the two, it is sunlight which has received the most attention. Because light interacts with matter on a shorter scale than charged particles do, we can manipulate light more easily than the charged particles. Radiation pressure is much weaker than the sun’s gravitational pull unless you mimic the dust grains . . . increase your surface area compared to mass. This can be done by spreading a thin collecting area—a reflecting sail—over vast tracts of space.
Fortunately, the free-fall conditions of space mean you don’t need a lot of mass to support your reflector. You don’t need the heavy masts or sturdy canvas sails of an earthly sailing ship. The result is a gossamer wonder, the lightsail, which has inspired this book.
While lightsails cannot do the grunt work, the heavy lifting from ground to orbit, they do appear to offer some wondrous opportunities for getting around once you’re up there. What’s more, they also appear to be cheap. By that I mean they may open the door for smaller groups to play a role in space than just the club of big national governments that now run the show.
Many grand ideas have been proposed for how photon sails might help us maneuver in, and make use of, interplanetary space. I will leave the experts to tell you of them.
I just want to mention, before I stop, one special application of light pressure—as a way to reach the stars. There are ways of converting the ordinary light of the sun into a laser beam, which is a wave of “coherent” light. This is light in which all the waves are the same length and move in the same direction. Whereas ordinary sunlight spreads out rapidly, so that far from the sun its pressure weakens into utter uselessness, a laser beam spreads out only very slightly, so its pressures, and its ability to move a ship, can remain constant over a very long distance.
A laser beam from Earth could drive such a ship through space by solar energy, burning no fuel and never running out of energy. Such a ship could be driven to the nearest star, Alpha Centauri, in just a few years.
It might seem that such a laser beam could drive the ship only outward, never to return; but with the use of still larger sails and ingenious ways of extending electrically charged systems, such ships could be brought to a halt in the neighborhood of Alpha Centauri and might even be made to take up the return journey. The requisite technology is a bit beyond us today, but a hundred years from now it may not be, and sailing vessels more magnificent than any we have ever seen may navigate distances vaster and emptier than anything our ancestors would have dreamed of.
This concept, and many others, await you in the pages ahead, as eminent scientists and gifted writers take you on a tour of the future. In fact and fiction, in essays and stories, you will catch glimpses of a tomorrow filled with wonder and possibility, as we and our descendants spread our sails and head forth, the wind at our backs, to the stars.
###
Isaac Asimov says: “My life is incredibly dull since I do nothing but write and have done nothing but write for fifty years. All I have to show for it is a number. Leaving quality aside as something that is moot, I have published to date 434 books, and have some 25 or 26 in press. I have written thousands of short pieces, both fiction and nonfiction, some, but not all, of which are included in the books. I might add that, dullness or not, it has been a very happy life.”
And let me add that Isaac has been a friend for a very long time. Thank you for the typically incisive introduction, Isaac. Now it’s my turn.
The Wind from the Sun
by Arthur C. Clarke
The enormous disk of sail strained at its rigging, already filled with the wind that blew between the worlds. In three minutes the race would begin, yet now John Merton felt more relaxed, more at peace, than at any time for the past year. Whatever happened when the Commodore gave the starting signal, whether Diana carried him to victory or defeat, he had achieved his ambition. After a lifetime spent in designing ships for others, now he would sail his own.
“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, Sunbea
m—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.