Deep-Space Probes To the Outer Solar System and Beyond (Second Edition) Gregory L.Matloff Deep-Space Probes To the Outer Solar System and Beyond (Second Edition) Published in association with Praxis Publishing Chichester, UK Gregory L.Matloff Assistant Professor of Physics and Astronomy Department of Physical and Biological Sciences New York City College of Technology Brooklyn New York USA SPRINGER±PRAXIS BOOKS IN ASTRONAUTICAL ENGINEERING SUBJECT ADVISORY EDITOR: John Mason B.Sc., M.Sc., Ph.D. ISBN 3-540-24772-6 Springer-Verlag Berlin Heidelberg New York Springer is part of Springer-Science + Business Media (springeronline.com) Bibliographic information published by Die Deutsche Bibliothek Die Deutsche Bibliothek lists this publication in the Deutsche Nationalbibliogra®e; detailed bibliographic data are available from the Internet at http://dnb.ddb.de Library of Congress Control Number: 2005922498 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency.Enquiries concerning reproduction outside those terms should be sent to the publishers. # Praxis Publishing Ltd, Chichester, UK, 2005 Printed in Germany The use of general descriptive names, registered names, trademarks, etc.in this publication does not imply, even in the absence of a speci®c statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: Jim Wilkie Project management: Originator Publishing Services, Gt Yarmouth, Norfolk, UK Printed on acid-free paper This book is dedicated to all those visionaries and dreamers who have dreamed of ¯ight beyond the con®nes of Earth's surface and travel to the stars. From the myth of Daedalus and Icarus,the early aircraft designs of Leonardo,the inspiring science ®ction of many masters of the craft,to the originators of modern-day astronautics, these men and women have established the philosophical and technological foundations upon which the ®rst starships will be designed. I fervently hope that some of the spirit of these pioneers has entered into this book. Contents Foreword............................................ xiii Preface to the second edition ............................... xv Preface to the ®rst edition................................. xvii Acknowledgements...................................... xix Contributors.......................................... xxi Figures ............................................. xxiii Tables ............................................. xxv Introduction .......................................... xxvii 1 Motivations for deep-space travel ......................... 1 1.1 An inventory of near-Earth objects .................... 4 1.2 Considering NEO origins .......................... 6 1.3 The dif®culty of telescopic exploration of NEOs near their point of origin ..................................... 7 1.4 Robotic exploration options ........................ 9 1.5 Directed panspermia . .......................... 10 1.6 Bibliography................................... 10 2 The realms of space .................................. 13 2.1 The question of origins. .......................... 13 2.2 Realms of ®re, water and ice ........................ 15 2.3 Solar radiant ¯ux and planet effective temperature.......... 17 2.4 The effect of atmospheric optical depth ................. 18 2.5 The lifetime of a planet's atmosphere .................. 19 2.6 Comparative planetology: an appreciation of the lifezone ..... 20 2.7 Beyond the planets: the reefs of space .................. 21 2.8 Bibliography................................... 23 viii Contents 3 Tomorrow's targets .................................. 25 3.1 The TAU mission: an early NASA/JPL extra-solar mission study 26 3.2 SETIsail and ASTROsail: Proposed probes to the Sun's gravity focus........................................ 27 3.3 The Aurora project: a sail to the heliopause .............. 30 3.4 The NASA Interstellar Initiative...................... 30 3.5 The NASA heliopause sail ......................... 30 3.6 The NASA Kuiper Belt explorer ..................... 31 3.7 A probe to the Oort Cloud ......................... 33 3.8 Bibliography................................... 34 4 Space propulsion today ................................ 37 4.1 Rocket history and theory.......................... 37 4.2 The solar-electric drive ............................ 41 4.3 Unpowered planetary gravity assists ................... 43 4.4 Powered solar gravity assists ........................ 46 4.5 The solar photon sail ............................. 49 4.6 The solar photon Thruster: Holographic solar sails ......... 57 4.7 Bibliography .................................. 58 5 The incredible shrinking spaceprobe ........................ 61 5.1 The small and the very small........................ 62 5.2 Nanotechnology: The art and science of the very, very small . 64 5.3 Nanotechnology and space¯ight: Near-term possibilities ...... 66 5.4 Nanotechnology and space¯ight: Long-term possibilities ...... 66 5.5 Possible limits to nanotechnology ..................... 67 5.6 Bibliography................................... 68 6 The nuclear option ................................... 71 6.1 Nuclear basics ................................. 71 6.2 Nuclear-electric propulsion ......................... 75 6.3 Nuclear-pulse propulsion: Orion, Daedalus and Medusa ...... 78 6.4 Inertial electrostatic con®nement and gas-dynamic mirror fusion . 82 6.5 Antimatter: The ultimate fuel........................ 83 6.6 Bibliography................................... 87 7 21st century star¯ight ................................. 91 7.1 Laser/maser sailing fundamentals ..................... 92 7.2 Starship deceleration using the magsail . .............. 95 7.3 Thrustless turning ............................... 98 7.4 Perforated light sail optical theory .................... 100 7.5 The Fresnel lens: A method of improving laser beam collimation . 103 7.6 Round trip interstellar voyages using beamed-laser propulsion . 104 7.7 Interstellar particle-beam propulsion ................... 105 7.8 Bibliography................................... 107 Contents ix 8 On the technological horizon ............................ 109 8.1 The hydrogen-fusing interstellar ramjet ................. 109 8.2 The ram-augmented interstellar rocket .................. 113 8.3 The laser ramjet ................................ 117 8.4 The ramjet runway .............................. 118 8.5 A toroidal ramscoop . .......................... 120 8.6 Bibliography................................... 123 9 Exotic possibilities .................................. 125 9.1 `Shoes and ships': The potential of magnetic sur®ng......... 126 9.2 `Sealing wax': Approaches to antigravity ................ 130 9.3 `A boiling-hot sea': zero-point energy and special relativistic star drives ....................................... 131 9.4 `Cabbages and kings': General relativity and space±time warps . 134 9.5 `Winged pigs': Some other exotic ideas ................. 136 9.6 Bibliography................................... 137 10 Of stars, planets and life .............................. 141 10.1 A short history of extra-solar planet detection efforts ....... 141 10.2 Methods of imaging extra-solar planets ................. 143 10.3 Extra-solar planets found to date that orbit Sun-like stars .... 146 10.4 How common are life-bearing worlds? .................. 149 10.5 Terraforming: A way to increase the odds ............... 152 10.6 Bibliography................................... 152 11 Life between the stars................................. 155 11.1 Environmental obstacles to interstellar ¯ight, and their removal . 156 11.2 Options for onboard power between the stars ............. 159 11.3 Close environment life support systems ................. 160 11.4 Of worldships and interstellar arks .................... 161 11.5 Hibernation for humans: The long sleep to Centauri ....... 164 11.6 Bibliography................................... 165 12 Conscious spacecraft.................................. 167 12.1 The von Neumann machine: Can the computer eat the Galaxy? . 168 12.2 The cryogenic star child . .......................... 169 12.3 The virtual star traveller . .......................... 169 12.4 Bibliography................................... 170 13 Meeting ET ....................................... 171 13.1 Are starships detectable? . .......................... 172 13.2 Motivations of star-travelling extraterrestrials ............. 174 13.3 Bibliography................................... 175 x Contents 14 Interstellar message plaques ............................. 177 14.1 Motivations for interstellar message plaques .............. 178 14.2 The Pioneer 10/11 and Voyager 1/2 message plaques ........ 178 14.3 Holographic message plaques........................ 181 14.4 Bibliography................................... 183 15 Appendix: Photon sail history, engineering and mission analysis ...... 185 A.1 Brief history of solar photon sailing ................... 185 A.2 History of interstellar solar-sailing concepts .............. 188 A.2.1 Recent Research: FOCAL, Aurora and the NASA ISP . 190 A.3