Journal of the British Interplanetary Society VOLUME 71 NO.10 OCTOBER 2018 General Interstellar Issue DIRECT MULTIPIXEL IMAGING OF AN EXO-EARTH with a Solar Gravitational Lens Telescope Slava G. Turyshev A TELESCOPE AT THE SOLAR GRAVITATIONAL LENS: Problems and Solutions Geoffrey A. Landis ET PROBES, NODES, AND LANDBASES: a Proposed Galactic Communications Architecture and Implied Search Strategies John Gertz NUMERICAL CONSTRAINTS ON THE SIZE OF GENERATION SHIPS from total energy expenditure on board, annual food production and spacefarming techniques Frédéric Marin, Camille Beluffi, Rhys Taylor & Loïc Grau EFFECTS OF ENHANCED GRAPHENE REFLECTION on the Performance of Sun-launched Interstellar Arks Gregory L. 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Opinions expressed in signed articles are those of the contributors and do not necessarily reflect the views of the Editor or the Council of the British Interplanetary Society. Security clearance, where necessary, is the responsibility of the author. Published by the British Interplanetary Society. Registered Company No: 402498. Registered Charity No: 250556. Printed by Latimer Trend & Company Ltd, Estover Road, Plymouth, PL6 7PY, England. © 2019 British Interplanetary Society. No part of this magazine may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying or recording by any information storage or retrieval system without prior permission from the Publishers. CONTENTS VOLUME 71 NO.10 OCTOBER 2018 358 Correspondence 361 DIRECT MULTIPIXEL IMAGING OF AN EXO-EARTH with a Solar Gravitational Lens Telescope Slava G. Turyshev 369 A TELESCOPE AT THE SOLAR GRAVITATIONAL LENS: Problems and Solutions Geoffrey A. Landis 375 ET PROBES, NODES, AND LANDBASES: a Proposed Galactic Communications Architecture and Implied Search Strategies John Gertz 382 NUMERICAL CONSTRAINTS ON THE SIZE OF GENERATION SHIPS from total energy expenditure on board, annual food production and spacefarming techniques Frédéric Marin, Camille Beluffi, Rhys aylorT & Loïc Grau 394 EFFECTS OF ENHANCED GRAPHENE REFLECTION on the Performance of Sun-launched Interstellar Arks Gregory L. Matloff OUR MISSION STATEMENT The British Interplanetary Society promotes the exploration and use of space for the benefit of humanity, connecting people to create, educate and inspire, and advance knowledge in all aspects of astronautics. JBIS Vol 71 No.10 October 2018 357 CORRESPONDENCE Correspondence STEPHEN ASHWORTH and JAMES SCHWARTZ correspond on the subject of Dr Schwartz's recent paper “Worldship Ethics: Obligations to the Crew”, JBIS, 71, pp.53-64, 2018. To: the Editor of JBIS the generations pass and as political fashions come and go. 19 July 2018 Those questions are therefore likely to be addressed in an Dear Sir, evolutionary setting, in which solutions most conducive to the growth and multiplication of space colonies inevitably James Schwartz’s new paper on worldship ethics makes some out-compete solutions which cater more for specific interesting points [1]. I believe he is perfectly correct to ideological stances, such as one which would prioritise “the conclude that the ethical and political problems he raises will best possible life” (p.56) for the individuals inhabiting those apply also to permanent space settlements within the Solar colonies. In the longer term one can perhaps foresee colony System, and that therefore by the time technology and the conditions converging on a range of solutions in which economy have advanced to the point where worldship travel the needs of the colony as a whole are balanced against the on an interstellar scale is possible, the planners of such voyages needs of the individual. The success of democratic societies will be able to call on extensive relevant practical experience. in the latter half of the 20th century has shown that free and happy citizens are more productive than heavily restricted This, however, raises new questions for ethicists to ponder. and unhappy ones. Yet there will presumably remain broad For, given that the problems characteristic of worldship cultural differences, causing cultures more tolerant of living will begin to be addressed well before interstellar flight crowding and employing stricter levels of social discipline to becomes possible, two new factors come into play. tend to numerically dominate the Solar System in accordance with evolutionary logic, regardless of any accusations of Firstly, unlike the worldship case, there would exist a exploitation of their own citizens which may be flung at them plausible scenario in which a sense of urgency is attached by their more ethically circumspect neighbours. to a space colonisation programme. This would be the case if it is undertaken in pursuit, not of species survival, but of At the same time, the learning curve will surely be eased the more deeply felt cause of national survival. Suppose that by the gradient of difficulty inherent in the Solar System. a great power struggle is underway on Earth similar to the Space colonies may be established first in Earth orbit, later 20th-century Cold War, and that extraterrestrial colonisation in the Main Asteroid Belt, then among the Jupiter Trojans is seen either as