by Duncan Lunan

In 1974 Prof. Gerard O’Neill published his proposals for large free-flying settlements in space, following earlier suggestions by Tsiolkovsky, Bernal and others.  O’Neill’s initial proposal was for paired, counter-rotating cylindrical habitats, stationed at the L4 and L5 points of the Earth-Moon system, and with even the smallest models to be capable of supporting 10,000 people.  Artificial gravity would be simulated by the rotation, and the pairing of the cylinders would cancel gyroscopic effects, so that the long axes could be kept pointing at the Sun and mirror systems would provide natural daylight.  Conditions inside the cylinders were to be as Earth-like as possible, including standard atmospheric pressure and full simulated Earth gravity (23).

The habitats were to be built from lunar materials, which lack the volatiles needed for life-support, and the very large quantity of nitrogen required seemed to be the biggest problem.  For his early settlements O’Neill therefore produced a less ambitious “Bernal sphere” design.  Even in that, however, the rotation rates required for 1-g simulation would be high enough to cause vertigo, and a 1975 NASA/Stanford University summer study evolved the “Stanford Torus”, a ring-shaped habitat a kilometre in radius, built of aluminium or steel and rotating within a stationary radiation shield of rock  (24).  D.J. Sheppard later improved the concept, using prestressed concrete as the building material so that the radiation shield was the hull itself  (25).

Meanwhile, out on the frontiers of speculation, the conventional idea of the starship was taking some severe knocks.  From the British Interplanetary Society’s “Project Daedalus” study, of an unmanned probe mission to Barnard’s Star, it emerged that the collision effects in the interstellar medium were more severe than had been supposed;  even at 12% of lightspeed, the cruise velocity of the Daedalus probe, a thick erosion shield would be needed for’ard.  The “photon drive” starship, which Eugene Sänger had supposed could approach the speed of light (26) requires a very large heat-emitting surface for its matter-antimatter engines, and would presumably disintegrate long before it reached top speed. 

That problem might have been solved by the hydrogen ramscoop, proposed by R.W. Bussard (27), which swept up the interstellar hydrogen ahead to provide power and thrust.  The bursting effect of the very powerful magnetic fields required posed structural problems, but these perhaps might be overcome by sufficiently elaborate arrangements of magnetic and electrostatic fields putting the principal flow of plasma round the outside of the ship.  However, T.A. Heppenheimer’s analysis showed that in practice, at anything over 5% of lightspeed, the ramscoop would begin to function as a brake (28).

(In itself that is not to be sneezed at.  Eliminating the need to carry fuel for braking manoeuvres greatly reduces the mass of launch mass of space vehicles, and most studies of manned Mars Missions assume some form of aerodynamic braking on arrival at Mars and on return to Earth.)

Our ideas about interstellar settlement have also changed radically.  Even in the Man and the Stars discussions, published in 1974, we had realized that integrating terrestrial lifeforms into the biosphere of another Earth-like world would be too formidable a task to accomplish with ‘foreseeable’ interstellar missions.  The late Ed Buckley illustrated a worked example in the book’s Plates 1, 2 and 3.  Plate 1 showed the approach to an imaginary Earth-like world of Alpha Centauri, which, although in the nearest star system to us, seemed the most likely one in our neighbourhood to have such a planet (29)– unless, of course, double stars could not have planets.  As we now know, most of the nearer stars have planets, starting with three orbiting Proxima Centauri, the nearest component of the Alpha Centauri system, 4.2 light-years from us.  Alpha Centauri B was thought to have one, though that has turned out to be a false alarm.  Nevertheless Barnard’s Star, Epsilon Eridani, Gliese 887, Tau Ceti and Kapteyn’s Star have all turned out to have planets, within 13 light-years of us.  With the two component stars of the Alpha Centauri binary currently nearing their furthest apart, an intensive search for planets is ongoing.  As numerous more distant binary stars have turned out to have planets, being in a multiple star system is not a problem.

Even on approach, Ed Buckley’s outwardly peaceful planet hinted at dangers on the surface.  Although the presence of liquid water and free oxygen in the atmosphere confirmed that the planet could support ‘life as we know it’, the large equatorial desert suggested more extreme conditions than Earth’s – perhaps reaching a peak when the two suns are close together.  Speaking of peaks, the cloud pattern in the Northern Hemisphere showed a very high plateau on the shoulder of the continent.  Buckley had told us that this world is larger and more massive than Earth, so perhaps there’s violent volcanic activity with the associated dangers of earthquakes and tidal waves.  If surface gravity is higher than Earth’s, then storms too may be more violent, and the cyclonic patterns visible may develop into hurricanes even on this planet’s temperate latitudes.

The temperate zones are obviously the candidates for landing sites, and he suggested that the first settlement should be on a large island, or a peninsula cut off by a natural barrier such as a desert or mountain range, so that dangerous lifeforms could be contained and controlled if necessary.  An offshore island about the size of Britain would be ideal, allowing for expansion to the mainland later.  It was not until after the publication of Man and the Stars that we realized we had duplicated the reasoning of H.G. Wells in The War of the Worlds, where the Martians do indeed target an offshore island the size of Britain – Britain itself – in order to contain and control the most dangerous lifeform on the planet, human beings.

Plate 2 showed a cargo landing craft leaving a large colony ship over the island.  The plug-nozzle vehicle is designed to land on water because a coastal site is wanted: it allows retreat inland from storms or tidal waves, and escape by water from animals and brush fires.  The continental shelf allows fishing and sea farming, and the mountain range inland provides rainfall for farming in the coastal strip, as well as mineral resources and a high ground refuge if tidal waves are common.  To protect the landing craft and the settlement sheltered waters would be best, such as the sealochs at lower left, and the upper one seems ideal because it is also protected by offshore islands. The same spot at ground level still looks peaceful in Plate 3, at first glance.  But the tree in the foreground has apparently been killed by parasitical growths, and the one behind does not look healthy.  The airborne specks clustering around the flowers (which are not quite flowers, just as the trees are not quite trees) could be pollen or could be insects, and might be harmless, but they are certainly clustering around the explorers in their biological isolation suits.  In the distance, flocks of birds (which, as we saw from the nearest one, are not quite birds) are taking to the air.  Perhaps something big and dangerous is approaching beyond the trees – but then again, the overall movement of the birds themselves is in the explorers’ direction.  Our heroes might soon be wishing they had not strayed so far from their hovercraft.  In the foreground are the ‘zozzles’ – many more of them than are apparent at first glance.   It’s not obvious how big, intelligent or dangerous they are, but they’re all watching the explorers – as is another creature, hiding in the grass which is not quite grass.  The whole outwardly friendly landscape is full of potential dangers, and those are only the visible ones.  Bacteria and viruses spring to mind, but as life on Earth uses only a few of the range of proteins available in nature, it may be that everything in Plate 3 would be either poisonous or inert to terrestrial life.  It could even be that life on that world is based on dextro-rotatory compounds instead of the laevo-rotatory ones used on Earth, in which case this blooming landscape would be as dead to us as the surface of the Moon.  [However, there are suggested reasons why life throughout the Universe might prefer laevo compounds(30)]

Trying to plan the exercise in detail, we swiftly realized that establishing a settlement of terrestrial life in such conditions would call for continuous links with Earth itself.  Only faster-than-light travel would allow that, and all the evidence to date suggests that can’t be done.  We nevertheless assumed for the sake of argument that an ‘acceptable’ method could be found, and went ahead to analyse in detail the practicalities and ethics of interstellar colonization and contact with other intelligences, in the sense of face-to-face meeting.  This drew some hostile reviews and the conclusions made no impression on spaceflight literature.  In Iain Nicolson’s Road to the Stars, for instance, it is repeatedly stated that nothing has been said or can be said about the issues to which we gave so much thought.  That is to say that you cannot discuss the ethics of the voyage unless you have a blueprint of the engines.

By the first appearance of this article, however, we could say that a blueprint was now available.  For their ‘Project Daedalus’ study the British Interplanetary Society postulated that their probe should reach Barnard’s Star within 60 years, an adult human lifetime.  The engine would run on pulsed nuclear fusion (triggered by converging electron beams) of pellets of frozen deuterium enclosing liquid helium-3.  It would take 50,000 tons of propellant to accelerate the probe to its interstellar velocity of 12% of lightspeed, and the Daedalus team proposed to gather these from the atmosphere of Jupiter.  In Man and the Planets, I pointed out that just 200 tons of propellant would suffice to move a 50,000 ton payload from Earth to Mars in five days, 500,000 tons – a metal Stanford torus – could be moved from here to Mars in a fortnight for the same fuel expenditure, and five million tons (the Sheppard design) could make the trip in less than a year.

When I checked these figures with Gerry Webb of the Daedalus team, he replied, “Within the Solar System, Daedalus is pure Flash Gordon in its potential”.  On my visit to the Jet Propulsion Laboratory in Pasadena, in 1986, I was surprised to have the same figures quoted back to me and attributed to the Lawrence Livermore Laboratory.  The Daedalus propulsion system  (or a very similar variant called VISTA)  was then under development there, and initial results had been so promising that the Laboratory was allowed samples of lunar soil for destructive testing.  From this it emerged that the solar wind deposits on the lunar soil contain  (relatively)  large amounts of helium-3 – at first sight, enough to provide the means for us to open up the whole Solar System for development.  The programme could be financed by importing helium-3 to Earth, if deuterium/helium-3 fusion can be adapted for energy generation (31)  – but later publications suggested that the volumes of lunar soil to be processed would be prohibitive.

Nevertheless, the Daedalus concept tied in directly with Project Starseed, another scenario I put forward to finance building O’Neill habitats, using nuclear waste disposal as the baseline of the programme (32).   Developing the scenario, I later pointed out that building and fitting out habitats will be much easier if the requirement for full simulation of Earth gravity is relaxed.  In the Starseeds themselves, the mobile factories I envisaged being built out of space shuttle external fuel tanks, the maximum rate of rotation without nausea would be enough only to simulate lunar gravity, one sixth of Earth’s.  But no other solid body in the Solar System has a surface gravity more than one-third of Earth’s – with the exception of Venus, whose otherwise hellish conditions rule out settlement in the foreseeable future.  If we were to settle on quarter-g as a compromise, giving acclimatized occupants access to every known solid world except Earth and Venus, then the slower rotation would allow the settlements to be built in cylindrical form as O’Neill originally envisaged, and would reactivate Matloff’s proposal to fit those habitats with Daedalus engines and make them mobile.

Matloff’s proposal was to use such habitats as space-arks, or ‘world ships’ as Ed Buckley termed them, for self-supporting communities to cross interstellar space.  The 50,000 tons of propellant of the Daedalus probe would accelerate an O’Neill habitat to 1% of lightspeed, giving a 430-year voyage to Alpha Centauri or 600 years to Barnard’s Star.  Again, the resources of Jupiter would be required; but a mobile habitat, fully shielded as it must be against galactic cosmic rays, could enter Jupiter’s radiation belts with impunity to ‘mine’ Daedalus propellants from the planet while in close orbit  – more efficiently than the Callisto based operation which the Daedalus team proposed.

In the first instance, the habitats will be using Jupiter’s resources to gain access to the outer Solar System, and that is enough for the politics of survival objective.  Creating the first mobile habitats was enough to ensure that humanity could not be wiped out by events under Politics of Survival headings 6 and 7; but a habitat culture spread over the halo of comets, up to two light years from the Sun, would not only be safe from the dictates of central government, (34)  but would represent a virtually impossible “sweeping up” operation for even a deliberately malevolent other intelligence.  Guaranteed survival of mankind can be achieved over a baseline of only four light years, rather than twenty as suggested in “Man and the Stars”, and can be attained in two centuries from now or less.

By that time von Hoerner’s ways in which technological civilizations can collapse will be completely irrelevant.  We are considering in effect a civilization of mobile worlds, with a wide choice of locations to occupy from the inner Solar System to the outer and beyond, and no reason to stop expanding.  If Alpha Centauri has an envelope of comets, one can see the mobile world civilization expanding into it simply because, for the cometary habitats on that side of our envelope, they will be the easiest targets to reach.  But if there is anything worth having in the Alpha Centauri system – planets, asteroids or what you will – the foreseeable combination of O’Neill and Daedalus technologies could send a mobile world there from the comets in only two hundred years, at a little over 1% of the speed of light.  Once you have mastered your own Solar System, the interstellar gulf has lost its terrors.

(To be continued). Check out part 1: The Fermi Paradox Part 1

Interested in the night sky?: The Sky Above You – May 2022

References

23.  G. K. O’Neill, “The High Frontier”, Jonathon Cape, 1977.

24.  Richard D. Johnson, Charles Holbrow, “Space Settlements, a design study”, NASA SP-413, US Government Printing Office, 1977.

25.  D.J. Sheppard, ‘Concrete Space Colonies’, Spaceflight 21, 3-8  (1979).

26.  Eugene Sänger, ‘Zur Flugmechanik der Phonetenraketen’, Astronautica Acta, 3, 89-99  (1957).

27.  R.W. Bussard, ‘Galactic Matter and Interstellar Flight’, Astronautica Acta, 6, 179-194  (1960).

28. T.A. Heppenheimer, ‘On the Infeasibility of Interstellar Ramjets’, JBIS, 31(6), 222-224  (1978).

29. Stephen H. Dole, “Habitable Planets for Man”, Blaisdell Publishing Company, 1964.

30. D. Phillips, ‘A Chemist Looks between the Stars’, IBM Heathrow Conference, 1987.

31.  ‘Lunar Initiative Updates’, Lunar & Planetary Information Bulletin, 44, 11  (1986).

32.  Duncan Lunan, ‘Project Starseed:  an Integrated Programme for Nuclear Waste Disposal and Space Solar Energy’, JBIS, 36, 9, 426-432  (September 1983);  reprinted Infinity, 1985;  ‘Project Starseed, or, Nuclear Waste Saves the World’, Analog, CV, 2, 54-73  (February 1985);  ‘Project Starseed’, revised version, Settlers Sentinel, 1987;   ‘Project Starseed’, (fourth version), Asgard, Christmas 1991.  Alternative, ‘slimmed-down’ and updated version in “Incoming Asteroid:  what could we do about it?’, Springer, New York, 2013.

33.  Gregory L. Matloff, ‘Utilisation of O’Neill’s Model 1 Lagrange Point Colony as an Interstellar Ark’, JBIS 29, 775-785  (December 1976).

34.  F.J. Dyson, ‘Human Consequences of the Exploration of Space’, in Eugene Rabinowitch & Richard S. Lewis, eds., “Men in Space”, Medical & Technical Publishing Co., Ltd., 1970.

The Politics of Survival, Project Starseed, Project Daedalus and other related topics are all updated in “Incoming Asteroid!  What could we do about it?” by Duncan Lunan  (Springer, 2013), available from the publishers, through Amazon or through bookshops.  For details of Duncan’s other books see his website, http://www.duncanlunan.com.