Science

PROJECT STARSEED

By Duncan Lunan

In 1979 ASTRA, then Scotland’s national spaceflight society, organised the largest spaceflight exhibition to date at the Third Eye Centre in Glasgow, now the Centre for Contemporary Arts.  As part of the supporting programme they asked us to arrange a seminar on the feasibility of nuclear waste disposal in space.  At that time the UK proposal was that all high-level nuclear wastes generated up to the year 2000 should be buried at a site near Loch Doon;  there was a great deal of controversy then and public concern on the issue remains high.  A succession of public enquiries have gone against burial at other sites, even to the extent of banning test drilling, though Finland has created a huge repository which is now open for business.

The case for burial was actually much better than the media discussion had suggested:  at Oklo in the Gabon, where volcanic activity had produced natural nuclear reactors in uranium-bearing rock, the resultant ‘wastes’ had remained trapped in the strata for 1800 million years.  The proposed Scottish repository would be in much more stable strata, with the wastes cast into glass blocks and sealed in steel cylinders before burial.  Once buried under a mountain, the access tunnels would be blasted shut:  not even glacial action during an ice age would be able to dig the wastes out again.  A few centuries after burial, the fission products’ dangerous ‘lives’ would be over and the radioactivity of the remaining actinides would be less than the ores from which they were first extracted.  An asteroid impact could bring the material back to the surface, but in a destructive event of that scale the scattering of nuclear waste would be the least of the human race’s worries.

The principal speaker was Capt. Chester Lee, then head of the Space Transportation System  (Space Shuttle)  Office, who said that space disposal could match burial for safety.  For the scientific stations left on the Moon by the Apollo astronauts NASA had to develop very tough canisters for the isotope fuel, and the flasks could have withstood the explosion of the Saturn V booster.  The one which re-entered the atmosphere on the Apollo 13 lunar module had evidently reached the Pacific floor intact.   Even if the steel canister were to be breached, the glass would take so long to leach away that the natural radioactivity of the surrounding seawater would be higher than the escaping waste’s.  After the loss of the Challenger in 1986 some environmental groups in the USA opposed the launch of radioisotope power generators on the Galileo and Ulysses spacecraft, but the canisters used would have withstood such an explosion without damage.

Fig. 1. Mass driver in Low Earth Orbit (Sydney Jordan & Theyan Rich, 1987)

The target options for waste disposal were subsequently examined by the late Prof. Archie Roy of Glasgow University.  Storage on the Moon would be dangerous if it went wrong, and could cause problems in later lunar development;  orbits around the Sun on the inside of the Earth’s lead eventually to collisions with Earth, Venus or the Moon;  disposal into the Sun or into Jupiter is difficult and dangerous, again, because if the target is missed the wastes can return to Earth.  The best option is launch out of the Solar System, by an electromagnetic launcher  (Fig. 1), with a launch window on every circuit around the Earth, whatever the time of day, month or year.  No further tracking or guidance is required, and by the time they reach the distance of even the nearer stars the wastes will be inert, so there’d be no question of ‘contaminating the Universe’.  In case by incredible chance any of the cylinders should end up in other star systems, since the harmful substances will by then have turned into lead, the cylinders should carry instructions for cutting the glass into thin slices and mounting them to face the sun.  The legacy of our brief flirtation with nuclear power  (which would be brief, on the proposal below)  would be our gift to the Galaxy of beautiful, abstract stained-glass windows.

At the Massachusetts Institute of Technology, at the time there was a prototype ‘mass driver’ which could accelerate payload to lunar escape velocity along 200 metres of track.  The late Prof. Gerard K. O’Neill told me that the MIT team, under contract to his Space Studies Institute at Princeton, were nowhere near the limits of the system, and although launch away from the Sun from Earth orbit would need a track seven times that length, he was sure that could be done.

Bob Parkinson of the British Interplanetary Society had designed an unmanned Heavy Lift booster using two Space Shuttle External Tanks, two Main Engine clusters, four clip-on boosters and the existing guidance system  (Fig. 1 foreground).  With no crew compartment to shield from radiation, its payload would be 250 tons – 42 waste cylinders at a time.  A launch every three days would keep pace with the entire anticipated world output of high-level nuclear waste during the 1990’s.  Once the steel canisters reach the mass driver, the front end caps can be removed and they can be decelerated at the end of the launch track, allowing the glass blocks to fly on.  Firing the steel jacket back the other way, at a velocity cancelling the retro-impulse of sending the glass out of the Solar System, it emerges almost at rest above the Earth’s surface, to tumble back to a prepared drop zone for re-use.

To handle that volume of traffic an equatorial launch site would be needed, to provide recurring launch windows throughout the day.  It would be a huge programme, and if we assumed that each launch costs as much as a Shuttle mission, on much-too-low 1970s estimates, ten years of the programme would cost the equivalent of Project Apollo  – 25 times the cost of burial.  It could only be justified if the programme was going to produce an alternative energy source for terrestrial civilisation, such as solar power satellites, so that the costs would be recouped and the flow of nuclear waste would eventually stop.

Fig. 2. Geosynchronous orbit SPS demonstrator (NASA)

The Solar Electric Power Satellite, or powersat, was the brainchild of Dr. Peter Glaser:  an array of solar cells 10 miles long, in geosynchronous orbit, broadcasting 5 to 10 Gigawatts of energy to Earth by laser or microwave beams  (Fig. 2).  It would take up to 500 of them to meet Earth’s anticipated energy needs in the 21st century.  Prof. O’Neill saw powersats, built of lunar materials shipped out by mass driver, as the major product of space habitats at the L4 and L5 points in the Earth-Moon system  (Fig.3), where an orbiting body can maintain a fixed relationship to the Earth and Moon with minimal station-keeping.  In a 1975 study by NASA’s Ames Research Center and Stanford University, powersats would be produced by year 13 of the programme and the energy needs of the USA could be met by year 25.

Fig. 3. Earth-Moon Lagrange points

It recalls a ‘Sea City’ which the Pilkington Group designed in the 1960’s as a base for exploiting the North Sea.  When that happened, what was built was not a city but a flock of bigger, stronger oil-rigs, and when powersat-building comes, there will be no delay for building space habitats.  There were ‘space-rigs’  (generally called ‘construction shacks’)  in the space habitat scenarios, but they received little attention although they would be the most ambitious space stations ever planned today.  O’Neill calculated that a workforce of 2000 would be needed, and the late John Braithwaite and I realised that the ‘shacks’ could be built from the paired STS Tanks of the nuclear waste programme.  Residual propellants – liquid oxygen and liquid hydrogen – would be used in fuel cells to generate power and drinkable water.

Space Shuttles de-orbited their ETs on every mission, using the less powerful Orbital Manoeuvring System thereafter.  Had they been retained, using the Main Engines for orbital insertion, the Shuttle payload would have risen enough to carry a large space station core module in a protected canister on the aft end of the Tank.  With one core module and 240 Tanks per year being delivered to a common destination in Low Earth Orbit, we proposed building a construction shack to be called the Starseed, because of its growth potential.

Fig. 4. Shuttle Tank space telescope, designed by John Braithwaite, drawn by Ed Buckley

John had been a consultant on the flexible, variable focus mirror project at the University of Strathclyde.  In the late 1970’s he designed a cruciform orbiting observatory which could be used in 12 different modes  (Fig. 4).  The same structure could form the core of the Starseed, spinning to provide artificial gravity for the occupants in the arms.  At the limit assumed in the Stanford Study, the maximum spin rate would generate one-sixth g, equivalent to gravity at the lunar surface.  With the steady addition of Tanks, avoiding the end-on couplings whose flexings are the bane of large structures in space, the Starseed could grow through a succession of ‘Outgrowths’.  At the end of Outgrowth 2  (Fig. 5), Starseed would be half-way to its final configuration of 198 Tanks, 180 of them with artificial gravity  (Fig 6), and if 100 Tanks were converted to living quarters, with ten decks four metres high, then O’Neill’s 2000 people would be living just two to a deck, in much more comfort than on the average oil-rig.  From the Glasgow Parks Department’s Methane Digester Project in the late 1970’s, a single Tank would reprocess the biological wastes of 2000 people and return the essential elements to the life-support system as fertiliser.  From experience with ‘gardens’ on space stations, a lot of food will be produced by plants which will also help to purify the atmosphere – again, better conditions than on an oil-rig.  Always under artificial gravity, except perhaps in emergencies, life on a Starseed will avoid many problems of long-stay missions in space.

In Tom Campbell’s Outgrowth 2 painting  (Fig. 7), a flexible solar mirror, bigger than the Starseed itself, is being prepared for mounting on the ‘top’ of the structure.  From the Starseed’s after end projects the first segment of a mass driver engine, which will use ground-up Tanks as reaction mass – because to do its job Starseed has to be able to move.

Fig. 7. Starseed at Outgrowth 2, Tom Campbell, 1985

On the lunar equator at longitude 33.1 degrees east, near the crater Censorinus A, it’s particularly easy to launch payloads of lunar soil by mass driver to the L2 position behind the Moon  (Fig. 8).  O’Neill didn’t place his habitats at L2 because the orbit is unstable and needs much more correction than the one at L5.  But the Starseed is much less massive, and can hold the required ‘Halo’ path around the L2 point.  Cutting out the operations of cargo transfer from L2 to L5, and manufacturing at L2, we can aim for continuous deliveries from the lunar surface and continuous processing on board.  

Fig. 8. Censorinus launch to L2, NASA, redrawn by Ed Buckley

Other studies assumed batch processing, but John Braithwaite planned instead to vaporise incoming rock at the focus of the mirror, and separate the products in the hollow core of the Starseed as in a huge mass spectrometer.  If Starseed could reach the output level of a major ground-based steelworks  (60,000 tons, mainly vapour-deposited aluminium and titanium), it could build a powersat in a month, to be launched into ‘2:1 resonance orbit’  (Fig. 9), for gentle delivery to geosynchronous orbit.  If each Starseed takes a year to work up to full productivity, and the nuclear waste programme is generating another Starseed each year to move out to L2, then after nine years nearly 500 powersats have been built – enough for all the  energy needs of the world in the 21st century.  The commercial return should justify the project, and on Earth, environmental and political benefits should be enormous.

Fig. 9. 2 to 1 resonance orbit, NASA, redrawn by Ed Buckley

If 500 powersats were built each massing 60,000 tons  (comparable with a large aircraft carrier), their total mass would be 30 million tons.   From 1975 Summer Study figures, 530 million tons of moonrock would have to be processed.  The 500 mt of residues will be mainly silicates and iron, which can be processed as pre-stressed concrete – the ideal hull material for space settlements, D.J. Sheppard has argued, providing integral radiation shielding rather than the Stanford concept of an aluminium torus rotating within a static rock shield.  Those 500 million tons would provide enough hull material to build 50 such ‘Island One’ space settlements.  Recovering the hydrogen, carbon and nitrogen deposits from the solar wind, on the surfaces of the lunar grains, would provide enough ‘volatiles’ for life-support to make six of those settlements habitable, each capable of supporting 10,000 people, with full shielding against solar storms and cosmic rays.

Those people, committed to human expansion into space, would now be adapted to the one-sixth g environment of the Starseeds and the lunar surface;  and apart from the Earth, that allows reasonable access to every other solid body in the Solar System except for Venus, which is not an early candidate for colonisation.  Dropping the requirement for O’Neill’s habitats to simulate Earth-surface 1g would allow his original cylindrical design for Island Ones, and Gregory L. Matloff’s proposal to use pulsed deuterium/helium-3 fusion to make them mobile.  The next step is to take at least one of them to Jupiter, and mine the atmosphere for those gases  (Fig. 10), for what the late Prof. Krafft Ehricke called ‘the strategic approach to the Solar System’, accessing all of its matter and energy resources for the future benefit of humankind.  Within 200 years mobile habitats could be spread through the Oort Cloud of comets, ensuring the continuation of humanity and terrestrial life despite any foreseeable catastrophe  (see ‘The Fermi Paradox’, Part 1, ON April 24th 2022).  In 20 to 30 million years  (assuming we don’t meet any competition), the two waves of human expansion will meet on the far side of the Galaxy.  They will meet as aliens, because they’ll have evolved differently on the way round, and after we’ve sorted out the problems which that causes, we can decide what the next objective is going to be.

Fig. 10. O”Neill habitat with Daedalus engine in Jupiter orbit, by Gavin Roberts for ‘Man and the Planets’

Afterword

The two Starseed papers by John Braithwaite and myself were published under my name as ‘Nuclear Waste Disposal in Space’ and ‘Project Starseed:  an integrated programme for nuclear waste disposal and space solar energy’, Journal of the British Interplanetary Society, April and Sept. 1983, followed by a 1985 article in Analog.  Prof. O’Neill asked me to present Starseed at his Space Studies Institute’s Space Manufacturing Conference at Princeton University that year, but unfortunately he was tied up with the launch of his company developing a precursor to the Global Positioning System, and the feedback I’d hoped for never took place.  (The first satellite was built, but launch delays allowed GPS to gain dominance of the market and O’Neill’s satellite never flew.)   Promised publication in Space Voyager didn’t happen because the magazine ceased publication, and although the nuclear waste part was published in World Magazine and The Journal of Practical Application in Space, the main concept never appeared in either, only in amateur publications, and in my 1983 book Man and the Planets.

In Incoming Asteroid!  What could we do about it?  (Springer, 2013), I suggested that a programme to deflect one could put enough Space Launch System tanks on-orbit to complete a ‘Starseed Lite’, a much more limited project which might eventually achieve similar objectives.  But since then there has been an unexpected development, with Elon Musk’s proposed Starship and its Superheavy booster.  The nuclear waste disposal programme could be run using uncrewed Superheavy upper stages, and allow the full Starseed project to run on something like the timescale above.  It’s not likely that any government will commit to nuclear waste disposal in space, but a private entrepreneur with his own launch site on the equator could do it.  With renewed interest in space solar power by the European Space Agency and others, maybe it’s time for these bigger ideas to make a comeback.

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