This was a a very sad book. The dreams and optimism of the post-apollo 1970s have collapsed completely. O’Neill was confidently predicting a significant space industry and lunar base by 2010 “at the latest” and of course that never happened. Our progress in space has largely stalled since the 1970s and 80s, likely another victim of the continuing productivity slowdown.

Despite never happening, his dream is still insipiring and, more importantly, possible. It uses only technology avaliable to him in the 1970s, which in many cases we have now far surpassed. The problems are economic and political, not technological. He sets out a roadmap to building an economically viable and rapidly expanding space presence. The core of which is the bootstrap principle. Space industries, even in their early stages, must pay. And they must pay enough to support continued expansion. Ideally at a rapid clip. This is possible becaues the major drag on space colonisation is that we start on earth. Once sufficient infrastructure is built up in space to enable the manufacture of new spacecraft and habitats and industry then space can bloom very fast indeed. The roadmap he sets out is quite simple:

The first place to be exploited must be the moon. It is close enough that it may be easily reached. From  the Apollo missions we know a lot about its composition and geography. It is a very valuable source of raw materials that can be used. Its gravity is tiny compared to the earth’s and it has no atmosphere, so a railgun on the surfac could launch material to space cheaply and efficiently.

Most industry should take place in space. The place he suggests is L5, a gravitationally stable area between the earth and the moon. This is where we should start building our industry and the habitats to house the people necessary to support them.

Living in space gets considerably easier the larger your habitat. A tiny environment like the ISS is tricky to live in and shield, is not self-sustainable and so must be constantly replenished from earth. A larger habitat several kilometers across - as O’neill suggests for Island 1 - would be considerably more robust and hospitable. The habitat would be a cylindrical shape which could be spun about its axis to give a constant 1-g of “gravity”. It would be self sufficient as it would recycle its oxygen and water (and if these were to be gradually lost over time, they could easily be replenished from lunar material). It could grow its own food. Space is actually surprisingly conducive to agriculture. There is strong sunlight 24/7. The atmosphere and environment can be precisely controlled. There are no seasons, no winters. There will be no need for pesticides or insecticides. Neither will there be any other form of crop loss. With plants specially adapted for this environment, and with the ideal environment, several harvests a year should be producable.

Meat will be trickier, but there is no reason that once large crop surpluses are produced, that animals cannot be reared. They will likely be efficient animals like chickens or pigs rather than cows, which will likely reain a luxury. Perhaps by the time large habitats will be being constructed, all meat can be grown in the lab anyway, rendering such considerations moot.

Power will be obtained through solar arrays around the habitat. It will be completely clean and significantly cheaper than it is today on earth. Radiation will initially be a problem, but waste slag from the industries could eventually be used as a very effective shield. Life on the habitats, once constructed, will generally be pleasant, and can be made very similar to earth life if desired.

The industries on the habitats will mostly be processing of lunar, and later asteroidal materials, the construction of solar power satellites to be sent to geosynchronous orbit to provide power to earth, or the construction of additional habitats and ships to fuel the industry. Beyond these core industries, there are many other industries which can be performed usefully in space. The hard vacuum and zero gravity environment make many industrial processes easier. Complicated products such as computer chips can be made with no danger of contamination. Much larger crystals can be grown in solution in zero-g than on earth. The temperature gradient between several hundred degrees in concentrated sunlight versus almost absolute zero in the shade can be used for many processes. There will also be various industries such as supporting the agriculture of the habitat, and supplying scientists working throughout the solar system.

From L5, dispatching probes all around the solar system will be almost trivial. As will the construction of enormous telescope arrays to survey our galaxy in detail. Space-based science will be another big business, and supporting the scientists and building their probes and many of their instruments will be another significant industry.

Once a significant amount of industry is created at L5, supported by the proceeds of selling solar satellites and other products to earth nations then expansion is possible to the asteroid belt and beyond. Despite Elon Musk’s dreams of terraforming Mars, the other planets are likely to remain backwaters, inhabited by only a few science stations. By settling on a planet you put yourself at the bottom of a large energy hole, for little benefit compared to an asteroid based habitat. Planets, fundamentally, are a boondoggle, useful as symbols but with little immediate economic value. A thriving, self-sustaining, civilisation of habitats and manufactures in the asteroid belts would be the ultimate goal. Once this is achieved, conquest of the rest of the solar system should follow automatically. Really, once the first economically viable self supporting habitat comes online, the dam will burst and humanity will spill out across the solar system, driven irresitably by the new incentive landscape suddenly opened to them.

If it is so easy though, why has it not happened? A large part can be blamed on the lack of national will and competition following the collapse of the Soviet Union. I think it’s undisputable that with the seemingly unchallenged American hegemony, the elites have become remarkably complacent, focusing their ambitions inwards rather than outwards at the world. In the current world there can be no new Apollo, but space could easily have been colonised by private interests and private capital long ago, just as SpaceX is attempting now. However,the true inhibitor of the dream has always been launch costs. They are simply too large for a self-sustaining space industry to be built up directly from Earth without substantial sacrifice and risk. Even the minimal amount of industry required to begin the bootstrapping is economically infeasible to be built with private capital alone.

The solution to this is obviously to decrease launch costs. There is a inherent energy cost to get out of the earth’s gravitational well which cannot be ameliorated, but that is a tiny fraction of the current cost. The biggest problem is single-use rockets. These are almost unimaginably inefficient as a paradigm. Not only do they suffer from the Rocket Equation - having to haul several times the payload weight in fuel - they also can only be used once so a whole new rocket needs to be built for every mission. Perhaps if they were cheap and mass-produced, this would be feasible, but this has simply not happened, and likely never will.

Reusable rockets would represent a substantial improvement. O’Neill pinned his hopes on the space shuttle, which, from his perspective, must have been a collossal dissapointment. SpaceX are now pushing reusable rockets hard, and they have had serious progress. Perhaps they will be able to reduce launch costs significantly.

However, I think that rockets are ultimately a dead end. The rocket equation is a harsh mistress, and no amount of clever engineering can get around it. For human passengers and expensive material, I can see rockets being viable, but I cannot see a way for them to economically transport the huge amount of bulk material which will need to be lifted into orbit to bootstrap a space based industry.

One possibility which I have been looking into is ground-based railguns to shoot bulk materials into orbit for a substantially lesser price. This paper (-/link to paper) has convinced me that such a method is not completely unfeasible.There mainsignificantly large issues such as building a long enough rail tube and keeping it a hardvacuum, though manu of the same techniques used in particle accelerators can probably be used here. Siting it in a place where the entire downrange trajectory is safe, and, critically building the electromagnets and capacitors which can accerlate an oject to such speeds.

The main problem, however, appears to be shielding. The projectile will hit the dense lower atmosphere at about 11,000 km/s. That is insane.  If it is to survive that, then it must have extremely powerful shielding, likely beyond current technology, which will ienvitably add to the weight. I don’t see any particular reason why such shielding would be impossible to develop however, especially if remotely comparable resources were devoted to the problem as were devoted to developing rocketry.

To keep the length of the gun to a reasonable size - a few tens of kilometers or less -the railgun will only be able to be used for bulk materials, not human passengers or likely complex and sensitive electronics which would be destroyed by powerful gees. Even with this restriction it will be extraordinarily useful. Undoubtedly it will eventually be obsceleted when the space-based industry takes off and shipping raw materials from earth becomes uncompetitive, however it should play a crucial role in allowing those industries to be bootstrapped and, in the process, might return a healthy profit before its inevitable obscelecence.

Perhaps the railgun could even be adapted to take human passengers by using it as simply te initial liftoff stage. The could be accelerated at several gees and shot out into the atmosphere to cruise ot a high altitude andthen the rocket enginestake them from there, costing much less fuel than a rocket lift off from the earth. I suspect reusable rockets would outcompete it though.

Thus the space program initially would have two different launch methods. Reusable rockets for humans and components which cannot tolerate high gees, and a ground base railgun for the rest. Together, these methods would hopefully be able to reduce launch costs to a level at which bootstrapping a space industry would become economical. Once that is achieved, the road to the galaxy is open, and our future as a true space-faring civilisation begins.