Peak oil, peak water, peak everything: human life on Earth faces imminent limits, many now believe. The essential Malthusian idea was formalised at the end of the 18th century. Populations will grow exponentially, but resources cannot. Its most influential modern incarnation appeared in 1972, when a Massachusetts Institute of Technology group published a study titled The Limits to Growth. Armed with what seemed at the time to be sophisticated computer models, it predicted ecological and economic collapse by the middle of the 21st century.

Then, as now, responses varied widely. Accept the conclusion, and activism or fatalism beckon. Critique it, and you must find a way of negating the “other things being equal” clause in the Malthusian argument. In the 20th century, two options seemed possible: leave the planet, or deploy radically new technology on Earth. Patrick McCray’s study reviews the work of two men who pursued those options. Gerard O’Neill was a tireless advocate of orbiting space colonies as a new habitat for humanity. Eric Drexler was first drawn to O’Neill’s project, but went on to develop a vision of nanotechnology that would revolutionise all manufacturing by giving us fine control over matter at the atomic and molecular scale.

Both men worked up a technological prospectus that they believed refuted The Limits to Growth’s thesis. For McCray, they were “visioneers”: visionaries who went beyond speculating about new technologies to develop disciplined design studies and some projects aimed at expediting their larger goals.

O’Neill, a Princeton University academic, began elaborating his ideas in a seminar for physics students in 1969. He had made important contributions to improving particle accelerators, but now wanted to apply his engineering nous to an idea that had long fascinated him - space colonies. Could we build on the technology that had sent Americans to the Moon to construct orbital homes for thousands of people? He thought so, and backed his conviction with detailed calculations about payloads, life support and the time it would take for the first colonists to build next-generation habitats using materials mined from the Moon or the asteroid belt.

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His plans attracted supporters ranging from Timothy Leary to Omni magazine, but the typical enthusiast was a libertarian technophile with an environmentalist streak (such as the agile ideas broker and intellectual impresario Stewart Brand). They wanted to go beyond spaceship Earth by building Earth-like spaceships.

The young Drexler, whose application to study at MIT in 1973 declared his ambition to investigate space colonies, shared that outlook. By the late 1970s he had moved on to molecular engineering, or nanotechnology as it would be known. He also supported his vision of molecular manufacturing with engineering calculations, with more controversial results. McCray relates how Drexler was gradually frozen out of the many well-funded nanotech programmes established in the US, whose work was generally more conventional than he had envisaged.

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This latter part of his story is recent, and familiar to those who follow the development of nanotechnology. This makes the book a little uneven. The material on O’Neill seems stronger, and is an important part of the story of how expansive visions of technological futures were sustained at a time when the general view of the human prospect took on a different cast. However, Drexler’s contribution to the same techno-progressivist history is still unfolding - a new book, Radical Abundance, is in press - and it is useful to have a fresh summary of his career so far.

On the whole, pairing O’Neill and Drexler works well. I am less convinced about McCray’s notion of the “visioneer” as a new kind of actor. The two men’s careers and work seem rather different, as do those of others one might want to try the label on for size. The author mentions computer interface pioneer Douglas Engelbart, for example, but pretty much all of his ideas have now been built into technology that is in daily use everywhere. As Engelbart himself said, one can create the (technological) future by inventing it.

It is easy to think of other candidates, but perhaps too easy. The category is fuzzy. A wide range of people help to build techno-social systems. Some have visionary moments. Some have a lifelong crazed gleam in their eye. Some just do routine research and development, lots of it. Maintaining technical progress needs all of them and more. If we are to deal with the real limits of the Earth system, we certainly need to do that.