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My favourite childhood reading was a comic called the Eagle, especially the adventures of Dan Dare - Pilot of the Future - with the brilliant artwork of Frank Hamson depicting orbiting cities, jetpacks and alien invaders. When space flight became real, the suits worn by the Nasa astronauts (and their Soviet "cosmonaut" counterparts) were therefore familiar, as were the routines of launching, docking and so forth.

My generation followed the heroic exploits. The first orbital flight, the first spacewalk, the iconic picture Earthrise taken by William Anders from Apollo 8, and of course the Moon landings. And the near-disaster of Apollo 13 reminded us how great the risks were - and the dependence on technology that was primitive by today's standards.


An exclusive look inside Nasa: from retro rockets to robots that will take us to Mars Gallery An exclusive look inside Nasa: from retro rockets to robots that will take us to Mars + 38

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Only 12 years elapsed between the first Sputnik and Neil Armstrong's "one small step". And this was a long time ago - in 1969. Had that momentum been maintained, there would surely be footprints on Mars by now: that's what our generation expected. But the Apollo programme was a "space race" against the Russians. Once that race was won, there was no motive for continuing massive expenditure.

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It's nearly 45 years since Apollo 17, the last lunar mission, returned to Earth. Today's young people know the Americans landed men on the Moon. They know the Egyptians built pyramids. But both seem ancient history, motivated by almost equally bizarre national goals.

Hundreds more have ventured into space in the ensuing decades - but, anticlimactically, they have done no more than circle the Earth in a space station. The International Space Station (ISS) is probably the most expensive artefact ever constructed. Its cost, plus that of the shuttles that until recently serviced it, ran well into 12 figures.


The scientific and technical pay-off hasn't been negligible, but it's been immensely less cost-effective than unmanned missions. Nor are these voyages inspiring in the way that the pioneering Russian and US space exploits were. The ISS only makes news when something goes wrong - when the loo fails, for instance - or when astronauts perform "stunts", such as the Canadian Chris Hadfield's guitar-playing and singing.

Space technology has of course burgeoned: we depend on satellites for communication, satnav, environmental monitoring, and weather forecasting - some of these satellites are large, but there is a growing market for cheap miniaturised ones. Telescopes have beamed back data from the remotest parts of the cosmos; spacecraft have journeyed to all the planets of our solar system.



Nasa's New Horizons probe beamed back amazing pictures from Pluto, 10,000 times farther away than the Moon. And the European Space Agency's Rosetta has landed a robot on a comet. These spacecraft took five years to design and build, and then ten years journeying to their remote targets. We're aware how mobile phones have changed in the last 15 years - so imagine how much more sophisticated today's follow-ups to these missions could be.

"I hope some people now living will walk on Mars - as an adventure and a step towards the stars" Martin Rees, Astronomer Royal

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During this century, the entire Solar System - planets, moons and asteroids - will be explored and mapped by flotillas of tiny robotic craft. The next step would be space mining and fabrication. (And fabrication in space will be a better use of materials mined from asteroids than bringing them back to Earth). Every man-made object currently in orbit has had to be launched from Earth. But later this century, giant robotic fabricators will be able to construct, in space, huge solar-energy collectors and other artefacts. The Hubble Space Telescope's successors, with huge gossamer-thin mirrors assembled under zero gravity, will further expand our vision of stars, galaxies and the wider cosmos.



It is robots, and not humans, that will build giant artefacts in space, and explore the outer planets. Moreover, these robots won't be humanoid in size and shape. Humans are adapted to the Earth's environment. Something more spider-like would be better suited to the weaker gravity of Pluto or the asteroids. But what role will humans play? There's no denying that Nasa's Curiosity, now trundling across Martian craters, may miss startling discoveries that no human geologist could overlook. But machine learning is advancing fast, as is sensor technology, whereas the cost gap between manned and unmanned missions remains huge. The practical need for manned space flight gets ever weaker with each advance made in robots and miniaturisation.


Martin Rees has been Astronomer Royal since 1995 Nick Wilson

Nonetheless, I hope that some people now living will walk on Mars - as an adventure, and as a step towards the stars. But Nasa will confront political obstacles in achieving this goal within budget. The American public is risk-averse. The Shuttle's two catastrophic accidents (out of nearly 140 launches) were national traumas in the US - each led to a three-year stalling of the programme as near-futile attempts were made to ensure even greater safety. The US public regarded a two per cent risk as unacceptable.



That's why I think the best future for Nasa is to share expertise and collaborate with outfits like SpaceX and Blue Origin - indeed, to let the private sector "front" the missions. These private ventures can tolerate higher risks than a western government could impose on publicly funded civilians; they can thereby cut costs compared to Nasa (or the ESA). There would, nonetheless, be many volunteers - accepting high risks and perhaps even "one-way tickets" - driven by the same motives as early explorers, mountaineers and the like.



These opportunities should be promoted as adventures or extreme sports - the phrase "space tourism" should be avoided. It lulls people into unrealistic confidence.

By 2100, courageous pioneers in the mould of (say) Felix Baumgartner, who broke the sound barrier in free fall from a high-altitude balloon (or Sir Ranulph Fiennes, who, among many feats, dragged a sledge to the South Pole in the Antarctic winter), may have established "bases" independent from the Earth - on Mars, or maybe on asteroids. Elon Musk (aged 45) says he wants to die on Mars - but not on impact. Development of self-sustaining communities remote from the Earth would also ensure that advanced life would survive, even if the worst conceivable catastrophe befell our planet.



But don't expect mass emigration from Earth. Nowhere offers an environment even as clement as the Antarctic or the top of Everest. It's a dangerous delusion to think that space offers an escape from Earth's problems. There's no "Planet B".

Indeed, space is an inherently hostile environment to which humans are ill-adapted. For that reason, even though we may wish to regulate genetic and cyborg technology on Earth, we should surely wish the space pioneers good luck in using all such techniques to adapt to different atmospheres, different g forces, and so forth.

"It's dangerous to think space offers an escape from Earth's problems. There's no Planet B" Martin Rees, Astronomer Royal

This might be the first step towards divergence into a new species: the beginning of the post-human era.


Nasa's Valkyrie robot in pictures Nasa's Valkyrie robot in pictures

To find an environment as clement as our Earth, we need to look far beyond the solar system to the exoplanets orbiting other stars. But the transit time to other stars, using known technology, exceeds a human lifetime. And it will remain so even if futuristic forms of propulsion can be developed and deployed - involving nuclear power, matter-antimatter annihilation, or pressure from giant laser beams.

Interstellar travel (except for unmanned probes, DNA samples, and so on) is therefore an enterprise for post-humans. They could be organic creatures (or cyborgs) which had won the battle with death, or perfected the techniques of hibernation or suspended animation. A journey lasting thousands of years is a doddle if you are near-immortal and are not constrained to a human lifespan.



There must be chemical and metabolic limits to the size and processing power of "wet" organic brains. Maybe we're close to these already. But fewer limits constrain electronic computers (still less, perhaps, quantum computers). And there's no limit to how widely such machines could spread. Earth's biosphere, in which organic life has symbiotically evolved, is not essential sustenance for advanced AI. Indeed, it is far from optimal: interplanetary and interstellar space, a hostile environment for humans, will be the preferred arena where non-biological "brains" may, in the distant future, far surpass human capabilities.