The unvarnished truth about interstellar travel

Art one day, interstellar space travel  the next – that’s the BRLSI. After Thursday’s tour de force on artists of the First World War (see below) tonight it was the turn of the Institution’s Herschel Astronomy Group to occupy the Elwin Room, with a speaker equally well qualified to speak on his subject, the prospects for travelling to the stars.

Dr Ian Crawford (right) is Reader in Planetary Science and Astrobiology at Birkbeck College, University of London, as well as a Fellow of the Royal Astronomical Society and a member of the European Space Sciences Committee, so he certainly knows about space. He gave us the unvarnished truth on the challenges of sending even an unmanned spaceship to the stars, beginning by pointing out that the nearest star (the binary pair Alpha Centauri) is over four light years away, and the fastest that known propulsion technology (detonation of ping-pong sized nuclear pellets) could hope to make a vehicle travel is around 12% of the speed of light, which means roughly 40 years journey time.
The vehicle would have to be massive, too – an astonishing 54,000 tons in one design, most of it fuel and engines. Then there’s the problem of slowing down, which is optional but only if you don’t mind travelling for 40 years just to spend a few hours flying past the target star. The only obvious answer is to use half the fuel for braking, which means half the outward speed and a journey time approaching a century.
All this seems a bit bleak, so why bother? Basically because when it comes to really finding out about a place there’s no substitute for being there. Space telescopes and fly-by probes can tell us a lot, but they can also be misleading. Dr Crawford showed examples from a Mariner fly-by whose few snapshots gave the impression that Mars was a moon-like cratered planet, and explained that remote spectroscopy can detect signs of life, but can’t distinguiish between microbes and quite complex organisms. Only when a craft lands (or at least orbits) can you really see what’s going on.
Perhaps surprisingly, the only serious study into building an interstellar craft has been in Britain. Project Daedalus, designed in the 1970s by the British Interplanetary Society, came up with the 54,000 ton design, while Project Icarus, of which Dr Crawford is a member, is building on it using newer technologies to produce a lighter design. Other propulsion systems, including light sails and antimatter reactors, remain tantalisingly on the horizon. Ultimately though, simple arithmetic shows that only something much more radical, which bypassed the laws of Newton and Einstein, would put us truly in reach of the stars. For that we’ll have to live in hope.