Friday, 11 June 2010

In The News: Solar Sailing

When you're a child, and a bit of a geek child at that, you have visions of the future.  Robots that act like humans.  People living on other planets.  Flying cars.  You know, the usual.

Sadly, the future all so often turns out to disappoint.  Yeah, we got mobile phones, big deal.  Shuttle is being retired, Concorde is no more, and frankly I can't put it any better than by referencing the excellent Edinburgh based band "We Were Promised Jetpacks"

Sometimes though, just sometimes, something happens that makes you realise that 2010 isn't entirely rubbish.  OK, we never quite did the Jupiter thing as promised by Arthur C Clarke, but by Jove we've gone and done the next best thing....

The Japanese IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) project has successfully unfurled a solar sail, a form of space propulsion most famously predicted in Clarke's lovely short story A Wind From The Sun.  I'm trying to get permission to reproduce the images here, but in the meantime you can find the originals at the IKAROS blog (english language translation, sans pictures, here)

Solar sails are seriously cool.  The idea is that when a photon bounces off a surface then it imparts a tiny amount of momentum.  You can use this force to power a spacecraft without using any fuel whatsoever, except a beam of light. This could be a ground based laser if you want to be all high-tech and efficient about it, but good old fashioned sunlight works just as well.  The only snag is that you need a big sail...a really big sail.  A twelve square metre kite will happily lift me off the ground, so that's a force of about 1000 Newtons, but solar sails aren't that efficient.  A solar sail several square kilometres in size will only provide a few Newtons of thrust.

But that's constant thrust, all the time, 24 hours a day.  Give it a few weeks and you're doing thousands of miles an hour.  Ten years and you're doing millions of miles an hour.  When it comes to interstellar travel, covering light years, that's a far better bet than the old fashioned, fuel carrying, excessively heavy chemical rockets we're using at the moment.  Ion engines are better, and currently being used, but they're still nothing compared to solar sails when it comes to interstellar travel.

Anyway, books are the point of this blog....

Firstly, if you haven't already, you should really read Arthur C Clarke's A Wind From The Sun.  It's just a little short story, included (along with the titular precursor to 2001: A Space Odyssey) in The Sentinal, a great collection of short works and novellas from an acknowledged grand master of sci-fi.

For a more modern version, including a description of a mission to a star and (importantly) actually getting back again, there's Charlie Stross's Accelerando, as also covered in my recent science/sci-fi post.  Stross also deals with the idea of using a ground based laser rather than sunlight, a logical next step from Clarke's concept.

And if you want to get really technical, there's the hefty but relatively cheap (for what it is) Solar Sailing: Technology, Dynamics and Mission Applications by Colin Robert McInnes, a comprehensive study of present and near future technology, science and, as the title suggests, applications of solar sailing.  The character development and plot aren't up there with Clarke and Stross, but we'll forgive that for the sheer depth of knowledge and the fact that Springer Publishing have been nice enough to make huge amounts of it available free on Google Books.

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