7. Solar Sails

“scientists think you can fly a spaceship with the stellar wind, the particles a star gives off when it shines. If the sail’s big and light enough.” p. 83

Credit: Rick Sternbach, The Planetary Society

Happy New Year!

One of the biggest difficulties in spaceship propulsion is having to carry your fuel on board. The more mass your ship has, the more energy it needs to accelerate to faster and faster speeds. Scientists have come up with an ingenious solution – not carrying any fuel. Instead, a solar sailing ship has been proposed to surf the currents between the stars. When the Sun shines, it gives off a steady stream of subatomic particles called the stellar wind. Individually these are insignificant, but add up all their effects and they can become quite sizable.

When solar sails were first mooted, it was thought that this “radiation” pressure might be enough to fly a ship on its own. Nowadays, scientists calculate that we have to give a solar sailing ship a helping hand by firing lasers into the sail to push it along. The Planetary Society have been at the forefront of solar sail research and launched Cosmos 1 back in 2005 to demonstrate the theory. Sadly, a rocket failure meant the first ever space-bound sailing ship never reached orbit.

Undeterred, Lightsail is a new initiative from the same organization – they plan to launch the first prototype before the end of 2010 (and you can even send your name or a message into space with it). Lightsail 1 will be restricted to flights in Earth orbit, but ships 2 and 3 will be more ambitious.

I first came across the concept of solar sails in Larry Niven and Jerry Pournelle’s 1974 novel The Mote in God’s Eye. Nowadays, I remember little else about the book, but think it was trying to use the same “science in fiction” approach that I’ve attempted with Johnny Mackintosh. After you’ve all read Star Blaze and while you’re twiddling your thumbs waiting for me to finish the third instalment, you may want to take a look at it. Jerry Pournelle also wrote A Step Further Out, which was a manifesto for investing in space travel.

Tomorrow we’re taking one of those steps, travelling to a star in the constellation of Orion the Hunter.


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