Solar Sails

Hundreds of years ago, man stood at a sandy beach gazing out longingly at the endless expense of ocean that lay before, yearning to unravel the mysteries that this unknown real might hold. He then built a boat, equipped it with a sail and harnessed the power of the wind to propel him into the unknown.

About 400 years ago, a man named Johannes Kepler had a similar longing but his focus was not the ocean. He gazed up at the night sky and dreamed of a day when mankindUntitled would be able to journey towards the stars. While studying comets, Kepler made an observation that intrigued him a lot. He observed that the tails of comets were always turned to a side as if blown there by the wind. He hypothesized that there was a “solar wind” blowing in space which caused this phenomenon to occur. He further proposed a plan to use this solar wind to propel space crafts in space much like sails on traditional sail boats.

Today we know that Kepler’s idea of a solar wind was wrong but he wasn’t completely wrong when it comes to the idea of solar sails. It turns out that we actually do not need a “solar wind” to propel a space craft in space; the light from the sun is enough to do it. Confused? Let me elaborate. As you might or might not know, light acts as both a particle and a wave. So when we take a closer look at the particulate nature of light, we realize that the photons in light (light particles) have momentum, which is basically a property of all moving objects. If we were to fit a space craft with a solar sail, the light particles would bounce off of the sail and thus transfer their momentum to the sail. This in turn would cause the spacecraft to accelerate.

Now on Earth this effect would be completely insignificant but in space, where most of the major forces are completely neutralized, this phenomenon would be far more significant.

Solar sails would solve a major problem in long distance space travel. The space craft would not have to worry about running out of fuel since its fuel is the sunlight which is readily available. It has also been calculated that even though the initial acceleration of a solar sail powered space craft would be far lower than a traditional spacecraft, over a longer period of time, the solar sailed powered space craft would be able to achieve higher velocities than a traditional space craft could.

There has been much research on solar sails over the years but until recently there were far too many constraints holding the technology back. The most major one was the lack of materials light enough to make the sail. The material also had to be extremely reflective. Luckily, there has been much progress in material sciences in the past decade which have allowed actual light sail powered space crafts, like IKAROS, pictured above, to be built and launched into space, proving the viability of this technology. Only time will tell how the sience of solar sails will pan out the the affects it will have on space exploration.

 

— http://www.space.com/25800-ikaros-solar-sail.html

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