Currently, we do not have the technology to travel to even the closest stars. The fastest spacecraft humans have ever built is the Voyager 1, which is currently traveling at roughly 17 km/s. However, even at these speeds it would take the Voyager I nearly 70,000 years to get to the nearest star system, Alpha Centauri. Clearly, this is not even close to the speed we need to obtain to make interstellar space travel feasible. One potential way to reach speeds that would make interstellar travel feasible in an efficient matter would be with a solar sail.
(Artist rendition of a solar sail)
Solar Sails work by using the solar wind to propel an aircraft forward. Every time light hits an object, it changes the object’s momentum ever so slightly. Thus, since a stream of photons is constantly being released by the Sun in all directions, we could use giant sails attached to spacecraft in order to reflect this light and propel the spacecraft. In fact, this technique has already been used for a few satellites. By using this method, we could theoretically accelerate a spacecraft to nearly the speed of light. The only problem with this is that we would need to build a solar sail that is thousands of miles across and is thinner than a human hair. However, as technology progresses, it is certainly feasible to think that we might someday be able to achieve interstellar travel through using a solar sail.
Chase's Solar System blog 
Interstellar travel has intrigued me for many years now. I have seen this Solar Sail concept a few times and have always wondered if it could work. It seems that the concept is there and there is potential but vastly unfeasible right now. Do you think this is our best shot at reaching other stars or are there other spacecraft being developed that could potentially work better? Nonetheless, interstellar travel, even interplanetary travel right now appears to be a one-way ticket. If we could develop a system to efficiently travel to other planets and other stars do you think our lives on earth would change that much? Would it just be something for a small group of people to experience or would it be world changing?
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I am not sure if it is the best possible way to reach other star systems since there are a number of other possible ways but using solar sails is intriguing because it requires nearly zero fuel. One major problem with solar sails, though, is that the farther the spacecraft is from a star, the less effective it is.
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So is the spacecraft propelled by the sail reflecting the light, similar to two billiard balls being bounced off each other? How exactly would this work? And what are solar sails made of that allows them to be propelled by light?
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Really cool technology! I am curious as to how big the sails need to be in order to propel the payloads for space missions. I have a feeling that you would need incredibly enormous sails to obtain any level of useful propulsion, possibly making the technology ineffecient
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I wonder how spacecraft with solar sails would be able to stop. I know that sailboats generally “point” their sails toward the wind when they want to slow down, but without friction in space it seems like the only option is really to use energy to rotate the spacecraft, which would pretty much negate the whole point of using solar sails in lieu of fuel, right? Maybe a solar energy powered space craft would work…
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This is an incredibly cool idea! If you’re into scifi, Wil McCarthy has an engineering background and has used solar sails as well as some other great almost-current-science ideas in his novels. The solar sail one is The Wellstone, which is actually the second of four.
Monica
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