What is this?First of all, solar sails have already been made.
http://en.wikipedia.org/wiki/IKAROSNow, here are some interesting facts about solar sails. Of course, we all know that solar sails are pushed by photons hitting the sails. But the thing is, even if the solar sails aren't getting hit by photons, they will stay at the speed they were at previously. This is where things get interesting. Now, lets say the solar sail ship has exited the solar system, and is not being hit by photons. Once it reaches the next solar system, it will begin to be hit by photons again. Every time it reaches another solar system, it will gain speed. Eventually, it will be going quite fast. Technically, it will never get fast enough to reach the speed of light, but it could get close.
Uses for Interstellar TravelNow, this is possibly going to be obvious, but I'm just going to say it anyways. This can easily be used to "hop" between solar systems, once it gains enough speed. Now, I can easily guess what you are all wondering.
"Can we use this for manned interstellar travel?" Sadly, it seems that the answer for that is no. First of all, by the time the ship reaches its maximum speed, the humans onboard will probably be dead by then. Also, attempting to dock with it would require a ship going at the same speed, which would require an improbably amount of fuel and very strong engines. Also, the two ships would probably hit each other when they would try to dock. Also, why dock if you have a ship that can go at the exact same speed with a crew onboard? So, manned interstellar travel with this ship wouldn't work.
Dangers
