If you read science fiction, you are probably familiar with the idea of a light or solar sail. A very large and lightweight sail catches solar “wind” that accelerates a payload connected to the sail. Some schemes replace the sun with a laser. Like most things, sails have pros and cons. They don’t require you to carry fuel, but they are also maddeningly slow to accelerate and require huge sails since there isn’t much pressure produced by a star at a distance. So far not many real spacecraft have used the technique, IKAROS was the first back in 2010. However, this month should see the launch of a crowdfunded cubesat that will use a solar sail to move to a higher orbit.
The 5 kg satellite built by Georgia Tech students is about the size of a loaf of bread. Once in orbit, it will deploy solar panels and a square solar sail nearly 20 feet long on each side. Despite the nearly 350 square feet of area, the sail is less than 5 microns thick. You can see more details about the mission in the video below.
It is tempting to think of solar sails as a true analog to wind sails, but the analogy only goes so far. Tacking with a sailboat depends on the interaction between the wind pressure above and water pressure below. In space, there’s no other pressure to work with. However, according to the Solar Sails Wiki, you can change the angle of attack on the sail to cause your orbit around the sun to get bigger or smaller, which is a bit like tacking.
Since light pressure can constantly accelerate a sailing vehicle, you can achieve interstellar speeds with some patience. Then again, some people think alien light sails are already whizzing through our solar system.