The only form of space travel that humanity currently utilizes are rockets. Rockets use fuel to propel themselves from the Earth’s surface into space. Once in space, spacecraft use more fuel to propel themselves either into Earth orbit or away from Earth orbit. Although rocket fuel has proven useful in the exploration of the solar system, it is also expensive and limited in its scope. Another potential way humanity could explore the solar system and beyond is through the use of a solar sail. What is a solar sail and how does it work?

　　

Sailing The Sea Of Space

Illustration of a spacecraft using a solar sail in Earth orbit. Image credit: NASA A solar sail works in much the same way as a sail on a ship. Rather than using wind generated within an atmosphere, a solar sail uses the solar wind to propel itself. The solar wind is the stream of energized particles constantly being emitted by the sun. These particles carry momentum, and thus they can push on objects in a way similar to how wind on Earth can push objects. Rather than using the same material as a boat sail, a solar sail would use large mirrors to reflect incoming light. Particles in the solar wind would impact the mirror, giving the spacecraft momentum. A spacecraft that utilizes a solar sail can be thought of as an interplanetary ship sailing the sea of space. 

　　

Other Forms Of Light

Since the solar wind is constantly being emitted, a spacecraft could constantly utilize the solar wind. However, the solar wind becomes weaker with distance, and even from Earth, it would take time for a spacecraft using a solar sail to gain a large amount of momentum. Another potential way to speed up a spacecraft would be to build large lasers here on Earth that focus beams of light on a solar sail. High energy beams of light could accelerate a spacecraft, allowing us to traverse the solar system at speeds higher than any current spacecraft. In fact, assuming technology is advanced enough, beams of light could even propel a solar sail to 10% the speed of light, potentially allowing us to travel to other solar systems. One such idea is to build microscopic nanobots that have tiny solar sails. Since nanobots are so small, it wouldn’t take a lot of energy to propel them to extreme speeds. A nanobot using a solar sail that is accelerated to 10% the speed of light could reach the nearest star in less than 30 years.