Because photons carry momentum, they impart a push when they bounce off a reflective surface—just like any other colliding object. With the right design, this momentum can be utilized to its fullest.
The fact that these sails don’t need any fuel is incredibly helpful when it comes to long-range missions. They can remain light, small, and travel for long periods of time without needing to worry about refueling or mass.
Reflective surfaces tend to scatter light, meaning the photons are sent in all different directions. Retro-reflective surfaces are able to perfectly reflect photons back the way they came, maximizing the amount of momentum transferred from the light to the sail. Our team’s light-sail design uses a particular retro-reflective polycarbonate material, allowing it to harness as much momentum as possible.
Beyond the material, the shape of the sail also maximizes its sailing capabilities. Two nitinol wires diagonally span the sail in an X-shape, unravelling a Miura fold upon deployment. The Miura fold design keeps the sail compact when folded up, allowing it to fit in small deployers, and lets it deploy much smoother than other fold designs. Cornell’s light-sail design is also much smaller than designs of the past, at just 57.5 centimeters long and wide, 100 grams in weight (including its ChipSats), and 0.04 millimeters thick. Its size means it can accelerate and travel faster than ever before.
