LONDON: The Planetary Society is preparing to test a spacecraft proposed by legendary astronomer (and founder of the Planetary Society) Carl Sagan. The vessel is called LightSail, and as you might expect, it uses a light sail for propulsion. The fascinating design has been successfully tested on Earth, but now it’s going to be launched to the upper atmosphere to test the deployment of its huge mylar sails in flight.
Solar sail technology relies upon a well-understood fact of spaceflight. While light doesn’t have mass, it does have momentum, which can be transferred to a vessel. It’s something space agencies have had to correct for since the early days of spaceflight. Of course, the effects on a small spacecraft are almost nil, but that’s why LightSail has big sheets of mylar. Basically, as photons make contact with the solar sail material, some of it is absorbed, while the rest is reflected. This exerts a small amount of pressure on the sail — enough to push a craft along.
This isn’t the first time a solar sail craft has been used, as both Japan and the US have deployed small solar sails in the past. LightSail, on the other hand, will have 32 square meters of mylar sail material. In addition to the sail, the craft needs to carry a comm system, batteries, solar panels, a computer, and other flight hardware. It all fits in a tiny 3U cubesat body that’s about the same size as a loaf of bread.
