The Planetary Society is preparing to test a spacecraft design first proposed by the organization’s founder, Carl Sagan. The spacecraft relies on solar sails, also known as photon sails or light sails, is essentially powered by sunlight.
Sagan set the current process in motion after discussing the technology on a talk show in 1976. The basic idea, however, is much older than that. In a letter to Galileo in 1610, Johannes Kepler suggested that if someone were to “provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void.” Kepler had noticed that comet tails point away from the sun, which suggested a sort of wind power in space. Since that time James Clark Maxwell, Jules Verne, Albert Einstein and others have played with the idea in fiction or contributed to the science.
Fans of the Star Trek franchise may also remember a similar technology being used in “lightships” in the Deep Space 9 episode “Explorers.”
So how does light move something through space? Light doesn’t have mass, but it does have momentum and that momentum can be transferred to move a spacecraft. When photons make contact with the LightSail’s large sheets of mylar, most of it is reflected but enough is absorbed to push the craft.
In a video Bill Nye, current head of the Planetary Society, said that the organization is almost ready to achieve the goal set by Carl Sagan almost four decades ago.
The LightSail spacecraft, which is about the size of a loaf of bread, contains about 345 square feet of mylar which will deploy into a massive “sail” once it is in space.
“These tiny spacecraft often hitch rides to orbit aboard rockets carrying bigger payloads. CubeSats have standard unit sizes of 10 centimeters per side. They can be stacked together—LightSail is a three-unit CubeSat about the size of a loaf of bread,” said the Planetary Society according to phys.org.
The spacecraft is getting a test flight this month in preparation for a full scale demonstration in 2016. For the demonstration, Lightsail won’t be deployed high enough to catch a solar wind. It will be just high enough to deploy the sail and take a few photographs before falling back down. The goal of the test is simply to ensure that all of the apparatus on the spacecraft function properly ahead of a full demonstration.
Both the United States and Japan have previously tested solar sail technology. However, as Darren Orf of Gizmodo points out, that doesn’t make the Planetary Society’s effort any less important. According to Orf, “the craft’s real importance relies on its makers. Much how SpaceX defined rocket development for the private sector, so too could The Planetary Society make solar sailing actually affordable and sensible to use. The project costs only $4.5 million and requires no fuel because, duh, solar-powered.”
It is also worth pointing out that the $4.5 million cost would likely go down because a first attempt at anything is more expensive than those that follow because of a streamlined process and fewer mistakes.
If all goes according to plan, the LightSail test will happen on May 20.
