ESA demonstrates viability of graphene solar sails

According to the European Space Agency (ESA) light sails are one of the most promising existing space propulsion technologies that could enable humans to explore other star systems within many decades.

Traditional spacecraft carry fuel to power their journeys and use complex orbital manoeuvres around other planets. The weight of the fuel makes them difficult to launch and intricate flyby manoeuvres considerably lengthen the journey.

Solar sails do not require an onboard source of fuel, making future spacecraft lighter and easier to launch.

So far, two spacecraft flown over the past decade have demonstrated the technology, but they used sails made of polyimide and mylar, a polyester film.

To test whether graphene could be used as a sail, researchers used a scrap just 3mm across. They dropped it from a 100m tall tower in Bremen, Germany, to test whether it worked under vacuum and in microgravity.

Once the sail was in free-fall they shone a series of laser lights onto it, to see whether it would act as a solar sail. Shining a 1W laser made the sail accelerate by up to 1m/s², similar to the acceleration of an office lift, but for solar sails the acceleration continues as long as sunlight keeps hitting the sails, taking spacecraft to increasingly higher speeds.

“Making graphene is relatively simple and could be easily scaled up to kilometre-wide sails, though the deployment of a giant sail will be a serious challenge,” said Santiago Cartamil-Bueno, leader of the GrapheneSail team and director of SCALE Nanotech, a research start-up company operating in Estonia and Germany.

SCALE Nanotech is now looking for strategic partners to scale up the technology for an eventual test in space. The product development of the sail technology is currently accelerated through ESA’s Business Incubator Centre in Hessen and Baden-Württemberg, Germany.