Sailing the galaxy with a graphene solar sail

The European Space Agency (ESA) developed a tiny sail made of graphene that has passed initial tests to one day function as solar sails for spacecrafts.

Graphene is the thinnest known material, measuring only one atom thick, but stronger than diamond. Its potential is unlimited and the material has been used in anything from condoms to dresses.

Light sails are said to be one of the most promising existing space propulsions technologies “that could enable us to reach other star systems within many decades”.

Traditional spacecrafts 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 harder to manoeuvre. In addition, the limited space available means the journeys are limited as well.

Solar sails, on the other hand, like sails on sailboats, have no need for fuel, and spacecrafts equipped with them can therefore be much lighter. Rather than wind, solar sails move thanks to photons, tiny light particles emitted by the sun. These photons give the sail a minuscule push, but because the pushes are constant without much friction, the speed of the craft continuously increases.

In the past decade, two spacecrafts have used solar sails to demonstrate the technology. These made use of polyamide and mylar (polyester film) sails.

A graphene sail has the potential to be much lighter. To test the concept, the researchers at ESA used a scrap of graphene material of 3 millimetres across. They dropped it from a 100-metre (330 ft.) tall tower in Bremen, Germany, to test whether it worked under vacuum and in microgravity. Once in free fall and the effects of gravity were eliminated, the researchers shone laser lights onto it. Shining. Shining a 1 watt laser made the sail accelerate by up to 1 m/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 higher and higher speeds.

Image: ESA