Graphene could improve solar sails

David Taft for redOrbit.com – Your Universe Online

Solar sails, a technology that allows spacecraft to be propelled by light from the sun, are about to become even more efficient with the wonder material Graphene– what can’t this stuff do?

Graphene, a single layer of carbon only one atom thick, has better solar energy absorption and reflection properties than other sail materials. Traditionally, solar sails have been built using beryllium, aluminum or Kapton.

According to Newscientist, the capabilities of graphene as a means of propulsion were tested at Nankai University in Tianjin, China earlier this year. A ‘sponge’ made of the atom-thick carbon sheets was pushed a distance of 40 cm by a laser in the Nankai lab. The movement is achieved through the release of electrons in the direction of the light source after photon absorption causes the graphene to build up a charge.

The work of Yongsheng Chen, a researcher at the University, could lead to the construction of a spacecraft with complicated graphene structures based on the sponge configuration. A ship coated or even built partially out of graphene could reduce the need for the large sail panels used in solar craft today.

Solar sail limitations

Although solar propulsion systems are efficient in the sense that they do not require fuel like traditional chemical rockets or ion thrusters, they are incredibly slow. The British Interplanetary Society estimates that, even with the addition of graphene, the travel time to Alpha Centauri for a solar sail spacecraft would be about a millennium under ideal conditions.

Another inherent limitation of solar sails is that they require a nearby star to provide light energy. Consequently, the farther a solar craft travels from a star, the slower it moves. In addition, if a large star is in front on the solar sail as it attempts to move forward toward its destination, the craft will by pushed backwards. Traversing interstellar distances would require complex tacking to achieve the desired flight path and orientation to various directions of solar wind, much like navigating a sailboat in atmospheric air currents.

While the freedom to move using sunlight without the need for fuel is certainly a wonderful asset, the slow acceleration, relatively low top speed, and dependence on proximity to stars will almost certainly limit the use of solar sails to short-range missions and unmanned missions during longer-range applications.

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