Until now, when NASA explores space, their crafts have been propelled by chemical rockets for fuel. In 2018 a new method will be introduced which could mark a vast shift in both the expense and abilities of space exploration – the solar sail.
The Near-Earth Asteroid Scout – or NEAS – is a probe which will be send to explore the 1991 VG asteroid. It is projected to be launched during the first trip of the new megarocket Space Launch System, which itself was created to replace the current space shuttle.
During two and a half years of travel, the NEAS will move through space propelled by sunlight. An ultra-thin and extremely reflective material has been used to build the 925 square foot sail, which carries a mini CubeSat satellite around the size of a shoebox. The surface of the sail bounces off photons from the sun, which creates momentum for the spacecraft.
The NEAS path will include at least one slow moving flyby where the sail will fly around half a mile above the surface of 1991 VG at 22mph. Equipped with technology for taking photos, measuring chemical composition, size and more, this trip will provide a better understanding of how this asteroid moves, which way it rotates and at what speed – all crucial information before manned missions can be planned.
The concept of using a solar sail is not a new one; in the 1920s, Soviet scientists theorized about using sunlight as a form of pressure on thin, mirror-like surfaces, while NASA has been experimenting with solar sail tech since the 1990s. Japan sent up a solar sail aboard their probe to Venus – the IKAROS sail –, which made a successful flight after being released into space at 4.3 million miles from Earth. The use of this technology makes much more sense now because electronics are so much more lightweight than in the past, so the size of the sail required to bear the weight of the satellites is not so extreme.
One of NASA’s advisors explained the benefits to using this type of technology over traditional propulsion by chemical rockets by comparing it to the story of the tortoise and the hare – while chemical rockets start the crafts off at immense speeds, the fuel eventually burns up. Without relying on fuel, a solar sail can be continuously thrust along on its journey by the sun. Furthermore, solar sails can be slightly maneuvered in subtle ways along the journey, steered in a similar manner to sails here on earth. The IKAROS sail was steered by darkening certain areas so that one part of the sail gets more sun than the rest, which tilts it in one direction or another, while the NEAS is going to use a sliding mechanism to adjust the way that the sail is centered on the satellite. Having a craft which can change course without having to use a slingshot maneuver opens up many possibilities for the future of space travel. “Right now, we’d have to send a spacecraft out to Jupiter for a gravity assist to get it out of the ecliptic plane and have a higher angle of orbit around the sun,” explains scientist Johnson, “With a sail, you can just kind of crank it up.”
Along with solar powered sails, researchers at NASA are beginning to look into using solar wind which can create electric charges to fuel spacecraft at much faster speeds than anything up until now. A prototype for that is expected in around five years.