Sailing the Sea of Stars
A zero-emisions spacecraft. The genii at Kampula Space Center have submitted documentation suggesting that it's possible: a positively-charged electron sail that would repel the negatively-charged solar wind, driving the craft away from the sun. Such a craft would have to be built in or brought up into orbit via a conventional rocket.
A spinning web of electrified wire 30 miles wide may become the spacecraft propulsion system of the future.
A team from the Kumpula Space Center in Finland is proposing a huge electronic sail for spacecraft that may dramatically reduce journey times across the solar system. The giant sail, which would be twice the length of Manhattan, is made from about 100 wires spun up into a whirling disk. Electrified by an onboard, solar-powered electron gun, the positively charged wires repel the negatively charged protons of the solar wind, providing thrust.
The solar wind is a high-speed plasma stream blowing outward from the Sun. The average pressure of the solar wind is miniscule (a mere 2 nanopascals, or 0.2 grams of weight per square kilometer), which explains the need for such a large sail.
"It's such a small force that it's really hard to imagine even," says Pekka Janhunen of the Finnish Meteorological Center, who leads the team behind the concept. "But it's still enough to move the spacecraft because it's doing it continuously over a large area." The sail is described (.pdf) in the latest issue of physics journal Annales Geophysicae.
Because the wires, or tethers, are thinner than human hair, they can create a sail (.avi) that is much larger than a solid surface -- up to 30 miles wide.
"The most difficult challenge is posed by the tethers and the tether reels," says Jahnunen. "Manufacturing 25-km-long tethers (the equivalent of 15 miles long) thinner than human hair is an engineering challenge, as is development of the mechanics of the reel."
Results drawn from computer simulations indicate that in an average solar wind, a 440-pound spacecraft could achieve final speeds of up to 62 miles a second (or 1.9 billion miles a year), allowing a spacecraft to reach Pluto in less than five years.
Because the electric sail needs no propellant or other consumables, it might also provide cheap transportation of raw materials in space.