Experts at the Electronics Research Laboratory at the University of Helsinki have managed to manufacture key components which allow the eled by Dr. Pekka Janhunen at the Finnish Kumpula Space Centre in 2006. Unlike traditional solar sails, which propel spacecraft using energy from sunlight, the ESAIL is propelled by the stream of charged particles released from the sun, called the solar wind.
In order to capture the energy from this extremely weak flow of ions a huge electric field is needed, created by long thin aluminium tethers which radiate out from the spacecraft to a distance of up to 20 km. Until now the manufacture of such tethers was deemed ‘impossible’ but the team at the University of Helsinki have used an automated ultrasonic welding technique to produce a 1 km long prototype. The tether must be made of several wires joined together every centimetre; this is so that if a single wire is damaged in space by rocks or dust it does not break the entire length of the tether. It is a simple enough idea, but the prototype, consisting of 90 000 ultrasonic welds, has taken the team at the University of Helsinki four years to develop.
It would appear that this development overcomes the final major challenge in the invention of the electric solar sail, allowing the ESAIL to be tested for the first time on the EST-Cube1 satellite to be launched in March 2013. This mission will be used primarily to measure the efficiency of the ESAIL, as developments so far have been based purely on theoretical calculations, but if the results are successful there are high hopes for the future of the ESAIL in space exploration.
