Is it a bird? No, it's a plane! Helios, NASA's 75-metre-long, solar-powered aircraft, can fly higher than any conventional plane. Its single wing is covered with 62,000 photovoltaic cells, generating electricity to run 14 small propeller motors which hold the ultra-light, remote-controlled plane aloft in very thin air. It won't revolutionize air travel, but could be used for investigating the surface of Mars, studying Earth's atmosphere for data on climate change and ozone layer depletion, and carrying telecommunications equipment without having to launch costly satellites. |