Sun-powered Wing Brushes Against Space!

	Some airplanes can transport hundreds of people.
	Some airplanes can travel several times faster than sound.
	Some airplanes can do dipsy-doodles and loop-de-loops.

The Helios Prototype airplane weighs less than most cars and carries no people. Flying at low altitudes, it is quite slow. You can ride your bicycle almost as fast! And forget loop-de-loops! It takes a minute to climb the height of a 30 story building. (Most elevators climb faster!)
But the Helios Prototype airplane can do some very useful things no other airplane can do.
	Helios Prototype flying wing on its first test flight using solar power over the Hawaiian Islands. Here's a Quicktime movie (1 Mb).
On August 13, 2001, remote-control pilots on the ground used a computer to fly the Helios Prototype to an altitude of 96,863 feet. That's over 18 miles straight up! Before the Helios Prototype, the highest recorded flight of any aircraft was about 85,000 feet. This was done in 1976 by the SR-71 spy plane, the fastest jet in the world. Only rockets and rocket-powered airplanes have gone higher. The air we breathe on Earth's surface is almost 100 times thicker than the air up where the Helios Prototype flew. Earth's atmosphere at this altitude is about as thin as the atmosphere on Mars. This altitude above Earth is so close to space that the sky is almost black, stars shine in the daytime, and the horizon looks curved.
	Helios takes off from Kauai, Hawaii, August 13, 2001, on its record-setting flight.
How did Helios do it? Airplane wings must have air under them to work. What is so special about Helios' wings that they can work with so little air?
First, Helios' wings--or rather wing, since it is really just one flying wing--is 247 feet long, about a classroom width longer than a Boeing 747. But Helios is very lightweight, so this huge wing doesn't have to lift very much. How can this plane be so light? Because it is made of very lightweight materials, doesn't carry any people or fuel.
Instead of jet fuel, Helios has about 62,000 solar cells across the wing. The solar cells collect energy from the Sun and convert it to electricity, which runs the 14 small motors, which turn the 14 propellers. The propellers are specially designed to pull the aircraft aloft even in the very thin air that's 18 miles high.
The five pods beneath the wing contain computers, electronic operating systems, and the landing gear (made from mountain bike and scooter wheels!) The next project for the Helios engineers is to develop fuel cells (sort of like batteries). This way, Helios can store enough of the sun's energy during the day to continue flying through the night. When this happens, Helios will be able to stay up for weeks and months at a time. It flies so slowly, that it will be able to circle over the same point on Earth and do the same job as a communication satellite. Making and flying a Helios airplane will be much, much cheaper than launching a communication satellite.
Helios is a project of NASA's ERAST program (for Environmental Research Aircraft and Sensor Technology). ERAST develops pilotless airplane technology. It also works on making science instruments very small so that they can be carried on these remote-controlled aircraft. The things that we learn from ERAST will help us make future aircraft that can do things like Fly through and study the plume of a volcano Fly very high over the North and South Poles Fly for weeks and months at a time collecting science data that varies with the position of the sun or the season of the year Or, explore conditions on Mars!

Helios flies over a dry streambed, as seen from an airplane above. This could be Mars!