When we first sent men into orbit they reported that the only man-made object visible from space was the Great Wall of China. Now astronauts report that at their altitude of about 100 miles they can plainly observe the environmental devastation caused by humans. Deforestation, the resulting erosion, and coastal pollution are visible from space.
Unfortunately, satellites to monitor these developments are expensive to launch and they orbit the earth about every 90 minutes. It would be better if observations could be made continuously at a lower altitude. Enter the UAV, the Unmanned Aerial Vehicles.
The goal is to develop a drone that will fly indefinitely over a chosen area, sending down pictures to observers on earth. The UAV will be the latest evolution of the unmanned drones first developed by the Israelis in their continuous struggle against Palestinian terrorism. The Israeli drones, controlled from the ground, sent back television signals to pinpoint the sites, for instance, where rockets were being launched.
The Israeli idea was further developed for the U.S. forces and it is estimated that as many as 800 such drones are now patrolling the skies of Afghanistan and Iraq. The drones are so small that they are virtually invisible to conventional radar. Follow the path, for instance, of a helium filled balloon some child has released. It rises higher and higher, but soon your eyes are no longer sharp enough to spot it. Thats the beauty of a drone thats invisible from the ground and doesnt risk the life of a pilot or the expense of a slow-flying plane if its shot down.
But the ideal UAV must fly indefinitely, circling the target area possibly for months without landing. To fly indefinitely means no refueling. To do that requires solar power.
After the first human-powered airplane crossed the English Channel, the feat was repeated by a solar-powered airplane. Of course, it could fly only as long as the sun provided energy to the panels on the wings.
Now for another acronym: HALE, standing for high-altitude long-endurance. A new HALE drone, built by former UK defense research lab QinetiQ, will push the boundaries for eternal planes a bit further. What it needs to keep flying at night is battery power. As Dr. Rogoyski, a key authority on the project, reports, the key to success of the HALE UAVs is the rapid advance in solar panels and lithium batteries.
If a lithium battery array with a 20% efficiency can be developed, those high-flying HALE drones will be able to stay up indefinitely, able to reach anywhere on the earth in less than 24 hours. Then those drones will be able to monitor crops, drought, and other agricultural factors. Drones are not just for fighting terrorists anymore.
I remember building model airplanes when I was a kid in the days of balsa wood, tissue paper, and propellers powered by a rubber band. My biggest model was able to take off and actually fly a few feet before running out of rubber power. Imagine what it would have been like to fly it on solar power alone.
Of course, thats what Pegasus is supposed to do. Its hard to imagine a plane with a wing span of 16m and a light weight of 27kg (thats 53.3 feet and 52 pounds for the metrically challenged). One person could easily carry it. To achieve that the solar panels must be paper thin, the skeleton of ultra light carbon fibers, and the batteries and the transmission equipment incredibly small and lightweight.
The drones already developed have broken altitude records, flying as high as 94,000 feet, the edge of space. The HALE will fly in the stratosphere. Maybe they should have named it Icarus.