High fliers

Soon a new high-powered solar aircraft will monitor pollution levels, hitherto done by satellites

 
Published: Monday 30 June 1997

A PILOTLESS aircraft, that should be able to stay in the air for weeks, circling the globe to monitor the state of the earth's atmosphere and to keep an eye on pollution levels is being developed by the National Aeronautics and Space Administration (NASA). Pathfinder, as it is galled, is controlled from the ground and flies at an altitude of 15392.4 m for solar-powered vehicles and hopes to achieve 30480 m within the next few months.

Scientists are assessing the vehicle as part of a programme to have lightweight aircraft circle the globe at 22860 m, or higher, by AD 2001.

The Pathfinder's wings have a span of 28.6416 m and are lined with solar panels and a battery that is capable of providing two hours of power to ensure the aircraft can remain in the air, or be brought back to base in an emergency, or if there is insufficient solar energy. Once the technology behind Pathfinder is proven, it can be used for many Commercial applications will come to light, including telecommunications, mapping the earth's surface and weather monitoring.

The flight is planned for this summer because the craft is best powered when the sun is directly above its wings. Ground crew will use radio controls to guide the craft. The wings are monitored by a video camera that can check if the propellers are turning or if ice is forming on the wings.

NASA scientists are keen to develop a fleet of unmanned craft that can take air samples at high altitudes so that environmental researchers can monitor pollution and ozone levels without the need for costly satellites. Pathfinder would be perfectly suited for this. Its 227 kg chassis, made mainly from carbon-fibre and kevlar, and vast wingspan give it a weight-to -wingspan ratio of less than I lb (I lb = 0.454 kg) per square foot, several hundred times better than conventional aircraft. This could potentially enable it to stay in the air for weeks, although so far the aircraft has been in the air for only 12 hours.

New tests will ascertain whether the craft's electric systems and fuselage can withstand the high winds that it must fly through at 9144 metres before enduring freezing temperatures and a severe rise in ultraviolet radiation.

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