With the graceful flight of hawks and eagles in mind, NASA aerospaceengineer Michael Allen recently hand-launched a 15-pound motorizedmodel sailplane over the Southern California desert. He was hoping itwould catch plumes of rising air called thermals.
The sailplane did just that several times without human interventionduring a series of research flights at NASA's Dryden Flight ResearchCenter, Calif. The tests validated Allen's premise that using thermallift could significantly extend the range and flight endurance of smallunmanned air vehicles. Thermal lift increases vehicle endurance andsaves fuel. This is significant, as small vehicle flight duration isoften restricted by limited fuel capacity.
Allen and his team of engineers and technicians flew theremote-controlled RnR Products sailplane 17 times from July throughmid-September. The sailplane was modified by Dryden aerospacetechnicians to incorporate a small electric motor and an autopilotprogrammed to detect thermals.
The 14-foot-wingspan model flew to an altitude of about 1,000 feet.The ground-based remote control pilot then handed off control to thesailplane's onboard autopilot. The autopilot software flew the plane ona pre-determined course over the northern portion of Rogers Dry Lake atEdwards Air Force Base, Calif., until it detected an updraft. As theaircraft rose with the updraft, the engine automatically shut off. Theaircraft circled to stay within the lift from the updraft.
Allen said the small sailplane added 60 minutes to its endurance byautonomous thermal soaring. The modified sailplane gained an averagealtitude in 23 updrafts of 565 feet, and in one strong thermal ascended2,770 feet.
"The flights demonstrated a small unmanned vehicle can mimic birdsand exploit the free energy that exists in the atmosphere," Allen said."We have been able to gather useful and unique data on updrafts and theresponse of the aircraft in updrafts. This will further the technologyand refine the algorithms used."
Small, portable, unpiloted, long-endurance vehicles could fulfill anumber of observation roles including forest fire monitoring, trafficcontrol, search and rescue.
For more information about flight research at Dryden on the Web visit:
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