NASA model uses thermals

"Robot Plane Can Find Thermals to Stay Aloft"

(Oct 6, 2005) NASA engineers tested out a prototype unmanned sailplane
this week at the Dryden Flight Research Center in California. This
robotic aircraft is capable of detecting and using rising air thermals,
similar to a glider or bird, to gain altitude. It launched from the
ground, and navigated to a likely location for updrafts. Once it found
a thermal, it turned off its engine and circled to stay within the
updraft. NASA hopes to develop techniques for using thermals that could
extend the range of unmanned aerial vehicles that often have very
limited fuel.

With the graceful flight of hawks and eagles in mind, NASA aerospace
engineer Michael Allen recently hand-launched a 15-pound motorized
model sailplane over the Southern California desert. He was hoping it
would catch plumes of rising air called thermals.

The sailplane did just that several times without human intervention
during a series of research flights at NASA's Dryden Flight Research
Center, Calif. The tests validated Allen's premise that using thermal
lift could significantly extend the range and flight endurance of small
unmanned air vehicles. Thermal lift increases vehicle endurance and
saves fuel. This is significant, as small vehicle flight duration is
often restricted by limited fuel capacity.

Allen and his team of engineers and technicians flew the
remote-controlled RnR Products sailplane 17 times from July through
mid-September. The sailplane was modified by Dryden aerospace
technicians to incorporate a small electric motor and an autopilot
programmed 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 the
sailplane's onboard autopilot. The autopilot software flew the plane on
a pre-determined course over the northern portion of Rogers Dry Lake at
Edwards Air Force Base, Calif., until it detected an updraft. As the
aircraft rose with the updraft, the engine automatically shut off. The
aircraft circled to stay within the lift from the updraft.

Allen said the small sailplane added 60 minutes to its endurance by
autonomous thermal soaring. The modified sailplane gained an average
altitude in 23 updrafts of 565 feet, and in one strong thermal ascended
2,770 feet.

"The flights demonstrated a small unmanned vehicle can mimic birds and
exploit the free energy that exists in the atmosphere," Allen said. "We
have been able to gather useful and unique data on updrafts and the
response of the aircraft in updrafts. This will further the technology
and refine the algorithms used."

Small, portable, unpiloted, long-endurance vehicles could fulfill a
number of observation roles including forest fire monitoring, traffic
control, search and rescue.

For more information about flight research at Dryden on the Web visit:
http://www.nasa.gov/centers/dryden

For information about NASA and agency programs on the Web, visit:
http://www.nasa.gov/home

Original Source: NASA News Release