Press Release

Helios Prototype to attempt flight at 100,000 feet altitude

By SpaceRef Editor
July 17, 2001
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The sky is black 100,000 feet above ground, and the curvature of the
Earth is clearly discernible. The air is so thin–only 1.4 percent of
the density at sea level–it is incapable of supporting life. It is
also incapable of supporting sustained horizontal flight of an
aircraft–until now.

It is into that hostile environment 19 miles above ground that a
small group of engineers from NASA’s Dryden Flight Research Center
and AeroVironment, Inc., plan to fly the unique unmanned
solar-powered Helios Prototype. The giant yet ultralight flying wing
could soar into the stratosphere on its quest as early as the second
week in August, after successfully completing an 18-hour functional
checkout flight July 14 and 15.

Should the Helios Prototype reach its objective, it would set a new
world’s altitude record for propeller-driven aircraft, surpassing the
80,201-foot record of its predecessor, the solar-electric
Pathfinder-Plus, set in August, 1998. It would also exceed the
highest reported altitude achieved in sustained horizontal flight by
jet-powered aircraft as well, 85,068 feet by a SR-71 aircraft in
July, 1976. Only short-duration rocket-powered aircraft have flown

The Helios Prototype flights are being conducted from the U.S. Navy’s
Pacific Missile Range Facility on the Hawaiian island of Kauai. The
location at 22 degrees north latitude gives the Helios Prototype a
sun angle advantage, and the protection of a vast test range and
restricted airspace over the Pacific Ocean west of the islands.

The Helios Prototype is one of the unique remotely operated,
uninhabited aerial vehicles (UAV) being developed for high-altitude,
long-duration earth science imaging and atmospheric sampling missions
under the Environmental Research Aircraft and Sensor Technology
(ERAST) project at NASA Dryden, located at Edwards, Calif.

John Del Frate, project manager for solar-powered aircraft at NASA
Dryden, noted that setting an altitude record is only one of several
goals for this summer’s flight tests.

“A 100,000-foot altitude record would be the icing on the cake,” he
said. “Our primary interest in testing this new aircraft is for
taking sophisticated lightweight science instruments to greater

“Another added bonus for NASA is the fact that flight at 100,000 feet
would be very similar to flight in the Martian atmosphere,” Del Frate
added. “In a way, we are going to school on these flights to learn
what the aerodynamics are like in these conditions.”

AeroVironment vice-president Robert Curtin noted that production
versions of the Helios could also serve as long-endurance commercial
telecommunications relay platforms, orbiting over major population
centers at 55,000 to 70,000 feet altitude for months at a time.
Disaster recovery agencies might one day be able to move a Helios
over the scene of a natural calamity where the normal communications
infrastructure has been destroyed.

“AeroVironment’s goal is to develop an airplane that is the
equivalent of an 11-mile-high tower in the sky,” he added.

The primary objective of Helios’ recent checkout flight was to expand
the flight envelope of the aircraft and verify proper operation of
aircraft systems at a range of altitudes up to 76,271 feet. Reaching
that altitude was considered necessary in order to reduce risk for
the upcoming effort to achieve sustained horizontal flight at 100,000
feet (30,000 meters) altitude.

The 247-foot-span ultralight flying wing flew six low-altitude
initial airworthiness validation flights on battery power at NASA
Dryden in the fall of 1999.

Since then, the Helios Prototype has undergone major upgrades,
including the installation of more than 65,000 high-efficiency solar
cells across the wing which can produce more than 35 kW of

The 100,000-foot altitude flight is one of two major flight
milestones set for the craft by NASA, the other being a four-day
non-stop long-endurance demonstration flight above 50,000 feet
planned for 2003. Development of a regenerative hydrogen-oxygen
energy storage system which would make the multi-day continuous
flight possible is progressing at AeroVironment. The system will use
excess power generated by the solar arrays during the daytime to run
an electrolyzer that separates water into its component parts,
hydrogen and oxygen, which are then stored in pressurized tanks. At
night, the hydrogen and oxygen are recombined by the fuel cells,
producing electricity as a by-product to power Helios.

AeroVironment, based in Monrovia, Calif., developed the Helios
Prototype at their Design Development Center in the Los Angeles
suburb of Simi Valley, Calif. The Dryden Flight Research Center,
located on Edwards Air Force Base, Calif., is NASA’s premier center
for atmospheric flight research.

– NASA –


B-roll footage of the Helios Prototype’s functional check flight this
past weekend will be fed on NASA Television’s Video File on
Wednesday, Thursday and Friday, July 18-20, at 12 noon Eastern, 9
a.m. Pacific time.

Still photos and video dubs are available from the Dryden Public
Affairs Office to support this release. For photo prints or video
dubs, please call (661) 276-2665. Photos are also available on the
NASA Dryden Flight Research Center internet website, URL:

More information about the Helios Prototype can be obtained on the
Dryden website at:

NASA Dryden news releases are also available on the Internet at:

SpaceRef staff editor.