Today, let us ride Helios' golden chariot. The University
of Houston's College of Engineering presents this series
about the machines that make our civilization run, and
the people whose ingenuity created them.
Helios, Greek god of the sun, rode
his golden chariot east to west each day. By night he
floated, in a golden bowl, back to his palace in the
East. Eos, goddess of the dawn, and Selene, goddess of
the moon, were his sisters.
Small wonder that the AeroVironment Company gave
the name Helios to a new craft it's built for
NASA. This huge pilotless airplane is a creature of the
sun. Helios' wingspan is almost the length of a
football field. Each of its fourteen engines drives a
propeller. Yet it weighs only four fifths of a ton --
less than most cars.
Helios is really little more than a long flexible
wing. Its top is covered with solar panels, which gather
all its energy from the sun. It carries no fuel and can
stay aloft indefinitely. It will eventually serve as a
poor man's geosynchronous satellite. Actually, it won't
quite stay in the same spot over Earth's surface but will
fly in a circle at around twenty miles an hour. By flying
at a very high altitude, Helios will be able to
serve the same functions as a communications
satellite.
Schematic views of
Helios, courtesy of NASA
Helios set out
from Kauai in the Hawaiian Islands before 9:00 AM on
Monday, August 13, 2001. Just over seven hours later, it
reached 96,500 feet. That was eighteen miles high and two
miles beyond the previous record. At that altitude,
atmospheric pressure is about a fiftieth of the value on
Earth. That, by the way, is only about three times Mars'
atmospheric pressure. Small aircraft of this type might,
one day, be used to survey Mars.
Helios returned to Earth in the early hours of the next
morning. On the way down, its propellers acted as
windmills to generate what battery power it needed. Later
versions of Helios will break water into hydrogen and
oxygen by day and re-burn those elements again by night
to supply energy. Like Helios of myth, this Helios will
also return each dawn to begin its ride once again.
While work on Helios has gone on in relative quiet
for some time, we've seen its precursors in the evolution
of very light aircraft. In 1986 Burt Rutan's Voyager carried two people around
the world in one seven-day flight. Human-powered
airplanes were also setting records by then. As early as
1979, the pedal-powered Gossamer Condor made it
across the English Channel.
The first successful solar-powered airplane was a direct
outgrowth of the Gossamer
Albatross with its extremely light construction.
In 1980, the
Gossamer Penguin became first in a long series
of purely-solar-panel-powered airplanes to carry a human
being. The pilot, Janice Brown, weighed only a hundred
pounds.
So, amid this world of rockets and jets we find a new
frontier of flight. We are, once more, creating a
birdlike intimacy with the air around us. As we enter the
new millennium, flight is reclaiming some of its old
grace and delicacy. We have again what we lost when we
first put engines in wooden and canvas airplanes.
I'm John Lienhard, at the University of Houston, where
we're interested in the way inventive minds work.
(Theme music)
You will find articles on Helios in most major newspapers
for Tuesday, August 14, 2001.
See also the various fact sheets and other web pages put
out by NASA's Dryden Flight Research Center. e.g.:
I am most grateful to Clay Creech in the Dryden Flight
Research Center's Public Relations office for his patient
counsel on this episode.
For an older program touching on these issues, see
Episode
1437.
Another view of Helios in flight. Image courtesy of NASA
The Engines of Our Ingenuity is Copyright
© 1988-2001 by John H. Lienhard.
