Fueling Persistent ISR
Navy researchers put liquid hydrogen
fuel cell-powered UAV through endurance test
By NICK ADDE, Special Correspondent
A Work in Progress
target and provide persistent ISR,
At present, the Ion Tiger experi-
ment is strictly a test project. There
are no end users yet in the military,
MacKrell said. Rather, the job he
shares with NRL research chemist
and principal investigator Karen
Swider-Lyons is to develop the
technology and find out if it works.
“Our conclusion is you can do it,
but it’s difficult,” said Swider-Lyons,
who holds a doctorate in chemistry.
Ion Tiger could be perceived as
the key milestone indicating that
hydrogen fuel cell technology is
emerging from infancy into tod-dlerhood — even though the concept has been around
for more than a century. The first prominent modern
proponent of hydrogen fuel cells, Al Gore, touted them
as a means to shed dependency on foreign oil when he
was vice president in the 1990s.
The George W. Bush administration initiated some
funding for research, beginning with a $1.2 billion
investment in 2003. The private sector — largely the
auto industry — has poured the most money into their
development, around $10 billion to date.
Swider-Lyons and MacKrell used existing technology,
borne from the auto industry’s extensive research-and-development efforts, to craft the power plant for Ion Tiger.
Their research began about 10 years ago. Ion Tiger
started in earnest in 2007, and made its first flight in
2009 using gaseous hydrogen as fuel. The fuel was compressed to 5,000 pounds per square inch, and stored in
a tank about the size of a pumpkin. The plane remained
airborne for 24 hours during that initial mission.
Because hydrogen fuel cells are electrochemical, there is
no combustion to generate energy that would be converted into thrust. Rather, electrons stripped away from hydrogen atoms in a fuel cell provide the power to move an
Despite the promise liquid hydrogen fuel cell technology holds for
unmanned aircraft based on the April flight of Ion Tiger, a host of
problems remain to be solved.
■ Hydrogen fuel cells are expensive to produce and highly sensitive to impurities.
■ While hydrogen is the most prevalent element on Earth,
extracting it for fuel and storing it are not easy tasks.
■ Researchers want to get a better understanding as to why the
process of transporting oxygen within the motors leads to significant voltage losses over time, hindering performance.
During a two-day stretch earlier this spring, U.S. Navy researchers achieved a significant mile- stone that someday could provide warfighters
with a new generation of efficient and enduring low-altitude intelligence, surveillance and reconnaissance
The flight of the Ion Tiger, an unmanned aircraft
powered by a liquid hydrogen fuel cell, proved to a
team from the Naval Research Laboratory (NRL) that
the technology is capable of eventually providing a
quiet and long-lasting eye in the sky. Taking place in
government-owned ranges along the mid-Atlantic, the
flight set an endurance record for aircraft of its genre
by staying aloft April 16-18 for more than 48 hours.
Hydrogen fuel cell power plants are less polluting
and more efficient than comparable platforms powered
by fossil-fuel engines, ideally suiting them, its developers believe, for service as future ISR platforms.
“Our intelligence, surveillance and reconnaissance
requirements are ever increasing,” said Joseph
MacKrell, an aerospace engineer with NRL’s Tactical
Electronic Warfare Division, who worked on the Ion
Tiger project. “The longer a platform can stay over a