Lee Rannals for redOrbit.com — Your Universe Online
U.S. Naval Research Laboratory researchers have broken their own endurance record with their fuel cell powered Ion Tiger Unmanned Aerial Vehicle (UAV).
The team was able to fly their UAV for 48 hours and one minute on April 16 through 18 using liquid hydrogen fuel in a new cryogenic fuel storage tank and delivery system. This flight broke their previous flight record of 26 hours and two minutes, which was set in 2009 using the same vehicle.
The research laboratory said they were able to complete this longer duration flight with the liquid hydrogen because it is three times denser than 5000-psi compressed hydrogen. The cryogenic liquid stored in the lightweight tank allows for more hydrogen to be carried onboard in order to increase flight endurance.
“Liquid hydrogen coupled with fuel-cell technology has the potential to expand the utility of small unmanned systems by greatly increasing endurance while still affording all the benefits of electric propulsion,” said Dr. Karen Swider-Lyons, NRL principal investigator.
According to the laboratory, although long endurance is possible with hydrocarbon-fueled systems, these aircraft are loud, inefficient, and unreliable. Battery-powered systems are limited to endurances of just a few hours, so the researchers turned to liquid hydrogen for fuel.
The team’s previous flight record was set on November 16 through 17 in 2009. It broke its own previous record from a month before of 23 hours and 17 minutes.
The world record for a long endurance UAV flight was set in 2010 by the UK-built Zephyr aircraft. This vehicle took flight for 336 hours, 22 minutes and eight seconds, according to the Federation Aeronautique Internationale (FAI). This aircraft is made out of ultra-light carbon fiber and weighs just 110 pounds. Its 74-foot wingspan and lithium-sulphur batteries are what helped it to achieve such great endurance. The Zephyr UAV broke the previous endurance record set by Northrop Grumman’s Global Hawk in 2001 after just 31 hours in the air.
“This aircraft can help track pirates off the Horn of Africa, alert the authorities about where and how fast forest fires are spreading, and ensure that soldiers´ communications remain unaffected when fighting in mountainous or hilly terrain,” technology firm Qinetiq´s chief designer Chris Kelleher told BBC News in 2010.