Ion Tiger UAV (image) Naval Research Laboratory Caption Fueled by liquid hydrogen, the Ion Tiger unmanned aerial vehicle (UAV) completes a record flight time of 48 hours and 1 minute. The electric fuel cell propulsion system onboard the Ion Tiger has the low noise and signature of a battery-powered UAV, while taking advantage of high-energy hydrogen fuel and the high electric efficiency of fuel cells. Credit U.S Naval Research Laboratory Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.