Researchers at the U.S. Naval Research Laboratory flew their fuel cell powered Ion Tiger UAV for 48 hours and 1 minute on April 16-18 by using liquid hydrogen fuel in a new, NRL-developed, cryogenic fuel storage tank and delivery system. This flight shatters their previous record of 26 hours and 2 minutes set in 2012 using the same vehicle, but with gaseous hydrogen stored at 5000 psi. The airplane had flown 23 hours, 17 minutes in 2009. The 550 Watt (0.75 horsepower) fuel cell onboard the Ion Tiger has about four times the efficiency of a comparable internal combustion engine and the system provides seven times the energy in the equivalent weight of batteries. The Ion Tiger weighs approximately 37 pounds and carries a 4- to 5-pound payload.” Gerard Thevenot, who flew the English Channel on a hydrogen-powered “trike” in 2009, used about 550 grams per flight hour, with the craft’s 5-liter tank allowing about one hour flying time. …