The Naval Research Laboratory (NRL) has developed a hydrogen-powered fuel cell electric Unmanned Aerial Vehicle (UAV) named Ion Tiger, which demonstrated 26.1 hr endurance carrying a 2.3 kg payload in 2009. Also, NRL-developed autonomous soaring algorithms have demonstrated dramatic daytime endurance improvements on a sailplane (5.3 hr flight time from a 3 min nominal flight) staying in the low atmosphere (＜1500 in) by actively orbiting in rising air to offset the vehicle's sink rate. This paper explores the marriage of the two technologies. Both technologies are well suited for high-endurance applications where precise vehicle positioning is not critical, such as a communications relay mission. Autonomous soaring techniques applied to Ion Tiger have demonstrated an endurance increase of 113% over a two-hour flight via energy extracted from the atmosphere.
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