This has potential for tremendous cost savings
Small unmanned aircraft systems (UAS) have become an increasingly important intelligence, surveillance and reconnaissance tool for the military and their use will only continue to expand. While vehicles that are small enough to be carried provide soldiers in the field with capabilities such as over-the-next-hill imagery or the short-term monitoring of convoys, much research is going into finding ways to extend mission duration through better battery systems. DARPA researchers say they have overcome this limitation with the development of a compact solid oxide fuel cell (SOFC) fueled by propane that quadruples the endurance of Lockheed Martin’s Stalker small UAS.
The new fuel cell formed the basis of the hybrid power source for the Stalker XE, (eXtreme Endurance), a variant of the Lockheed Martin-developed Stalker UAS that boasts a wingspan of 120-in (305 cm) and is powered solely by a battery-driven electric motor that gives it a flight time of around two hours. By combining a high density fuel cell system with a conventional lithium polymer battery to handle peak power requirements, the Stalker XE is able to quadruple the endurance of the baseline Stalker version to provide a flight time of over eight hours.
By using propane, which is a very high energy density hydrocarbon fuel, rather than a relatively low energy density battery, the Stalker XE is able to achieve the extended flight time without impacting its mobility or payload capabilities. It is launched by a 22-pound bungee-launch system and operates without the large footprint and high cost associated with current tactical UAS platforms.
“A small unmanned aircraft system with long-endurance capability could give the military the ability to do with a small craft what has previously been doable only with larger airframes. This has potential for tremendous cost savings – we can maintain and even improve on our UAS capabilities with a much smaller footprint and lower operating cost,” said Brian Holloway, DARPA program manager.
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