US Navy's Ion Tiger drone leans on liquid hydrogen for longer-lasting spy flight

The US Navy's quieter way to spy, the Ion Tiger, just bested its own 2009 flight record with a key assist from liquid hydrogen. The unmanned aerial vehicle had previously relied on 5000-psi compressed hydrogen for fuel, but for its latest flight test the Naval Research team swapped that out for a new cryogenic tank and delivery system that relies on the liquid stuff; a choice made for the element's increased density. With that one significant change in place, the craft was able to outperform its...