This fuel cell-powered coaxial octacopter just stayed aloft for 70 minutes of continuous flight, while carrying a 5-kg (11-lb) weight. The record demonstrates the flight endurance capabilities of hydrogen-powered electric aircraft over their lithium-ion battery-powered brethren.
It also highlights Intelligent Energy's work around building lightweight, compact and power-dense fuel cell stacks. A similar UAV around the same weight running lithium batteries could be expected to fly for around 12 minutes, so the endurance gains here are huge.
The test aircraft, dubbed Project Rachel, carried a 6-liter tank of hydrogen gas, compressed at 300 bars. Its lightweight carbon airframe featured two props per arm, one on top and one underslung, that contra-rotate to cancel out each other's torque while providing thrust.
You should theoretically be able to get a much longer endurance out of a similarly specified gasoline-powered drone – gasoline gives about 3.5 times the energy of hydrogen per liter carried in liquid form, which itself is more energy dense than this 300 bar gas. But combustion engines are poorly suited to the rapid adjustments of torque you need at each rotor to stabilize a multicopter in the wind. A fuel cell arrangement gives you long endurance, with the instant torque of electric motors to stabilize things.
The test was run, and the record set, at the behest of Batcam, a UK-based company that does UAV filming as well as live streaming for sports matches. It's easy to see how a company like this could use the extra flight time and a 5-kg payload could represent a pretty serious video or cinema camera rig.
Batcam is looking to explore possible commercial opportunities with the hydrogen power technology in the next 12 months, getting around logistical refueling difficulties using a "user-friendly, cost-effective, portable refueling station from NanoSun."
You can watch the full 70-minute video of the record-setting flight below – just don't expect it to be riveting viewing.
Source: Intelligent Energy
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