An unmanned drone using liquid hydrogen as its fuel has successfully completed the first of many tests needed before being cleared for flight. The aircraft, known as the Phantom Eye, undertook a medium-speed taxi along 4,000 feet of runway at Edwards Air Force base, reaching speeds of 34.5 mph.
The Boeing aircraft will eventually be put into service as a high altitude, long-endurance (or HALE) drone with a 450-pound payload. The plane is expected to stay airborne for up to four days and will likely be used for intelligence, surveillance and communications missions. In other words, it will need to fly high and stable.
To that end, the Phantom Eye has a wingspan of 150 feet, and is powered by 150 horsepower engines with 16-foot diameter propellers. It carries 1,900 pounds of liquid hydrogen in two tanks.
You might be asking if NASA has been using hydrogen for fuel for years and on a much bigger scale than this drone, what is the big deal with it being adopted aviation?
The fact is there have been a handful of experiments using hydrogen in aircraft occurring as early as the 1950s. But, for a large portion of the 20th century fossil fuels were considered cheap and could be delivered efficiently into an engine to power it so there was no need to actively pursue hydrogen.
Now, as we've come to understand the effects of fossil fuels on global warming and given its mounting cost, hydrogen is again being considered as a clean and safe option. The task ahead is perfecting the engines and fuel delivery to make it cost effective.
While the liquid hydrogen options may work for unmanned drones that will stay aloft for days, it is likely for commercial use researchers will look to creating hydrogen fuel cells — such as the ones used in some cars. But, on a much bigger scale.
The future of hydrogen for use in aircraft is wide open, which is what makes the progress made with the Phantom Eye so important, and this first test a milestone.
"It's huge to capture the data that we did today," Drew Mallow, Phantom Eye program manager, told UPI, "to allow the team to evaluate it so we can fine-tune the models, understand if the software is correct and understand how the propulsion system is going to react as it moves forward."
The medium-speed taxi will be followed with tests that take it up to 46 mph on the runway before the team allows it to go airborne. No target date for the airborne tests of the Phantom Eye have been released.