World-straddling arms'n'airliners behemoth Boeing yesterday announced successful testing of a hydrogen-fuelled aircraft engine which will power the company's future High Altitude Long Endurance (HALE) robo-plane.
The Boeing release made an unexpectedly loud splash, with the new motor being described as a "wunderengine" and the "future of aviation", not to mention "a good option for reducing carbon emissions". It even got Slashdotted, by the put-it-in-a-car dept.
Actually, it's in a car - the Ford Fusion. That's because it's really just an ordinary four-cylinder car engine, fitted with a turbocharger so as to run at 65,000 feet. Ordinary car petrol engines can run on hydrogen without too much trouble; the problem is building a tank which will hold the cryogenic fuel without it all boiling off.
HALE isn't really a name for a specific project. It's a class of different aerial platforms which parts of the US military establishment would like to have.
Aurora Flight Sciences, the recent Boeing acquisition which carried out these latest engine tests, has been working on its Orion hydrogen HALE drone for some time now - the Reg reported on it last June, when US Army Space & Missile Defence* put some more money into it.
Orion isn't really the stratospheric hydrogen robot that hydrostratobot aficionados should be excited about, though. The Boeing/Aurora job is years away from service.
By contrast, the rival Aerovironment Global Observer did its engine testing last year, and has now got its first order from the US special-ops command this month. It has a bit of special tech sauce, too: rather than coupling its propeller mechanically to the car engine, like Orion, it seems to use a generator and electrically-spun props. Aerovironment claims the same 65,000 height and seven-day endurance as Boeing will eventually produce, and it's ready to go now.
As for this sort of gear being the future of aviation, or reducing carbon emissions, steady on. Very slow prop planes aren't going to be much use for anything except surveillance and comms relay, really - that's what the military want them for. Maybe it will become easier to run ordinary piston engines on hydrogen lower down, where it's noticeably warmer and the fuel will boil off somewhat quicker - indeed, BMW has a demonstrator car that can run on hydrogen now (though its fuel does all boil away in a matter of days, potentially causing the garage to explode if you've rashly parked it inside).
You could run ordinary turbofans on hydrogen too, with a bit of fiddling; but you'd never fit much of it into ordinary planes. It would only be a goer in various exotic hypersonic designs, where advantages in speed might make it worth one's while to fill most of the fuselage with weight-efficient cylindrical hydrogen tank. That might be the future of aviation; car engines and propellors won't.
And when it comes to reducing carbon emissions, don't hold your breath. Hydrogen is normally made with steam and natural gas, during which loads of carbon gets emitted. Aerovironment's field refuelling plants for Global Observer probably work like this, though details are scanty.
Even in the case of nice hydrogen made out of water using electrolysis, you need a carbon-free source of electricity.
The Boeing release is here. ®
*Not the same as the Missile Defence Agency, which does the "Son of Star Wars" missile shield which has been causing so much kerfuffle with the Russians lately.