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Boeing Hydrogen Powered Drone First Flight 160

garymortimer writes with news of the test flight of a hydrogen powered UAV. From the article: "Phantom Eye's innovative and environmentally responsible liquid-hydrogen propulsion system will allow the aircraft to stay on station for up to four days while providing persistent monitoring over large areas at a ceiling of up to 65,000 feet, creating only water as a byproduct. The demonstrator, with its 150-foot wingspan, is capable of carrying a 450-pound payload."
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Boeing Hydrogen Powered Drone First Flight

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  • by EmagGeek ( 574360 ) <gterich AT aol DOT com> on Monday June 04, 2012 @08:34PM (#40215279) Journal

    One of the coolest things about Hydrogen is that at the pressures required to keep it liquid at room temp, it is a supercritical fluid, which means it is both liquid and gas.

    What makes this cool is that, upon loss of the pressure that is keeping it liquid, it will spontaneously switch to its gaseous state. And, this change is not mediated at all since a supercritical fluid has no heat of vaporization.

    In other words, the fuel source works at all temperatures, even the -50C found at altitude, without requiring an external source of heat.

    Of course, the bad part happens when there's an accident, and hundreds of gallons of supercritical H2 suddenly become several hundred thousand cubic meters of H2 gas, which is not exactly what you want to have around when there's a lot of energy being dissipated by mangling metal.

  • by cduffy ( 652 ) <> on Monday June 04, 2012 @09:05PM (#40215473)

    What does it take to get that liquid hydrogen in the first place. I bet this is as environmentally friendly as the process to make all the batteries in hybrid vehicles.

    Funny thing -- the higher-end batteries (NiCd, LiPO) aren't all that environmentally unfriendly. It's the cheap lead-acid ones (which happen to be widely used in Chinese electric scooters) that are pretty nasty.

    And what it takes... really depends on the approach taken. I mean, splitting hydrogen out from water is something I'd expect every child who graduated primary school to have done in science class, though there's been plenty of work on more efficient approaches. (Not that it doesn't require plenty of energy... but again, that's a matter of where folks choose to get that energy from; if it's solar, hydro, responsible nuclear, &c...)

  • Re:Green death (Score:3, Informative)

    by Darkness404 ( 1287218 ) on Monday June 04, 2012 @09:27PM (#40215645)
    Actually, if you read the rhetoric of the far-left environmentalists, its not ironic at all.
  • by fluffy99 ( 870997 ) on Monday June 04, 2012 @11:40PM (#40216313)

    While hydrogen sucks for density per volume at 5.6 MJ/liter versus gasoline at 34 MJ/liter, it's actually has good energy density by weight with 123 MJ/kg versus gasoline at 47 MJ/kg. The huge bulbous body of this thing is simply to store all the fuel. I suspect their main reason for going hydrogen was that it's easier to burn at high altitude and has a wide useable fuel/air ratio.

    This low energy density per volume, is also the reason why it can't really be used for trucking. You'd take up half of the usable cargo room just to get the equivalent amount of energy as a normal diesel fill.

1 Angstrom: measure of computer anxiety = 1000 nail-bytes