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Boeing Hydrogen Powered Drone First Flight
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."
Those 450 pounds won't be flowers and kittens, right?
Environmentally-responsible airplane that can also carry a wicked-heavy bomb....*sigh*
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.
Are they going to use them for watering the crops or something?
Is the facility where these violations of our privacy are orchestrated going to be solar powered?
Along with water, isn't there quite a bit of heat produced as part of the fuel cell process? It would seem to me that this may take away some of the stealth benefits, no?
The problem with quotes on the internet, is that nobody bothers to check their veracity. -- Abraham Lincoln
Actually, if you read the rhetoric of the far-left environmentalists, its not ironic at all.
Taxation is legalized theft, no more, no less.
It's pronounced "Nuke-u-ler"; the "s" is silent.
Which is why under enough pressure it becomes a super critical liquid.
Isn't that what you want it to do in case it gets captured by the Iranians again?
Traces of thermite... You mean rust and aluminum? I find it hard to imagine that a plane made almost entirely of aluminum crashing into steel beams would leave traces of rust and aluminum!
All these shenanigans about Hydrogen being a perfectly clean fuel ignores the fact of where it comes from.
We don't get hydrogen from splitting water. That costs too much. We get it from natural gas, which has 1 carbon atom and 4 hydrogen atoms. This is done by steam reforming, and while it's possible to sequester the resulting CO2 by injecting it underground, it's not done by anyone. Because, again, it costs money.
We can also get it from coal, after conversion to "town gas" and that's not the cleanest of processes either.
Yes, I'm jaded. I used to be a true believer in this stuff, then I read more and grew up.
--
BMO
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.
So you think. It's so good at being silent that you don't even know it's there. It's what's known to orthography researchers as a "ninja letter". Very rare. Well, we think it's rare, because since it's a ninja, we can't tell for sure if it exists or not.
You are welcome on my lawn.
I am surprised that no poster so far mentioned the Boeing Condor. Same layout, same propulsion concept, same mission, only a different fuel this time. I guess some guys at Boeing never stopped working on this plane.
You know it's time for the next revolution when your rulers' names end with roman numerals.
Liquid hydrogen has long been used as a rocket propellant (including the Saturn V upper stage) and environmental impact has nothing to do with it. Liquid hydrogen has triple the specific energy density of jet fuel, which is awfully handy for pushing the limits of endurance.
Back when I was young, and dirt was new, a "clean-burning" engine was "clean" when it produced only water vapor and carbon dioxide (and didn't produce, say, carbon monoxide or carbon particulates, et al.). The reason given for this assertion was that both water vapor and carbon dioxide were "natural" constituents of the atmosphere -- i.e., they were already there, in measurable amounts -- so no harm could be done by their production. People then just could not understand how water vapor and carbon dioxide could cause any harm: After all, animals -- including people -- had been exhaling them both for millennia.
Now, however, it has become clear that one can cause a problem not just by putting a *new* component into the atmosphere (e.g., CFCs), but by putting an existing component into the atmosphere (e.g., CO2) in such large quantities that the natural balance is disturbed.
I think we should keep in mind that anything done can be overdone. Water vapor is a natural part of the atmosphere, too, but if hydrogen-powered aircraft become popular we could see the CO2 problem redux, with water vapor.
"I'd love to drive a bomb."
Buy a used Pinto.
"This post is an artistic work of fiction and falsehood. Only a fool would take anything posted here as fact."
Not sure if you're trolling or not, but the atmosphere is currently more or less saturated with H2O. In fact, it frequently condenses and precipitates out of the atmosphere to fall on land in great quantities.
Creation of new clouds at altitude has been shown to play a bit of havoc with earth's albedo, IIRC, but it really isn't possible to put more water vapor into the atmosphere than is already there.
Um, no, the atmosphere is nowhere near saturated with H2O; even in the tropics the relative humidity only approaches 100% near the surface, in the lower troposphere. At altitude there is plenty of opportunity to add H2O; think of the number of aircraft contrails you've seen in your life.
My point is that the same type of argument you make about water vapor was made in 1965 about CO2 -- there is a natural atmospheric regulatory mechanism (in the case of CO2, it was plant photosynthesis), so there's nothing to worry about -- and that that type of argument is specious: Adding all that water to the ecosystem, in a place that has never seen that quantity before, is going to have consequences. One aircraft flight per day? Sure, unmeasurable on a global scale. 100,000 aircraft flights per day? Well. . . .