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Liquid Hydrogen UAV
From the same company that brought you the Wasp MAV, Aerovironment announced yesterday that they have successfully completed the world's first liquid hydrogen powered Unmanned Aerial Vehicle (UAV) flight tests. From the press release: " AeroVironment's Global Observer High Altitude Long Endurance (HALE) platform will be able to operate at 65,000 feet for over a week with a flexible payload-carrying capacity of up to 1,000 pounds." Applications include government and military surveillance operations, communication relays, and the potential for persistent real-time imagery of wildfires, hurricanes, and other natural disasters. More pictures here.
I understand the need for good intelligence in making national security policy, but flying spyplanes over the airspace of your friends and enemies alike isn't going to win you any brownie points, and as the US has already experienced with the U2 (the crashed plane, not the band that's selling out), one crashed spyplane can lead to a hell of a lot of trouble.
Spying is a nasty business, and I guess it's a necessary evil, but the person in charge of announcing new toys at Aerovironment must be completely braindead. Someone at the State department ought to go have a talk with those good folks.
You've got to be kidding me. How exactly would this have changed the situation? We already had satellites, spy, fighter, and electronic warfare planes, Predator UAVs in Iraq. Please explain how this UAV changed the situation in any way.
You mods are getting ridiculous here. I love how you guys would mod any anti-US comment "insightful" if it fit your agenda.
It wouldn't have helped the US avoid falsely accusing Iraq of making WMDs, partly because it's not good enough to tell a "baby milk factory" or "pharmaceuticals factory" from a "chemical weapons factory". But the big problem was that the US government *wanted* the conclusion to be "Iraq has SCARY WMDs" to convince the US public to let them invade again, and anything that simply flies over and says "no, didn't see anything suspicious on the outside of those factory buildings" isn't going to either change the propaganda policy or tell the military planners not to target a factory-shaped building.
On the other hand, better UAVs would help improve targeting for the things they did want to blow up, or at least let them see whether groups of people were wearing uniform-colored cloths or not.
Bill Stewart
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I would like to know how they solved the problem of cryo storage of liquid hydrogen. Sure the air temperature and thermal conductivity at high altitudes is decreased but this can help only so much. I just dont see how they can keep it at minus 259C for one week. Dewar made of plastic? Pressurizing it would not help because at -240C hydrogen stops being liquid regardless of the pressure.
My guess is that one big tank fills up most of the pregnant-looking belly. The craft may need some teflon coating on the surface to prevent ice buildup. Also, it is apparent from the video that landing it in even modest crosswind will be tricky business (as with any large-wingspan ultralight).
I doubt that we will ever figure out - and I suspect that even if we did figure out we couldn't do much about it
The problem is that the closest supply of gaseous hydrogen is on Jupiter. So here on earth, it's artificially manufactured from natural gas, whose price correlates very closely to the price of oil.
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I believe the RIAA is suffering from the lack of hydrogen-fueled airships. All they have now are rock stars looking old, male hip-hop artists looking mean, and female hip-hop artists looking
Give me a snapshot of burning hell falling from the sky once in a while, and maybe I'll pay $19.95 for your amelodious drivel.
And I'm not even a Led Zep fan.
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Dumping liquid hydrogen on a fire to extinguish it, as you seem to be suggestiong, is not the smartest idea... Firstly, and least significantly, much of the hydrogen would vaporise very quickly in 1 atm pressure and 20 degrees temperature. Secondly, hydrogen is highly flammable.
First of all you have the weight, the craft is as skinny as rail, and only carries 1000 pounds. That is in the sub-feather-weight class of airplanes. I doubt that this same powertrain could drive a plane full of cargo and/or passengers.
You also have the functional question. This technology is for staying in the air for a week. It does not have what the airlines need. Passengers are looking to get from A to B as fast as possible.
Basically this is a great idea, but I cannot see it impacting the commercial air industry any time soon.
What makes you think hydrogen has any advantages over kerosene (jet fuel) for commercial aircraft? Hydrogen has a lower energy density, it's far more expensive, and it's much harder to store. The only (debatable) advantage is environmental and that hardly outweighs the crushing disadvantages.
The press release is mighty short on details, but I assume this UAV uses electric motors. Presumably liquid hydrogen and a fuel cell is lighter than batteries. It's a great solution if your goal is to fly very slowly for a long, long time. Not so good if you want to move half a million pounds at 600mph.
Martin
Solar UAVs for spying would have a problem - if they're over the clouds, the camera sees nothing but clouds. If they're below the clouds, the solar panel sees nothing but clouds. Either way, it's not really that useful.
Clouds aren't the issue. There are lots of other ways to look at or listen to things than visible light. The problem with the solar version is payload. Helios had to be incredibly light to fly on solar power - it had a 247 ft wingspan, yet weighed only 1500 pounds. It broke up in flight two years ago. AV's Global Observer has a 1000 pound payload.
The hydrogen-powered UAV would be good for exploring hurricanes over a prolonged period of time, as it could sit in the clouds near the eye and just monitor stuff
For endurance you need high aspect ratio wings. Think U-2, think Steve Fossett's round the world flight. To survive in the clouds near a hurricane, you have to be built like a P-3 - short, stubby, stronger than hell wings. This thing might fly high over a hurricane, but it would never survive in one.
A potential civilian use for this kind of technology would be in fighting wildfires. The late Red Adair...
Red Adair fought well fires.
On the other hand, if you were to have a remote-control aircraft with a large amount of liquid hydrogen aboard, it could potentially have much the same effect (deprive the fire of oxygen) but with a lot less environmental impact.
Now there's a great idea. Starve the fire of oxygen by having all of the oxygen combine with a bunch of free hydrogen, creating nothing but water vapor... oh, and a little bit of heat. Heck, you could just use a KC-135 and dump raw gas or jet fuel on it for the same effect, no new technology needed.
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