Hydrogen-Powered Aircraft == Anti-Terrorist Device? 701
maladroit asks: "Today on NPR's Talk of the Nation/Science Friday , Harry Braun of the Phoenix Project said that a hydrogen-powered airplane would not have produced the fire and intense heat that brought down the World Trade Center towers. Is this true ? What are the other advantages and disadvantages of hydrogen fuel ? Details on the Phoenix Project's website are a bit sketchy, but I'm sure the Slashdot crowd has some answers (and Richard Dean Anderson jokes)." Sounds like a good theory, it doesn't account for the hostage aspect, but it would prevent the use of aircraft as cheap bombs. Would there be any drawbacks? How much would such a refit cost for your average commercial aircraft?
low energy density (Score:5, Interesting)
It's the same reason why automotive engineers are having such a big problem getting hydrogen-powered cars economically feasible (apart from the storage problem). Compared to gasoline, hydrogen has an abominally low energy density. What does that mean? To get the same amount of energy on-board, you'd need to carry many times the amount of gas in hydrogen. That means either HUGE fuel tanks, or severely curtailed range. Not being an aerospatial engineer, I can't comment about the former, but the latter just won't fly (pardon the pun) with commercial carriers. "Yes, we can get you from New York to Los Angeles. You have seven brief layovers for refuelling..."
Interesting idea, but not practical. If you're still worried about planes flying into buildings (it's been used once, if they're smart they'll now switch tactics) maybe installing fire-suppressing foam (like the systems they have in McDonalds' in the kitchen) on tall buildings to smother any high-temperature fires that break out.
A simpler method may be simply to install nose radar in *all* sizable airplanes, and automatically engage the autopilot when flying within 1000m of an object (building, mountain, etc.) to avoid it. We have the technology, folks.
No idea what they're talking about (Score:5, Interesting)
Point two: Hydrogen is NOWHERE NEAR dense enough to use as an airliner fuel. You'd need all the room in the entire ship including the cabin taken up with hydrogen tanks, and then some, in order to fly cross country.
Re:It's not only the fuel (Score:2, Interesting)
Note: part of the reason the fire at WTC was so devistating was that the do-gooder environmentalist whackos stopped the use of asbestos from being used to fireproof the steel columns which supported the structure. The building's chief design engineer is on record as saying that any large fire above the 70th floor would cause failure of the structure due to pancaking caused by lack of adequate fireproofing on the support columns. He said this before the building was ever occupied.
Bad idea.. (Score:4, Interesting)
The fuel tank sizes need to be changed. Hydrogen has a LOT of energy, but it's not especially dense.
You'd also have to change the current petrol-based fuel distribution system. Might I mention that, despite the Hindenberg disaster being more related to the design of the craft rather than the use of hydrogen, hydrogen is much less safe to deal with than petrol-based fuels.
Plus, there are exactly zero hydrogen fueled aircraft in existence. This is for a reason. During the cold war, some pretty intelligent folks tried to make it work, and failed.
It IS somewhat likely that hydrogen would avoid the exact circumstances that brought about the world trade center crash. But there are problems.
For one, the aircraft will have a nasty tendancy to explode. One of the reasons why the Chalenger disaster was so bad was because the entire hydrogen tank, filled with liquid hydrogen, evaporated very fscking fast, blowing the top and bottom off the tank and atomizing it. Then it burned very quickly.
Hydrogen is very light. So in the case of massive fuel leakage, most of the hydrogen would float upwards and leave the area relitively quickly. If you can keep it from forming a fuel-air-explosive.
I consider that more of a way for scientists to get more funding for hydrogen experiments than anything else. Sure it might be nicer if you crash into a building, but there's so many other things that can go horibly wrong. The only hydrogen powered craft in existence are rockets, which do not have anything CLOSE to an airliner level of reliability. There are not any production-grade hydrogen-powered jet engines.
Re:New anti-terroristic way of travel! (Score:3, Interesting)
What if you are carrying luggage packed with C4? Or one of these "suitcase nukes" that I keep hearing about?
If these attacks had taken place at street level, even more people would have died.
Additive (Score:3, Interesting)
Unfortunately, when the data was analyzed, it was shown that the metal skin of the aircraft survived. Seats made of that cushy foam junk survived the fire. In fact, most of the damage to the plane (mind you it was missing a wing...) was soot, not intense heat. The test was a spectacular POSITIVE result, not a blatant failure... how many fires currently result in nothing left of an airplane?
Of course, show anyone the video with a 'fireproof' substance in a tremendous fireball moments after impact and they'll say it's a failure, regardless of the fact that the metal skin of the aircraft, usually the first thing to 'melt', survived. Illogical? Yes. Political? Probably. Good Science? No.
Re:Similar ideas have already been rejected. (Score:2, Interesting)
great idea, they had a demo where they crashed a 747 chock full of the stuff. instead of a huge rolling fireball, it caught fire and then almost immediately snuffed out.
still trying to find a link tho.
Re:It's not only the fuel (Score:2, Interesting)
Can you provide a reference for this statement? There are other fire-proofing materials aside from asbestos that are used to coat steel columns.
Great idea, but the tech's not there yet. (Score:3, Interesting)
Having a hydrogen-powered airplane would have been far preferable to a hydrocarbon-powered one, because the hydrogen, being a gas, would have gone out of the buildings. Sure, it would probably have gotten to places that the liquid fuel didn't, but much less of it would have burned, because it would have diffused to essentially normal conditions pretty quickly (there's hydrogen gas in air, remember). Sure, it would have left the building pretty effectively on fire, but such buildings are rated to be able to withstand a fire fueled by the stuff normally found in them for long enough to put the fire out and evacuate the building.
On the other hand, just switching the fuel is beyond our current technology. Jet engines are rather carefully-designed devices, and you can't just switch the fuel in them without changing a lot. And we don't yet have the fuel tanks and support systems for hydrogen; it needs to be kept under high pressure in order to fit in the airplane, and that means something strong, and designed for high fuel and low fuel situations, which will be heavy. Gas just needs a container that doesn't leak, since it's a liquid anyway.
Furthermore, the support systems for hydrogen-powered stuff aren't nearly as well in place; no big generation plants, no suitable fuel trucks, and so forth.
Re:Well, ONE problem (Score:3, Interesting)
The towers were able to withstand the impact of the jets just fine, as they were designed to. It was the burning of the fuel that softened the support columns that ran vertically through the building. When those support columns became too soft, they fold. The sheer weight of the building above the soft spot caused the collapse.
That's why Tower 2 fell first - the plane hit near the 70-80th floor or something. Tower 1 was hit at the 103rd, meaning the columns there had to soften up a lot more than Tower 2's columns before they collapsed.
The idea of using hydrogen as jet fuel is that it burns at a much lower temperature. Hence if a hydrogen powered jet were to strike a sky scraper, firefighters would have a large amount of time to put the fire out and engineers time to build up support to save the building as a whole.
One place this did happen was (IIRC) in the 1930s. During heavy fog, a twin engine biplane rammed the Empire State Building. Granted it's a much smaller plane, but it still caused a fire, just not as large as a few weeks ago.
Re:Cost Effective (Score:2, Interesting)
Now, the same principle holds in the buisiness world. Spontaneous == Profitable; Energy of Activation == Initial Cost. If you can't cover the initial cost, the buisiness plan won't go into effect.
In Chemistry, we use Catalysts to jump over Energy of Activation barriers. In buisiness we use banks. So, what you're saying is, the airline industry will go heavily in debt to convert their airplanes. That'll only happen with a government mandate. Furthermore, if the government mandates that airlines convert to hydrogen fuel, exactly what makes you think banks are going to cover that mandate? (Remember, too, that saving has been negative for n quarters--the banks may not have the money, even if would loan it if they had it.)
Neither the airline industry nor the banking industry has unlimited pockets. If the initial costs are too high, it doesn't matter what the long-run profits are, it won't happen.
Re:Liquid Hydrogen no safer than Jet Fuel (Score:2, Interesting)
Would have helped. (Score:4, Interesting)
The WTC towers were constructed with, essentially, redundant substructures. The exterior supporting beams, placed only 1 meter apart rather than the normal 6, could support the entire weight of the building without the internal supporting structure (which, of course, could support the full weight itself). While tower number 2 may have collapsed from the hit it received (it fell rather quicly after being hit), the prevailing theory is that at least tower 1 required the intense heat of the fire to weaken the remaining support before falling. Even if the hydrogen tanks ruptured and the Hydrogen ignited, you'd only have one hell of a flash fire, leaving only normal combustables in the building and on the plane burning after a few seconds. This could have allowed at least one of the buildings to have remained standing, and very possibly allowed those trapped above the impact point to make their way down.
Just how easily aircraft can be retrofitted with Hydrogen engines or electric/fuel-cell based power I've no idea.
Re:Jet Fuel (Score:3, Interesting)
I didn't realize that 1800 to 2000 C [soton.ac.uk] was relatively cool .
Re:Intermediate energy source (Score:3, Interesting)
-Paul Komarek
Re:Right, but... (Score:2, Interesting)