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?
It's not only the fuel (Score:4, Insightful)
Electrical fires can still result from such an impact.
Less Boom, Yes, but Safer? (Score:1, Insightful)
But... I would imagine a full size jet liner weighing how many tons dry, would still be enough of an impact at over 400 mph to bring down the WTC.
Hydrogen is a high-energy-density fuel.. (Score:4, Insightful)
This is good news, to be sure, but a plane crash is clearly not the same as an oil spill. How the burning would proceed would depend completely on how the fuel was contained in the plane, and what happened to the containment. Clearly, it has the potential to burn just as hot as hydrocarbons -- it has to contain the same amount of energy as the jet fuel, 'cuz the plane still has to fly.
Since, as far as I know, no one is even remotely close to building plane-engine-type hydrogen-powered engines (fuel cells are about as close as its gotten) discussion about relative safety is all going to be wild speculation.
Liquid Hydrogen no safer than Jet Fuel (Score:1, Insightful)
After reading on the Phoenix Project website that they plan to use liquid hydrogen (as opposed to hydrogen fuel cells) their claim of increased safety lacks merit. We have only to look at the Challenger catastrophe to realize that liquid hydrogen is an extremely volatile and flammable element. Substituting one highly flammable fuel for another does not increase safety.
"Not fighting the last battle" (Score:1, Insightful)
We should stop worrying about planes so much, and start focusing on other possibilites.
However much you might not like terrorists, you ought realize not all of them are stupid, and they won't strike twice in the same way.
K.E. = .5 * m * v * v (again) (Score:5, Insightful)
I wrote about this [slashdot.org] the day after the attack:
Something I just thought of a little while ago, to help me gain some perspective on what happened:
A Boeing 767-400ER [boeing.com] [boeing.com] has a maximum takeoff mass of a shade more than 200,000 kg. It has a typical cruise speed of 840 km/h.
Using our favorite formula for kinetic energy, that comes to about 5.6 billion Joules, or between one and two tons of TNT.
Or, in other words, just the force of that much mass at that speed is about the same as a WWII blockbuster bomb. Add in some twenty thousand gallons of jet fuel...and I still can't wrap my mind around that much destructive force.
And I thought cars on the freeway were deadly!
May such magnificient machines never again be used for such awful, awful purpose.
b&
Very true... (Score:5, Insightful)
Hydrogen is unlikely to be seen as a viable fuel, however, because for so many years it was believed that the Hindenburg was destroyed because of the hydrogen that held it aloft. Even now that the truth is known (The Hidenburg went down because the skin was painted with powdered aluminum, AKA rocket fuel, and when the mooring line grounded arcing electricity caught the aluminum on fire.), it is rarely spoken of because so many sources still quote hydrogen as the source of the explosion.
Re:Hindenburg (Score:3, Insightful)
Nope. The intense heat of the burning jet fuel weakening the structural steel is what supposedly caused the buildings to ultimately collapse.
The structure was designed to withstand temperatures of a 'normal' fire for something like two hours. The intense heat of the burning jet fuel caused the steel girders to weaken and collapse in much less time.
But think about it. If the impact of the planes were enough to bring down the towers, shouldn't they have toppled over right away?
Umm ... hydrogen ... blimp ... Hindenburg ... (Score:1, Insightful)
just floating down (Score:3, Insightful)
Everyone's been focusing on the technical aspect.. (Score:3, Insightful)
I don't see the recent security clampdown going away anytime soon.
Just my opinion.
Re:It's not only the fuel (Score:2, Insightful)
Guess what? Asbestos is much more dangerous than terrorism. It just kills you slower, and allows some corporation to profit from your demise.
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.
Either this is a lie, or faulty design played a part in the collapse. You don't have to be an engineer to figure out that the lower the fire, the more likely the collapse due to the increasing weight on the affected area.
Re:Less Boom, Yes, but Safer? (Score:3, Insightful)
But... I would imagine a full size jet liner weighing how many tons dry, would still be enough of an impact at over 400 mph to bring down the WTC.
Untrue. NPR had an interesting interview with a structural engineer the evening of the eleventh. His professional opinion was that the force of the impact was insignificant in comparison to the weight that the steel structure had to hold up every day. The plane simply disintegrated. The fire was what caused the collapse.
Remember that infrastructure was designed to support thousands (millions?) of tons constantly, and it was able to support those top floors for a considerable amount of time after the impact. The only thing heavy enough to collapse the WTC was, well, the WTC. Without the fire, the towers would have stood and the loss of life wouldn't have been anywhere near as great.
Re:It's not only the fuel (Score:5, Insightful)
Besides asbestos is not an environmentilst issue, its a heath issue. For what asbestos did there are better ways of doing it. If you'd like me to cover your house in asbestos than feel free. But don't come complaining when you get cancer from it, or other lung problems.
Alas, we're talking Liquid hydrogen here.... (Score:5, Insightful)
Unlike hydrogen gas (which burns relatively safely), liquid hydrogen when it ignites will do it with a force that makes a dynamite explosion seem like a minor event. If the planes that crashed into the World Trade Center were fuelled by liquid hydrogen, the initial fuel explosion would have so much kinetic force that the building would have collapsed right there and then.
If I remember from the Challenger explosion, when the solid rocket booster leak ignited the fuel in the external fuel tank the force of the explosion was equivalent to a 1 kT tactical nuclear warhead. That's why liquid hydrogen must be handled with extreme care.
asbestos (Score:3, Insightful)
Asbestos in solid form (like insulation) is perfectly, 100%, safe. Until it starts to crumble and asbestos dust starts to fly around. The preferred treatment for a house with old asbestos insulation is to encapsulate it - not remove it. Removal will get more of it flying around the building than sealing it in place.
Re:just floating down (Score:3, Insightful)
Re:Hydrogen powered aircraft have been tried befor (Score:3, Insightful)
Yes, one of the more entertaining parts of Skunk Works [amazon.com], IMHO, is the section where Ben Rich talks about his research and experimentation with liquid hydrogen.
~Philly
Re:low energy density (Score:3, Insightful)
As a pilot, I feel I should respond to this suggestion. Anytime you take control of an aircraft from the pilot you are going to have serious problems in certain situations. Let us say you install some sort of "terrain avoidance" system. Sounds like a good idea, nobody can fly too close to objects, as the aircraft will steer away from them.
Now say we have a 757 in distress. Upon takeoff, the number one engine disassembles itself, and in the process renders the flaps and ailerons on the left side useless. Now we have a plane near stall speed, at low altitude with reduced control. Perhaps there is enough speed and power to take the plane around and put it back on the runway. Keep in mind we are dealing with a fully fueled and loaded aircraft. If in bringing the craft back around, the terrain avoidance system decides it is too close to a line of buildings or a ridge, what does it do? Turn away? A sharper turn increases the stall speed of an aircraft. Stall a 757 at low altitude, and it is in the ground. Does it pull up? Again, it could easily stall a slow moving, fully loaded aircraft. Or if the pilot's only option is a "controlled crash" in a nice big flat field, does the avoidance system again try to prevent that?
There are countless other situations where such a system could cost lives. In addition, if the system went haywire mid-flight, can the pilot override it? If the pilot can override it, so can a trained hijacker. Even on autopilot, you can grab the yoke and push the plane around. Somehow, I don't think anybody would feel happy with a system that is capable of completely ignoring the pilot's input.
The problems in such a system outweigh the benefits. And frankly, I doubt we'll ever see commercial airplanes used as missiles again.
stupid (multiply times three for filter) ideas! (Score:4, Insightful)
Public concern has been so missdirected. Airplane fuel, crypto, nuclear power plants, give me a freaking break! It's like all the anti-technology trolls are having a field day with the national press. There is no way to think of all of the devious things people can do, and no way to block them all without crippling eveyone's ability to do anything.
Wanna kill lots of people? Let's see, how can we do that? How about blowing up a train load of chlorine tanks in a major urban area? How about a distributed fire bomb attack? A few timers and gassoline containers placed here and there over a few months can light up something that no one could stop. How about hijacking a truck load of fuel and another full of fertilizer? Drive it into a tunnel, into a parking garage, a crowded football stadium and boom. Why not break a gas main in the food court of a very large mall? Then there are the traditional targets, dambs and what not. Hey, that was easy, all the gaurds were at the airport waiting for yesterday's strike.
What are you going to do about it? Stop making plastics? Outlaw possesion of more than ten gallons of fuel? Make farmers go back to manure? Fuel everything with liquid hydrogen? Why not safe and dependable rubberband power? Right.
I'm not having a good day. Does it show?
Re:Hindenburg (Score:2, Insightful)
The outer skin burned very fast, the hydrogen burned up, but the diesel fuel tanks ruptured when the skeleton buckled. This fire rained down on those that managed to survive the fall.
I cannot remember the actual amount of reserve fuel on board, but it was substantial.
Re:And this is the post that makes me delete Slash (Score:3, Insightful)
There are a lot of people on Slashdot that know a little bit about the science and technology outside their area of expertise.
What amazes me is the belief by so many people that the experts and specialists who work in these fields must be idiots who cannot see the obvious solutions that seem to occur to the "brilliant" outsiders that reside here at Slashdot.
A little hint people. If it is a completely obvious solution, then at least one of the "experts" has probably also thought of and analyzed it. If a completely obvious solution has not been implimented then it is probably because there is some subtle problem with it that is beyond your ability to forsee.
Re:Hindenburg (Score:3, Insightful)