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Hydrogen-Powered Aircraft == Anti-Terrorist Device?
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?
The fuel made the explosion worse, but anything the size of an airplane hitting a building at 350+ MPH will do some serious damage.
Electrical fires can still result from such an impact.
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The Hindenburg's problem wasn't that it was full of hydrogen; it's the fabric the outer covering was made of that did it in.
Please read up on these things before spouting retardedness.
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Well at the very least, hydrogen is a renewable intermediate energy source, unlike the oil used to formulate AvGas these days. And presumably it would be less polluting as well. Both excellent reasons for gradually making the switch, but I don't really see how it would make a plane less of a bomb. The synopsis claims it's safer in an auto crash (presumably because it disperses rapidly), but would that necessarily apply to an airplane? Sure, it wouldn't have burned in the WTC as long, and possibly not as hot, but H2 being a gas wouldn't it have been more explosive?
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Whoa, someone's trying to crash a blimp into the Sears tower!
... Sheesh. This is getting boring.
*BOOOOIIIINNNGGGGGG*
Well, there he goes again...
*BBBBOOOOIIIINNGGGG*
And again
Change the channel.
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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.
Mr. Ska
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.
Hydrogen burns very hot but (1) it requires mixing with considerable air to produce an explosion and (2) being very light it tends
to burn "up", i.e. to rise. The plane would be
fueled with liquid hydrogen at 20 degrees K
(only Helium liquifies at a lower temperature) and would evaporate quickly into a gas. Unlike the current JPx fuels, the hydrogen disipates rapidly and would stick to stuff and burn. The hydrogen would burn and disipate rapidly and
leave behind only those pre-existing materials which have been ignited.
One problem is that even liquid hydrogen is very light (very low density) and so requires very large tankage. The Shuttle's external fuel tank is mostly a hydrogen tank (something like 80% of the volume?) with a surprisingly small liquid
oxygen tank at the top. I have seen a liquid hydrogen bubble chamber being filled and marveled at the droplets of liquid hydrogen entering the chamber and just floating down (drifting really, not falling like water droplets do).
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Actually, the Hindenburg burned due to a special treatment applied to the canvas, which made it highly flammable. Add to that the diesel fuel for the engines, and your real culprit is > dead dinosaurs, aka fossil fuel. According to reports I have read, hydrogen will, essentially, evaporate and disperse immediately, since it is the lightest element in the whole big Universe.
Mmmmmm... Bold, yet refreshing!
Point one: don't bring up the Hindenburg unless you know what you're talking about. The Hindenburg disaster was NOT initiated by a hydrogen explosion, it was improper maintenance and a highly flammable skin. In reality hydrogen *is* safer than liquid fuels. Think about it, if you were trapped in a wrecked car, would you rather have hydrogen leaking 10 feet from your head, or gasoline? Keep in mind that pure hydrogen in a tank can not explode, there's no oxygen. I'll take hydrogen any day.
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.
The "Impact did not bring down the WTC, the super heating of the steel infrastucture did
each "cube" of the building was designed to withstand a certain amount of pressure, when the ones that were superheated colapsed, it increased the pressure on the lower cubes that they could not handle it, thus they collapsed, thats why the building fell straight down and not fall over when the plane hit
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This might prevent some of what happened on the 11th, but you still have the kinetic energy of a 200-ton plane with 60,000 lbs of thrust hitting the target at 500 mph.
It wasn't the jet fuel that rammed the plane all the way THROUGH tower two on live TV. It might not have burned hot enough to cause the tower collapses, but having hydrogen fuel wouldn't have made the planes bounce off the towers, either...
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I wrote about this 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] 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&
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A hydrogen powered plane's fuel tanks would have blown up all at once. The reason the WTC attacked worked is that airplane fuel is sticky and burns slowly when there are massive amounts of it, so it got all over the inside of the building and generated insane amounts of heat over time, starting other fires, etc. Hydrogen would have just blown up, with a small explosion and a lot of fire at impact, but little other damage.
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.
The space shuttle Challenger had a fair bit of hydrogen. It blew up just fine.
Now, as to continued flame, that's a different matter. It is unlikely that the hydrogen would act as an effective fuel to continue the fire for much after the initial impact.
The fundamental energetics of hydrogen combustion suck compared to fossil fuel combustion.
Hydrogen comes into its own more in the context of things like fuel cells. I don't think that the high demands of take-off powering would be well met by fuel cells. Cars can take longer to accelerate on a highway for instance with less loss of functionality. Either the airplane gets off the ground by the end of the runway, or it doesn't. The ability to abort a landing and lift off again is an important safety consideration.
The reason the site is short on details is that anyone who can make hydrogen work better than fossil fuels will make billions in the first year. It's a fantasy for anything but fringe applications. (Compare the Motorola fuel cell story today. Even that is methane-based, not hydrogen.)
Looks like our journalist at NPR had to fill a slot by deadline and went with what he could get to fill it.
> belive the explosion only had to weaken the metal substructure for the buildings to fall
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?
First, you would have a hard time refitting an existing aircraft to be hydrogen fueled. I'd rate it as impossible. You need fuel lines that can handle cryogenic temperatures. You need to replace the whole fuel-tank assembly. You need to replace the entire engine. Along with that, a lot of other systems and fluids will need to be changed.
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.
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Hydrogen has some drawbacks as a fuel, in general, though is also has some advantages. (I don't really understand them that well, but I do know they exist.) In terms of crashes, a hydrogen-fueled plane that crashed would explode all at once - once the fuel tank was ruptured, all the fuel would either burn quickly or blow away, rather than continue to provide fuel for the fire as avgas does.
A hydrogen fueled 747 crashing into the WTC would likely have caused a bigger explosion on impact, but the resulting fire wuoldn't have stayed so hot for so long - if the building didn't collapse right away, it may not have collapsed at all.
In a topic a while back, the idea that if you took a compressed cylinder of H2 to a field, and shot at it with a bullet, it would be unlikely that you'd cause the cylinder to explode; however, because of the rate at which that gas will escape, the cylinder will suddenly have a huge amount of kinetic energy in a random direction. If you ever saw the crap flick 'Chain Reaction', at one point Keanu axes off the top of a cylinder, using the reverse force to push a multi-ton slab of concrete away from his escape route. While that does approximate real life, typically a damaged cylinder can break through brick walls and do tremendous amounts of physical damage before it's exhausted. And this is the stuff that's common in most academic settings.
Imagine the amount of H2 gas you'd need to power a 747 from NY to LA. Sure, you can compress it to maintain the same volume, but the higher the amount of compression, the thicker you'd need to make the fuel storage, which means more mass to fly, which means more fuel in order to accelerate that mass. If you go too thin, then a small amount of wear can lead to gas vent; I very much doubt that a pilot would be able to steer a plane effectively if it was venting a large amount of expanding gas.
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Project Phoenix??? You would think they could choose a more reasuring name for hydrogen powered aircraft, given people's perceptions!
Of course, by now it's also a bit of a cliché...
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The Hindenburg disaster was not caused by the use of hydrogen, but rather by the material used on the skin of the zeppelin.
I've read a few things here which only help to spread the myths about hydrogen. Here are some of the common misconceptions and why they are untrue.
1. Hydrogen is extremely explosive - Hydrogen is not *extremely* explosive. It can be explosive, but it needs a certain amount of oxygen in order to explode.
2. The Hindenburg explosion was caused by the hydrogen. - It is widely believe that the explosion was caused by the flammable fabric covering of the ill-fated airship.
3. Myth#1 is why we don't have Hydrogen-powered cars - Actually, the biggest problem is that hydrogen is, for lack of a better term, sparse. (Opposite of dense). It's difficult to package a sufficient amount of it in a reasonable volume. There is ongoing work to change this by combining it / embedding it in other materials or packages, i.e. Carbon nanotubes.
4. Hydrogen is hazardous flammable substance - Because of its being the lightest (least dense) gas, a hydrogen fire will bascially burn in an upward direction. In addition, the gas will dissipate quite rapidly - imagine what would happen if you 'spilled' some Helium - it would just float straight up, even if it was on fire. Hydrogen does the same.
5. The fire was not a significant part of the tower collapse - While the kinetic energy of a fully loaded 757 / 767 cannot be ignored, if that was *all* there was, the towers would be standing today, and probably repairable as well. The collapse was caused by the extremely hot (1500+ degree) fires burning long enough to weaken the steel structure. The beams were rated for 1 hour of fire resistance. They held for at least that long, and then gave way, causing the 6 million lb. floor to fall and begin the domino effect.
It wasn't hydrogen burning.
From the DOE H2 website:
Its called "Walking". There is no possible way you can take down buildings with this new form of travel.
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.
Huh? Wouldn't H and H20 fall at the same rate? Or is the chamber not evacuated? Or do I need more coffee before posting?
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Bullshit. Jet fuel is simply slightly better refined kerosene, basically diesel. High flash point, relatively cool burning. It's about like charcoal lighter fluid, doesn't go poof!
Why do I know? I'm a general aviation pilot. As such, I'm pretty close to jets frequently, and I've asked the fueler monkeys.
On to the topic. I'm not sure why hydrogen isn't used for jets, other than the fact that it's a bitch to store and transport. I'd think it'd be an ideal fuel for just about everything, since in it's pure form the only burn by-product is water.
BTW, the Hindenberg got smoked mainly because of the aluminum-oxide paint on it's exterior surfaces. Think solid fuel rocket.
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You are right, but not because of the Hindenberg. As others have pointed out, the Hindenberg was destroyed by something else. You also seem to have this strange notion that commercial jet fuel (kerosene basically) is safe. In a crash, I'd rather be in a hydrogen powered plane than a jet fueled one: I'd probably survive. Hydrogen burns up, jet fuel splatters and sprays and burns on the ground. In a crash, the hydrogen would vaporize into a gas (absorbing a fair bit of heat in the process thus cooling the airframe and reducing explosion risk) and float up. If it ignites, it's going to be doing it above your head.
But to your principle point, at least twice as powerful, you are right but not because jet fuel is safer. The hydrogen-oxygen combination is the second most powerful rocket fuel known to science. Per kg, hydrogen burns way more energetically and more effeciently than jet fuel. The only problem is getting enough hydrogen in the plane: you'd have to use cryogenic hydrogen. Then the fuel tanks would have to become giant thermos bottles which ups the weight of the plane and you pretty much loose the advantages of hydrogen.
Hydrogen is safer than gasoline and all those other liquid fuels. It burns more efficiently with a greater conversion into mechanical energy. The only problem we face is how to store it without adding an extra hundred pounds or more to our fuel tanks.
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No they won't. It would take exactly the same amount of energy to split out the hydrogen as you would get back in recombining it in a fuel cell. When you consider the unavoidable efficency losses, that means you're behind.
The paint on the skin of the aircraft was most likely ignited by a static discharge (According to eyewitness accounts) but the hydrogen contributed to the burning. If they hadn't painted the ship with some volatile paint, however, it would likely never have caught fire in the first place.
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As it stands, the terrorists have already blown their wad with reference to planes - they likely wouldn't use them in a subsequent attack - there are still plenty of transportation systems (land, sea) that are still wide open and completely insecure.
The main thing that will most likely prevent planes from being used as cheap bombs is the fact the four planes were already used as cheap bombs.
I don't see the recent security clampdown going away anytime soon.
Just my opinion.
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This topic comes up a lot especially in alternative fuels discussions. This is the info that I have. It may not be 100% accurate, though.
Issue 1: Hydrogen is a gas, which means that you need to compress it in order to get enough fuel onboard. Fuel equipment now has to deal with the increased pressure. This adds expense and weight to whatever it is you are building. Weight is bad for airplanes. Liquid petroleum fuels are very dense and do not need pressurized containers. Thus a full load can be carried without the need for bulky equipment.
Issue 2: The economy is designed to handle liquid fuels. Gasses are handled, but in much smaller quantities. Changing the infrastructure to deal with handling gasses is probably the most prohibitive part of using gaseous hydrogen as a fuel. And don't bother with liquid hydrogen. The handling issues associated with that are worse than compressed gas (insulation, boil-off vents, etc).
On the plus side, hydrogen is well suited to gas turbines and jet engines. Clean and efficient. It's just a bitch to store and handle.
When someone makes room-temperature liquid hydrogen, that'll be the day we all switch.
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The additive you refer to was placed into a jet that was deliberately crashed. The wing was severed in the process in a very spectacular manner, resulting in a tremendous fireball. At once the test was deemed a failure before any of the data was analyzed. Since it was 'expensive', the fireball produced all the justification the airlines needed to kill the project.
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.
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.
---
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Hindenburg exploded because its envelope was coated in the same chemicals that Morton-Thiakol uses in the Space Shuttle's solid rocket boosters.
It doesn't matter if I've eaten Taco bell or not, wearing boxers soaked in rocket fuel is a bad idea.
First of all, hydrogen isn't all that explosive. The Hindenberg situation was different from this situation in two ways: it was coated in rocket fuel (not known to be explosive at the time), which airplanes would not be, and it used the hydrogen for lift (lighter than air gas), rather than just for fuel.
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.
Reminds me of the adage "If frogs had wings, their asses wouldn't smack the ground when they land". There is a 0.00000000000000000% chance that future terrorist attacks will share any implementation details with the WTC attacks. This is just yet another example of someone trying to capitalize on the general populace's temporarily inability to think rationally. He may as well take out a full page newspaper ad, complete with a statement condemning "the cowardly attacks" by those "hiding in the shadows" augmented by a picture of his product's packing, or offer up a national I.D. card so that American Citizens can be more heavily identified.
I think the problem--and the solution--lies in our foreign policy. Will the Pashtuns, about to recieve aid from the West, be the next ones to bite us in the ass?
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They tend to use helium in blimps these days, since the gas doesn't have to burn at all; it just has to be lighter than air.
The Hindenburg's demise was not a result of an initial hydrogen-fueled explosion.
It caught fire because of the way the airship was designed, and how it dissipated the electrostatic charge that built up on the outer skin.
The ship's skin was a series of panels that were stitched (not really, more like tied) together. When the landing lines are lowered, the charge in these panels are supposed to flow through the entire skin of the airship and down the landing lines.
Because of poor design/construction, some of these panels retained their electric charge because of poor contact with their surrounding panels. The voltage between the charged panels and the non-charged panels was great enough to produce a spark.
BUT... the spark did NOT ignite the hydrogen.
The spark ignited the SKIN.
Since the skin had to be reflective to reflect heat, the germans coated the skin with a mixture that contained aluminum oxide powder.
Sound familiar? Aluminum oxide powder is used as solid rocket booster propellant in the space shuttle.
It was the fire on the skin that ignited the hydrogen cells. Hydrogen burns clear, and is barely visible in daylight. The initial fire on the airship was orange-red.
- Ben
I had to think about this for a minute, but look at the following. If the weight to energy ratio of jet fuel is better than hydrogen, they'd need to carry more hydrogen. More fuel adds more weight, and thus you need more fuel to carry the extra weight.
Of course hydrogen is flammable, but that's not the whole story of what happened to the Hindenburg. The simple story is that the discharge from the tower to envelope (or envelope to tower) started the envelope burning. The fire on the ship ignited the hydrogen in the gasbags, and the disaster resulted. A fire-resistant envelope would have prevented the fire from penetrating to the hydrogen, or would at least have held it off for quite a while, giving firefighters time to try to stop it. Also, hydrogen is no more flammable (and is less explosive) than jet fuel, and so in a modern vehicle (aluminum skin doesn't burn very well) it's not really an issue.
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These fuel cells will carry water or hydrocarbons. They will split the hydrogen out as it is needed
This got an "insightful" moderation???
It takes more energy to split hydrogen from water, than you get back by running the fuel cell on the hydrogen. This makes sense in some situations, for example a solar-power application where you can build up a supply of hydrogen when the sun's shining and then convert it back to electricity at night. It's like a storage battery, and as far as commercial aviation is concerned it'd be about as useful as a cargo hold full of lead-acid batteries.
As for splitting the hydrogen out from a hydrocarbon as needed, well, wasn't the whole point of the exercise to get rid of the hydrocarbons so that they wouldn't cause high-temperature fires in a crash?
Maybe there's a compromise, like using methane to power the jet engines (probably don't even need a fuel cell). Methane is a lot more volatile than traditional jet fuel, so it might disperse more quickly in a crash situation [and no jokes about the smell please; pure methane is odorless]. However this probably isn't economically viable.
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.
This
I don't know how feasible powering a plane with hydrogen is - I sort of follow hydrogen energy news and don't recall ever coming across any prototype jets or prop planes. I don't know that hydrogen could power a jet sufficiently. Storage methods (tanks etc.) are heavy, possibly too heavy for economical flight. I question whether this is a realistic scenario or just wild speculation.
The big problems with hydrogen are cost, lack of a production infrastructure, lack of a distribution infrastructure, difficulty of storage, and the unlikllihood of a widespread manufacture of any kind of hydrogen vehicle lacking resolution of all these other issues. Making a plane fly on hydrogen would certainly not be a simple "retrofit". This would be a transition from a liquid to a gasseous fuel with totally different combustion characteristics.
Hydrogen is clean to burn either chemically (fuel cell) or through combustion and simple (if not easy or necessarily efficient) to generate, and therefore may become a valid way to transform renewable forms of energy into a storable fuel, and to make energy from conventional fuels more efficeintly and cleanly. But I doubt very much it will be the fuel of choice in planes any time soon
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While hydrogen would not have burned like the jet fuel, I'm not sure it's practical in airliners because of the huge distances they travel. Hydrogen as a fuel doesn't provide a lot of bang for it's volume.
What really gets me is the possibility that abestos could have delayed the colapse for up to 4 hours longer. They stopped spraying asbestos in the buildings above the 64th floor becase NYC banned it. They were wetspraying, which was a technique used to eliminate asbestos from getting in the air. While we'll never know how long if any those building would have stayed up, the belief at the time was that asbestos would provide 4 hours longer before the girders melted, hopefully giving time to evacuate the building.
Asbestos, much like hydrogen has been demonized, somewhat unfairly. While there is no argument that it is not dangerous, there can be safe ways to utilize dangerous materials. Unfortunately people jump on these bandwagons too quickly to make informed decisions.
I remember when they removed asbestos from my elementary school, the teacher told us that dust from the ceiling tiles was asbestos, probably exactly what she thought. In actuality, it was normal dust, and the asbestos was covered by fiberglass and foil insulation, and was harmless, until they started scraping it all off that is...
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Even though it was a leak from the solid rocket boosters that caused the catastrophic ignition of liquid hydrogen and liquid oxygen in the external fuel tank during the launch of Challenger in 1986 (as pointed out by others), I do understand the extreme dangers of LH2. I have read that when the Challenger's external tank exploded it did it with the force of a 1 kT tactical nuclear warhead.
In fact, while hydrogen gas burns with a benign-like invisible flame that goes upward, LH2 will ignite with a force that makes TNT seem like a minor incident. That's why when Lockheed looked at building a LH2-fuelled Mach 2.5 spyplane in the late 1950's EVERYBODY worried that a LH2 fuel explosion would flatten everything in the equivalent of a couple a city blocks.
Indeed, if those hijacked planes that crashed into the World Trade Center was fuelled by LH2, the kinetic force of the explosion from the LH2 igniting would be so strong that the towers would probably have collapsed almost immediately.
Actually, yes, they have. The reaction to the Hindenburg disaster would have been, in jet powered aircraft terms, grounding jets world-wide for years. The Zeppelin aircrafts enjoyed tremendous success in Trans-Atlantic crossings and were an efficient, albeit slower, and far more comfortable method of travel. Consider, too, that they lacked all the modern advantages of satellite weather, radar and materials which would make them perform very well today.
Although, at the peak speed of a zepplin, one could still have done significant damage to a building such as one of the WTC towers.
Seems there was some bad movie back in the 70's, Black Sunday, or something about a Goodyear blimp being hijacked and run into a stadium full of football fans. Never saw it, tho.
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perhaps it would have prevented WTC from collapsing, but they still could of flown into it.
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Buildings eventually come down. Hopefully it's a controlled process after a long and useful life, to make way for a new building; or it may be due to natural or man-made disaster. When the inevitable end comes, you do not want a large building falling over sideways (IIRC, this was the objective of the WTC truck bomb several years ago); you want it to collapse in on itself.
So it's not a question of designing ot to collapse - it's designing how it will collapse when the time comes.
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There are no naturally occurring terrestrial sources of H2, so we have to manufacture it. The 2nd law of Thermodynamics says that any time we use energy to create energy, we're losing some energy. So the question is -- where does the energy to create the hydrogen come from?
Oil? We're back to the same pollution problems we had before, plus we'd use MORE oil than just burning it as a jet fuel.
Nuclear? That's probably the best solution, but we'd have to build new plants to create the energy, and then deal with the waste.
Wind or Solar? They are clean, but aren't economically viable yet. Who wants to pay $10,000 for a coast-coast flight?
Hydrogen doesn't really make economic sense yet, since most of the sources we could use to make it are either too expensive or are easier to use directly, without converting to hydrogen in the middle.
Then there are the storage problems. Hydrogen is a very low energy fuel, so the planes would have to carry a MUCH larger volume of it in order to achieve the same energy content. For airplanes, greater volume = greater energy costs.
How many people could a conventional 747 carry, if it was fueled by hydrogen - 4? 5?
Help find a cure for Gidget.
Way I heard it, the envelope was covered with a very flammable material for some engineering reason.
A hydrogen-powered aircraft would almost definately have to use liquid hydrogen as a fuel, as it's very unlikely that you could fit enough compressed gaseous H2 into an aircraft's fuel tanks. Liquid H2 is a bitch to handle and expensive to produce.
Also, remember that aircraft engines have to have a VERY high power/weight ratio. If your engines + fuel are too heavy, you don't have any payload capacity. It would be very difficult to build an air-breathing hydrogen motor that was suitable for aviation. It seems likely that any H2 powered craft would also need an oxidizer in order to generate enough power to carry a meaningful payload. This means carrying LOX (Liquid Oxygen) or some other oxidizing agent -- rocket fuel, in other words. Oxidizers are corrosive, explosive, and very nasty to handle; not somthing you want on a passenger aircraft. A planeload of H2 + O2 would probably make a far better weapon than one full of gasoline.
It's a nice idea on the surface, but I don't see hydrogen being a replacement for gasoline in aircraft anytime soon. The power requirements are just too high to get away without an oxidizer, the fuel would be expensive, and refuelling would be a logistical nightmare. It's an entirely different engineering problem than powering a ground vehicle -- for which a hydrogen-powered fuel cell IS a viable power source.
Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
in most parts of the globe, it's still wednesday, but many of those people are asleep. Some people are in thursday already, but it's definitely not friday where the show is produced (U.S.)....?
- passion
Yup, and taking away everything including people's tweezers means that only someone insane enough to not understand their odds of success would attempt to perform a copy-cat crime.
While the terrorists who crashed into the Pentagon and WTC were ruthless, they seemed to understand their chances of success very well. The next terrorist act (assuming there will be another one) will most likely be as difficult to see coming as this one was. And, in retrospect, it will probably seem just as easy to prevent, if only we'd been looking in the right place.
Dear hippie Earth child,
I'M NOT GOING TO WALK FROM NEW YORK TO LOS ANGELES!
Thank you.
"All your base are belong to this file I send in order to have your advice."
The main advantage to hydrogen is that it would disperse if there was a leak.
The main disadvantage is that its density is horribly low, even when liquified.
Why not use propane instead? It too will disperse (though it'll drift down instead of up), and it can be stored at a density approaching that of gasoline.
If you want something that won't pool, ethane will work, though that's harder to liquify by pressure alone. It's about as dense as air, and so will just tend to spread out if released.
Methane would drift upwards, but you'd need a cryogenic tank to hold liquid methane. Much higher energy density per unit _volume_ than liquid hydrogen, though.
Unfortunately, I think people forget that hydrogen-fuelled jet airliners would likely use liquid hydrogen as its fuel.
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.
Hydrogen isn't a naturally occurring fuel. We're dependant on oil today because it IS a naturally occurring fuel, and therefore cheaper to use than other, man-made fuels. If we were to use hydrogen as a fuel, we'd have to burn MORE oil to produce the hydrogen than if we just used the oil directly.
How does that help matters?
Help find a cure for Gidget.
Ok, I'll bite. Here's an example from Chemistry: 2H2 + O2 -> 2H20. This reaction is spontaneous at room temperature. However, if you release a bottle of H2 into air (which contains a lot of 02), it won't burn. Know why? Activation energy. You have to have a match to jump over the Energy of Activation barrier.
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.
There are reasons why democracy does not work nearly as well as capitalism.
-- David D. Friedman
Ok, after reading this article and many of the replies, I have come up with some observations.
First, the planes would be using liquid hydrogen, not gaseous, so all the comments about needing to compress the gas, or contain the gas, or the gas not having as much energy as jet fuel need to read the damn article!
Secondly, there are about a zillion different opinions based on guesses and I didn't see a single person who was qualified (at least no one say why they were qualified) to say what would happen when the plane hit a building. It's all just a bunch of speculation.
Third, we know what caused the Hindenburg to explode. About half the messages are saying that it wasn't the hydrogen, it was the coating. It should also be noted that the Hindenburg was not filled with liquid H2 so the comparison again is not really valid.
What I'd like to see is someone who works with H2 in a liquid form to post their thoughts on what would happen based on their own observations and experiments with liquid H2. The closest I saw was one individual who talked about seeing the drops of H2 liquid just kind of floating downwards instead of just falling like water.
The other point is that I saw many posts saying how H2 contains a lot of energy, and others saying it contains very little. Logic would say that one of those is wrong. Once again, I would like to see someone who knows what they are talking about post something and include either a reference or a credential, or something to compare H2 and jet fuel in regards to energy density.
I guess this is slashdot, I'd just like to see more people that do know what they are talking about post and less people that think they know what they are talking about claiming that they do... But again, this is slashdot, so I cannot expect much different.
<-- end rant...
I'm also interested in reasons why this system might be practical or not practical in automobiles, if anyone feels like going a bit off topic
I don't care if it's 90,000 hectares. That lake was not my doing.
Right, but helium is 4 times the weight of hydrogen (yes weight, not mass), so it doesn't work as well.
You'd think that he'd charge less then $28 considering he's a complete idiot! Using liquid hydrogen to power jets is just one of his ideas, and it could be an OK idea. His grand plan, which is the subject of his book, is not to power just jets with hydrogen, but that he thinks we should replace all our power generating machines with hydrogen fueled devices. This includes nuclear power plants. Where does he propose we get all that hydrogen from? Solar and wind power. He says we'd only have to cover 0.1% of the surface of North america with windmills to generate the power. When he comes up with that number it seems like he fails to take into account that you are going to get far less energy out of the hydrogen then you put into refining and condensing it. There is 18.8 million square miles of area in North America, so he is proposing we build enough windmills to cover at least 18,800 square miles. The guy's a loon.
Oops.. I just read it again. He actually said we'd need 0.5% of the area... That's 94,000 square miles... Even worse.
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.
The Challenger violently exploded because of the liquid oxygen. Fuel is important, but oxidizer is usually the limiting factor.
Dave Barry (iirc) even covered this in a column on the world's ultimate barbeque grill. Charcoal brikets, hardly an explosive, a tank of liquid oxygen, a lit cigarette in the charcoal as an ignition source, and a long rope. One tug, *boom*, and the charcoal burned fast enough to vaporize most of the cheap grill. In the Challenger explosion, you had that oxidizer dumped into the middle of gaseous hydrogen so there was an even quicker burning than you have with charcoal and its relatively low surface area/fuel ratio.
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
The simple answer is way the Hell too much. The airline industry (and the leasing industries associated with it) operate on very tight profit margins. Just look at how disasterous the last month has been for the airlines. They are NOT going to be paying to design, much less paying to install, an entirely new type of engine. The bill would be trememdous!
My father runs a small aircraft leasing business, and basically the industry, which already had a glut of aircraft, is looking at total and utter devestation. This is an industry where every time the government imposes new noise level limits for aircraft, firms go out of business by the dozens. His firm is small enough to find a way through it, and well diversified besides, but the firms that own most of the aircraft that the airlines fly, firms like GE Capital, are going to take huge hits. There simply will not be any money available for refits, and barely enough to meet government mandated maintainence checks, much less a project of this magnitude.
"The question of whether a computer can think is no more interesting than that of whether a submarine can swim" -EWD
Like most flammables, Hydrogen doesn't truly explode unless it is contained. It will burn rapidly, but it is the container that causes shrapnel.
Advantages of H2:
--being lighter than air, will rise upwards before it ignites,
--the combustion product of hydrogen is H2O, better known as water. None of the nasty smoke that kerosene, plastics and the like put out.
The reason you don't see it in cars is twofold. Fuel Cells are very expensive, and storage of a significant amount of H2 is difficult. It is either highly pressurized or stored in a heavy metallic matrix.
I suppose you can add to that that Hydrogen filling stations aren't on every street corner yet.
Michael
(Most likely, they'd use plain hydrogen, which has no neutrons, and merely reacts with any element on the further side of the periodic table. Which means you REALLY don't want to collide with a tanker containing fluorine.)
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
True, you don't need to burn oil to get hydrogen, but you do need an energy source. While H2 may be the most abundant element in the universe, it isn't just sitting around waiting for us to pick it up (at least, not on Earth). To get H2 from the oceans, we'd have to use more energy to liberate the hydrogen than we'd be able to get out of the hydrogen thus libreated (2nd law of Thermodynamics).
Where does that energy come from? Well, today, the bulk of our energy comes from oil, so that's why I said we'd need to burn more oil to make hydrogen than we would if we simply used the oil directly.
Help find a cure for Gidget.
I don't know if you're joking, so I'll be pedantic...
If a molecule weighs four times as much, any given volume of the gas (in the same conditions) will weigh four times as much. Molecule size is (mostly) irrelevant when considering the number of molecules / volume.
The pressure vessel could burst violently, but it would not be thousands of degrees---decompressing something cools it off. Then you would have 60,000 lbs of hidrogen gass which would burn but not explode. It could only explode if it were mixed with oxygen correctly. The resulting 60,000 lb ball of hydrogen would burn on the edges but at the same time it would be dicipating.
--Ben
Re-read your point #5. You start by saying the fire was not a signifigant part of the collapse, but then your further explanation says just the opposite. Was this just a writing mistake or am I missing something?
Don't label something "offtopic" unless you know the topic well enough to tell what's on topic.
The fuel handling problems would need to be addressed, but I think the bigger problem is where does the hydrogen come from? There's no naturally occurring H2 supply on Earth, so we'd have to manufacture it (probably from water). The energy it takes to manufacture hydrogen is much greater than the energy that would be released by burning it. It really makes a lot more sense to just directly use the energy that would have gone into hydrogen production.
Help find a cure for Gidget.
How many more times do you think there will be a coordinated group of hijackings of airplanes which are then flown into buildings?
I'm thinking that it was a one-time shot and the terrorists will come up with a new idea for the next attack. They're pretty creative when it comes to mass destruction.
I mean, if a terrorist does hijack a hydrogen powered plane and flies it into the White House, being hydrogen powered probably wont help too much.
-J5K
The libertarian solution to the failures of capitalism is to apply more capitalism til the failures are fixed.
(When Oxygen and Hydrogen reacts, to form water, you get energy. You must put in EXACTLY that amount of energy to seperate them again. Any less is no good, and any more than that, you're losing out, since you won't get the difference back, later.)
The best "fuels" are those which are already in a form that can be used. The reason being is that you're otherwise playing the Great Energy Shuffle, just moving energy round, and loosing some on every conversion. (See Thermodynamics, Laws Of, II).
Really, the entire concept of a "terrorist-proof" aircraft is as futile as a child-proof bottle, an indestructable toy or a secure web server. You are much better off to confine and limit the problem. Sure, the hydrogen solution does this, to some extent, but in ways that could produce still worse problems. (Hydrogen hits the chlorine vapour in the air conditioning, and merely dissolves the locals, rather than incinerates them.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Seastead this.
Yes, the fuel in the shuttle ET had a lot of energy. This is a necessary property of rocket propellants. Hydrogen, kerosene, whatever would have burned to produce a large energy release in the Challenger accident. Note that the hydrogen there did not *explode* in the sense of detonating, it just burned rapidly (without a detonation wave being produced). And this burning did not cause the accident, or destroy the orbiter -- the orbiter was torn apart by being thrown sideways into a supersonic airstream.
But it wasn't the impact of the planes that brought down the towers. It was the intense heat created by the jet fuel-fed fires caused by the planes that truly spelled the end for those buildings.
Perl - $Just @when->$you ${thought} s/yn/tax/ &couldn\'t %get $worse;
> Hydrogen as safe alternative fuel... Um... Hindenburg, anyone?
Two points: the Hindenburg burned because of the envelope, not the hydrogen (see the many posts explaining this), and the Hindenburg used diesel fuel for power, and hydrogen for lift.
> No, it wouldn't burn for a sustained time, like jet fuel did,
> but it would burn even more violently, hence causing more initial
> injuries. In fact, a more violent explosion mith have collapsed
> the towers right away, and those 10,000 or so folk wouldn't have
> had the chance to escape like they did.
Not likely a problem. Most of the experts consulted believe that the sustained fire is what caused the collapse of the buildings. As the videos show, the force of the initial explosions was mostly external anyway (remember that huge fireball?) so even if the force of the hydrogen was significantly more powerful (which it wouldn't have been, for reasons below), the extra force would simply have thrown debris farther, not done much more damage. It's very likely that if the planes used to hit the WTC towers had been hydrogen powered, they'd still be standing. In addition to not having burning jet fuel all over the building (which actually trapped people in the floors directly below the impact, by running down the stairwells), the force of the explosion would tend directly out along the impact vector, then upward. The rapid expansion of the hydrogen as it escapes the tanks tends to inhibit explosive force (increase in volume means decrease in temperature and pressure), so the extra force gained by the fact that hydrogen burns very efficiently is offset.
> Then there's the issue of storage... wouldn't high-pressure
> crtyogenic fuel tanks be prohibitively heavy for an aircraft?
Yes, they are, and that's why hydrogen fuel cells aren't more popular. Once that problem can be solved (materials scientists have been working on this for a long time, mostly for space vessels) hydrogen has a chance against fossil fuels, but not until then.
Virg
Not so. We're not CREATING fossil fuels, we're just picking them up out of the ground. The 2nd law of Thermo doesn't apply to drilling for oil in the same manner it applies to creating hydrogen.
Help find a cure for Gidget.
On a related note, it's only three weeks till mol day!! Aren't we all excited?
I don't want free as in beer. I just want free beer.
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.
When people talk about Hydrogen powered aircraft, they are talking about using rocket engines, not fuel cells. Using hydrogen as a fuel pretty much dictates that you need to use an oxidizer as well, as there is not enough free oxygen in the atmosphere to get the energy levels required for flight. Liquid Oxygen is nasty stuff; you don't want to get it anywhere near a flame.
Also, fuel cells don't have a high enough power-to-weight ratio to get an airplane off the ground. To move an airplane (or a car, for that matter) you need KINETIC energy. Fuel cells produce ELECTRICAL energy. In order to convert the electrical energy into kinetic energy, you need an electric moter. Electric motors are nowhere close to having the kind of efficiency needed for an aircraft engine.
Why is it that the proponents of "one nation under God" are so eager to get rid of "liberty and justice for all"?
Even at 5000psi, it's still a relatively low energy density compared to refined petroleum products.
Mr. Ska
> Isn't sugar a hydrocarbon?
No, sugar is a carbohydrate, not a hydrocarbon. The difference is the "-ate", which is chemist's talk for "oxygen", which means it only works for fuel if you "-ate" it. However, after eating enough sugar, I could power a jetliner with my fidgeting....
Virg
/.
Excuse me? Speaking as an ex-employee of Thiokol Chemical Corp. (was briefly Morton-Thiokol, but only until the salt boys finished stealing Thiokol's diversified holdings, bankroll, and reputation) I'm wondering exactly which chemicals you're talking about.
I've watched the Hindenburg film and it sure looks like burning hydrogen gas to me. And burning magnesium, wood, and aluminum, too - granted. But what are these "same chemicals" you are referring to?
I don't think Thiokol's produced an explosive fuel compound since the sixties.
--Charlie
One of the ongoing ways to make plane crashed more survivable is research into jellied fuel. The big problem with jet fuel is that it atomizes very easily, and that creates nasty fire clouds surrounding the plane.
I don't think it would have helped in this case, though.
It doesn't mean much now, it's built for the future.
Jet fuel is a far cry from diesel. Relative to jet fuel, diesel may as well be crude oil.
I dunno...I know some chicks who dig some pretty weird stuff - but probably not that weird.
I'm the stranger...posting to
A few days after the attacks, I read an interview on either the jeruslaem post or haaretz daily's websites with an architect who had been one of the lead designers for the WTC towers. He compared the construction of skyscrapers in the US (steel frame) and Israel (reinforced concrete).
Architects know steel is more vulnerable to damage by fire than concrete. So the WTC structure was encased in concrete to provide additional time to evacuate the building. IIRC, he stated that they did not expect the building to survive a fire such as the one following the crashes, but to survive long enough to evacuate following impact of a smaller aircraft (B-707, I believe). Designing a building to be "safe" against all threats is impractical - you have to make a tradeoff at some point.
As to why Israelis use concrete and not steel, it's a matter of cost. Reinforced concrete is far cheaper in Israel than structural steel. In the US, lower costs for steel and resulting faster construction times overall make steel a better choice.
also, don't change the supply voltage from 28 to 65 volts along the way, causing the thermostats to weld themselves shut. This will then lead to the failure of teflon insulation on the power leads, and make a big boom once you put power into those leads.
There are good reasons to overengineer things, to compensate for stupidity and the unknown. We need a good safety net, even if it doesn't always make sense to the MBAs of this world.
--Mike--
The Challenger didn't run on pure liquid hydrogen, but on a special compound called Hydrazine ( H2NNH2), which is VERY explosive (and corrosive too if I remember correctly) and extremely reactive. It will never make a safe commercial fuel for airliners, if for no other reason than manufacturing and safe storage costs.
To make things more interesting, it's also highly toxic (hydrogen - h2 - is not).
Osha comments on it as:
1.1.2. Toxic effects (This Section is for information only and should not be taken as the basis of OSHA Policy.)
Hydrazine is a severe skin and mucous membrane irritant in humans; in animals, it is also a convulsant and a carcinogen. In humans, the vapor is immediately irritating to the nose and throat and causes dizziness and nausea; itching, burning, and swelling of the eyes develop over a period of several hours. Severe exposures of the eyes to the vapors causes temporary blindness lasting for about 24 hours. Recurrent exposure to hydrazine hydrate has been reported to cause contact dermatitis of the hands without systemic intoxication.
In humans, hydrazine is absorbed through the skin, by inhalation, and orally; systemic effects include weight loss, weakness, vomiting, excited behavior, and convulsions; the chief histologic findings are fatty degeneration of the liver and nephritis. (Ref. 5.6.)
Of course hydrogen still reacts well in the presence of oxygen, but unlike hydrazine, requires a spark or other catalyst to start cumbustion.
- The Ravnos
FreeSpiritMind.com
Kyndar: Exotic Imports, Jewelry, Candles, and Incense http://www.kyndar.com
Don't forget that the SR-71 was developed from a lot of work that went into designing a hydrogen fueled aircraft.
Yes, one of the more entertaining parts of Skunk Works, IMHO, is the section where Ben Rich talks about his research and experimentation with liquid hydrogen.
~Philly
A witty saying is worth nothing - Voltaire
There safety of hydrogen as a fuel source depends on how it is stored in the aircraft.
One method of storing this is just to store it as a compressed gas. This is not a very efficient way to store it, and it will have considerable negative impact on the range and or cargo capacity of the aircraft. In other words, air travel would get a lot more expensive and more rare. Not likely to happen. This method would also be dangerous because a rupture of a compressed hydrogen storage tank would release a lot of energy just from the bursting of the pressurized tank. The hydrogen would then be mixed with the surrounding air in a potentially VERY explosive combination, much like an FAE bomb. It is unlikely that a large portion of the hydrogen cloud would have the right fuel/air mixture to explode, but even a small percentage would be a big explosion. In an open area a large portion of the hydrogen might escape without burning, but in an enclosed area like the WTC, a large portion of it would probably still have burned. No benefit to using this method, and a lot of negatives.
The Hydrogen could be stored in a metal hydride. Basically the hydrogen is "soaked up" into metal like water soaking up into a sponge. Amazingly you can get quite high hydrogen storage densities with this method, even higher than storing it as a compressed gas. It will be much less of a fire hazard than conventional jet fuel. The hydrogen will not come out of the metal-hydride "sponge" all at once; so even if there is a fire it will be a small but long fire instead of a big, quick one. This method will be even safer because of the fact that the planes will never leave the ground. Metal-hydride may give good storage densities for automobiles, but the fuel tanks would be way too heavy to use on an aircraft.
The third method is cryogenic storage, as either liquid or slush hydrogen. This method gets the best storage densities as hydrogen storage goes; but it is still a lot less dense than normal jet fuel. That means you still need much bigger fuel tanks to get the same range. This might not be more expensive (and might even be cheaper) because of possible engine improvements. But you have the problem of handling a cryogenic fuel, which adds to costs (and the possibility of a ground crew injury). Then you have the problem of where to put the fuel. There isn't enough room in the wings to put all the fuel there, like is done with normal jet fuel. One possibility is to put it in the fuselage, but that is VERY dangerous because you now have the double threat in a crash of killing the passengers with cryogenic hydrogen before they have a chance to be killed in the resulting fire. Putting the extra tanks out on the wings makes sense from a structures point of view because you have shorter load paths, and would get the cryogenic fuel somewhat further away from the passengers; but it still would not eliminate the fuel as a risk. Yes a puddle of liquid hydrogen WILL burn. As the liquid boils it mixes with the air, creating a flammable mixture. As the mixture over the puddle burns the heat increases the rate of boiling of the puddle. This is actually not too different from what happens when a puddle of non-cryogenic fuel burns. Will it be less of a fire hazard? Maybe. A hydrogen fire will not emit as much thermal radiation, which seems safer; but for the same reason it is invisible and therefore harder to fight (a problem that might be solved with trace impurities). In an open area a hydrogen fire will dissipate more quickly and cover less area, but that doesn't apply to the WTC case because it wasn't in an open area and hydrogen might have actually been worse because of the possibility of explosion instead of just fire. I also wonder what that high a volume of cryogenic hydrogen would have done to the steel structure upon impact; the huge temperature swings from ambient temperature to cryogenic to a hydrogen flame might have caused the collapse to happen sooner. In a normal crash that happens in an open area hydrogen is theoretically safer, but modern jet fuel is not as explosive as most people believe, thanks to evolutionary refinements in its composition and I have not seen any full up aircraft tests (such as have been performed with modern jet fuel) that assesses the added hazard of storing large volumes of cryogenic fuel in a passenger aircraft.
On the plus side, hydrogen powered aircraft could have smaller (possibly cheaper and more quiet) engines. They would not pollute as much (though they still generate NOx). Despite the extra tankage, the aircraft might even be lighter and cheaper. It is possible, therefore, that a fleet of hydrogen-powered airliners might be cheaper to buy and operate than a fleet of normal ones. Or at least it would be if you didn't have to factor in the capital cost of rebuilding the entire fuel production, fuel transport, and refueling infrastructure. But of course you do. If something (a huge terrorist campaign or a sudden shortage of oil) were to wipe out our current fuel infrastructure and we had to rebuild it from scratch, then we might want to look at hydrogen again. Until then it will take a revolution in fuel storage density, hydrogen production and transport technology, or some new super hydrogen-only super engine to justify junking a fuel infrastructure we have already paid for.
This is not a new idea. Hydrogen has been considered as an alternate fuel in airliners since at least the 1970s. There are good reasons why it has not been adopted.
Bottom line, for now liquid or slush hydrogen is the only practical storage method for large aircraft. Even then, the storage densities of Hydrogen suck. Fire hazards are safer, but it almost certainly would not have prevented the WTC collapse (it might even have hastened it). The added hazards of cryogenic fuel (especially if stored in the fuselage) may more than make up for the reduced fire hazard. Like so many other technologies, it offers the tantalizing potential for reduced costs; if only we didn't have an already-paid-for infrastructure that supports the current technology of choice... but we do. If you are building a scramjet then it is probably worth the effort to put up with the extra tankage and the cryogenics and the custom fuel infrastructure. If you are building a passenger jet, then you are just asking for more cost with only incremental benefits that have yet to be demonstrated in full up testing. If the gov't wants to help this along, they could have an X-plane program to demonstrate full up development of a hydrogen cargo plane or bomber (the engineering would be similar enough to a civilian airliner for lessons to carry over), then slam one of the planes into the ground in a simulated crash when the program is over to get data on the actual safety of large hydrogen powered aircraft. Until then, the technology will (rightly) lie dormant until something makes it more economically attractive (i.e. a more efficient use of resources).
References: Hawkins, W.M. and Brewer, G.D., "Alternate Fuels Make Better Airplanes: Let's Demonstrate Now," _Astronautics_and_Aeronautics_, Sept. 1979
Raymer, D.P., _Aircraft_Design:_A_Conceptual_Approach_, AIAA, 1992
I don't know off the top of my head. If you've seen the Hindenburg film, then you haven't seen hydrogen burning. Hydrogen burns almost invisibly, with a dark blue flame, not billowing red and orange flame.
Basically the gist of it was that the envelope was doped in a sealant that uses the same chemincal composition as solid rocket fuel. An electrical discharge (static charge is the commonly accepted source) ignited the envelope. It burned for quite a while before the hydrogen exploded.
It was ages ago that I did a report on a number of different kinds of fuel, and the information could have been out of date by that point, for all I know. Somebody mod Mista Blue Informative. :>
I didn't realize that 1800 to 2000 C was relatively cool .
-- @rjamestaylor on Ello
You don't use fuel cells in jets. You pump the H2 directly in, its just a fuel that burns and creates thrust. It even works better than JP-4 (jet fuel) because it gassifies at STP. No sprayers or injectors required.
********* sig: If you don't like the law, get filthy stinking rich, and buy a better one.
The oil companies already know this and have started calling themselves energy companies for a few years now. Hydrogen, whether you get it from biomass as methane (for those environmentalists out there) or out of the ground via natural gas or whatever, it's still a profit opportunity for these firms and they are busy gearing up to take advantage of the opportunity. Eventually, we will get the direct hydrogen infrastructure because it's simpler and cleaner but the vicious circle is broken, the multi-fuel aspects of fuel cells mean that we can shift from one fuel to another as infrastructure matures and we will never again have to pay homage to the sheikhs or anybody else because the fuels are so varied that nobody is going to be able to get monopoly power over all of them.
Since the oil companies are very aware and actually seem to like the idea of varying their markets and profit opportunities, I'd guess that the two Texas oil men in the White House are going to grease the wheels and make the hydrogen transition as easy as possible because it's going to make their campaign contributors lots of money, is going to clean up the environment, and is going to erase the US' national security vulnerability due to dependence on foreign energy sources. That's a very rare political three-fer.
DB
The Hindenburg accident, with all it's 'nasty explosive hydrogen', resulted in a lot more survivors than any modern jet-powered aircraft, which basically ignite into gigantic fireballs immediately upon any sort of impact.
A hydrogen fueled aircraft accident would at least allow the structure of the aircraft to give its passengers a chance or two in hell of surviving the impact, rather than going up in flames every time no matter what.
**>>BELCH
I'm not sure what you're getting at...
You'd agree that a litre of hydrogen at STP and a litre of helium at STP both have the same number of molecules, right?
So molecule size (ie, "4 times as massive") is irrelevant, when considering gasseous storage. Right?
Of course, I guess hydrogen would be stored as a liquid, so it's a moot point.
It's true that fire suppressing foam can be nasty stuff, but it's not usually outright poisonous. One problem is that foam works by smothering out the fire, and if a person got caught in the foam blast, they'd have the same problem, as humans and fires both need a constant supply of oxygen. However, the main reasons water is used are:
1.) Water is cheap compared to foam.
2.) Water is sufficient to put out most building fires (grease at Mickey D's and jet fuel excluded).
3.) Water is cheap compared to foam.
4.) Water is not very likely to kill someone caught in the suppression zone like halon can.
5.) Water is cheap compared to foam.
Virg
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?
Friends don't help friends install M$ junk.
High speed nuclear powered aerial gondolas.
--Blair
"No? Dang."
> One place this did happen was (IIRC) in the 1930s. During heavy fog, a twin engine biplane rammed the Empire State Building.
The plane that hit the Empire state building in dense fog was a B-29 bomber (four engines, single stage wings), and it was in 1945.
Virg
The hydrogen-oxygen fireball didn't destroy Challenger, it was destroyed by the aerodynamic forces that occurred when the external tank disintegrated and the orbiter lost attitude control. At those speeds, any loss of control is likely to be catastrophic.
Mea navis aericumbens anguillis abundat
You mis-read the article and/or the temperaure.
l _L eak_Simulation.pdf
e ne rgy/sol_thermal/powertower.html
It is probably about 3,500 degrees, not 60,000. A 60,000 degree temperature is 6 TIMES HOTTER than the Sun, which is only at 10,000 on the surface, and where the corna gas is at 100,000 degrees it would take more than a cubic mile of that very thin plasma to warm a cup of coffee.
Hydrogen would be a VERY SAFE fuel, either as a liquid or a gas. Here is a url of a paper demonstrating the difference. A Hyrdrogen powered car is MUCH safer than a gasoline powered car. First, gasoline is much heavier than air, and a leak would result in flashback ignition, even if the ignition source were many many feet away. Secondly, Hydogen burns UP, not down. Even the liquid form vaporized into gas much lighter than air, so it won't accumulate or get trapped. The Challanger disaster was caused by the leak in the solid booster burning a hole in the liquid Hydrogen tank. Seventy seconds into the flight, just after maximum powerup, the tank ruptured, spewing liquid Hydrogen into a Mach 5 slipstream, instantly vaporizing and igniting the Hydrogen. The rupturing liquid Oxygen tank added to the malstrom, a factor that wouldn't be present in most Hydrogen fires related to cars or planes.
http://www.eren.doe.gov/hydrogen/pdfs/Swain_Fue
The USA and the rest of the Free World needs to began a "Manhatten Project" designed to covert our countries to Hydrogen. The best way is with Solwer Power Tower II installations. Excess power can be used to convert non potable water to Hydrogen , releasing the Oxygen to the atmosphere.
http://rhlx01.rz.fht-esslingen.de/projects/alt_
This technology is 'low tech' and could be built and maintained by craftsmen in any community.
Running with Linux for over 20 years!
While the paint on the outer skin may have started the fire, the diesel fuel used to power the engines actually caused most of the deaths due to fire.
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.
Courtesy of the Anonymous Coward who replied but has not been modded up yet:
Supposedly, no one wanted to figure out how to make a fuel pump for diatomic flourine. It would dissolve even the hardiest fuel pump in seconds. It also produces some nasty byproducts, including Hydroflouric Acid which makes Sulfuric Acid look as mild as vinegar.
Does anyone know if anyone has made a Fl-H rocket engine? Has it flown?
The bitter lessons of a veteran coder: http://bitterprogrammer.blogspot.com
I don't think you quite understand, fuels such as ethanol, methane, natural gas, even gasoline are converted inside the vehicle/generator before they get to the actual fuel cell. The major energy transportation systems don't have to change on day 1 to allow for proper hydrogen distribution. New construction will eventually take care of the problem of piping pure hydrogen but you won't need to bottle the stuff and transport it, just use current fuels or home grown ones like methane or ethanol that may be locally available but currently unusable for transportation needs.
If you really wanted an airplane that did not have any explosive or flammable fuel on board, there are two options.
One, of course, is physical energy instead of chemical energy. I am, of course, refering to a big rubber band. I had a small model airplane that worked on the same principle when I was young. Of course this is not practical, since range would be incredibly short.
The second solution would be to use nuclear energy. A small atomic pile could provide power for the engines. A heat exchanger could take heat from the reactor and input it into the engine in place of the normal fuel combustor. Considerable research was done on this concept during the 1950s and 1960s and the theory is sound. I am sure that some people are going to immediately complain that this design replaces the danger of fire with the danger of a release of radioactive material in the event of a crash. I am happy to report that as part of the Nuclear Aircraft research previously mentioned a reactor design was developed that could survive a high-speed, worst-case-scenario crash without releasing any radioactivity. The technology was demonstrated by slamming a prototype into a hardened concrete target at the aircraft's top speed. Given the current advances in materials and nuclear technology since the Nuclear Aircraft program, surely even greater safety could be achieved with present designs.
I do not expect either of these solutions to be implimented, but then I don't expect to see Hydrogen airliners either (or at least until oil gets a LOT more expensive).
Light a large quantity of kerosene or even heavy fuel oil, and it "goes poof" better than gasoline. Ask any military demolitions man or firefighter. It's not real easy to light, but crashing an airliner provides more than enough ignition.
Of course, what brought down the WTC wasn't the bang but the continuing fire. Jet fuel stayed mostly on the floors that were originally hit and kept on burning as air came in through the blown-out windows, until after an hour or so the heat soaked through the concrete cladding and softened the steel posts. I think even liquid hydrogen would have evaporated too fast to do this. It would have made quite a flash and wiped out a few floors, then had to vent out of the building to find more air, and soon been all gone.
As to why H2 isn't used for jets: It's a bitch to store and transport. You need fuel tanks several times as large, even for liquid H2. And finally, in the system we have now H2 would be derived from fossil fuels, with enough energy lost there to make the overall cycle less efficient than directly burning the fossil fuel. You'd use more oil, not less (unless you based the cycle on coal), and put more CO2 into the air...
A little knowledge is a dangerous thing.
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.
If anyone is familiar with the theory well enough maybe he/she can explain what would happen if some plutonium fell into a tokomak plasma generator? Basically the question is what happens to a heavy radioactive particle if it is hit with billions of overheated neutrons and some He4 alpha particles? Would there be an electrical discharge?
You can't handle the truth.
It's true, if the plane were filled with Hydrogen instead of jet fuel there wouldn't have been that big orange fire... There'd have been a big BLUE fire, and a nice explosion to boot.
For the people who want to say that Hydrogen is perfectly safe, I have two words for you: The Challenger. Space shuttles run on Hydrogen after all, so I guess there's no danger of explosion or fire....
This guy is an opportunistic fuckwit, and nothing more.
Not necessarily. A jet turbine could be built with just about any flammable fuel, although its geometry and compression ratios would be different for anything but Jet-A... Jets already compress the incoming air to improve combustion efficiency. I'd like to see the math. Anyway, newer fuel cells are getting smaller and lighter...
Also, fuel cells don't have a high enough power-to-weight ratio to get an airplane off the ground. [...] Electric motors are nowhere close to having the kind of efficiency needed for an aircraft engine.
Again, let's see the math. Electric motors are extremely efficient, but I tend to agree that the weight of the electric motors and their energy supply has made electrical propusion undesirable for airplanes (although you can get one off the ground, it won't go far or lift much). But I'd be interested to see whether we can do better with current or nearly-here tech. That fuel cell we heard about earlier this week was about half the weight of equivalent batteries, wasn't it?
I suspect that a turbofan is still more likely, but who knows, if we can get the fuel cell membrane incorporated into the skin or structure of the plane (to take advantage of free oxygen and reduce added weight) and maybe supplement with solar power (planes spend a lot of time above the clouds, especially going west), maybe it would be do-able.
Also, H by itself doesn't contain any usable energy that we can liberate (except through nuclear reactions). The energy that you can liberate by burning H2 is actually less than the energy it takes to separate existing H out of whatever molecular bond it's already in, to make it into H2. So, in essence, by electrolysis, or whatever method we choose to use, we are "creating" H2, in the same way that if we combined gaseous H2 and gaseous O2 to get H2O - we would be essentially "creating" water out of its constituent components.
Refining oil is not the same at all - we already have the really long carbon chain, which contains a fair amount of usable energy. To liberate that energy, we burn the oil as a fuel - in whatever form we need it - fuel oil, gasoline, kerosene, etc. All forms already contain energy, we're just releasing it through an exothermic reaction. The energy that we put into refining doesn't actually add any energy to the oil, we're just changing it's form somewhat to make it easier to use. All of the energy we get out of it is already there.
Think of it this way: burning oil is like dropping a brick from the top of a building. The potential energy already exists, we're just releasing it. "Creating" and then burning H2 to release energy is like picking up a brick, climbing the stairs to the top of the building, and then dropping it off. There's no useful potential energy in the brick until we climb the stairs to the top of the building to increase the energy. However, in "useful" terms, it's usually better to use the energy it would take us to climb the stairs and drop the brick by directly throwing the brick. Same results, less energy used.
See the difference?
Help find a cure for Gidget.
Simple -- use nuclear power to crack the water. This does actually mean we need to build some efficent recyclers for spent fuel (we don't have any commercial ones AFAIK). That would seriously reduce the output of nuclear waste from these plants, but even if we don't the nuke plant doesn't have to fly over my house at 300+ knots.
Ok, those of you who don't beleive in nuclear power can consider your favorite power source, but the point is that H2 combustion permits you to move the power from a fixed site, to the airplane (just like we move fossil fuels from where they are), and in general it's a lot more feasible than using those other sources in the plane. Anybody care to comment on the efficiency of h2 as a power transmission medium?
The DOE site points to the ttcorp.com site, also mentioned in another 5-modded post. Ttcorp.com has changed its URL for that directory ("nha") to point to hydrogenus.com, the official site of the National Hydrogen Association. The NHA promoted the study and produced an "informative video", Correction History: Hydrogen and the Hindenburg, with an introduction by U.S. Senator Harkin. This so-called "exoneration of hydrogen" was done by a single "retired scientist" and "hydrogen advocate", without peer review.
It seems to at least raise questions of credibility when the primary evidence comes via an industry trade group with an overriding interest in promoting hydrogen, which has gained the favor of a US Senator (lobbying money perhaps?), promoting the research of an unaffiliated researcher's study (could the NHA have been funding him?), which they report without citing any other substantiating studies, scientific journals, or scientists.
The lone researcher's findings were introduced into the Congressional Record, as US Senator Harkin (same guy from the video) presented them to the President of the United States, citing as apparent substantiation that the findings had recently been reported on the cover of Popular Science(!). (For those not familiar with Popular Science, it's a pop newsstand magazine, not a peer reviewed journal). The article itself was also included in the Record, and you'll note that there's a fair amount of discension even within the article.
As others have pointed out, the coating was certainly a factor. As was the weather, and bad luck. But by any conventional accounts, so was the hydrogen. And if you read what the lone scientist writes and listen to what he says carefully, you'll note that he never denies the role of hydrogen in the disaster, he merely promotes the role of the fabric covering. The National Hydrogen Association takes it a step further, with press releases and lobbying efforts about hydrogen being "exonerated," and the coating being "to blame."
I don't know, I'm not expert, but it looks to me like the NHA has done an effective job of rewriting history (or "Correcting History" as their video is called). Type in "hindenburg" and "hydrogen" into Google, and the first hit is to the NHA's site (redirected via ttcorp.com), and most of Google's other first-page hits are unquestioning coverage of the same single researcher's theory. Given the impact it had on this thread, it's disturbing how effective such a simple tactic can be in swaying public opinion.
The intense heat may have caused the towers to collapse which cause thousands of deaths, but the intense heat would also have sterilised any attempt at biological warfare which could have affected millions. This sprang to mind following the hype and the sales of gas masks etc when CNN was waffling about the threat of biological warfare regarding these attacks. Of course there are better methods (eg putting in water supply) but just a thought.
Phillip.
Property for sale in Nice, France
Besides close packing, this limits the rate of release. To some extent, the rate can be tailored (to, say, 120% of maximum consumption in nromal operation). In the case of the WTC, the slow release would have resulted in a slow burn rather than an ultra-hot explosion (the big orange flash just after the second plane got eaten by a building). If the fuel tanks were thoroughly enough ruptured, the H2 concentration might even be too low to support continuous combustion.
As well as all of this, H2 doesn't make as good an explosive as jet fuel (it burns slower). The H2 in jet fuel is packed closer together, kind of like in the special catalytic tanks, than in the wild state.
However, all of this would require a complete redesign of passenger aircraft and their engines for the considerably different storage, transfer and burning properties of H2. You could not realistically retrofit existing aircraft, with the possible exception of short-haul jets. There would be other prices to pay for the reduced efficiency of pure H2, such as bigger storage facilities and more frequent supply runs.
Hindenburg died firstly due to badly chosen material for the skin and bladders, and secondly because of poor design (inadequate facilities for static discharge, for example).
Got time? Spend some of it coding or testing
No! Really? (-:
Splitting the H from the O requires energy (which is why you get energy back when you burn it again). If you could reclaim the H2O after burning, you wouldn't need to carry much fuel at all.
So where do you get stupendous amounts of energy from? The most efficient source would be a pair of small nukes (for balance and redundancy). If you could pull a political rabbit out of a hat and get permits for flying sundry reactors around 24x7 you would be much better off simply using the nukes to heat air directly, or at least to heat a denser fuel than H2.
Another proposal I've seen which is much better is to use a big flat satellite to convert sunlight to microwaves and focus the result onto the 'plane. No chemical pollution at all (clean reaction mass like water or just heat air), no storage problems, little or no explosion if you crash. And cheaper to run, too. If another WTC was in the offing, it would help to turn the aircraft off; unless the hijackers knew how to switch over from microwave power to the backup system, you'd cut your casualties from circa 6000 to circa 300.
BOC, that's all science-fiction stuff (even though we could have built it in the '60s) which takes longer than a term of office to do, and so nobody wants to fund it.
Got time? Spend some of it coding or testing
That is a metal hydride cell, these ae fine for cars where a little added weight doesn't harm your performance as much as an airplane. On a airplane you want as little fuel containment structure for as much fuel volume as possible. Metal hydrides don't store nearly enough hydrogen for its weight to make it effective in anything you have to put in the air. The most effective way to store hydrogen is in a cryogenic tank and even those are bulky.
I'm a loner Dottie, a Rebel.
who cares how easily aircraft can be redesigned with safer fuel -- the government, under threat of arrest, confiscation, and imprisonment, is taking your tax dollars and giving them to the airline companies.
My beef is with the insurance companies who bail out on you when something happens... you pay so much to cover the premiums and then when their bottom dollar is threatened they pull out. The mine subsidence in the Pittsburgh, PA area is another example... It's a sacred cash cow.
The government should not be paying off any industries but instead be going after the damn insurance business. Of course, this (along with Copyright and Patent laws) is a sacred cash cow they don't dare try to slaughter.
The way I heard it a lot of the hydrogen (which being lighter than air tends to travel straight up rather quickly if not restrained in some way) escaped en route to the upper atmosphere instead of burning.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
So you have to move the burning match from far enough away not to ignite the fumes to under the surface of the liquid gasoline fast enough to keep from igniting the fumes before the match is smothered, and you only have to do it not quite fast enough just once to probably render yourself and any onlookers unable to perform that or any other experiment ever again.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
If you've read the book Skunk Works (of which the late Ben Rich--who headed Lockheed's Skunk Works for many years--was the co-author), he mentioned that when Lockheed looked at using liquid hydrogen as fuel for a Mach 2.5 spyplane (code named Suntan) he got a lot of extreme concerns from scientists who have dealt with LH2. In fact he mentioned a university lab that had done some research on LH2 and the lab sported small craters in the walls from LH2 explosions. The chapter of that book that dealt with the Suntan project was called Blowing Up Burbank, which was a pretty apt description given that Lockheed had enough LH2 at Burbank Airport that if there was an explosion caused by the LH2 igniting, it would have destroyed most of the Lockheed factory there and then some.
Liquid hydrogen propulsion was considered and rejected for the SR-71. And there was talk of it for the National Aerospace Plane from the Reagan era. But it's not an easy thing to do.
How about the Spruce Goose? Large wooden airplanes are nothing new.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
I think Israel has enough bombs going off with sufficient regularity for them to not consider anything that tall as anything other than an all too tempting target.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
The U.S. military has converted to less-volatile fuels, from JP-4 to JP-8. But the airlines already used JET-A, which is essentially the same as JP-8. There's JP-5, which is less volatile and is used by the Navy for carrier aircraft, but it's considered too expensive for the USAF and the airlines. We probably won't see a change there.
OK, so the energy to volume ratio is lower, so you have to compress it. That way when you get a leak, it becomes a real danger much faster...
And since it is highly pressurized, that will be more likely...
On the whole, I think Hydrogen would be a gad idea...
Also, for the historical record, the Hindinburg was not unprecidented. There had been other, even more serious zepplin accidents. And Zepplin Metalworks now is getting ready to produce a new line of Zepplins, called the Zepplin NT. I hope this is not an omen of things to come...
LedgerSMB: Open source Accounting/ERP
I will grant you that if someday, we were to have an abundance of electrical energy that we didn't know what to do with immediately, then hydrogen would appear to be a likely storage container for that energy.
Help find a cure for Gidget.
The production of hydrogen also makes it pretty inefficient. You're only going to get the same number of ergs out of the hydrogen as you put in to extract it. So the energy you spent getting the fuel for a plane you could have put into an magnetodynamic slingshot to shoot it into the air. Airplanes are also inconvenient shapes for storage of hydrogen which really wants to be stored in spherical chambers since you're going you have to keep it in a liquid for and thus under pressure. It works for the STS because the main fuel tank stores hygroen in a spherical tank inside the skin of it. To put hydrogen tanks inside of jet liners you'd need to put them in the cabin. Tanks aren't going in the wings like you can do with kerosene base jet fuels.
I'm a loner Dottie, a Rebel.
Fusion is not yet a goer, and it is still not certain that it will ever be a goer. Beamed microwave from powersats is a most definite goer, could be built with 50 year old technology and still turn a profit. Fusion (CanDu and the like) is much cleaner than coal, oil or petrol and could be on-line by next year but for politics.
Hydrogen takes energy to make. That energy doesn't pop out of thin air. You need energy to get hydrogen.
Which savages? Mao? Trotsky? Lenin? Stalin? Hitler? Got the point?
As for meddling in the Middle East to protect energy sources, why not buy LNG from Australia instead? We've got plenty of it, it's called ``the North West Shelf.'' And there are other places in Oz and elsewhere. Or use WW2 technology for making diesel from coal, of which the USA has (pun intended) heaps? The official excuses for continuing to muck around in the Middle East are starting to sound pretty thin now.
Got time? Spend some of it coding or testing
You'd harpoon it from a suitable mooring tower, then reel it in like a jellyfish on a ten-pound line. Of course, actually stopping it would be a bit of an issue... (-:
Got time? Spend some of it coding or testing
You'd harpoon it from a suitable mooring tower, then reel it in like a jellyfish on a ten-pound line. Of course, actually stopping it would be a bit of an issue... (-:
Got time? Spend some of it coding or testing
No matter what type of fuel you put in your aircraft, it needs to have a certain (very large) amount of chemical energy. When it burns, it will release all of that energy. True. But it does make a difference whether that energy is released over a couple of hours from a big puddle of oil burning in one area, or in a few minutes from a gas cloud rising in a big fireball. If 767 went splat on a runway, the fireball might be worse -- most of the heat would go up, but that radiated downward might cook the passengers immediately, while with kerosene there's a chance to get away before it gets too hot. In the WTC, I think the liquid H2 would be boiling off so fast it wouldn't let much air come in, unless open doors on the stairwells and elevator shafts allowed it to suck air from below. (This is NOT supposed to happen in a skyscraper fire.) So you'd get hydrogen gas pouring out the windows and burning outside, which would be bad for the people in the floors above, but would not have melted the central pillars and allowed a collapse.
Or else it would have melted the outer wall supports on one side and let the top part of the building tip over and wreck half of Manhattan instead of hammering the towers straight down into the basement...
The plane itself is not yet feasible, but for cost reasons, not scientific. It can be built, but it'd be too costly to operate at this point. As to the solar engines, I'm assuming you're discussing solar collectors, although I must have missed any mention of it in the discussion. They do clog up the landscape, insofar as anything visible does, and they can take up a lot of area, but if it's properly built, it's very un-shiny from the sky. Since the point of a reflecting solar collector is concentration of the light, all of the mirrors catch light from the sun and direct it toward the collector in the center, like a radar dish. From above, you'd just see a hundred different views of the collector.
Virg
> Why not take a Relevant Disaster like the Challenger Explosion
> for an example of how a hydrogen fuel jetliner would explode?
Actually, the Challenger disaster is not a good example of this, since the hydrogen burn isn't what destroyed Challenger. When the Solid Rocket Booster burned through its standoff and broke loose, it pivoted nose into the ship. This increased the yaw force significantly, which essentially turned the ship and the main tank sideways into its flight vector. As soon as the ship was turned sideways into its airstream at more than 6,000 mph, the wind shear tore it to pieces. The main tank suffered the same fate, and the ruptures left a big wad of H2 and a big wad of O2 which then made a big cloud, but the shuttle had already been blown to bits by shear force before that explosion ever happened.
> Any fuel that can fly a jetliner is going to be dangerous, and burn at high temperatures.
This is true, but there's one thing that hydrogen does that AirG (or AvGas or any other petroleum product, for that matter) doesn't: dissipate. It would burn hot, but it doesn't burn long, which was the original issue that started the discussion.
Virg
That alone makes the acts of the September 11 terrorists impossible to repeat IMHO.
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
I suggest that instead of replacing jet fuel with hydrogen to make airplane crashes safer, we concentrate on doing away with the fuel altogether. The aircraft could be made to fly using only the atmosphere it travels in as the fuel source. Of course, this would be a monumental technical challenge. In order to reduce its diffuclty to a manageble level, our initial airliner design could focus on just eliminating the fuel used during cruise, and could still carry a small amount of fuel for climb-to-altitude and descent-to-landing. This will mean that there is still a slight fuel danger on the aircraft, but it would be much reduced over current designs.
With the problem reduced to merely eliminating the fuel used during cruise, the problem becomes easier. The proposed airliner could be designed to cruise in the Ozone Layer. Once in the Ozone Layer, the use of conventional engines could be stopped and the aircraft could cruise on engines powered by the catalyitic decay of ozone. Ozone is only a meta-stable arrangement, and its decay into normal oxygen releases energy. The proposed airliner's engines could contain a catalytic bed that would greatly accellerate the decomposition of ozone. The heat released in this process could be used to replace the heat normally gained by burning fuel. An added benifit of such an ozone burning airliner would be that it could have effectively unlimited range, as long is it remained in the Ozone Layer.
I think the only thing to do now when an aircraft is hijacked in mid-air is to shoot it down before it gets near a city. Sorry, all you passengers, but it's too much of a risk. And yes, I'm prepared to take that risk myself. I'm thinking of coming to NY next month. Any recommendations?
Pure hydrogen does indeed burn nearly invisibly.
So does pure methane, but if you ignite a juicy fart you'll find it lights up a dark room with all kinds of colors, depending of what you've been eating. (NOTE: reproducible experiments are the basis of the scientific method.)
The Hindenburg was not entirely composed of pure hydrogen, therefore it should not be expected to have burned as pure hydrogen does. This does not mean hydrogen was not burning.
The dopant used on the Hindenburg had very little in common with solid rocket fuel; it had more chemistry in common with the roll of tape on my desk, in fact.
--Charlie