Question:
Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications… From whatI recall, it wasn’t the aluminum per se, but the nitrate dope the aluminum was mixed into that was horribly flammable. Lots of airplanes painted with nitrate dope burned, until butyrate dope was developed (and universally used for the top coats).
Bingo! Now the pieces fall into place. Nitrates are oxidisers. Powdered Aluminum mixed with a nitrates would fall somewhere between rocket fuel and high explosive. It would have been the Aluminum that burned, and the nitrate that burned it. IIRC, much of the Hindenberg’s framework was magnesium and it DIDN’t burn. — FF
Response:
- Hide quoted text — Show quoted text – Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications… From whatI recall, it wasn’t the aluminum per se, but the nitrate dope the aluminum was mixed into that was horribly flammable. Lots of airplanes painted with nitrate dope burned, until butyrate dope was developed (and universally used for the top coats). -Dana — —
Aiviation triva… Nitrate is still used as the first coat on dope treated dacron cover. This is because dacron fibers don’t have the fuzz that cotton does. There is nothing for the dope to latch on to, so we try to encapsulate the fiber is dope. Nitrate has superior adhesion properties, hence the first coat technique. But the flamibility issue is so extream that the rest of the buildup is done with butyrate. Nitrate dope is also known as gun cotton (for good reasons). I prefer Stitts Poly Fiber. Quicker surface build, easier repairs, and NON flammible. Richard Lamb
Response:
- Hide quoted text — Show quoted text – This was documented within the last couple years on the TV program NOVA. The explosion was not caused by the hydrogen but rather by the skin of the Hindenburg itself igniting. Had it been made of just about anything else, it would never have burned. Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications and few others have burned up like the Hindenberg. Did an unstable hydride form in the paint or something? It is clear that the Hindenberg’s hydrogen did burn (not that you said it didn’t), but also clear that it had to escape from the gas bags befor it burned as the atmosphere in the gas bags was well above the Upper Explosive Limit. Further, hydrogen diffuses rapidly. A small leak would not cause an explosive atmosphere to form in the Gondola. BTW, there has been recent news about the developement of a catalyst that can crack the hydrogen off of ethanol. So you can carry your spare hydrogen in the form of ethanol, rather than in a pressure cylinder, and supply it on demand both for lift and to run through fuel cells for power. Meaning no disrespect to the OP but his comments on the dragon fly implies a certain lack of understanding of buoyancy and the scales involved. The application of a little bit of arithmetic would help to put things in perspective. Thanks for the comments. Buoyancy? An H2 pressurized bug wing might gain a *very* small advantage over air in terms of effective weight, lift, drag, and energy cargo requirements, depending on the pressurization. At what over pressure does H2 weigh as much as air? 8 atmospheres when cooled? How about warmed by the sun?
A while ago I showed you how to estimate all that stuff yourself. If you want my estimate sans math the answer is that a dragon fly displaces so little air that nothing you are taling about matters. What’s left of the ethanol after you catalyze the H2 out of it?
Carbon Dioxide and Water. Could oil then be used as a storage system for H2?
What do you mean by Storage system? Could a special oil or form of carbon, perhaps Bucky tubes be used in an electrolysis cell to capture low pressure H2?
What for? Oh, do you want to produce the hydrogen by the electolysis of water? That doesn’t make any sense, it would be more effcient to use the electricity to do the work, rather than use it to make hydrogen then burn the hydrogen to do work. Aluminum and water will form an explosive, I gather.
News to me. Hard to light, I hear. Other explosives contain aluminum powder. Dope, a form of plastic varnish like coating, was, I believe, an ingredient in the Hindie’s paint. I think it contains cellulose, of kinescope film and fire hazard fame.
Nitrate dope (nitrocelluose) according to another poster. Remember, this blimp is semi rigid, from internal pressure tubes containing excess H2 fuel and lift gas. It could have a quick shape, even resembling a fat ray fish / body in wing design.
Not likely. Do the arithmetic. Then again, why not telecommute?
Why not? — FF
Response:
– Hide quoted text — Show quoted text – This was documented within the last couple years on the TV program NOVA. The explosion was not caused by the hydrogen but rather by the skin of the Hindenburg itself igniting. Had it been made of just about anything else, it would never have burned. Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications and few others have burned up like the Hindenberg. Did an unstable hydride form in the paint or something? It is clear that the Hindenberg’s hydrogen did burn (not that you said it didn’t), but also clear that it had to escape from the gas bags befor it burned as the atmosphere in the gas bags was well above the Upper Explosive Limit. Further, hydrogen diffuses rapidly. A small leak would not cause an explosive atmosphere to form in the Gondola. BTW, there has been recent news about the developement of a catalyst that can crack the hydrogen off of ethanol. So you can carry your spare hydrogen in the form of ethanol, rather than in a pressure cylinder, and supply it on demand both for lift and to run through fuel cells for power.
How much weight advantage is this ethanol tank / mill / catalyst, over a large moderately pressurised tank still soft enough to provide bouyancy in air, say at 5 atmospheres pressure? What happens to lift as fuel is consumed in transit? I’m not good with math and perhaps Your Aghustness would deign to provide an estimeate? – Hide quoted text — Show quoted text -Meaning no disrespect to the OP but his comments on the dragon fly implies a certain lack of understanding of buoyancy and the scales involved. The application of a little bit of arithmetic would help to put things in perspective. Thanks for the comments. Buoyancy? An H2 pressurized bug wing might gain a *very* small advantage over air in terms of effective weight, lift, drag, and energy cargo requirements, depending on the pressurization. At what over pressure does H2 weigh as much as air? 8 atmospheres when cooled? How about warmed by the sun? A while ago I showed you how to estimate all that stuff yourself.
No, you didn’t, you puked up about 50 pounds of pearls before a mere pigheaded wonderer. Is this how you would teach your son? If you want my estimate sans math the answer is that a dragon fly displaces so little air that nothing you are taling about matters.
If you played drums, you would know just how important a little tiny advantage like removing your wrist watch makes if you are playing for very long. It sounds like a tiny difference, but I can tell you it does make a difference. As an engineer you may think it insignificant, but as a runner, you might appreciate saving a few grams, far less than one percent of the weight of your leg and foot, by choosing a lighter sneaker. In a few miles you might see a decided advantage, however tiny, accumulate to winning a race. In evolution, a tiny advantage could become huge in it’s result, especially over time. It’s not a major point, but illuminates how narrow minded some can be. Rocket science is easier. What’s left of the ethanol after you catalyze the H2 out of it? Carbon Dioxide and Water. Could oil then be used as a storage system for H2? What do you mean by Storage system?
Anything that will receive and deliver enrgy can be considered a battery, or storage system. I like to consider hydrogen as a medium for battery storage, accepting charge from it’s rest state as a component in water during hydrolysis, delivering energy IN DIFFERENT FORMS OF ANALYSIS, like comparing powered conventional flight energy requirements to the lift provided by bouyant systems, considering weight, distance, and speed. As odd as it may seem, humanity probably accomplished more exploration under paddle and sail than ever by rocket, compared on a cost per customer mile satisfaction basis. Not everybody wants an air race competitor, but just a quiet cruise for sport. Hydrogen flight can be safe. Could a special oil or form of carbon, perhaps Bucky tubes be used in an electrolysis cell to capture low pressure H2? What for? Oh, do you want to produce the hydrogen by the electolysis of water? That doesn’t make any sense, it would be more effcient to use the electricity to do the work, rather than use it to make hydrogen then burn the hydrogen to do work.
Even in terms of weight,lift, drag, and fuel cost in short cruising flights? Not everyone is a speed freak. snip Remember, this blimp is semi rigid, from internal pressure tubes containing excess H2 fuel and lift gas. It could have a quick shape, even resembling a fat ray fish / body in wing design. Not likely. Do the arithmetic.
Relatively fast shape, then?, birdlike, body in wing, propelled and steered mainly by orthinopter principles and bouyancy bladder? Please do me the courtesy of neglecting high windage difficulties. It goes beyond mere deprecatory reference to arithmatic. It is serious math, not my forte. Terry K – Hide quoted text — Show quoted text -Then again, why not telecommute? Why not?
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There is in fact an inflatable aircraft already out there, I forget what it is called. It sure looks weird though. I’m not sure , but I have a pretty strong feeling that lighter than air craft come under their own riles and regulations, and thus do not conform to the same as ultralight and/or the soon to be ratified american LSA regs. Only 5 gallons of fuel??? wow I don’t think there is any such fuel restriction here in AU. If it DID fall under the ultralight rulings, it would have to be weighed with it’s full loading, that means, inflated, with full fuel and gas, YOU and a passenger (or a ballast bag if you cannot find anyone brave enough) if to are 2 seat capable. An insect’s wings may well be supported by positive pressure cells, but I doubt that it is hydrogen.
Me too, actually. Moller’s skycar is a concept that has been around for well in excess of ten years, (well that’s about when I first encountered the idea). At the current aceleration of today’s society, I woul;d not be at all surprised if an idea like this is soon to be put to use. maybe not at skyscraper level, but to deal with congeston levels on the ground, they are going to have to look at moving in 3 dimensions. A scary thought for those of us up there now, Imagine getting caught up withg a drunken driver at 1000ft? This is the reason for the autopilot, to take the human factor out as much as possible. You cannot expect the ordinary joe, tired, in a hurry and pissed off at the world to be considered safe to fly
Oh, no? Says who, you an airline hostess? Next, you’ll disallow surface drivers over 4 hours a day. , so in order for the system to work, it HAS to he a push button piece of equipment, at least within city boundaries. This same autopilotiing system could very easily and capably deal with the effects of wind turbulence easier, quicker and more efficiently than a human pilot can. The immensly successful F16 is a prime example of an unstable platform made safe by computer systems. A dirigible would be practical, but not for the high speed nature of city life.
You mean like rush hour, cabs full, busses stuck in traffic too? High speed planes between skyscrapers? Better they weigh almost nothing. A computer guidance system? Why not, with modern AI? Even a slow dirigible would outpace direct travel by ground roads with pedestrians, etc. Close in, a human hand must always be able to do, especially if the digibrain farts. Out in the country, otto flies straight and steady, while you eat dinner enroute skiing. So, it’s a little slower than a GTX. Superior commuting. As for the safety, yes, anti static materials would help prevent a hindenburg type disaster, but a stray bullet from you local gangsta, a bird strike, someone throwing a cig butt out the window or just a plain old crash (remember eveyone’s got one of these) could certainly create a HUGE explosion risk.
No explosion, only a rising fireball that quickly goes out. The means of using differential pressure to compensate for ballast would indeed work, under water. Not in air I’m afraid.
Same, same. The pump would need to be as strong as if it was driving an elevator in a building (for one person, naked and slowly going up or down). It could burn some H2 to run the prop to pull the gasbag down, using the hot exhaust gas to heat the bag and rise, while casting off water ballast in the exhaust. Take your pick of controllable elements. The need as I see is for about a 1 HP fan motor with the capability of running a propellor fan or a gaseous H2 pump. It would be fed by flex pipes, and would steer up and down and side to side in gimbals. A small steerable tail fan driven by exhaust gas turbine pressure might help with trim or steering. Because of the differing densities of the medium, in order for a gaseous substance (in this case H2) do become densely concentrated enough to have a significant effect on bouyancy, you would need to compress it to such a stage that a heavy pressure vessel will be required to hold it, and to do it at any speed even closely resembling the rate required to effect altitude control, you would need a fairly massive ram to compress it with.
Oh, I don’t know… A heavy bellows with snowshoe style squeezers might not do, 2 or 3 big sausages with sliding sections and a bunch of strings pulled by a pedal gear drive might do, one fore, one aft, spanwise, but a fan strong enough to blow gas between two balloons, one stretchy, one not, wouldn’t be such a big deal, either. The "pump" could surpass the efficiency of an elevator motor in a building, considering the mechanics. Going up would be the easy part. We don’t have to raise and lower a cage, in effect, only need to trim the weight (displacement?) of the craft by a few pounds to start it going up or down. High vertical velocity shouldn’t occur in a guided balloon. Once set for neutral bouyancy, a small force is all that would be required. Automatic altitude control isn’t difficult with a little patience. Sensing barometric ambient pressure would be more of a problem. It could be broadcast by radio. A laser or gps altimiter / rangefinder might be of use. Park the whale on your tennis court by hooking a baseball on a string into a rake with entry guides and a windsock rotator, hook on the seat anchor, step off the now straining up balloon. Suck all the gas up, roll the bag up, and throw it in your pickup. Sport flying, an experimental rig, fun for everyone! The large spine tank would be not very heavy, and might resemble a canoe on a volkswagen, with van fuel inside. Why not? It would lift stuff essentially for free, fuel wise. It could do for lumbering, or picnicing. Sail cloth, mylar film, and string. It works for the rose bowl and other parades, except they must use helium, controlled by the US government. Why would they not want easy flight for everyone? Perhaps Hitler might not want the public free to fly anywhere, perhaps the US colluded with him to stage the Hindenburg disaster, as a matter beneficial to both regimes and then current airial manufacturers? More conspiracy madness? I think, er, ah, not sure, really…
In the event of a power loss you could just bleed gas to desend.
Or pump it with pedals? If you squeese the heavy sausage inside the lighter outer gas bag, don’t you also reduce the volume of the outer lift bag? I really does work for fishes, and should for big smart birds like us. as for effecting the infrastracture by removing the public transport equation from the highways,
Consider not building only the part we might otherwise need for future expansion. Remember the big dig in Boston? It’s really about sewage, isn’t it? You don’t hear about the cost of cleaning up the harbour, do you? Corporations polluted it, so now the public must pay for their abuse, by building roads better for business? Whatta ya mean, reduce *their* taxes? I doubt that would have much effect, as there is still plenty of stuff that is cheaper to freight by road, and hey, flying is not for everyone
If it was cheap, easy, quiet, and more efficient than present methods, why not? If it could be as much fun as bumper cars, and as safe, why not? No road gas tax for homegrown H2. Tether your dirigible to your chimney? Landing platform on the roof? Just my two cents…
How about 75% of gasoline cost is taxes overall? -Terry K – Hide quoted text — Show quoted text – Sarah In Oz
How about making an ultralight hybrid aircraft / dirigible inflated with hydrogen? Would you weight it empty (deflated) for weight restrictions if it was aircraft like? Would the 5 gallon gasoline fuel restriction for ultralights convert in any useful way into a volume of gaseous hydrogen equivalent? A dragonfly’s wings are stiffened by internal gas pressure, that’s obvious if you look at one. So are other insect wings, and they are the most efficient flyers there is. Are they inflated with hydrogen? That would seem like an advantageous evolution. Now, I can’t wait to capture one and see if the wing burns especially brightly. After watching the Discovery channel about Moller’s skycar, I can’t help wondering if an anti static hydrogen dirigible using fat wings shaped for lift would be more a conventional a/c or a dirigible. Seems a dirigible would make a far more practical aircar than a million dollar 8 engine robot flyer, at least for relatively short commutes to downtown from a suburb without roads, that would make housing developments cheaper. Besides, who is going to do a hundred miles an hour between skyscrapers in traffic on auto pilot, with the way winds flip around near them? I believe Moller’s idea is doomed, a millionaire’s pipe dream. Totally impractical and inefficient in a hydrogen powered world. If a dirigible had a hydrogen bouyancy compensating tank of variable but still relatively low pressure and volume inside a lower pressure bouyancy envelope, would pumping hydrogen gas between high and low pressure envelopes control lift and gross altitude in an efficient and effective manner, like some fish do, without needing inefficient ballast? What would happen if you lost power and coudn’t compress lift gas, and continued to rise out of control as the gas in the envelope expanded at increasing altitude? Would you need to dump H2 to come down, until you lost the capability to maintain altitude? Parachute time? Wouldn’t a dirigible inherently display good fuel efficiency, considering it doesn’t need to utilise power to generate lift, but perhaps only a little to fine control altitude for landing, etc? How good is the lift drag speed fuel
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Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications…
From whatI recall, it wasn’t the aluminum per se, but the nitrate dope the aluminum was mixed into that was horribly flammable. Lots of airplanes painted with nitrate dope burned, until butyrate dope was developed (and universally used for the top coats). -Dana — — If replying by email, please make the obvious changes.
Response:
– Hide quoted text — Show quoted text – This was documented within the last couple years on the TV program NOVA. The explosion was not caused by the hydrogen but rather by the skin of the Hindenburg itself igniting. Had it been made of just about anything else, it would never have burned. Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications and few others have burned up like the Hindenberg. Did an unstable hydride form in the paint or something? It is clear that the Hindenberg’s hydrogen did burn (not that you said it didn’t), but also clear that it had to escape from the gas bags befor it burned as the atmosphere in the gas bags was well above the Upper Explosive Limit. Further, hydrogen diffuses rapidly. A small leak would not cause an explosive atmosphere to form in the Gondola. BTW, there has been recent news about the developement of a catalyst that can crack the hydrogen off of ethanol. So you can carry your spare hydrogen in the form of ethanol, rather than in a pressure cylinder, and supply it on demand both for lift and to run through fuel cells for power. Meaning no disrespect to the OP but his comments on the dragon fly implies a certain lack of understanding of buoyancy and the scales involved. The application of a little bit of arithmetic would help to put things in perspective.
Thanks for the comments. Buoyancy? An H2 pressurized bug wing might gain a *very* small advantage over air in terms of effective weight, lift, drag, and energy cargo requirements, depending on the pressurization. At what over pressure does H2 weigh as much as air? 8 atmospheres when cooled? How about warmed by the sun? I was really just wondering if evolution had any chance to find an advantage that small. It is a remarkable process. You agree an inflated chamber could be used as pre-stress and stiffen spars in a wing? How much over pressure and overweight might be used to stiffen a spar using air? How much structural weight might be saved using air pressure over a regular spar? ….. is that enough perspective? What’s left of the ethanol after you catalyze the H2 out of it? Charcoal smoke / clinkers? Sludge? Oil? Could oil then be used as a storage system for H2? Could a special oil or form of carbon, perhaps Bucky tubes be used in an electrolysis cell to capture low pressure H2? Aluminum and water will form an explosive, I gather. Hard to light, I hear. Other explosives contain aluminum powder. Dope, a form of plastic varnish like coating, was, I believe, an ingredient in the Hindie’s paint. I think it contains cellulose, of kinescope film and fire hazard fame. It was commonly employed on a/c wing fabric, as it shrank as it dried, providing a tight, clean airfoil surface. The Hindie’s paint’s flammability was demonstrated on TV. Almost explosive. Have you any idea how big a charge accumulates on a moving aircraft? If a section of envelope was not well bonded, after hurried repairs with needles and thread, as was apparently the scenario, from the movie, the arc of the grounding cable could spark elsewhere on the craft. If personal air travel is to come downtown in quantity, there would have to be noise abatement regulations. Can you imagine a thousand heli-cars throbbing and screaming over crowded streets? Dirigibles can be very quiet, especially with larger, slow moving props, even orthinopter oar / wing tips. How fast could you row a blimp? Remember, this blimp is semi rigid, from internal pressure tubes containing excess H2 fuel and lift gas. It could have a quick shape, even resembling a fat ray fish / body in wing design. It could be very light indeed, needing only enough lift skin / envelope strength to survive a collision with a bird. As a powered ram air parachute with a little lift from H2 chambers, perhaps human powered flight might become a lot easier, if not chainsaw engine driven? I want a cheap flying lawn chair. Burning airships send flames up, not down on pedestrians. All a/c are vulnerable to aggressive ground tactics, or even from bricks dropped from above. Why did someone worry so much about a flare gun or something? Worry about idiots throwing rocks at bicyclists, too? Murder is murder. I can see tall buildings with lots of balcony parking for tethered blimps, even in regular modified window openings, kinda like diving boards with tethers. An executive mode of travel? Imagine a place like Vancouver. You could blimp around traffic, and could fly direct to a mountain lake perch with no roads only a few miles away. What a vehicle for the traffic guy! Lots cheaper than a chopper. Open a valve to go up, crank a pedal to compress a little gas, go down. Once trimmed to your weight, small buoyancy changes would make altitude adjustments free. Or, a small steerable engine could be an option. It would have to work harder to pull you down, as fuel was consumed, it it burned gasoline. Cold, precipitation and atmospheric pressure changes would complicate things, let alone a breeze. Then again, why not telecommute? Terry K
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Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications and few others have burned up like the Hindenberg. Did an unstable hydride form in the paint or something? IIRC, that’s exactly what they demonstrated. They took a swatch sample of unburned skin paint from the Hindenburg and exposed it to a normal static discharge from typical near thunderstorm weather. It burned very rapidly.
Aluminum burns like hell (literally) once it is ignited (Remember the Sheffield?) but it takes a lot of energy to ignite it. Helium filled dirigibles like the Macon ALSO used aluminum pigmented paint as do a lot of stick and rag aircraft so I wonder if there was something else in the paint on the Hindeberg not found on others. It is clear that the Hindenberg’s hydrogen did burn (not that you said it didn’t), but also clear that it had to escape from the gas bags befor it burned as the atmosphere in the gas bags was well above the Upper Explosive Limit. Further, hydrogen diffuses rapidly. A small leak would not cause an explosive atmosphere to form in the Gondola. That’s what the NOVA program pointed out. Had the outer skin not been made from that highly flammable aluminum based paint, the hydrogen would have escaped above the blimp and would not have had the combustive force observed in the original disaster. Worst case scenario would have been that the escaping gas could have burned in a nearly invisible blue flame, and later extinguished itself.
Just for fun I tried the aluminum and sodium hydroxide process to generate some hydrogen which I trapped in a lightweight produce bag. Then I lit it with a candle and the flame that burned the hairs off the back of my hand was quite yellow in color, not blue. Quite warm too. — FF
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The means of using differential pressure to compensate for ballast would indeed work, under water. Not in air I’m afraid Blimps sych as the Goodyear do use such a pressure mechanism, IIRC.
In fact, it would work MUCH better in air than underwater. However it is far more practical to rely on differential VOLUME, which is exactly what submarines do, and also I suspect, what Blimps do too. — FF
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This was documented within the last couple years on the TV program NOVA. The explosion was not caused by the hydrogen but rather by the skin of the Hindenburg itself igniting. Had it been made of just about anything else, it would never have burned.
Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications and few others have burned up like the Hindenberg. Did an unstable hydride form in the paint or something? It is clear that the Hindenberg’s hydrogen did burn (not that you said it didn’t), but also clear that it had to escape from the gas bags befor it burned as the atmosphere in the gas bags was well above the Upper Explosive Limit. Further, hydrogen diffuses rapidly. A small leak would not cause an explosive atmosphere to form in the Gondola. BTW, there has been recent news about the developement of a catalyst that can crack the hydrogen off of ethanol. So you can carry your spare hydrogen in the form of ethanol, rather than in a pressure cylinder, and supply it on demand both for lift and to run through fuel cells for power. Meaning no disrespect to the OP but his comments on the dragon fly implies a certain lack of understanding of buoyancy and the scales involved. The application of a little bit of arithmetic would help to put things in perspective. — FF
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Did they identify the ignition source? I have a hard time believing that a static discharge less energetic than a lightnig bolt ignited the paint. Powdered aluminum pigment was, and still is used in lots of applications and few others have burned up like the Hindenberg. Did an unstable hydride form in the paint or something?
IIRC, that’s exactly what they demonstrated. They took a swatch sample of unburned skin paint from the Hindenburg and exposed it to a normal static discharge from typical near thunderstorm weather. It burned very rapidly. You’d be amazed just how much static charge can be released from a wind across a conductive surface. I speak from the personal experience of having flown kite-supported short-wave antennas in bright and sunny weather. It is clear that the Hindenberg’s hydrogen did burn (not that you said it didn’t), but also clear that it had to escape from the gas bags befor it burned as the atmosphere in the gas bags was well above the Upper Explosive Limit. Further, hydrogen diffuses rapidly. A small leak would not cause an explosive atmosphere to form in the Gondola.
That’s what the NOVA program pointed out. Had the outer skin not been made from that highly flammable aluminum based paint, the hydrogen would have escaped above the blimp and would not have had the combustive force observed in the original disaster. Worst case scenario would have been that the escaping gas could have burned in a nearly invisible blue flame, and later extinguished itself. Jake Brodsky "Never mind the Turing Test, what about the Turing Graduates?"
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Moller’s skycar is a concept that has been around for well in excess of ten years, (well that’s about when I first encountered the idea). More than 15, actually. And it will be more than 4 yet before the craft is actually approved.
Actually, I remember Moller from the late 1970’s. There is widespread belief that his aircars will *never* fly. Some believe his claims for engine performance are thermodynamically ridiculous. hindenburg type disaster, but a stray bullet from you local gangsta, a bird strike, someone throwing a cig butt out the window or just a plain old crash (remember eveyone’s got one of these) could certainly create a HUGE explosion risk. There would be no Hindenburg danger if you used helium in place of H2. The Germans used H2 only because they could not buy helium.
In fact, there would never have been a Hindenburg disaster if those silly folks at the Graf Zeppelin factory hadn’t been looking for an aluminum based paint for the envelope. It turns out that they accidentally stumbled upon a formula for an explosive. This was documented within the last couple years on the TV program NOVA. The explosion was not caused by the hydrogen but rather by the skin of the Hindenburg itself igniting. Had it been made of just about anything else, it would never have burned. Jake Brodsky "Never mind the Turing Test, what about the Turing Graduates?"
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… Well, maybe we’d all be better off taking the bus from the fly-in park. Else, we might see skyscrapers looking like flowers with a crowd of airships tethered to the hitching rails around the roof top, waving in the wind like a tall tree? Do you really think Moller’s skycars are going to make his hypothetical future better than that by some alchemy?
I never heard of Moller’s skycars befor now. Just what the hell do all those people in all those 50 th floor offices actually do? With computers, surely all clerical duties can be handled by robot telephone servers and email cheques?
I’m sure that quit q bit more work could easily be done by telecomuting. Would you be allowed to wiegh the craft while full of ‘fuel’ gas and how would that affect fuel quantity allowance? You lost me. There was a discussion about U/L weight restrictions, and it occurred to me that a hydrogen fuel bag possesses ‘negative weight.’ Do U/L regs presently make any allowance for fuel other than gasoline? How would the regulation apply to an U/L A/C with a large H2 fuel bag?
I expect the FAA has seperate regulations for lighter than air vehicles. Even the largest dirigibles were ‘ultralight’ in that sense. So far as U/L construction is concerned, I wondered about the construction technique used by that most admirable of nature’s flyers, the dragonfly. Like all insects, it’s wing is constructed using stretched membranes inflated with a gas to assist in maintaining it’s shape. I wondered, and still do, if dragonflys or any other insects had evolved a method to use hydrogen to inflate it’s wings. It just seems so attractive, so beneficial that I would expect it to occur in nature, if it is possible.
I don’t see what benefit there would be for insects. Do the arithmetic and you’ll see why. OTOH, fish have swim bladders. For a fanciful tale about lighter-than-air beings, see a chapter in _Venus on the Half Shell_ by Kilgore Trout. – Hide quoted text — Show quoted text – Or would there need to be a seperate regulation to cover airship hybrids? Maybe it would be covered under ‘experimental’. I also thought about using a low pressure fuel tank in a lightweight car the size of a tractor trailer instead of a heavy strong hydride tank. If you had a large H2 fuel bag, it would generate bouyancy. If you wanted to carry enough low pressure H2 fuel for long range, might it make sense to lose the heavy wheels, frame and other heavy stuff, …
A group recently announced the developement of a new catalyst that will crack ethanol and water into hydrogen, and carbon dioxide. Their process will allow the production of hydrogen on demand from ethanol made from biomass. The hydrogen can be used in a fuel cell to make electricity. The biomass used to make the ethanol will recature the carbon dioxide. Try a web search for ethanol, catalyst, and hydrogen. In my childhood I read an anthology of short (fictional) stories about a group of kids in a small town somewhere who entertained themselves by making neat contraptions. One story was called "The Great Balloon Race" or some such and instead of ahot air balloon with ballast they used a helium balloon and carried a gas powered compressor up with them. To go up, they let gas out of the bottle into the balloon. To go down, the compressed helium and put it back in the bottle. That is about the same consideration as my previous question, below. I would like to see that anthology.
I think it was called _The Monster of such and such Lake_ or some such. – Hide quoted text — Show quoted text – How much bouyancy would you ‘lose’ if you pumped say, half of the gas in the lift bag into a 10 atmosphere bag? At what pressure does H2 weigh the same as stp atmosphere? Hydrogen at stp wieghs about what, about .2 of air? You might want to check a freshman physics text to see if my memory is accurate below. For P = pressure, V = Volume, T = absolute temperature, n = number of molecules, N = number of moles, M = molecular weight, and R = universal gas constant, A = avogodro’s number (6.022E23), m is mass and k is a constant. Avogdro’s law: Equal volumes of gas at the same temperature and pressure have equal numbers of molecules. Boyle’ law: PV = k at constant temperature Charles law: V2 = V1(T2 – T1) at constant pressure (1,2 are subscripts, not factors) The ideal gas law: PV = NRT = nkT where k = N/A or: PV = mrT, where r = R/M, so r is a different constant for each gas. Light gases within the temperature and pressure ranges of this discussion are very well modeled by these equations. Using them, you can answer all your questions. As a fun exercise, you can prove that water vapor is lighter than air. Have fun. It’s a gas.
– FF
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There is in fact an inflatable aircraft already out there, I forget what it is called. It sure looks weird though.
It’s not in production. It was a US military project that was abandoned about forty years ago. It was never named, but was in Kitplanes a few years back. Moller’s skycar is a concept that has been around for well in excess of ten years, (well that’s about when I first encountered the idea).
More than 15, actually. And it will be more than 4 yet before the craft is actually approved. At the current aceleration of today’s society, I woul;d not be at all surprised if an idea like this is soon to be put to use.
If it was ever going to happen, 11 September, and the rising cost of fuel are quite likely to stop it (lamentably). A dirigible would be practical, but not for the high speed nature of city life.
Dirigibles are too *big* for practical commuting. Consider the size of the Goodyear gasbag in relation to its crew cabin. hindenburg type disaster, but a stray bullet from you local gangsta, a bird strike, someone throwing a cig butt out the window or just a plain old crash (remember eveyone’s got one of these) could certainly create a HUGE explosion risk.
There would be no Hindenburg danger if you used helium in place of H2. The Germans used H2 only because they could not buy helium. The means of using differential pressure to compensate for ballast would indeed work, under water. Not in air I’m afraid
Blimps sych as the Goodyear do use such a pressure mechanism, IIRC.
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There is in fact an inflatable aircraft already out there, I forget what it is called. It sure looks weird though. I’m not sure , but I have a pretty strong feeling that lighter than air craft come under their own riles and regulations, and thus do not conform to the same as ultralight and/or the soon to be ratified american LSA regs. Only 5 gallons of fuel??? wow I don’t think there is any such fuel restriction here in AU. If it DID fall under the ultralight rulings, it would have to be weighed with it’s full loading, that means, inflated, with full fuel and gas, YOU and a passenger (or a ballast bag if you cannot find anyone brave enough) if to are 2 seat capable. An insect’s wings may well be supported by positive pressure cells, but I doubt that it is hydrogen. Moller’s skycar is a concept that has been around for well in excess of ten years, (well that’s about when I first encountered the idea). At the current aceleration of today’s society, I woul;d not be at all surprised if an idea like this is soon to be put to use. maybe not at skyscraper level, but to deal with congeston levels on the ground, they are going to have to look at moving in 3 dimensions. A scary thought for those of us up there now, Imagine getting caught up withg a drunken driver at 1000ft? This is the reason for the autopilot, to take the human factor out as much as possible. You cannot expect the ordinary joe, tired, in a hurry and pissed off at the world to be considered safe to fly, so in order for the system to work, it HAS to he a push button piece of equipment, at least within city boundaries. This same autopilotiing system could very easily and capably deal with the effects of wind turbulence easier, quicker and more efficiently than a human pilot can. The immensly successful F16 is a prime example of an unstable platform made safe by computer systems. A dirigible would be practical, but not for the high speed nature of city life. As for the safety, yes, anti static materials would help prevent a hindenburg type disaster, but a stray bullet from you local gangsta, a bird strike, someone throwing a cig butt out the window or just a plain old crash (remember eveyone’s got one of these) could certainly create a HUGE explosion risk. The means of using differential pressure to compensate for ballast would indeed work, under water. Not in air I’m afraid. Because of the differing densities of the medium, in order for a gaseous substance (in this case H2) do become densely concentrated enough to have a significant effect on bouyancy, you would need to compress it to such a stage that a heavy pressure vessel will be required to hold it, and to do it at any speed even closely resembling the rate required to effect altitude control, you would need a fairly massive ram to compress it with. In the event of a power loss you could just bleed gas to desend. as for effecting the infrastracture by removing the public transport equation from the highways, I doubt that would have much effect, as there is still plenty of stuff that is cheaper to freight by road, and hey, flying is not for everyone
Just my two cents… Sarah In Oz
– Hide quoted text — Show quoted text – How about making an ultralight hybrid aircraft / dirigible inflated with hydrogen? Would you weight it empty (deflated) for weight restrictions if it was aircraft like? Would the 5 gallon gasoline fuel restriction for ultralights convert in any useful way into a volume of gaseous hydrogen equivalent? A dragonfly’s wings are stiffened by internal gas pressure, that’s obvious if you look at one. So are other insect wings, and they are the most efficient flyers there is. Are they inflated with hydrogen? That would seem like an advantageous evolution. Now, I can’t wait to capture one and see if the wing burns especially brightly. After watching the Discovery channel about Moller’s skycar, I can’t help wondering if an anti static hydrogen dirigible using fat wings shaped for lift would be more a conventional a/c or a dirigible. Seems a dirigible would make a far more practical aircar than a million dollar 8 engine robot flyer, at least for relatively short commutes to downtown from a suburb without roads, that would make housing developments cheaper. Besides, who is going to do a hundred miles an hour between skyscrapers in traffic on auto pilot, with the way winds flip around near them? I believe Moller’s idea is doomed, a millionaire’s pipe dream. Totally impractical and inefficient in a hydrogen powered world. If a dirigible had a hydrogen bouyancy compensating tank of variable but still relatively low pressure and volume inside a lower pressure bouyancy envelope, would pumping hydrogen gas between high and low pressure envelopes control lift and gross altitude in an efficient and effective manner, like some fish do, without needing inefficient ballast? What would happen if you lost power and coudn’t compress lift gas, and continued to rise out of control as the gas in the envelope expanded at increasing altitude? Would you need to dump H2 to come down, until you lost the capability to maintain altitude? Parachute time? Wouldn’t a dirigible inherently display good fuel efficiency, considering it doesn’t need to utilise power to generate lift, but perhaps only a little to fine control altitude for landing, etc? How good is the lift drag speed fuel economy tradeoff for a dirigible at useful speeds? How much could you gain or lose to headwinds and tailwinds? Why don’t we hear more about personal dirigibles fuelled and / or lifted by hydrogen, especially since modern anti static materials would seem to remove the Hindenburg terror factor? If the vectored propellors used to drive and control a dirigible were perhaps partly powered by thin film solar cells, hydrogen fuel cells, or hydrogen or gasoline internal combustion engines in various configurations, might there be a capability to build an affordable, quiet, backyard vtol vehicle, fuelled with H2 generated by home electrolysis? A hydrogen powered dirigible "car" doesn’t need expensive infrastructure like roads or bridges. How would that affect the national economy, considering fuel scarcities, especially if roads were abandoned? Is the box too small to think about this? Is there any comprehensive research on this? It seems a one or two person H2 dirigible might only be about as big as a bus, and it could be tethered to your rooftop. The fuel could be hydrolized from waste water during low hydro demand hours, or while the sun shone on solar shingles. Opinions? Don’t bother telling me I’m crazy, I suspected that decades ago, after talking to many of the sane dullards I meet. Most just need a consuming interest to become as crazy as me. Terry K
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– Hide quoted text — Show quoted text – Or a small lawn chair with a lawn mower engine twirling a prop for short range fun? http://tlc.ousd.k12.ca.us/~acody/larry.html On top of a typical skyscraper you’ll have room for about one dirigible at a time–where are you going to park the thing when it’s not being used? To a trapline, of course. Clothesline pullies with a balloon at the top, and several others on tethers. Just reel in the one you want, get in, and go. You would need to pull the thing down to get in it, unless the bouyancy compensator bladder could be pumped up and down quickly enough. Cool, until you get high winds which are commonplace on top of skyscrapers. The Bernouli effect can make the wind over the top of a skyscraper much faster than ‘ambient’.
Well, maybe we’d all be better off taking the bus from the fly-in park. Else, we might see skyscrapers looking like flowers with a crowd of airships tethered to the hitching rails around the roof top, waving in the wind like a tall tree? Do you really think Moller’s skycars are going to make his hypothetical future better than that by some alchemy? – Hide quoted text — Show quoted text -Perhaps dirigible was not the right word, as I envision an ultralight soft bladder held in shape by internal webs and pressure, divided into several tubular gas bags, … The airship’s shape would resemble in principlal a bunch of banannas trying to straighten out, centered around and stretching the wire centre frame. A couple of bags could be shaped to take advantage of aerodynamics to direct the craft, as well as possibly contribute some lift at speed. My thinking is that you want a lifting body that generates lift primarily by deflection from the lower surfaces. But probably you should not expect any more than a small amount od lift, basicly enough to trim the vehicle, because the bulkiness of the vehicle will make it impractical to generate a lot of aerodynamic lift. BTW, I think on the old DIrirgibles the props typically could rotate from horzontal to vertical.
Welcome to the trap. While this discussion stemmed from a consideration of mass air transit downtown, it was really motivated by my concern for traffic downtown generally, national fuel economy concerns, and road infrastructure finances. Fuel dealers want you to increase your consumption. You should reduce your wasteful consumption, for many reasons. People’s desire for status urges them to be more conspicuous in thies consumption. I prefer to think that mu status is such that I do not need a bigger shinier car or gun, because my dick is really quite big enough, and I don’t need a bunch of people looking admiringly at it. The only real solution is to use some office tower space for dwelling units for the people employed in these hi rise temples to business, to save on commuting concerns. But, common sense being as common as it is, it seem we are all doomed to poisonous air, water, fish, beef, etc, unless we all get busy doing something about it, most importantly, thinking. Just what the hell do all those people in all those 50 th floor offices actually do? With computers, surely all clerical duties can be handled by robot telephone servers and email cheques? – Hide quoted text — Show quoted text -Large fabric or inflatable oars or rotors, or regular, but large slow, quiet propellors might enable the operator to row or pedal some distance in calm air, semi-orthinopter style. Could it qualify as a human powered helicopter? Maybe 15 or 20 years ago I saw a picture of the Comedian Gallagher flying a contraption that was a sort of ballon (maybe a hot air balloon) with a pedal operated propellor. I think it was a real working machine, not just a stage prop. When I did this calculation in my head I think I must have slipped a decimal point. Using a calculator, it appears that a hydrogen filled gas bag 10 meters long by 4 meters in diameter would just about lift a bit over 156 kilos, about 350 libs, at sea level. Hmm, it might be practical after all. Would you be allowed to wiegh the craft while full of ‘fuel’ gas and how would that affect fuel quantity allowance? You lost me.
There was a discussion about U/L weight restrictions, and it occurred to me that a hydrogen fuel bag possesses ‘negative weight.’ Do U/L regs presently make any allowance for fuel other than gasoline? How would the regulation apply to an U/L A/C with a large H2 fuel bag? Could you weigh the A/C without it’s fuel, or with it? What if you considered the non-empty fuel bag as a safety device like a float? So far as U/L construction is concerned, I wondered about the construction technique used by that most admirable of nature’s flyers, the dragonfly. Like all insects, it’s wing is constructed using stretched membranes inflated with a gas to assist in maintaining it’s shape. I wondered, and still do, if dragonflys or any other insects had evolved a method to use hydrogen to inflate it’s wings. It just seems so attractive, so beneficial that I would expect it to occur in nature, if it is possible. That leads me to question what kind of metabolistic process might yield H2 as a product. Perhaps the microbes living near the deep ocean’s ‘black smoker’ vents might produce H2 as a byproduct? Could that metabolistic process be transplanted into, say, soybeans, or kelp? Might it be already used by some flying insect that perhaps required special food, like nectar from a certain flower growing in a certain soil containing a certain catalyst, to produce H2 for it’s wings? It doesn’t seem likely, since if it was possible, we might be familiar with great numbers of airship insects, flying around without wings, more like fishes floating in the air. – Hide quoted text — Show quoted text -Or would there need to be a seperate regulation to cover airship hybrids? Maybe it would be covered under ‘experimental’. I also thought about using a low pressure fuel tank in a lightweight car the size of a tractor trailer instead of a heavy strong hydride tank. If you had a large H2 fuel bag, it would generate bouyancy. If you wanted to carry enough low pressure H2 fuel for long range, might it make sense to lose the heavy wheels, frame and other heavy stuff, … In my childhood I read an anthology of short (fictional) stories about a group of kids in a small town somewhere who entertained themselves by making neat contraptions. One story was called "The Great Balloon Race" or some such and instead of ahot air balloon with ballast they used a helium balloon and carried a gas powered compressor up with them. To go up, they let gas out of the bottle into the balloon. To go down, the compressed helium and put it back in the bottle.
That is about the same consideration as my previous question, below. I would like to see that anthology. – Hide quoted text — Show quoted text -How much bouyancy would you ‘lose’ if you pumped say, half of the gas in the lift bag into a 10 atmosphere bag? At what pressure does H2 weigh the same as stp atmosphere? Hydrogen at stp wieghs about what, about .2 of air? You might want to check a freshman physics text to see if my memory is accurate below. For P = pressure, V = Volume, T = absolute temperature, n = number of molecules, N = number of moles, M = molecular weight, and R = universal gas constant, A = avogodro’s number (6.022E23), m is mass and k is a constant. Avogdro’s law: Equal volumes of gas at the same temperature and pressure have equal numbers of molecules. Boyle’ law: PV = k at constant temperature Charles law: V2 = V1(T2 – T1) at constant pressure (1,2 are subscripts, not factors) The ideal gas law: PV = NRT = nkT where k = N/A or: PV = mrT, where r = R/M, so r is a different constant for each gas. Light gases within the temperature and pressure ranges of this discussion are very well modeled by these equations. Using them, you can answer all your questions. As a fun exercise, you can prove that water vapor is lighter than air. Have fun. It’s a gas.
When did moles take up airship flying? Seriously, I can envision personal H2 airships using this bouyancy bladder thing. It won’t do for Moller’s downtown flight plans, niether will Moller’s aircar toy, but for retreat camps, and way out in the lands of no roads, it might. Especially if you consider unserviced land is cheap, and cheapies like me like the idea of getting far away without a lot of fuel expense. Even thinking about ‘free’ flight slips me beyond the surly bonds of the earth.
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Or a small lawn chair with a lawn mower engine twirling a prop for short range fun?
http://tlc.ousd.k12.ca.us/~acody/larry.html On top of a typical skyscraper you’ll have room for about one dirigible at a time–where are you going to park the thing when it’s not being used? To a trapline, of course. Clothesline pullies with a balloon at the top, and several others on tethers. Just reel in the one you want, get in, and go. You would need to pull the thing down to get in it, unless the bouyancy compensator bladder could be pumped up and down quickly enough.
Cool, until you get high winds which are commonplace on top of skyscrapers. The Bernouli effect can make the wind over the top of a skyscraper much faster than ‘ambient’. Perhaps dirigible was not the right word, as I envision an ultralight soft bladder held in shape by internal webs and pressure, divided into several tubular gas bags, … The airship’s shape would resemble in principlal a bunch of banannas trying to straighten out, centered around and stretching the wire centre frame. A couple of bags could be shaped to take advantage of aerodynamics to direct the craft, as well as possibly contribute some lift at speed.
My thinking is that you want a lifting body that generates lift primarily by deflection from the lower surfaces. But probably you should not expect any more than a small amount od lift, basicly enough to trim the vehicle, because the bulkiness of the vehicle will make it impractical to generate a lot of aerodynamic lift. BTW, I think on the old DIrirgibles the props typically could rotate from horzontal to vertical. Large fabric or inflatable oars or rotors, or regular, but large slow, quiet propellors might enable the operator to row or pedal some distance in calm air, semi-orthinopter style. Could it qualify as a human powered helicopter?
Maybe 15 or 20 years ago I saw a picture of the Comedian Gallagher flying a contraption that was a sort of ballon (maybe a hot air balloon) with a pedal operated propellor. I think it was a real working machine, not just a stage prop. When I did this calculation in my head I think I must have slipped a decimal point. Using a calculator, it appears that a hydrogen filled gas bag 10 meters long by 4 meters in diameter would just about lift a bit over 156 kilos, about 350 libs, at sea level. Hmm, it might be practical after all. Would you be allowed to wiegh the craft while full of ‘fuel’ gas and how would that affect fuel quantity allowance?
You lost me. Or would there need to be a seperate regulation to cover airship hybrids?
Maybe it would be covered under ‘experimental’. I also thought about using a low pressure fuel tank in a lightweight car the size of a tractor trailer instead of a heavy strong hydride tank. If you had a large H2 fuel bag, it would generate bouyancy. If you wanted to carry enough low pressure H2 fuel for long range, might it make sense to lose the heavy wheels, frame and other heavy stuff, …
In my childhood I read an anthology of short (fictional) stories about a group of kids in a small town somewhere who entertained themselves by making neat contraptions. One story was called "The Great Balloon Race" or some such and instead of ahot air balloon with ballast they used a helium balloon and carried a gas powered compressor up with them. To go up, they let gas out of the bottle into the balloon. To go down, the compressed helium and put it back in the bottle. How much bouyancy would you ‘lose’ if you pumped say, half of the gas in the lift bag into a 10 atmosphere bag? At what pressure does H2 weigh the same as stp atmosphere? Hydrogen at stp wieghs about what, about .2 of air?
You might want to check a freshman physics text to see if my memory is accurate below. For P = pressure, V = Volume, T = absolute temperature, n = number of molecules, N = number of moles, M = molecular weight, and R = universal gas constant, A = avogodro’s number (6.022E23), m is mass and k is a constant. Avogdro’s law: Equal volumes of gas at the same temperature and pressure have equal numbers of molecules. Boyle’ law: PV = k at constant temperature Charles law: V2 = V1(T2 – T1) at constant pressure (1,2 are subscripts, not factors) The ideal gas law: PV = NRT = nkT where k = N/A or: PV = mrT, where r = R/M, so r is a different constant for each gas. Light gases within the temperature and pressure ranges of this discussion are very well modeled by these equations. Using them, you can answer all your questions. As a fun exercise, you can prove that water vapor is lighter than air. Have fun. It’s a gas. — FF
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Isn’t Kimo Jim working on the "lighter than air" catagory of Sportpilot / LSA? I bet he would have some insight. Bart
– Hide quoted text — Show quoted text – How about making an ultralight hybrid aircraft / dirigible inflated with hydrogen? Would you weight it empty (deflated) for weight restrictions if it was aircraft like? Would the 5 gallon gasoline fuel restriction for ultralights convert in any useful way into a volume of gaseous hydrogen equivalent? [snip]
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One word: helium.
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One word: helium.
Another word: expense. Helium has to be extacted from natural gas and shipped in pressure cylinders. Hydrogen can be produced locally. One problem with personal lighter than air craft is the size. Calculate how much volume you have to displace to lift your body. A dirigible is distinguished from a blimp by virtue of rigid or semirigid construction. That structure has to be lifted too, as well as the engine, fuel, gondola etc. On top of a typical skyscraper you’ll have room for about one dirigible at a time–where are you going to park the thing when it’s not being used? As the volume of the gas bag gets bigger and bigger the craft will be less able to move upwind. Even in still conditions it will be limited to speeds comparable to ground traffic. The advantage of dirigibles in the past has been that they can stay aloft for many days. That advantage was important when heavier than air craft were slower, less reliable and could not hover. A personal dirigible would be way cool however! — FF
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– Hide quoted text — Show quoted text – One word: helium. Another word: expense. Helium has to be extacted from natural gas and shipped in pressure cylinders. Hydrogen can be produced locally. One problem with personal lighter than air craft is the size. Calculate how much volume you have to displace to lift your body. A dirigible is distinguished from a blimp by virtue of rigid or semirigid construction. That structure has to be lifted too, as well as the engine, fuel, gondola etc. On top of a typical skyscraper you’ll have room for about one dirigible at a time–where are you going to park the thing when it’s not being used? As the volume of the gas bag gets bigger and bigger the craft will be less able to move upwind. Even in still conditions it will be limited to speeds comparable to ground traffic. The advantage of dirigibles in the past has been that they can stay aloft for many days. That advantage was important when heavier than air craft were slower, less reliable and could not hover. A personal dirigible would be way cool however!
Clearly the best option would be to maximise lift by combining the lifting gas with a burner to heat the gas like in a hot air ballon, by using hydrogen that would guarantee a rocket like performance and rate of climb, although endurance might be slightly limited! Alternatively instead of filling the structure of your ultralight with expensive helium to gain that precious two pounds of lift, just pipe the exhaust into the wings – that will fill the wings with hot air – if we assume a 10 metre wingspan, 1 metre cord, and an average wing depth of 10 cm, then the 1 cubic metre of air in the wings could easily provide a pound of lift. Andy
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One problem with personal lighter than air craft is the size. Calculate how much volume you have to displace to lift your body. A dirigible is distinguished from a blimp by virtue of rigid or semirigid construction. That structure has to be lifted too, as well as the engine, fuel, gondola etc.
Or a small lawn chair with a lawn mower engine twirling a prop for short range fun? On top of a typical skyscraper you’ll have room for about one dirigible at a time–where are you going to park the thing when it’s not being used?
To a trapline, of course. Clothesline pullies with a balloon at the top, and several others on tethers. Just reel in the one you want, get in, and go. You would need to pull the thing down to get in it, unless the bouyancy compensator bladder could be pumped up and down quickly enough. So now, we need what, a 1 hp hydrogen gas pump, about 20 pounds, to manage bouyancy without ‘ballast?’ Note, you would only need this power to descend without dumping gas. Perhaps dirigible was not the right word, as I envision an ultralight soft bladder held in shape by internal webs and pressure, divided into several tubular gas bags, one or more of which would be sturdily enough made to accept a considerable portion of the lift gas into a higher pressure bouyancy control and excess fuel bladder. The airship’s shape would resemble in principlal a bunch of banannas trying to straighten out, centered around and stretching the wire centre frame. A couple of bags could be shaped to take advantage of aerodynamics to direct the craft, as well as possibly contribute some lift at speed. Sort of a wing in body shape. Large fabric or inflatable oars or rotors, or regular, but large slow, quiet propellors might enable the operator to row or pedal some distance in calm air, semi-orthinopter style. Could it qualify as a human powered helicopter? Would some bouyancy assist nontheless allow a man to power an orthinopter style ‘bird suit?’ When I did this calculation in my head I think I must have slipped a decimal point. Using a calculator, it appears that a hydrogen filled gas bag 10 meters long by 4 meters in diameter would just about lift a bit over 156 kilos, about 350 libs, at sea level. Hmm, it might be practical after all.
Would you be allowed to wiegh the craft while full of ‘fuel’ gas and how would that affect fuel quantity allowance? Or would there need to be a seperate regulation to cover airship hybrids? This, naturally, is an attempt to figure out a way to enable common backyard flight, by eliminating as much noise as possible. I do believe the main objection to any sort of backyard aeroplane or helicopter would be the noise. The idea sprang out of seeing Moller’s impractical aircar on TV, and a vision for a method to store home made solar shingle derived hydrogen for a landcar using a large low pressure H2 gasbag tethered to and serviced by an unused chimney. I also thought about using a low pressure fuel tank in a lightweight car the size of a tractor trailer instead of a heavy strong hydride tank. If you had a large H2 fuel bag, it would generate bouyancy. If you wanted to carry enough low pressure H2 fuel for long range, might it make sense to lose the heavy wheels, frame and other heavy stuff, float under a gasbag in a swing seat and skidoo suit, and stop paying maintenance on road infrastructure, as well as energy penalties imposed by flight produced drag? No sense in moving next door to the factory, eh? We are thinking about a feasable low energy future, non? How much bouyancy would you ‘lose’ if you pumped say, half of the gas in the lift bag into a 10 atmosphere bag? At what pressure does H2 weigh the same as stp atmosphere? Hydrogen at stp wieghs about what, about .2 of air? If that bag springs a leak and empties, how much bouyancy would you lose? Consider that some of the H2 aboard would be intended as fuel and paradoxically, seemingly weighs first less, then more as it is consumed. What would be the most efficient shape for any airship using bouyancy for takeoff and aerodynamics for flight and a gliding landing, near empty of hydrogen fuel? Would it be a flattened, cambered, cut-off teardrop? So many silly questions from a tyro, eh? It is all very interesting. Terry K
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One problem with personal lighter than air craft is the size. Calculate how much volume you have to displace to lift your body. A dirigible is distinguished from a blimp by virtue of rigid or semirigid construction. That structure has to be lifted too, as well as the engine, fuel, gondola etc. On top of a typical skyscraper you’ll have room for about one dirigible at a time–where are you going to park the thing when it’s not being used?
When I did this calculation in my head I think I must have slipped a decimal point. Using a calculator, it appears that a hydrogen filled gas bag 10 meters long by 4 meters in diameter would just about lift a bit over 156 kilos, about 350 libs, at sea level. Hmm, it might be practical after all. — FF
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Try to remember the key words "Lighter than air". Helium is lighter than air and hydrogen is even lighter than helium. However, a vacuum is lighter than everything. You can’t fill a rubber balloon with a vacuum, but you can create one in your tubing structures. If you really feel its that important, just evacuate the air in the tubing. It will create more lift than filling it with hydrogen or helium. However, I think we’re talking grams and not pounds in either case, Dennis. Alternatively instead of filling the structure of your ultralight with expensive helium to gain that precious two pounds of lift, just pipe the exhaust into the wings – that will fill the wings with hot air – if we assume a 10 metre wingspan, 1 metre cord, and an average wing depth of 10 cm, then the 1 cubic metre of air in the wings could easily provide a pound of lift.
Dennis Hawkins n4mwd AT amsat DOT org (humans know what to do) "A RECESSION is when you know somebody who is out of work. A DEPRESSION is when YOU are out of work. A RECOVERY is when all the H-1B’s are out of work." To find out what an H-1B is and how Congress is using them to put Americans out of work, visit the following web site and click on the "Exporting America" CNN news video: http://zazona.com/ShameH1B/MediaClips.htm
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How about making an ultralight hybrid aircraft / dirigible inflated with hydrogen? Would you weight it empty (deflated) for weight restrictions if it was aircraft like? Would the 5 gallon gasoline fuel restriction for ultralights convert in any useful way into a volume of gaseous hydrogen equivalent? A dragonfly’s wings are stiffened by internal gas pressure, that’s obvious if you look at one. So are other insect wings, and they are the most efficient flyers there is. Are they inflated with hydrogen? That would seem like an advantageous evolution. Now, I can’t wait to capture one and see if the wing burns especially brightly. After watching the Discovery channel about Moller’s skycar, I can’t help wondering if an anti static hydrogen dirigible using fat wings shaped for lift would be more a conventional a/c or a dirigible. Seems a dirigible would make a far more practical aircar than a million dollar 8 engine robot flyer, at least for relatively short commutes to downtown from a suburb without roads, that would make housing developments cheaper. Besides, who is going to do a hundred miles an hour between skyscrapers in traffic on auto pilot, with the way winds flip around near them? I believe Moller’s idea is doomed, a millionaire’s pipe dream. Totally impractical and inefficient in a hydrogen powered world. If a dirigible had a hydrogen bouyancy compensating tank of variable but still relatively low pressure and volume inside a lower pressure bouyancy envelope, would pumping hydrogen gas between high and low pressure envelopes control lift and gross altitude in an efficient and effective manner, like some fish do, without needing inefficient ballast? What would happen if you lost power and coudn’t compress lift gas, and continued to rise out of control as the gas in the envelope expanded at increasing altitude? Would you need to dump H2 to come down, until you lost the capability to maintain altitude? Parachute time? Wouldn’t a dirigible inherently display good fuel efficiency, considering it doesn’t need to utilise power to generate lift, but perhaps only a little to fine control altitude for landing, etc? How good is the lift drag speed fuel economy tradeoff for a dirigible at useful speeds? How much could you gain or lose to headwinds and tailwinds? Why don’t we hear more about personal dirigibles fuelled and / or lifted by hydrogen, especially since modern anti static materials would seem to remove the Hindenburg terror factor? If the vectored propellors used to drive and control a dirigible were perhaps partly powered by thin film solar cells, hydrogen fuel cells, or hydrogen or gasoline internal combustion engines in various configurations, might there be a capability to build an affordable, quiet, backyard vtol vehicle, fuelled with H2 generated by home electrolysis? A hydrogen powered dirigible "car" doesn’t need expensive infrastructure like roads or bridges. How would that affect the national economy, considering fuel scarcities, especially if roads were abandoned? Is the box too small to think about this? Is there any comprehensive research on this? It seems a one or two person H2 dirigible might only be about as big as a bus, and it could be tethered to your rooftop. The fuel could be hydrolized from waste water during low hydro demand hours, or while the sun shone on solar shingles. Opinions? Don’t bother telling me I’m crazy, I suspected that decades ago, after talking to many of the sane dullards I meet. Most just need a consuming interest to become as crazy as me. Terry K
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