Re:Blimps are airships, and stratellites are good
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Broadband Blimps
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· Score: 1
In order to compete with the kinds of big ships you are talking about here, an airship would have to be a large fraction of a mile long--true even for a low altitude ship, I don't think you mean a high-altitude one, what would be the point? I think it can be done but it is fair to say that the skepticism on this point is pretty overwhelming. It certainly would cost a lot--I hope it can be done (after the first few prototypes) no more expensively than for surface ships of the same cargo-hauling potential (that is, a smaller faster airship equals a bigger slower surface ship) or maybe even for the same price as a surface ship of the same tonnage--which would be a very great price reduction compared to the current cost of a blimp per the (few) tons it lifts.
Now the nice thing about a 40,000 ton airship that is a kilometer long or more is, if you are hauling hazardous cargo you might design the ship to spread the cargo out all along its length to minimize the danger of chain reactions, and I even think that such cargo can be hauled in compartments designed to deflect the blast downward and outward, saving the ship.
It still would not be knucklehead-proof but it would be better. The anchor (there might be an anchor on an airship) might still wind up in Michigan, but only if you were flying over Michigan.
As for the Bermuda Triangle--I've heard the speculation that there are areas over big methane deposits on the continental shelves and that those deposits are unstable--it is possible for large amounts of the gas to bubble out all at once in a cascade, and if this happens the sea would turn to foam and any ships above this would drop like rocks to the sea floor.
If something like that happened I suppose a low-flying airship would be in some danger too. The methane would make a flammable mix in the air, but it would also lower its density and rob the airship of lift--until the gas diffused enough the airship might follow the surface ships into the foam and get wrecked when the bubbles slack off and the water thickens up again.
Or maybe the Bermuda Triangle is a big myth based on circumstantial evidence and spectacular selection of evidence--I remember on a NOVA epidsode once someone pointed out airplanes disappear over the continental United States--it is no big mystery then if ships and planes vanish out at sea.
Re:Stratellite altitude
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Broadband Blimps
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· Score: 2, Informative
There really isn't much call for using hydrogen these days; helium costs more but it will be only a small part of the total outlay, it's not like in the 1930s.
BTW Hindenburg was _not_ covered in flash powder! That theory is dead wrong. Its main proponent made a complete fool of himself by staging a demonstration where he ignited a piece of the Hindenburg's skin with a blowtorch, and the damn thing just smoldered a little. It was the hydrogen, which was equivalent in heat release potential to 50 tons of gasoline but burned a lot faster, that burned up the ship and there is zero evidence the skin had anything to do with it. Or how come this guy had a piece of it to abuse on camera?
As for hurricanes--how fast does the wind blow 65000 feet _above_ a hurricane? Probalby no faster than winds are already blowing up there is my guess. If not, you can always have extra airships and station then upwind so new ones are being blown in as fast as old ones blown out, and bring the displaced ones down afterward and use them later. For the latter option it helps not to use hydrogen!
Re:Blimps are airships, and stratellites are good
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Broadband Blimps
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· Score: 1
You've pretty much rediscovered the basic rationale behind all US military support for airships. The brass (those who weren't hostile that is) always saw the mission as being primarily observation. The Army used to have the blimps because they used to have the mission of coastal defense, even many miles out to sea. The Navy at that time focused on big rigids as long-range scouts that could locate enemy fleet elements quickly--and cheaply, for though the rigids suffered lots of criticisms as being expensive _as an airplane_ they were a lot cheaper than the surface ships they would relieve from scouting duties. And frankly they were supposed to be expendible too. Possibilities they could also be strike force platforms were always speculative. The main thing they overlooked (they thought of it but didn't develop it) was the potential of the big airship as a long-range heavy transport.
After the war the Navy kept its blimps for about 15 years, slashing back their numbers but the few they had were very good. They were huge and carried radars for both long-range early warning and for vectoring warplanes to targets at sea--they were much better at this than the AWACS planes of the day.
It would have been nice if the Coast Guard had been given a good share of the LTA development pie; I imagine airships could have proven themselves as maritime search and rescue craft--blimps were used that way to an extent , but I am thinking of a bigger airship that could actually pull people or even whole boats out of the water!
" 65000 on a rigid frame ship is pretty unlikely. "
Why? Why would a blimp be better?
It is often said that blimps are simpler and lighter but neither is really true. The fact is the airships that have had the best ratio of useful lift to total lift have always been the rigids!
Today we have made great progress with blimp materials since the 1930s, the last time a direct comparison could be made. But the useful lifts on pressure ships are still not in excess of 50 percent of total lift, and rigids were able to manage better than that. Furthermore, much of the weight of an oldtime rigid was fabric and lines, the very stuff that has been greatly improved since then, and the Zeppelin philosophy of optimizing each part to do its specialized job best would probably mean these fabrics can be lighter than on a pressure ship. Meanwhile we can also hope for some improvement of the rigid materials--better alloys, or maybe composites, or both as in the Zeppelin NT. The most daunting aspect of making a rigid (aside from the politics which damns it) is the labor involved in assembling it--however the individual parts are much easier to design and fabricate than good pressure hulls! This is why I would focus efforts on figuring out ways to mechanize and automate the assembly of a rigid. I think we can turn one out that is both cheaper and lighter than a pressure ship, especially for these high-altitude missions. A blimp on those must solve the problem of its lift gas being just a tiny fraction of its volume near the ground and sloshing around the envelope. But a rigid would apportion its gas ration into lots of separate gas cells and the gas would slosh within these but overall be properly distributed along the ship's length, solving the trim problem at low altitude,
They aren't thinking of rigids because "everybody knows" they are obsolete. I have friends who condemn rigids for being too fragile if they get bashed--but actually when that happened the damage tended to be confined to a limited section of the ship and was reparable, while blimps which _can_ take a certain amount of abuse will, if that amount is exceeded, rip and lose all their structure. They too are repairable but I think my friends' affinity is really based on the virtues of _small size_ and this giant Lockheed HAA is not small. Also in order to fly so high it will be as delicate as all hell here near the ground. A rigid might be like it was made of pretzels but the blimp will be make of like Kleenex! Either way you have serious handling issues, you just have to choose your days for ground operations carefully for still weather and avoid leaving it outside near the ground longer than you have to. And either get insurance or pray.
The military blimp is probably useless for any civil application but a similar project in rigid construction would develop techniques and materials that could easily be used for stronger low-altitude civil rigids (or military ones, for airlift).
But blimps fit beautifuly in the "airship" definition, don't they? I suppose some people have it in their heads that the grander words "airship" and "dirigible" must be reserved for the bigger rigid airships like Zeppelins, but both words apply to all airships and the first airships were blimps. That is, they relied exclusively on internal pressure to give their envelopes both aerodynamic and load-bearing structure. Actually in the old days this was hardly workable and they generally also had some kind of external keel that the gasbag lifted with lots of wires. (So did the earliest Zeppelins, and when the British decided to lighten their first attempt at a rigid, they removed the keel they had on it and it snapped in two when they tried to take it out of the hangar!) Move that keel inside or faired up tight against the gasbag and you have a semirigid.
"Blimp" is a colloquial word that refers to the sound the pressurized fabric hull makes when you thump it. The Navy preferred that they be called the more dignified "pressure ship." This term applies to semirigids too (like the modern Zeppelin NT that has a 3-sided internal frame that fills the interior but still relies on gas pressure to tension the skin for good aerodymnamic performance). I imagine the FAA defines pressure ships somewhere and distinguishes between "nonrigid" and "semirigid," Then again neither rigids nor semirigids have flown in the USA since the Hindenburg crashed and we operated the most numerous fleet of airships the world has ever seen during World War II--those were all blimps (mostly bigger one than the ones we have today; modern manned advertising blimps are about like the small trainer/close-in patrol "L-ships" of the war years. So American regulators got used to the idea that blimps are indeed airships and just call them airships, since there aren't other kinds to distinguish from and if there were there are other terms to more accurately make the distinction, when it matters.
Here it doesn't matter what structure these HAAs have, except that structural choices affect options. A rigid would be easy to keep in trim going up or coming down for instance while a blimp or normal design would be impossible since its little bubble of helium would be free to slosh around inside the big, mostly air-filled hull. But if we are just talking about performance aloft, any structure can work. I'd prefer rigid for several reasons but no one is asking me.
Re:Blimps are airships, and stratellites are good
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Broadband Blimps
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· Score: 1
It is quite true that a prop of a given size, turning at a given speed, with its blades held at a given angle, creates less thrust in less dense air, in proportion to the air density.
It is also true that this is bad news for _airplanes_. Airplanes need a fixed thrust since their lift comes from their wings and drag, relative to lift, is minimized at a fixed angle of attack, and so the plane must fly faster (in inverse proportion to the square root of the density) to get the same overall aerodynamic pressure to maintain this minimal thrust demand, or else it needs _even more_ thrust to stay airborne at some lesser airspeed. And to maintain the same thrust at higher speeds means more power so the engine has to get bigger and bigger. Meanwhile in order to get more thrust in thinner air the prop blades have to be pitched up higher meaning _they_ are less efficient.
But there is precious little understanding of LTA on Slashdot! Airships do not need to rely on aerodynamic lift and their aerostatic lift is fixed by the quantity of gas. Until they climb past where the gas expands beyond their volume (and must therefore vent some and lose lift) their lift is constant, barring variations due to temperature and humidity changes.
So there is no induced drag, and the profile drag area stays the same--and the air density falls, so the drag at a given speed also falls with it, and the thrust the prop makes falls at the same rate. The same prop and unsupercharged engine that propells it to a given speed near the ground attains the same speed up high, because the power demand on the engine falls with the falling thrust (less torque, same RPM) and so the engine needs no supercharging and runs cooler and uses less fuel. It is a big big _win_ for a prop-propelled airship to operate up near its pressure height then.
Lots of people make this same mistake and talk foolishly of needing ion drives etc for high altitude airships. They have not thought through what they are saying, just going by HTA reflexes.
The airships will be about 1/1000 the distance from recipients that geosynchronous comsats are at. This means that with the same power output its signal would be a million times stronger--or of course it can use a weaker output and _still_ have plenty of power to punch through the clouds.
And it is pretty much above most of the weather and completely above clouds itself.
The Sanswire FAQs were written by an LTA illiterate, clearly.
All airships have some nitrogen--and oxygen, and atmospheric trace gases--inside them when they are below their pressure height, the altitude where their helium has expanded to completely fill the hull (or gas cells, in the case of a rigid). This mix is called "air" and people who know stuff about LTA don't think of it as a lift gas at all because it isn't unless it is heated.
Pure nitrogen would be a bit LTA because O2 is heavier.
The thing is, they design for a particular altitude where the wind force is least. (Winds are fast, but the air is thin, and it works out to the least force). To descend from there means taking on stronger winds though if you plan to operate there all the time you can put more helium in and have a more robust ship. Vice versa to ascend beyond design height means you need to scant the helium meaning you cut weight to the bone--or have to redesign, and since wind speeds really pick up up there the forces are actually greater.
So until we have airships with _lots_ of structural margin, stratellites will pretty much have to operate at one level they are designed for, probably this optimum minimum wind force height.
Blimps are airships, and stratellites are good
on
Broadband Blimps
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· Score: 5, Informative
Any aircraft that gets most of its lift from lighter-than air gases and can be propelled against the wind is an airship. It floats in air and it goes where you want it, so it is an air-ship. Ok? Blimps are airships. Or dirigibles--different verbal approach, same idea, because the word emphasizes you can _direct_ the motion.
Several operations have tried this high-altitude business. There are issues with it but if you can make it work, the advantages over satellites should be clear. Why not use an airplane? Because the damn things use a lot of fuel and must move faster than the airship might be forced by shifting winds to move--relative speed matters with high-bandwidth connections.
The high altitude is chosen in part for the coverage range, but also to seek a layer of air where the average wind _force_ is lowest, to minimize the power needed to stay in place. With this design of airship they are going to have to turn to keep drag down if the wind shifts. True of all practical designs yet except spheres which have unacceptably high drag in _every_ direction--flattened disks called "lenticular" layouts might have lower inherent profile drag but have a tendency to pitch sideways to the wind that can only be combatted with fins that break the symmetry. So inevitably they will be blown off their ideal station point from time to time, the question is can they turn into the new wind fast enough to keep the divergence small. It depends on what the system users consider a small deviation at that range.
I would wait and see if their next demo comes off. Their last demo was about a year and a half ago, using Techsphere spherical airships. Just before the scheduled launch date their demo airship blew away! Nowadays Techsphere is persuading the Navy they can reliably operate for surveillance missions--I don't know if they paid attention to suggestions from people like me about how to reduce the drag of a sphere or if they have just had the good luck not to encounter severe winds in their demos yet. But meanwhile Sanswire has clearly washed their hands of Techsphere! Anyway they have been here before. We'll see I hope.
Re:Iron oxide, cellulose acetate, and aluminum pow
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Zeppelin Flies Again
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· Score: 1
With airships what looks nice and what is right are often the same thing. The doping and painting of airship hulls was done pretty much the same way for the American Naval rigids. The dope is first of all to shrink the fabric so it is taut on the girders and wires that shape it, so it does not flutter which would tend to create drag and damage it. Then too it seals it and creates a surface that can be sanded smooth. The aluminum was added to make it reflective, to ward off damaging solar radiation from the fabric components below, including solar heat that would otherwise render the lift very unpredictable by superheating the lift gas. All this was necessary and much of it was normal for airplanes too, which were only beginning to be made all of metal in this period. This stuff was definitely the right paint and efforts were made specifically to minimize its flammibility.
Also--although the fabric panels were indeed separate patches, the German practice, followed also by Americans making our 3 homemade rigids, was to paint on all the dope and surface paint layers on the fully constructed airship. It was done in layers allowing weeks between them, which cost a lot of time but resulted in one smooth aerodynamic surface--and also one smooth electrical surface, though the notion that the skin sparked the fire demands that the separate panels developed potential differences. This was impossible for the German or American ships.
In the last 2 British ships, R100 and R101, they tried to simplify construction by pre-doping the panels off line and then installing them, hoping to tie them down and tension them afterward. For a variety of reasons this worked out very badly. In theory these panels could have developed potential differences but among all the other problems the R-ships had that one was not observed!
This is the best case I have seen made for ammonia, but remember it is both stinky and poisonous. But that squirting in water to shrink it trick is a new one on me.
Weather: actually none of the latest rigids were terribly vulnerable to weather as such. Certainly they were not more vulnerable because they were bigger.
The Shenandoah was, like most of the vulnerable rigids of the 1920s, designed too closely after German "height-climber" designs that were meant to enable very high flight to get above British antiaircraft defenses. The late war Zeppelins designed for this mission achieved very impressive useful lift ratios but were quite fragile near sea level, where the Germans handled them very carefully. They did not explain this to the Allies who were generally too haughty to ask. After a lot of ships of that generation came apart in the air the next thing was to make them stronger; the British R100 and R101 were at least not likely to snap like twigs in the air, nor were Akron or Macon.
Akron was caught in a nasty storm all right, which tossed the whole ship down almost into the sea; trying to climb back up away from the sea brought her tail down into it, trapping the ship--but the near-100 percent fatality rate was due in part to a lack of boats, lifejackets, etc aboard. Just 3 men made it ashore, rescued by a passing freighter.
Macon lost her tail fin in a manner that was largely foreseen. It was already known from experience and improved theory at that point (1935) that the forces on the tailfins were underestimated (actually it was the _distribution_ of these that was wrong; it had not been realized how concentrated the force would be) and reinforcements were planned. Had these been undertaken sooner, I doubt the ship would have lost the fin. Once the fin was gone it took a lot of skin with it, and this exposed the rear gas cells to winds that deflated them. After that, many people do think the ship could have been saved with more skill but as it was communications were not very good and steps were taken that doomed the ship to come down. However all but 2 men were saved.
OTOH the Zeppelin captains were famous for using powerful winds as much as avoiding them; it came down to very careful study of the weather. When you are traveling intercontinental distances and the name of the game is to make good time between two distant cities, there are a lot of options available as to route; they used that. The American military ships had a lot to prove to skeptical Navy brass that they could take rough weather; that anxiety had a lot to do with why Akron was out there in bad weather (that and poorly developed weather forecasting) and why Macon's retrofitting was delayed.
Generally speaking, an airship moves with the air and only violent changes and transitions in the air (which do happen of course) threaten it. The Zeppelin captains tended to go _down_ to surface level when they had to go through rough air, on the theory that winds don't blow up or down near the surface.
Vectored thrust probably makes no difference in cruise maneuvering; the tail surfaces are very effective then. It is during ground handling that they help a lot and ground handling is the most vulnerable aspect of airships. This is where size brings the big penalties. Aloft I believe size will enable stout construction (high volume to surface ratio helps there) and a slower turning rate is not a serious impediment. But near the ground agility matters more. Really big airships should avoid coming down basically; fortunately airplanes can hook on to them and now we have helicopters too though I am nervous about their landing on top, and it is hard to see how to enable them to hook on from below.
Well, there is speed. An airship is a lot slower than a modern plane but could carry a lot; it is a lot faster than a ship so it can get away with carrying less. To compare to really big ships you'd need really big airships but there is a lot of room in the sky and such big ships would not need to land often.
Then too as others have said they can go just about anywhere, delivering cargo directly to otherwise inaccesible destinations. And wherever they go they can fly over reasonably low land whereas surface ships must circumnavigate obstacles; this often doubles the distance they need to cover which halves their effective speed relative to the airship.
Airships can also have airplanes take off and land from them which opens up vistas of integrated systems that multiply the value of both planes and the airships.
It would be silly to expect airships to do exactly what ships do now since we already have the ships to do that.
Re:Iron oxide, cellulose acetate, and aluminum pow
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Zeppelin Flies Again
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· Score: 1
Kind of hard to believe that German engineers in the 1930s would be quite that stupid, isn't it? Let's suppose Nazism addled their brains. Even addled, German engineers came up with some pretty impressive technology across the board, they didn't miss many boats technically speaking and frankly were way ahead of the Allies in many important applications--getting their wonder weapons built in quantity was another story of course, what with the whole world being at war with them and denying them supplies and all, and bombing what they did make. Anyway Hugo Eckener, the brains behind Zeppelin at that point, was about as anti-Nazi as anyone could be in the Third Reich and survive. Quite a decent man really. No, we have to face the fact that German engineers were not idiots and would not compound their problems lightly.
Nor did they in this case. It is just not true that the skin material burnt easily--if it did they'd have seen it go up the first time the engines made sparks. The diesel engines were very well-behaved but the skin material near the engine cars did have burns in it--they just didn't spread. Nor can anyone make a good case for the skin being a sparky material likely to set the hydrogen off.
I just figured out how much heat release potential the ship's hydrogen represented. Hydrogen is an excellent fuel on a weight basis all right, burning one kilogram of it would release more heat than burning over 2 1/2 kg of hydrocarbon fuel. And gaseous H2 is about 1/15 as dense as air which masses 1.225 kg/cubic meter under standard conditions at sea level, so given the ship's volume (about 220,000 cubic meters for lift gas) the hydrogen had about as much energy to release as would 50 tons of gasoline!
Maybe that does not sound like much but imagine it all burning up in 30 seconds or so. Let me help--the ship was 245 meters long (806 feet) so imagine a trough 800 feet long and about one and 1/2 feet deep and wide--full of gasoline from end to end. Every foot of it would be about 16 gallons or so, about like a very big car's fuel tank worth, only there are 800 of them. How close do you want to get to that trough, and how much assurance do you want that there are no sparks around if you have to come within 60 feet of it? And if someone did toss a match at it, how long do you think it would take the flames to get from one end to the other?And how much heat would the resulting conflagration release? How long would it take to burn to the bottom of the trough?
Now I don't have mass figures handy but I think the outer skin was about 10 tons in mass. For it to match the performance of this trough, it would have to release 5 times the heat per kilogram as gasoline does. You know, explosives don't contain more chemical energy than fuels do, they can just release what they have instantly. But if they were more energetic we'd use them for fuels instead of oil!
So I find it hard to believe that even if the skin were made of pure guncotton (as I myself have mistakenly compared the skin of these airships to in the past) it could possibly have contributed more than 1/10 or so of the total fire energy. And in fact I imagine gaseous hydrogen would burn up much more rapidly than merely volatile gasoline. The Hindenburg's diesel fuel burned for something close to 10 hours after the crash--but it was depleted by then; imagine 50 hours worth of diesel fires--released in one minute. That is what the hydrogen did; the skin did not do it.
So we might question their judgement in using hydrogen at all but once that decision was made, they having no useful alternatives but to give up airships completely, they did their best. The skin did not demonstrate any of the arcane and volatile properties some irresponsible people project on it today; it was chosen to minimize problems not create them.
Despite the risks he ran I envy Harold Dick's frequent flight's in the two grandest passenger airships ever made (or two of three, the last one LZ-130 was really something, and the Nazis commandeered it for th
Re:Iron oxide, cellulose acetate, and aluminum pow
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Zeppelin Flies Again
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· Score: 1
Whatever do you mean by "fireproof?" Airships are very diffuse, low-mass things, about 1/100 or so the density of a normal ship. Any materials enclosing big volumes like gas cells or the outer skin have to be thin stuff. It does not matter if they burn or not, the heat of a significant amount of loose hydrogen burning would _melt_ holes in anything that thin. Then there would be more hydrogen--and as you point out the cells would be expanding too. At not so much expansion, maybe 10 percent, they would valve more gas that would normally be vented up vents but in this case the vents would be hot--more flame. And the cells would burst or at least split seams if heated too fast--need I go on? What happened was not an "explosion" but a very rapid spreading gas fire--and all its heat was trapped inside the hull. It was a lot of heat; even if the surrounding materials did not burn somehow, they would glow. And melt; the gas would then quickly escape and the ship come crashing down just as it did. The long fire _after_ the crash was from flammible materials, mostly fuel, aboard. The crash, and the terrible burns some people suffered, were due to the immediate hydrogen fire. It would not matter to them whether the rest of the ship were made of asbestos or not.
Re:Iron oxide, cellulose acetate, and aluminum pow
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Zeppelin Flies Again
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· Score: 1
First of all the "total mixture" was not mixed, it was separate layers painted on separately.They could not seep into each other or anything. Even if the components were of the right nature and proportions to serve as a rocket fuel if mixed, they would need to be mixed and they were not. Second, it is not true that these materials were of a suitable mix, and if they were, solid rocket fuels actually burn rather slowly, much more slowly than the flames could be seen racing along the body of the stricken Zeppelin.
The iron oxide is particularly interesting--it was painted only on the upper hull. If it played any major role in the conflagration surely the upper hull should have burnt much more rapidly than the lower! But it did not, the flames gave every appearance of being a blowtorch from _inside_ the hull.
Color is irrelevant when the hydrogen is contained inside other materials--burning hydrogen sets these afire and superheats them too, they glow in their characteristic frequencies and not hydrogen's even if the hydrogen is supplying the heat!
The fire "burned down" because it took time for the hydrogen to burn through and in that time (just seconds to be sure) the interior air/gas cell volume was heated to the flame point of many substances inside, including those below. And there was hydrogen at considerable distances down the hull, especially once its cells were heated and they expanded before bursting.
Once a huge hydrogen conflagration, very largely contained inside the hull, was under way of course just about everything else burned too. Even the skin.
But have you ever seen the pathetic demonstration of Addison Bain, author of this false theory, trying to set an alleged sample of Hindenburg skin afire? It would take something like a hydrogen fire to get it really going!
http://spot.colorado.edu/~dziadeck/zf/LZ129fire. ht m
Blessed are you for you have been misled by completely bogus pseudoscience for less time than these smug others.
The doping material was not rocket fuel, no element of the skin could plausibly have caused any of the contributions toward catastrophe that are attributed to it by this false theory.
Why would all the people interested in LTA techology from the 1930s until the late 1990s have ignored the possibility it was the skin if it were in fact possible? But it is not a possibility:
http://spot.colorado.edu/~dziadeck/zf/LZ129fire. ht m
What has gone on here is that people with agendas to use hydrogen for various purposes including as a lift gas for LTA have indulged in massive wishful thinking and 60 years after the fact it is easy to create this mirage of the "rocket fuel skin." Which for some reason or other only actually burned this once, whereas if you believe the modern myth, all those other hydrogen-filled ships that did burn up in rapid conflagrations were all the victims of completely different mishaps--fuel explosions for instance--that only coincidentally stopped happening when various parties shifted over to helium for lift gas.
No, it was the hydrogen. Hydrogen might have been an acceptable, manageable risk when there was no good alternative but now that there is one (and at least one other I know of that is not as good but still avoids the fire risks) there is no good reason to take the risks anymore.
It certainly was not the skin. Bain himself tried setting some on fire (consider that he had a piece of this allegedly incidiary stuff someone allegedly found lying around on the wreck site--why didn't it burn up? And what kind of scholar is anyone who destroys some authentic Hindenburg skin for a demonstration?) and it sort of fizzled after he tried to light it with a blowtorch. Forget the Incidiary Paint Theory! Or remember it as a lesson in bogus science.
Here it's me again--if you don't believe me read this:
http://spot.colorado.edu/~dziadeck/zf/LZ129fire. ht m
It was not the skin material that caused or comprised most or even much of the Hindenburg fire; it was the hydrogen. Which explains why many many hydrogen ships of diverse construction have gone up rapidly in totally destructive flames while few helium ships (there have been lots of blimps and a few other kinds) have burned at all, and those slowly and clearly due to fuel fires.
Nope, the skin was not "rocket fuel," if it were it would not have burned from stern to bow in less than a minute, it could not self-ignite nor is there reason to think it played a role in igniting the hydrogen either.
Hindenburg burned because of the hydrogen, the paint did not even contribute much to the conflagration. How else could there be surviving pieces of the skin for revisionists to stage self-defeating, embarrassing demonstrations for cameras with?
http://spot.colorado.edu/~dziadeck/zf/LZ129fire. ht m
Check it out. There are a thousand holes in the paint theory and related arguments (eg that hydrogen airships were perfectly safe) and this one nails four of them, each sufficient to put the false claims to rest.
Re:using up the planet's supply of helium?
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Zeppelin Flies Again
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· Score: 2, Interesting
No you can't! Forget vacuum, it is too difficult to make it work. If you have materials that can keep vacuum _out_ you can much more easily keep gas in--if the material is that strong maybe it would be safe to keep hydrogen in it.
Or you can use steam for lift gas.
www.flyingkettle.com
Or if you have a supply of helium (painfully extracted from the atmosphere for instance, given enough work you can do it) I have a trick to _conserve_ the helium that would stretch its usefulness to the point where slow extraction of replacement gas from the atmosphere would keep up with the reduced rate of loss. The original version involved a thin layer of steam outside the helium, another involves a thin layer of hydrogen--there is risk of fire but limited risk if the layer is thin enough.
Any of this is preferable to trying to hold vacuum out of a volume. I suppose it could be done someday with a light enough container to leave some lift, but whatever wonder material you might be using can be put to more efficient uses.
Aerogels come up a lot in this context for instance. Well, besides being very light they are also great insulators--so instead of trying to keep a vacuum inside the gel you heat up the air a whole lot inside, and most of it goes out, leaving almost a vacuum--very hot air. Which is easy to keep hot because the aerogel does not conduct heat well, and it is easy to make this structure light because it does not have to bear the terribly strong compression forces a vacuum would leave the hull to bear.
There will always be a better way than vacuum. which strikes me as damn unstable anyway--any leak you get, you lose lift _fast_! Might as well contemplate a photon gas--that might work if you had a perfect reflector, but one pinhole and your pressure gas is out at 3E8 meters per second...
Re:Old news...is sometimes false
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Zeppelin Flies Again
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· Score: 2, Informative
You are referring to Addison Bain's misleading claims.
He is quite wrong about the skin in many different ways. It could not generate sparks in the ways he claimed, and if such sparks were applied to it they would not ignite it, and if someone did set the skin on fire it would not burn nearly as fast or energetically as he claimed, not by orders of magnitude. He compares the mix to "rocket fuel" but first of all this is false, it lacks the right components in the right proportions to burn as a rocket fuel. Actually solid fuel rocket fuel does not burn at the rapid rates he assumes either. But anyway the skin was not a uniform mix of all the chemical components (which he gets wrong) it was a layered composite, with the various chemicals separated.
Bain himself made a hash of his claims that the skin self-ignited and then burn furiously, so vigorously as to eclipse the heat of hydrogen combustion, when he took a piece of Hindenburg's own skin and tried to set it afire for cameras. He used an arc torch, making no attempt to demonstrate that static discharges alone could do the job, and even so it burnt very weakly.
Bain's real agenda is to prove that hydrogen is reasonably safe to use, mainly because he works with liquid hydrogen as a fuel. It is a bit silly to try to prove LH2 safe by claiming hydrogen was never at fault in the numerous cases of hydrogen-filled airships that went up in flames, since a huge bag of gaseous hydrogen separated from air by thin membranes is very different from a tank of cryogenic liquid inside thick insulation. Anyway lots of hydrogen airships of all types, using lots of different types of skin, burned spectacularly generally with great cost of lives and sometimes property damage. Some helium-filled airships have indeed burnt, but not easily and never with the kind of rapid chain reaction evident in the Hindenburg fire. Clearly most of the energy that consumed the ship in just seconds came from burning hydrogen; the bright visible light that Bain tries to claim proves it was some other materials (pure hydrogen flame is in UV and invisible to the human eye) comes from that hot fire setting the other materials afire and superheating them, just as the mantle on a gas lantern transforms the pale blue flame of propane into bright redder light.
It is quite true that the old Zeppeliners did their best to minimize the dangers of hydrogen and generally carried it off. It is false that helium is so much worse than hydrogen that using it spelled doom for airships. What spelled doom for airships IMHO was the determined opposition of many interests that preferred to develop airplanes and helicopters and regarded the market as too limited to support both HTA and LTA. Hydrogen fires, and the cost and limited supply of helium, were good excuses to divert development funds away from airships.
But it is ridiculous to suggest that the NT could carry a lot more pax if it used hydrogen! Maybe 3 or 4 more, at risk of their lives--a hydrogen _pressure ship_ is much more risky than a hydrogen rigid, which is bad enough.
A bigger airship could be made using helium that would work just fine. The second-largest rigids were made in the USA and were wonderful ships, the USS Akron and Macon.
It is a semirigid not a rigid since the helium fills the interior instead of being in separate cells, and is pressurized by an air ballonet so as to tension the skin, which is also the gas containment as on a blimp. So on one hand there is no need to stiffen the hull, and on the other the aerodynamics depends on maintaining pressure, and a rip in the hull would threaten to leak all the helium out instead of just a portion. But they thought it would be easier to make or something; I have my doubts.
But it is flying and a good-looking ship, one of several actually. I just hope they will make much bigger ones soon, maybe go for a true rigid.
1) It's a Zeppelin because Zeppelin company makes it. They make treaded tractors too.
2) it's not a blimp because it has a frame--I've comented on that elsewhere and so have others.
3) yes, blimps are airships-pressure airships to be exact. And they tend to be much smaller than the rigids were. A rigid, or a semi-rigid like the NT, _can_ be as small as any blimp--the smallest rigid that ever flew manned was about half the volume of the average advertising blimp. There is considerable doubt on the other hand how big a blimp can safely be made. The danger is rips or other accidents resulting in loss of pressure and also lift gas.
4) the NT is indeed about the same size and shape as a large modern blimp (considerably smaller than the big blimps the US Navy operated in the 1950s, even smaller than the standard patrol K-ship of WWII). So I feel your frustration--and there are very few of all of these small ships flying.
5) I say "small" only in the relative sense--even a small manned blimp is generally longer than 60 meters, which is the wingspand of a Boeing-747. If you ever get close to one you'll be impressed! Hindenburg was 245 meters long and 40 in diameter. That is big. And yet I think they should have been bigger still.
The NT has ribs--3 longitudinal ribs made of aluminum, spaced by triangular transverse frames made of composites. It is classified as a "semirigid," meaning that the frame helps keep the overall shape and distributes the lift, but the lift gas has to be pressurized to put tension on the skin, which contains the gas and also serves as the aerodynamic surface, as in blimps.
Blimps are nonrigid or pressure ships--all of their structure results from pressurizing the lift gas by means of air ballonets inside them. They have no rigid members.
The alternative is a rigid frame and stiff external skin; this approach frees you of the need to pressurize the lift gas. Generally this means a complex structure like the classic Zeppelins--but that structure was often, even taken altogether with its numerous parts of gas cells, netting, frame members, wiring, and outer skin, lighter per unit of lift volume than blimps, even the best modern blimps.
The big drawback of pressure ships, including semirigids, is that if you lose pressure for any reason you lose structure. On a semirigid it is not quite as bad, especially on the NT with its three ribs which pretty much would maintain the basic shape, but you'd lose skin tension hence get a lot more draggy. On a blimp loss of pressure is a disaster. Also, pressure ships are hard to partition so any big leak or rip will tend to spill _all_ the lift gas, whereas on the rigids the gas was kept in numerous separate cells and total deflation of one or several might still leave the ship airborne--I know of several instances of that.
The semirigid form does allow you to distribute weights all along the length of the ship which is important, and the NT version also allows elements like the props to be moved up along the width of the hull, kind of like what was possible on the old rigids. What is most "new" about the New Technology Zeppelin is its vectored thrust system. Modern blimps have used pairs of vectored props (though attached to the gondola, their only rigid element, rather than up along the hull sides which is clearly better) but the NT adds an arrangement on the tail tip that greatly increases the control available; this is possible because of the ribs.
Still a number of us wish they'd gone ahead and made a modern rigid while they were at it; such a ship would have enabled all this, freed them of pressurization issues, and given the crew access to the entire interior so if an engine gave trouble in mid-air someone could go and try to fix it. Happened all the time on the rigids! Fortunately modern engines are more reliable, but a major issue of the NT is that you need special equipment to get at the engines, mounted up high as they are, for maintenance, it restricts their operations.
I also think a modern rigid would have been as light or lighter, and very possibly cheaper to make and maintain. All they'd need to do to make the NT a rigid would be to devise some kind of very light aerodynamic shell to replace the skin, and then design some gas cells--just basically balloons-to fit inside the spaces betweent the frames. Well actually the frames are braced with wires so either the cells would have to contain those or else the structure would have to be redesigned to avoid running the wires there.
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In order to compete with the kinds of big ships you are talking about here, an airship would have to be a large fraction of a mile long--true even for a low altitude ship, I don't think you mean a high-altitude one, what would be the point? I think it can be done but it is fair to say that the skepticism on this point is pretty overwhelming. It certainly would cost a lot--I hope it can be done (after the first few prototypes) no more expensively than for surface ships of the same cargo-hauling potential (that is, a smaller faster airship equals a bigger slower surface ship) or maybe even for the same price as a surface ship of the same tonnage--which would be a very great price reduction compared to the current cost of a blimp per the (few) tons it lifts.
Now the nice thing about a 40,000 ton airship that is a kilometer long or more is, if you are hauling hazardous cargo you might design the ship to spread the cargo out all along its length to minimize the danger of chain reactions, and I even think that such cargo can be hauled in compartments designed to deflect the blast downward and outward, saving the ship.
It still would not be knucklehead-proof but it would be better. The anchor (there might be an anchor on an airship) might still wind up in Michigan, but only if you were flying over Michigan.
As for the Bermuda Triangle--I've heard the speculation that there are areas over big methane deposits on the continental shelves and that those deposits are unstable--it is possible for large amounts of the gas to bubble out all at once in a cascade, and if this happens the sea would turn to foam and any ships above this would drop like rocks to the sea floor.
If something like that happened I suppose a low-flying airship would be in some danger too. The methane would make a flammable mix in the air, but it would also lower its density and rob the airship of lift--until the gas diffused enough the airship might follow the surface ships into the foam and get wrecked when the bubbles slack off and the water thickens up again.
Or maybe the Bermuda Triangle is a big myth based on circumstantial evidence and spectacular selection of evidence--I remember on a NOVA epidsode once someone pointed out airplanes disappear over the continental United States--it is no big mystery then if ships and planes vanish out at sea.
There really isn't much call for using hydrogen these days; helium costs more but it will be only a small part of the total outlay, it's not like in the 1930s.
BTW Hindenburg was _not_ covered in flash powder! That theory is dead wrong. Its main proponent made a complete fool of himself by staging a demonstration where he ignited a piece of the Hindenburg's skin with a blowtorch, and the damn thing just smoldered a little. It was the hydrogen, which was equivalent in heat release potential to 50 tons of gasoline but burned a lot faster, that burned up the ship and there is zero evidence the skin had anything to do with it. Or how come this guy had a piece of it to abuse on camera?
As for hurricanes--how fast does the wind blow 65000 feet _above_ a hurricane? Probalby no faster than winds are already blowing up there is my guess. If not, you can always have extra airships and station then upwind so new ones are being blown in as fast as old ones blown out, and bring the displaced ones down afterward and use them later. For the latter option it helps not to use hydrogen!
You've pretty much rediscovered the basic rationale behind all US military support for airships. The brass (those who weren't hostile that is) always saw the mission as being primarily observation. The Army used to have the blimps because they used to have the mission of coastal defense, even many miles out to sea. The Navy at that time focused on big rigids as long-range scouts that could locate enemy fleet elements quickly--and cheaply, for though the rigids suffered lots of criticisms as being expensive _as an airplane_ they were a lot cheaper than the surface ships they would relieve from scouting duties. And frankly they were supposed to be expendible too. Possibilities they could also be strike force platforms were always speculative. The main thing they overlooked (they thought of it but didn't develop it) was the potential of the big airship as a long-range heavy transport.
After the war the Navy kept its blimps for about 15 years, slashing back their numbers but the few they had were very good. They were huge and carried radars for both long-range early warning and for vectoring warplanes to targets at sea--they were much better at this than the AWACS planes of the day.
It would have been nice if the Coast Guard had been given a good share of the LTA development pie; I imagine airships could have proven themselves as maritime search and rescue craft--blimps were used that way to an extent , but I am thinking of a bigger airship that could actually pull people or even whole boats out of the water!
" 65000 on a rigid frame ship is pretty unlikely. "
Why? Why would a blimp be better?
It is often said that blimps are simpler and lighter but neither is really true. The fact is the airships that have had the best ratio of useful lift to total lift have always been the rigids!
Today we have made great progress with blimp materials since the 1930s, the last time a direct comparison could be made. But the useful lifts on pressure ships are still not in excess of 50 percent of total lift, and rigids were able to manage better than that. Furthermore, much of the weight of an oldtime rigid was fabric and lines, the very stuff that has been greatly improved since then, and the Zeppelin philosophy of optimizing each part to do its specialized job best would probably mean these fabrics can be lighter than on a pressure ship. Meanwhile we can also hope for some improvement of the rigid materials--better alloys, or maybe composites, or both as in the Zeppelin NT. The most daunting aspect of making a rigid (aside from the politics which damns it) is the labor involved in assembling it--however the individual parts are much easier to design and fabricate than good pressure hulls! This is why I would focus efforts on figuring out ways to mechanize and automate the assembly of a rigid. I think we can turn one out that is both cheaper and lighter than a pressure ship, especially for these high-altitude missions. A blimp on those must solve the problem of its lift gas being just a tiny fraction of its volume near the ground and sloshing around the envelope. But a rigid would apportion its gas ration into lots of separate gas cells and the gas would slosh within these but overall be properly distributed along the ship's length, solving the trim problem at low altitude,
They aren't thinking of rigids because "everybody knows" they are obsolete. I have friends who condemn rigids for being too fragile if they get bashed--but actually when that happened the damage tended to be confined to a limited section of the ship and was reparable, while blimps which _can_ take a certain amount of abuse will, if that amount is exceeded, rip and lose all their structure. They too are repairable but I think my friends' affinity is really based on the virtues of _small size_ and this giant Lockheed HAA is not small. Also in order to fly so high it will be as delicate as all hell here near the ground. A rigid might be like it was made of pretzels but the blimp will be make of like Kleenex! Either way you have serious handling issues, you just have to choose your days for ground operations carefully for still weather and avoid leaving it outside near the ground longer than you have to. And either get insurance or pray.
The military blimp is probably useless for any civil application but a similar project in rigid construction would develop techniques and materials that could easily be used for stronger low-altitude civil rigids (or military ones, for airlift).
But blimps fit beautifuly in the "airship" definition, don't they? I suppose some people have it in their heads that the grander words "airship" and "dirigible" must be reserved for the bigger rigid airships like Zeppelins, but both words apply to all airships and the first airships were blimps. That is, they relied exclusively on internal pressure to give their envelopes both aerodynamic and load-bearing structure. Actually in the old days this was hardly workable and they generally also had some kind of external keel that the gasbag lifted with lots of wires. (So did the earliest Zeppelins, and when the British decided to lighten their first attempt at a rigid, they removed the keel they had on it and it snapped in two when they tried to take it out of the hangar!) Move that keel inside or faired up tight against the gasbag and you have a semirigid.
"Blimp" is a colloquial word that refers to the sound the pressurized fabric hull makes when you thump it. The Navy preferred that they be called the more dignified "pressure ship." This term applies to semirigids too (like the modern Zeppelin NT that has a 3-sided internal frame that fills the interior but still relies on gas pressure to tension the skin for good aerodymnamic performance). I imagine the FAA defines pressure ships somewhere and distinguishes between "nonrigid" and "semirigid," Then again neither rigids nor semirigids have flown in the USA since the Hindenburg crashed and we operated the most numerous fleet of airships the world has ever seen during World War II--those were all blimps (mostly bigger one than the ones we have today; modern manned advertising blimps are about like the small trainer/close-in patrol "L-ships" of the war years. So American regulators got used to the idea that blimps are indeed airships and just call them airships, since there aren't other kinds to distinguish from and if there were there are other terms to more accurately make the distinction, when it matters.
Here it doesn't matter what structure these HAAs have, except that structural choices affect options. A rigid would be easy to keep in trim going up or coming down for instance while a blimp or normal design would be impossible since its little bubble of helium would be free to slosh around inside the big, mostly air-filled hull. But if we are just talking about performance aloft, any structure can work. I'd prefer rigid for several reasons but no one is asking me.
It is quite true that a prop of a given size, turning at a given speed, with its blades held at a given angle, creates less thrust in less dense air, in proportion to the air density.
It is also true that this is bad news for _airplanes_. Airplanes need a fixed thrust since their lift comes from their wings and drag, relative to lift, is minimized at a fixed angle of attack, and so the plane must fly faster (in inverse proportion to the square root of the density) to get the same overall aerodynamic pressure to maintain this minimal thrust demand, or else it needs _even more_ thrust to stay airborne at some lesser airspeed. And to maintain the same thrust at higher speeds means more power so the engine has to get bigger and bigger. Meanwhile in order to get more thrust in thinner air the prop blades have to be pitched up higher meaning _they_ are less efficient.
But there is precious little understanding of LTA on Slashdot! Airships do not need to rely on aerodynamic lift and their aerostatic lift is fixed by the quantity of gas. Until they climb past where the gas expands beyond their volume (and must therefore vent some and lose lift) their lift is constant, barring variations due to temperature and humidity changes.
So there is no induced drag, and the profile drag area stays the same--and the air density falls, so the drag at a given speed also falls with it, and the thrust the prop makes falls at the same rate. The same prop and unsupercharged engine that propells it to a given speed near the ground attains the same speed up high, because the power demand on the engine falls with the falling thrust (less torque, same RPM) and so the engine needs no supercharging and runs cooler and uses less fuel. It is a big big _win_ for a prop-propelled airship to operate up near its pressure height then.
Lots of people make this same mistake and talk foolishly of needing ion drives etc for high altitude airships. They have not thought through what they are saying, just going by HTA reflexes.
The airships will be about 1/1000 the distance from recipients that geosynchronous comsats are at. This means that with the same power output its signal would be a million times stronger--or of course it can use a weaker output and _still_ have plenty of power to punch through the clouds.
And it is pretty much above most of the weather and completely above clouds itself.
The Sanswire FAQs were written by an LTA illiterate, clearly.
All airships have some nitrogen--and oxygen, and atmospheric trace gases--inside them when they are below their pressure height, the altitude where their helium has expanded to completely fill the hull (or gas cells, in the case of a rigid). This mix is called "air" and people who know stuff about LTA don't think of it as a lift gas at all because it isn't unless it is heated.
Pure nitrogen would be a bit LTA because O2 is heavier.
The thing is, they design for a particular altitude where the wind force is least. (Winds are fast, but the air is thin, and it works out to the least force). To descend from there means taking on stronger winds though if you plan to operate there all the time you can put more helium in and have a more robust ship. Vice versa to ascend beyond design height means you need to scant the helium meaning you cut weight to the bone--or have to redesign, and since wind speeds really pick up up there the forces are actually greater.
So until we have airships with _lots_ of structural margin, stratellites will pretty much have to operate at one level they are designed for, probably this optimum minimum wind force height.
Any aircraft that gets most of its lift from lighter-than air gases and can be propelled against the wind is an airship. It floats in air and it goes where you want it, so it is an air-ship. Ok? Blimps are airships. Or dirigibles--different verbal approach, same idea, because the word emphasizes you can _direct_ the motion.
Several operations have tried this high-altitude business. There are issues with it but if you can make it work, the advantages over satellites should be clear. Why not use an airplane? Because the damn things use a lot of fuel and must move faster than the airship might be forced by shifting winds to move--relative speed matters with high-bandwidth connections.
The high altitude is chosen in part for the coverage range, but also to seek a layer of air where the average wind _force_ is lowest, to minimize the power needed to stay in place. With this design of airship they are going to have to turn to keep drag down if the wind shifts. True of all practical designs yet except spheres which have unacceptably high drag in _every_ direction--flattened disks called "lenticular" layouts might have lower inherent profile drag but have a tendency to pitch sideways to the wind that can only be combatted with fins that break the symmetry. So inevitably they will be blown off their ideal station point from time to time, the question is can they turn into the new wind fast enough to keep the divergence small. It depends on what the system users consider a small deviation at that range.
I would wait and see if their next demo comes off. Their last demo was about a year and a half ago, using Techsphere spherical airships. Just before the scheduled launch date their demo airship blew away! Nowadays Techsphere is persuading the Navy they can reliably operate for surveillance missions--I don't know if they paid attention to suggestions from people like me about how to reduce the drag of a sphere or if they have just had the good luck not to encounter severe winds in their demos yet. But meanwhile Sanswire has clearly washed their hands of Techsphere! Anyway they have been here before. We'll see I hope.
With airships what looks nice and what is right are often the same thing. The doping and painting of airship hulls was done pretty much the same way for the American Naval rigids. The dope is first of all to shrink the fabric so it is taut on the girders and wires that shape it, so it does not flutter which would tend to create drag and damage it. Then too it seals it and creates a surface that can be sanded smooth. The aluminum was added to make it reflective, to ward off damaging solar radiation from the fabric components below, including solar heat that would otherwise render the lift very unpredictable by superheating the lift gas. All this was necessary and much of it was normal for airplanes too, which were only beginning to be made all of metal in this period. This stuff was definitely the right paint and efforts were made specifically to minimize its flammibility.
Also--although the fabric panels were indeed separate patches, the German practice, followed also by Americans making our 3 homemade rigids, was to paint on all the dope and surface paint layers on the fully constructed airship. It was done in layers allowing weeks between them, which cost a lot of time but resulted in one smooth aerodynamic surface--and also one smooth electrical surface, though the notion that the skin sparked the fire demands that the separate panels developed potential differences. This was impossible for the German or American ships.
In the last 2 British ships, R100 and R101, they tried to simplify construction by pre-doping the panels off line and then installing them, hoping to tie them down and tension them afterward. For a variety of reasons this worked out very badly. In theory these panels could have developed potential differences but among all the other problems the R-ships had that one was not observed!
This is the best case I have seen made for ammonia, but remember it is both stinky and poisonous. But that squirting in water to shrink it trick is a new one on me.
Weather: actually none of the latest rigids were terribly vulnerable to weather as such. Certainly they were not more vulnerable because they were bigger.
The Shenandoah was, like most of the vulnerable rigids of the 1920s, designed too closely after German "height-climber" designs that were meant to enable very high flight to get above British antiaircraft defenses. The late war Zeppelins designed for this mission achieved very impressive useful lift ratios but were quite fragile near sea level, where the Germans handled them very carefully. They did not explain this to the Allies who were generally too haughty to ask. After a lot of ships of that generation came apart in the air the next thing was to make them stronger; the British R100 and R101 were at least not likely to snap like twigs in the air, nor were Akron or Macon.
Akron was caught in a nasty storm all right, which tossed the whole ship down almost into the sea; trying to climb back up away from the sea brought her tail down into it, trapping the ship--but the near-100 percent fatality rate was due in part to a lack of boats, lifejackets, etc aboard. Just 3 men made it ashore, rescued by a passing freighter.
Macon lost her tail fin in a manner that was largely foreseen. It was already known from experience and improved theory at that point (1935) that the forces on the tailfins were underestimated (actually it was the _distribution_ of these that was wrong; it had not been realized how concentrated the force would be) and reinforcements were planned. Had these been undertaken sooner, I doubt the ship would have lost the fin. Once the fin was gone it took a lot of skin with it, and this exposed the rear gas cells to winds that deflated them. After that, many people do think the ship could have been saved with more skill but as it was communications were not very good and steps were taken that doomed the ship to come down. However all but 2 men were saved.
OTOH the Zeppelin captains were famous for using powerful winds as much as avoiding them; it came down to very careful study of the weather. When you are traveling intercontinental distances and the name of the game is to make good time between two distant cities, there are a lot of options available as to route; they used that. The American military ships had a lot to prove to skeptical Navy brass that they could take rough weather; that anxiety had a lot to do with why Akron was out there in bad weather (that and poorly developed weather forecasting) and why Macon's retrofitting was delayed.
Generally speaking, an airship moves with the air and only violent changes and transitions in the air (which do happen of course) threaten it. The Zeppelin captains tended to go _down_ to surface level when they had to go through rough air, on the theory that winds don't blow up or down near the surface.
Vectored thrust probably makes no difference in cruise maneuvering; the tail surfaces are very effective then. It is during ground handling that they help a lot and ground handling is the most vulnerable aspect of airships. This is where size brings the big penalties. Aloft I believe size will enable stout construction (high volume to surface ratio helps there) and a slower turning rate is not a serious impediment. But near the ground agility matters more. Really big airships should avoid coming down basically; fortunately airplanes can hook on to them and now we have helicopters too though I am nervous about their landing on top, and it is hard to see how to enable them to hook on from below.
Well, there is speed. An airship is a lot slower than a modern plane but could carry a lot; it is a lot faster than a ship so it can get away with carrying less. To compare to really big ships you'd need really big airships but there is a lot of room in the sky and such big ships would not need to land often.
Then too as others have said they can go just about anywhere, delivering cargo directly to otherwise inaccesible destinations. And wherever they go they can fly over reasonably low land whereas surface ships must circumnavigate obstacles; this often doubles the distance they need to cover which halves their effective speed relative to the airship.
Airships can also have airplanes take off and land from them which opens up vistas of integrated systems that multiply the value of both planes and the airships.
It would be silly to expect airships to do exactly what ships do now since we already have the ships to do that.
Kind of hard to believe that German engineers in the 1930s would be quite that stupid, isn't it? Let's suppose Nazism addled their brains. Even addled, German engineers came up with some pretty impressive technology across the board, they didn't miss many boats technically speaking and frankly were way ahead of the Allies in many important applications--getting their wonder weapons built in quantity was another story of course, what with the whole world being at war with them and denying them supplies and all, and bombing what they did make. Anyway Hugo Eckener, the brains behind Zeppelin at that point, was about as anti-Nazi as anyone could be in the Third Reich and survive. Quite a decent man really. No, we have to face the fact that German engineers were not idiots and would not compound their problems lightly.
Nor did they in this case. It is just not true that the skin material burnt easily--if it did they'd have seen it go up the first time the engines made sparks. The diesel engines were very well-behaved but the skin material near the engine cars did have burns in it--they just didn't spread. Nor can anyone make a good case for the skin being a sparky material likely to set the hydrogen off.
I just figured out how much heat release potential the ship's hydrogen represented. Hydrogen is an excellent fuel on a weight basis all right, burning one kilogram of it would release more heat than burning over 2 1/2 kg of hydrocarbon fuel. And gaseous H2 is about 1/15 as dense as air which masses 1.225 kg/cubic meter under standard conditions at sea level, so given the ship's volume (about 220,000 cubic meters for lift gas) the hydrogen had about as much energy to release as would 50 tons of gasoline!
Maybe that does not sound like much but imagine it all burning up in 30 seconds or so. Let me help--the ship was 245 meters long (806 feet) so imagine a trough 800 feet long and about one and 1/2 feet deep and wide--full of gasoline from end to end. Every foot of it would be about 16 gallons or so, about like a very big car's fuel tank worth, only there are 800 of them. How close do you want to get to that trough, and how much assurance do you want that there are no sparks around if you have to come within 60 feet of it? And if someone did toss a match at it, how long do you think it would take the flames to get from one end to the other?And how much heat would the resulting conflagration release? How long would it take to burn to the bottom of the trough?
Now I don't have mass figures handy but I think the outer skin was about 10 tons in mass. For it to match the performance of this trough, it would have to release 5 times the heat per kilogram as gasoline does. You know, explosives don't contain more chemical energy than fuels do, they can just release what they have instantly. But if they were more energetic we'd use them for fuels instead of oil!
So I find it hard to believe that even if the skin were made of pure guncotton (as I myself have mistakenly compared the skin of these airships to in the past) it could possibly have contributed more than 1/10 or so of the total fire energy. And in fact I imagine gaseous hydrogen would burn up much more rapidly than merely volatile gasoline. The Hindenburg's diesel fuel burned for something close to 10 hours after the crash--but it was depleted by then; imagine 50 hours worth of diesel fires--released in one minute. That is what the hydrogen did; the skin did not do it.
So we might question their judgement in using hydrogen at all but once that decision was made, they having no useful alternatives but to give up airships completely, they did their best. The skin did not demonstrate any of the arcane and volatile properties some irresponsible people project on it today; it was chosen to minimize problems not create them.
Despite the risks he ran I envy Harold Dick's frequent flight's in the two grandest passenger airships ever made (or two of three, the last one LZ-130 was really something, and the Nazis commandeered it for th
Whatever do you mean by "fireproof?" Airships are very diffuse, low-mass things, about 1/100 or so the density of a normal ship. Any materials enclosing big volumes like gas cells or the outer skin have to be thin stuff. It does not matter if they burn or not, the heat of a significant amount of loose hydrogen burning would _melt_ holes in anything that thin. Then there would be more hydrogen--and as you point out the cells would be expanding too. At not so much expansion, maybe 10 percent, they would valve more gas that would normally be vented up vents but in this case the vents would be hot--more flame. And the cells would burst or at least split seams if heated too fast--need I go on? What happened was not an "explosion" but a very rapid spreading gas fire--and all its heat was trapped inside the hull. It was a lot of heat; even if the surrounding materials did not burn somehow, they would glow. And melt; the gas would then quickly escape and the ship come crashing down just as it did. The long fire _after_ the crash was from flammible materials, mostly fuel, aboard. The crash, and the terrible burns some people suffered, were due to the immediate hydrogen fire. It would not matter to them whether the rest of the ship were made of asbestos or not.
First of all the "total mixture" was not mixed, it was separate layers painted on separately.They could not seep into each other or anything. Even if the components were of the right nature and proportions to serve as a rocket fuel if mixed, they would need to be mixed and they were not. Second, it is not true that these materials were of a suitable mix, and if they were, solid rocket fuels actually burn rather slowly, much more slowly than the flames could be seen racing along the body of the stricken Zeppelin.
. ht m
The iron oxide is particularly interesting--it was painted only on the upper hull. If it played any major role in the conflagration surely the upper hull should have burnt much more rapidly than the lower! But it did not, the flames gave every appearance of being a blowtorch from _inside_ the hull.
Color is irrelevant when the hydrogen is contained inside other materials--burning hydrogen sets these afire and superheats them too, they glow in their characteristic frequencies and not hydrogen's even if the hydrogen is supplying the heat!
The fire "burned down" because it took time for the hydrogen to burn through and in that time (just seconds to be sure) the interior air/gas cell volume was heated to the flame point of many substances inside, including those below. And there was hydrogen at considerable distances down the hull, especially once its cells were heated and they expanded before bursting.
Once a huge hydrogen conflagration, very largely contained inside the hull, was under way of course just about everything else burned too. Even the skin.
But have you ever seen the pathetic demonstration of Addison Bain, author of this false theory, trying to set an alleged sample of Hindenburg skin afire? It would take something like a hydrogen fire to get it really going!
http://spot.colorado.edu/~dziadeck/zf/LZ129fire
Blessed are you for you have been misled by completely bogus pseudoscience for less time than these smug others.
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The doping material was not rocket fuel, no element of the skin could plausibly have caused any of the contributions toward catastrophe that are attributed to it by this false theory.
Why would all the people interested in LTA techology from the 1930s until the late 1990s have ignored the possibility it was the skin if it were in fact possible? But it is not a possibility:
http://spot.colorado.edu/~dziadeck/zf/LZ129fire
What has gone on here is that people with agendas to use hydrogen for various purposes including as a lift gas for LTA have indulged in massive wishful thinking and 60 years after the fact it is easy to create this mirage of the "rocket fuel skin." Which for some reason or other only actually burned this once, whereas if you believe the modern myth, all those other hydrogen-filled ships that did burn up in rapid conflagrations were all the victims of completely different mishaps--fuel explosions for instance--that only coincidentally stopped happening when various parties shifted over to helium for lift gas.
No, it was the hydrogen. Hydrogen might have been an acceptable, manageable risk when there was no good alternative but now that there is one (and at least one other I know of that is not as good but still avoids the fire risks) there is no good reason to take the risks anymore.
It certainly was not the skin. Bain himself tried setting some on fire (consider that he had a piece of this allegedly incidiary stuff someone allegedly found lying around on the wreck site--why didn't it burn up? And what kind of scholar is anyone who destroys some authentic Hindenburg skin for a demonstration?) and it sort of fizzled after he tried to light it with a blowtorch. Forget the Incidiary Paint Theory! Or remember it as a lesson in bogus science.
Afraid it was:
. ht m
. ht m
http://spot.colorado.edu/~dziadeck/zf/LZ129fire
PS--I did preview this and I don't know why the system inserts a space between the "t" and the "m" of "htm"
I'll try retyping the whole thing from scratch:
http://spot.colorado.edu/~dziadeck/zf/LZ129fire
It did it again--don't ask me why, just paste the url into your browser and correct it, and take a look, it's interesting.
Here it's me again--if you don't believe me read this:
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http://spot.colorado.edu/~dziadeck/zf/LZ129fire
It was not the skin material that caused or comprised most or even much of the Hindenburg fire; it was the hydrogen. Which explains why many many hydrogen ships of diverse construction have gone up rapidly in totally destructive flames while few helium ships (there have been lots of blimps and a few other kinds) have burned at all, and those slowly and clearly due to fuel fires.
Nope, the skin was not "rocket fuel," if it were it would not have burned from stern to bow in less than a minute, it could not self-ignite nor is there reason to think it played a role in igniting the hydrogen either.
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Hindenburg burned because of the hydrogen, the paint did not even contribute much to the conflagration. How else could there be surviving pieces of the skin for revisionists to stage self-defeating, embarrassing demonstrations for cameras with?
http://spot.colorado.edu/~dziadeck/zf/LZ129fire
Check it out. There are a thousand holes in the paint theory and related arguments (eg that hydrogen airships were perfectly safe) and this one nails four of them, each sufficient to put the false claims to rest.
No you can't! Forget vacuum, it is too difficult to make it work. If you have materials that can keep vacuum _out_ you can much more easily keep gas in--if the material is that strong maybe it would be safe to keep hydrogen in it.
Or you can use steam for lift gas.
www.flyingkettle.com
Or if you have a supply of helium (painfully extracted from the atmosphere for instance, given enough work you can do it) I have a trick to _conserve_ the helium that would stretch its usefulness to the point where slow extraction of replacement gas from the atmosphere would keep up with the reduced rate of loss. The original version involved a thin layer of steam outside the helium, another involves a thin layer of hydrogen--there is risk of fire but limited risk if the layer is thin enough.
Any of this is preferable to trying to hold vacuum out of a volume. I suppose it could be done someday with a light enough container to leave some lift, but whatever wonder material you might be using can be put to more efficient uses.
Aerogels come up a lot in this context for instance. Well, besides being very light they are also great insulators--so instead of trying to keep a vacuum inside the gel you heat up the air a whole lot inside, and most of it goes out, leaving almost a vacuum--very hot air. Which is easy to keep hot because the aerogel does not conduct heat well, and it is easy to make this structure light because it does not have to bear the terribly strong compression forces a vacuum would leave the hull to bear.
There will always be a better way than vacuum. which strikes me as damn unstable anyway--any leak you get, you lose lift _fast_! Might as well contemplate a photon gas--that might work if you had a perfect reflector, but one pinhole and your pressure gas is out at 3E8 meters per second...
You are referring to Addison Bain's misleading claims.
He is quite wrong about the skin in many different ways. It could not generate sparks in the ways he claimed, and if such sparks were applied to it they would not ignite it, and if someone did set the skin on fire it would not burn nearly as fast or energetically as he claimed, not by orders of magnitude. He compares the mix to "rocket fuel" but first of all this is false, it lacks the right components in the right proportions to burn as a rocket fuel. Actually solid fuel rocket fuel does not burn at the rapid rates he assumes either. But anyway the skin was not a uniform mix of all the chemical components (which he gets wrong) it was a layered composite, with the various chemicals separated.
Bain himself made a hash of his claims that the skin self-ignited and then burn furiously, so vigorously as to eclipse the heat of hydrogen combustion, when he took a piece of Hindenburg's own skin and tried to set it afire for cameras. He used an arc torch, making no attempt to demonstrate that static discharges alone could do the job, and even so it burnt very weakly.
Bain's real agenda is to prove that hydrogen is reasonably safe to use, mainly because he works with liquid hydrogen as a fuel. It is a bit silly to try to prove LH2 safe by claiming hydrogen was never at fault in the numerous cases of hydrogen-filled airships that went up in flames, since a huge bag of gaseous hydrogen separated from air by thin membranes is very different from a tank of cryogenic liquid inside thick insulation. Anyway lots of hydrogen airships of all types, using lots of different types of skin, burned spectacularly generally with great cost of lives and sometimes property damage. Some helium-filled airships have indeed burnt, but not easily and never with the kind of rapid chain reaction evident in the Hindenburg fire. Clearly most of the energy that consumed the ship in just seconds came from burning hydrogen; the bright visible light that Bain tries to claim proves it was some other materials (pure hydrogen flame is in UV and invisible to the human eye) comes from that hot fire setting the other materials afire and superheating them, just as the mantle on a gas lantern transforms the pale blue flame of propane into bright redder light.
It is quite true that the old Zeppeliners did their best to minimize the dangers of hydrogen and generally carried it off. It is false that helium is so much worse than hydrogen that using it spelled doom for airships. What spelled doom for airships IMHO was the determined opposition of many interests that preferred to develop airplanes and helicopters and regarded the market as too limited to support both HTA and LTA. Hydrogen fires, and the cost and limited supply of helium, were good excuses to divert development funds away from airships.
But it is ridiculous to suggest that the NT could carry a lot more pax if it used hydrogen! Maybe 3 or 4 more, at risk of their lives--a hydrogen _pressure ship_ is much more risky than a hydrogen rigid, which is bad enough.
A bigger airship could be made using helium that would work just fine. The second-largest rigids were made in the USA and were wonderful ships, the USS Akron and Macon.
Well it is made by Zeppelin!
It is a semirigid not a rigid since the helium fills the interior instead of being in separate cells, and is pressurized by an air ballonet so as to tension the skin, which is also the gas containment as on a blimp. So on one hand there is no need to stiffen the hull, and on the other the aerodynamics depends on maintaining pressure, and a rip in the hull would threaten to leak all the helium out instead of just a portion. But they thought it would be easier to make or something; I have my doubts.
But it is flying and a good-looking ship, one of several actually. I just hope they will make much bigger ones soon, maybe go for a true rigid.
1) It's a Zeppelin because Zeppelin company makes it. They make treaded tractors too.
2) it's not a blimp because it has a frame--I've comented on that elsewhere and so have others.
3) yes, blimps are airships-pressure airships to be exact. And they tend to be much smaller than the rigids were. A rigid, or a semi-rigid like the NT, _can_ be as small as any blimp--the smallest rigid that ever flew manned was about half the volume of the average advertising blimp. There is considerable doubt on the other hand how big a blimp can safely be made. The danger is rips or other accidents resulting in loss of pressure and also lift gas.
4) the NT is indeed about the same size and shape as a large modern blimp (considerably smaller than the big blimps the US Navy operated in the 1950s, even smaller than the standard patrol K-ship of WWII). So I feel your frustration--and there are very few of all of these small ships flying.
5) I say "small" only in the relative sense--even a small manned blimp is generally longer than 60 meters, which is the wingspand of a Boeing-747. If you ever get close to one you'll be impressed! Hindenburg was 245 meters long and 40 in diameter. That is big. And yet I think they should have been bigger still.
The NT has ribs--3 longitudinal ribs made of aluminum, spaced by triangular transverse frames made of composites. It is classified as a "semirigid," meaning that the frame helps keep the overall shape and distributes the lift, but the lift gas has to be pressurized to put tension on the skin, which contains the gas and also serves as the aerodynamic surface, as in blimps.
Blimps are nonrigid or pressure ships--all of their structure results from pressurizing the lift gas by means of air ballonets inside them. They have no rigid members.
The alternative is a rigid frame and stiff external skin; this approach frees you of the need to pressurize the lift gas. Generally this means a complex structure like the classic Zeppelins--but that structure was often, even taken altogether with its numerous parts of gas cells, netting, frame members, wiring, and outer skin, lighter per unit of lift volume than blimps, even the best modern blimps.
The big drawback of pressure ships, including semirigids, is that if you lose pressure for any reason you lose structure. On a semirigid it is not quite as bad, especially on the NT with its three ribs which pretty much would maintain the basic shape, but you'd lose skin tension hence get a lot more draggy. On a blimp loss of pressure is a disaster. Also, pressure ships are hard to partition so any big leak or rip will tend to spill _all_ the lift gas, whereas on the rigids the gas was kept in numerous separate cells and total deflation of one or several might still leave the ship airborne--I know of several instances of that.
The semirigid form does allow you to distribute weights all along the length of the ship which is important, and the NT version also allows elements like the props to be moved up along the width of the hull, kind of like what was possible on the old rigids. What is most "new" about the New Technology Zeppelin is its vectored thrust system. Modern blimps have used pairs of vectored props (though attached to the gondola, their only rigid element, rather than up along the hull sides which is clearly better) but the NT adds an arrangement on the tail tip that greatly increases the control available; this is possible because of the ribs.
Still a number of us wish they'd gone ahead and made a modern rigid while they were at it; such a ship would have enabled all this, freed them of pressurization issues, and given the crew access to the entire interior so if an engine gave trouble in mid-air someone could go and try to fix it. Happened all the time on the rigids! Fortunately modern engines are more reliable, but a major issue of the NT is that you need special equipment to get at the engines, mounted up high as they are, for maintenance, it restricts their operations.
I also think a modern rigid would have been as light or lighter, and very possibly cheaper to make and maintain. All they'd need to do to make the NT a rigid would be to devise some kind of very light aerodynamic shell to replace the skin, and then design some gas cells--just basically balloons-to fit inside the spaces betweent the frames. Well actually the frames are braced with wires so either the cells would have to contain those or else the structure would have to be redesigned to avoid running the wires there.