Nuclear Zeppelins

[KyleB]

Surely, it must be the epitome of AH.com fantasies.

It was designed by a Russian engineer. Any thoughts?

http://steampunk-blog.dailysteampunk.com/__oneclick_uploads/2009/07/nuclear-powerd-zeppelin.jpg

[Beedok]

That doesn't look like it has enough gas.

Still atompunl airships :eek::cool::eek::cool:

[General_Finley]

I just had a nerdgasam seeing that.

America would have to build a fleet of them if the soviets build one.

[Glen]

Damned fine title and toy - now make a timeline with it!!!:D:D:D

[Rogue Shadows]

YESSSSSSS!!!!!!

[Sachyriel]

Disaster waiting to happen. Unrecoverable loss and an unimaginable nightmare for cleanup.

[Beedok]

Question: What advantage does nuclear power give it?:confused:

[General_Finley]

Question: What advantage does nuclear power give it?:confused:

Don't ask such questions, just accept it :D as and advantage even though we know it would be bad.

[MRig]

I just had a nerdgasam seeing that.

America would have to build a fleet of them if the soviets build one.

Oh my cripes you just might be right.

The irrationality of Cold War politics has met the implausibility of widespread airship use and mutated into a glorious, glorious symbiote.

[KyleB]

Question: What advantage does nuclear power give it?:confused:

It could fly for years at a time at high power without needing to refuel,

If it explodes, it will be aweseome,

It is totally cool.

[Cook]

Holy Flying Chernobyls Batman!
:eek:

[Westbrook 49]

It sounds like an awesome name for a band:

"Ladies and Gentlemen! Give it up for.....NUCLEAR ZEPPELINS!"

[Cook]

It sounds like an awesome name for a band:

"Ladies and Gentlemen! Give it up for.....NUCLEAR ZEPPELINS!"

A Lead Zep cover band or Lead Zep in an Alternative History?

[Beedok]

Still it isn't British/Byzantine so it isn't really the ultimate AH.

[LordVetinari]

I love zeppelins, and whenever I read an old book on them, they always seem to speculate "Nucular Power is the future, isn't that scary kids!" But coolness aside, the weight of the thing is impracticle versus the heavy lifting gas. Given the technology of the time, the thing would have barely got off the ground. Heck, the US Air Force wanted to build nucular bombers. Which also wouldn't have worked, however cool it may be.

[Shevek23]

Question: What advantage does nuclear power give it?:confused:

One problem airships have is that, insofar as their lift comes from the static lightness of their lift gas, when you burn fuel you lose some of the weight that gas was lifting. After that, the ship will rise until its gas volume expands beyond the volume available inside to contain it. Unless of course one simply valves off some of the gas. Which is what hydrogen-lifted airships routinely did. With helium, the stuff is too expensive and hard to replace (not exactly the same thing--I mean by the latter that it has only a few sources in the world and to replace some at a given location you'd have to ship it there; hydrogen can be generated in practically any moderately industrialized setting) to contemplate doing that routinely, though of course helium-lifted airships did (still do) wind up valving some anyway, in emergencies or to prevent emergencies.

With nuclear power, you don't have any significant change in the mass of the system, so the same gas is lifting essentially the same amount of weight.

There are other tricks instead of nukes to try of course. An airship can get lift--including negative lift, downward instead of up--by flying at some angle of attack to its course--this is called dynamic lift. Thus US Navy blimps developed the technique of "flying heavy"--they'd load up with more weight than the gas could lift, and make a takeoff run from a field, like a very STOL airplane. They also would sometimes scoop up water from the sea for more ballast.

There is the nifty idea of water recovery. When you burn typical hydrocarbon fuel, somewhat more water by weight than the fuel weighed is part of the exhaust. (As common atoms go, oxygen is one of the heavier ones...) so if you can condense most of that water, you can recover ballast equivalent in weight to the fuel you just burned. In practice it did work but it was a bit of a hassle; it impeded engine efficiency a bit, required extra equipment to carry, maintaining the recovery units (they tended to get clogged with soot) was a nasty chore. It was used on all the US Navy's rigid airships--all four of the ones that actually were flown in the USA that is; a fifth one (actually the first to fly) the ZR-2, broke apart during test flights in Britain where it was constructed--it was the only one that never had water recovery installed. Also the only one that never flew with helium.

Even though they used hydrogen, the Zeppelin people were interested in water recovery too; hydrogen is a lot cheaper than helium but it still costs something, so keeping in trim without valving it was attractive. They developed a rather fancy and apparently efficient system for their last rigid, the LZ-130 Graf Zeppelin "II" (officially it was not named "II" because it replaced the original Graf, the LZ-127, which was grounded)--it was a successor/sister ship to Hindenburg, and like Hindenburg there was some hope to get helium from the USA. But since the Germans never got helium they never used the water recovery devices.

However they did develop yet another bunch of tricks to try and get water for ballast from the air; both the original Graf and Hindenburg had rain gutters and they would sometimes be flown into clouds to get water from them!

The Graf also had yet another good trick--using a hydrocarbon fuel gas tailored to be exactly the density of air. Burn a kilogram of that instead of gasoline and you simply stop displacing exactly a kilogram of air, so the weight stays the same. Actually the Graf's engines, which could also burn gasoline, were somewhat more efficient with the fuel gas (called "Blaugas" after the inventor) than with petrol. One drawback was that Blaugas--or any other buoyancy-neutral mixture--would be even more of a fire danger than hydrogen, since being the same density as air, it would have no tendency to be lifted away if it leaked, and would also diffuse much more slowly than hydrogen would. Ironically, the Graf had some close calls but never suffered any serious fire or any other fatal accident in its 9-year flight history, by far the longest career of any rigid airship. The US Navy also tried a neutral-lift fuel gas mix in an experimental blimp, the K-1, but it was not popular with the naval aviators--for one thing, the fuel gas cell was housed inside the helium volume, which greatly lowered the risk of fire but also meant the helium was getting contaminated by the fuel gas--this meant that the helium could not be safely repurified by standard methods and so had to be vented--kind of defeating the purpose.
-----

OK, this particular Russian nuke rigid is completely silly of course; there obviously isn't anything like the volume of helium inside there should be to lift all that junk. But there have been serious proposals for nuclear powered-airships, ones that did the math a bit more rigorously. It only makes sense for a very large airship. Ironically, the bigger the airship, the less fuel is burned per mass unit lifted at a given speed, and the more margin there is for stuff like water recovery, more secure fuel gas cells, and so on. And the better the fuel economy per unit of payload, so that an airship big enough to justify a nuclear power plant would also be so big that its fuel load using conventional engines instead, even for a globe-circling flight, would be modest and it would be quite a trick to get the total weight of the nuke plant down lower than the fuel plus conventional engine weight.

Still, if you must have airborne nuclear plants for some reason or other (rule of cool, let us say) it makes way more sense to have them in airships than in airplanes. For one thing, the power requirements are modest (compared to total payload--on an absolute scale they are substantial--still, Hindenburg at 200 tons of mass only needed something like 6000 horsepower; the big US Navy rigids had a similar installation). For another, the huge volume of the ship, mostly "empty" space for the lift gas, gives some opportunity to put a power plant well away from inhabited parts of the craft. Then too, while airships can (and mostly did:() crash, they do so relatively gently, so it isn't so impossible to design the nuke plant so it can survive a likely crash without the containment bursting. Worst-case scenario--the airship breaks up in mid-air, a la the ZR-1 Shenandoah and the nuke plant unit falls out of the sky, maybe several miles down--not likely a lot more than that. Such a free-fall is bad news, but not as bad as a nuke-powered jet (yes, I've seen concepts of a jet that would use a nuclear power plant and heat exchangers to power turbojets--not talking about a fan here) slamming into the ground at Mach .7 or so. A nuke airship accident would be bad, but not as bad as a crashing nuke airplane would be!

(OTOH, one reason to put a nuke power source in an airplane is to give it extremely long endurance--measured in days, or months, or as long as the crew can stand--up to years until the power plant needs to be replaced--whereas an airship already has very long airborne endurance by its nature).

All that said, I have to admit that no matter how much time this helium head spends dreaming of really big airships doing really cool things, I don't think nuclear power does a lot to enhance them. It would be great if your airship gets ISOTed to ancient Rome or some such, but barring such unlikely events fuel for more conventional power plants is going to be forthcoming after all.

Now, the solar powered airship on the other hand...:D

[W.W.A.F.T.]

I do remember someone on this site doing a timeline with an american built nuclear zeppelin. in that one though it crashed in a storm off the cost of florida and zeppelins in general were shelved.

[DuQuense]

looking at the picture - I immediately thought of Anti Gav units. Course it would require 3 sets of triple redundancy units.

If built today it would use the Sky-Cat lifting body style --instead of the 30's cigar shape.

[Shevek23]

http://www.eoearth.org/article/Small_nuclear_power_reactors

BTW, is something up with Wikipedia? When I tried to search it tonight (earlier, for something unrelated to this) I couldn't get past the intro page--only in English, the German and Spanish versions seemed OK. But absolutely nothing in English!

So, since AH scorns Teh Wikipedia anyway, here's a non-Wiki link.

Apparently the smallest power reactor here was the one used at McMurdo station, in Antarctica, which put out 1.5 megawatts of power (about 2000 horsepower) for 11 megawatts of thermal output. That's pretty poor efficiency IMHO. That's the only one that is actually smaller than the Hindenburg's power requirement of 4.5 megawatts or so--three of these would do the job for the biggest airship ever to have flown. I have no idea what that plant weighs.

More typical of the small end offered is something like 25 MW power output--say this Hyperion (http://www.hyperionpowergeneration.com/product.html) design--70 MW thermal output, 25 MW power generated (so about 1/3 efficiency or twice the efficiency of the McMurdo plant) weighing "under 50 tons."

Well, that's about the weight of Hindenburg's fuel load, but 25 MW is over 5 times the power that airship needed. Therefore to use the power of one Hyperion unit (and the other low-power plants mentioned in the top article all are in that ballpark or higher) the drag area of the ship would have to be 5 times greater--linear dimensions about 2.25 longer, which gives us a 540 meter long (over half a kilometer!), 90 meter diameter airship (nearly the length of an American football field then) with volume 12.5 that of Hindenburg, implying a total static lift in the range of 2500 tons!

That, my friends, is an airship. No joke, the mass of a small destroyer, with length that dwarfs an aircraft carrier or supertanker. Of course I've fantasized about bigger ones, but something in the 500-600 meter range might be the limit of realistic possibility! I believe something that size really could be done, in our current state of the art--if only we had the hangars...

Hyperion might of course be mainly emphasis on the hype. It could be that either the product doesn't work as advertise, is far less safe than they claim, or weighs a lot more than they hope.

Still, I have to admit that 50 tons for a power plant that can drive a 2500 ton airship at 60 knots or a bit more, and do so for 8 years straight, is pretty impressive.

Even a plant that totaled out weighing ten times that for the same output would be quite competitive with more conventional fuel options. And if the Hyperion really can do what they say, then wrapping the core in 100 tons of containment--or more, up to 500 let us say--ought to secure it even if it does fall two miles or more out of the sky one day.

(To be sure, even with perfect containment, you have to worry about someone shooting down the airship mainly to get the fissionables, nicely delivered to them for the cost of a few missiles--and of course bringing down some major military police action on their heads:p).

It's too late for me to let myself swirl around in this vortex much more tonight...

[Inquisitor Tolkien]

It sounds like an awesome name for a band:

"Ladies and Gentlemen! Give it up for.....NUCLEAR ZEPPELINS!"
I thought Holy Flying Chernobyls was a good name.

[Hendryk]

It was designed by a Russian engineer. Any thoughts?
I remember seeing this drawing in the early 1980s.

One problem airships have is that, insofar as their lift comes from the static lightness of their lift gas, when you burn fuel you lose some of the weight that gas was lifting. After that, the ship will rise until its gas volume expands beyond the volume available inside to contain it. Unless of course one simply valves off some of the gas. Which is what hydrogen-lifted airships routinely did. With helium, the stuff is too expensive and hard to replace (not exactly the same thing--I mean by the latter that it has only a few sources in the world and to replace some at a given location you'd have to ship it there; hydrogen can be generated in practically any moderately industrialized setting) to contemplate doing that routinely, though of course helium-lifted airships did (still do) wind up valving some anyway, in emergencies or to prevent emergencies.
Forgive this complete layman's question, but would it have been technically feasible to liquefy the excess helium instead? or would the necessary equipment have been too cumbersome?

[skullangel]

http://images1.wikia.nocookie.net/__cb20060618173554/cnc/images/1/16/Kirov_1.jpg
http://images4.wikia.nocookie.net/__cb20081125010702/cnc/images/1/13/RA3_Soviet_Kirov1sm.jpg
Red Alert 2 and 3... So thats where they got the idea!

Very fine Alternate Reality Games...

In as much as practicality... If you think about it not such a bad idea... Like a sub and carrier it can loiter in an area for an extended period of time... One problem though might as well paint a big bullseye on the side if hostile planes and AA artillery get in range.

[MRig]

Perhaps the Soviets build it because they know that the United States will assume there is some hidden strategic purpose and be forced to build ten times as many? Sort of like a reverse Star Wars. Bait the military-industrial complex with this and eight other ridiculous projects that are at some level or another just combining two or three technologies they already know how to make.

"And then watch, Vasily. Watch the Americans over-engineer."

[Telemond's_Lamb_Chop]

How absolutly f$£^&*g stupid - I love the idea! The Hindenburg disaster with radioactives spread for hundreds of miles by the updraft from the flames. Who could not want that in their ATL? Who would not run screaming to the HSE when discovering that a company was thinking about it seriously?

Just a though suppose that instead of a nuclear airship you built a very large hydrogen airship and put a radioisotope heater in it and a hydrogen recover system. How high could you get it to fly? It should be good for at least 120,000 ft I would have though.

[Mad Bad Rabbit]

Question: What advantage does nuclear power give it?:confused:

Make a huge hot-air airship that doesn't need helium?

[Satrap]

Mummy! Mummy! I want one for Christmas :p:p:p:D:D:D:D

[9 Fanged Hummingbird]

Hmm, this is actually a better design than most of you realize. There seems to be a little plane and a helicopter on board the airship, so if anything did start to go wrong with the reactor the crew can evacuate giving the passengers in the lounge just enough time to ask, "Hey, where'd the waiter go?" before they are vaporized in a massive explosion.

[lothaw]

Clearly we need Byzantine Nuclear Zepplins. That'd be so much epic.

Though Japan building one and naming it the Kamikaze would be almost as awesome. :p

[Telemond's_Lamb_Chop]

Make a huge hot-air airship that doesn't need helium?


No, as I explained earlier to make it go really really high you need to fill the envelope with H2. H2 is around 4 times the lift of He and then you use a radiothermal device (sort of a poor man's reactor) to heat up the H2 and reduce its density still further which is why you need either a hydrogen recovery system or to increase the total volume of the envelope as the airship climbs.

H2 you may say, how dangerous is that! To which I reply nothing compared to spreading radioisotopes from high altitude into the jet stream. This is so 1950s US or Soviet military lunatic it is wonderful I can't believe nobody built one.

[zoomar]

I do remember someone on this site doing a timeline with an american built nuclear zeppelin. in that one though it crashed in a storm off the cost of florida and zeppelins in general were shelved.

That was me, in my US Naval Airships timeline. I also included nuclear airships in my British Imperial Airship servive timeline.

Actually, mating nuclear power with rigid airships has been a common idea and not just in fiction, Not only the Russians, but the US (Goodyear and the USN), and the British have seriously proposed the idea. It's really a natural fit and there are numerous reasons the idea keeps coming back:

- The only effective limitation on the range and endurance of large rigid airships is fuel and ballast. Give one a nuclear powerplant and this could both power electric engines indefinitely and help provide water ballast or helium superheat to control attitude and altitude.
- Rigid airships are so large than a contained reactor buried near the center of the ship would be so far from regular crew/passenger areas that the need for extremely heavy shielding would be limited.
- Such a craft would be free of carbon exhaust emissions and could provide heavy lift capabilities greater than any traditional airplane at faster speeds than a ship.
- Even today, large airships could have military/naval/anti-terrorism purposes, and unmanned, they could operate a high altitudes

It'll never happen though because of:

- irrational anti nuclear hysteria in most countries
- somewhat less irrational belief rigid airships are just not that reliable
- we are talking about something really large to be useful (1000' long or more). It would require a massive investment in infrastructure (building sheds, suitable hangars, and a virtual re-learning of a largely abandoned industry
- the advantages offered by such a craft are probably not sufficient to warrant any serious financial interest by private industry or governments, when other technologies (surface effect craft, true hybrid airship/aircraft, faster ships, etc) are likely to close whatever functional gaps that exist now betwee ships/rail and aerial transport

[Dathi THorfinnsson]

No, as I explained earlier to make it go really really high you need to fill the envelope with H2. H2 is around 4 times the lift of He and then you use a radiothermal device (sort of a poor man's reactor) to heat up the H2 and reduce its density still further which is why you need either a hydrogen recovery system or to increase the total volume of the envelope as the airship climbs.
.
Bzzt! Wrong! about 1/4 again the lift. only just significant improvement, not major at all.

[Cook]

From the Wikipedia page (yes I know and I apologise, but it’s late and I’m tired and nuclear powered zeppelins isn’t something anyone should take too seriously):
The density at sea-level and 0°C for air and each of the gases is:

Air (ρair) = 1.292 (g/L).
Hydrogen (ρH2) = 0.08988 g/L
Helium (ρHe) = 0.1786 g/L
Thus helium is almost twice as dense as hydrogen. However, buoyancy depends upon the difference of the densities (ρgas) - (ρair) rather than upon their ratios. Thus the difference in buoyancies is about 8%, as seen from the buoyancy equation:

Buoyant mass (or effective mass) = mass × (1 - ρair/ρgas)
Therefore the buoyant mass for one liter of hydrogen in air is:
0.08988 g * (1 - (1.292 / 0.08988) ) = -1.202 g
And the buoyant mass for one liter of helium in air is:
0.1786 g * (1 - (1.292 / 0.1786) ) = -1.113 g
The negative signs indicate that these gases tend to rise in air.

Thus hydrogen's additional buoyancy compared to helium is:

1.202 / 1.113 = 1.080, or approximately 8.0%

http://en.wikipedia.org/wiki/Lifting_gas (http://en.wikipedia.org/wiki/Lifting_gas)

[LordVetinari]

I currently have Lee Paynes "Lighter than Air An Illustrated History of the Airship (published 1977). In the future of the airship section he mentions this. To quote several references "For example, the Hindenburgs four Deimler-Benz diesel engines weighed a total of only nine tons, but they required sixty-seven tons of fuel and oil to fly eight-thousand miles. The sixty-ton atomic engine engine could fly that distance and farther on only a few pounds of fuel," (Paynes 253.) He also says that "In addition to the insurmountable weight problem of its nuclear engine, the AEC was also unable to overcome the danger of a plane crash that would spread the atomic contamination all over the crash site. This problem too is solved by the use of an airship, for at her lower speeds there is much less chance of a shattering crash" (Payens 253.)
While I'm not sure of the actual real world physics and problems being mixed into what I think is idealism, another thing he mentions ealrier is a design for a nuclear airship by Boston University. The basic size and so on of it are as follows.
"a rigid aiship 980 feet long and 172 feet in diameter, with a gas capacity of 12,500,000 cubic feet. With a total lift of 380 tons and a disposable lift of 150 tons, it would be able to carry a ninety-ton payload of passengers and cargo. A four thousand-horsepower nuclear powered gas turbine would drive two slow-rotating, contrarotating sixty-foot propellers at the stern. Two additional one thousand-horsepower turbo-fan engines could be run on either nuclear or conventional fuel in case of reactor shutdown. With a top speed of ninety-five miles per hour, the ship would carry four-hundred first class passengers across the atlantic in thirty-five to forty hours,"(Payens 252.)
Make of this what you will.

[Albidoom]

Hmm, this is actually a better design than most of you realize.

While I also like that design I strongly doubt that those rather small gasbags inside will create enough lift to get that thing airborne, although it's admittedly rather unclear with this cut-up view how much space is used for creating lift and how much for anything else.

[Cash]

Just the fact that it's a nuclear-powered Zeppelin is so frigging cool that all other considerations must be cast aside in awe of the idea.

Instead of steampunk, perhaps a nukepunk world?

[Dathi THorfinnsson]

Forgive this complete layman's question, but would it have been technically feasible to liquefy the excess helium instead? or would the necessary equipment have been too cumbersome?
You probably wouldn't have liquified the helium, as that would be incredibly cumbersome and costly. Pumping it into high pressure tanks would be much more feasible, although still pretty cumbersome. Modern SCUBA tanks are 200 atmospheres+. You could probably do better with fancy composite tanks...

[Nik]

As the other poster suggested, perhaps it is a hot-air craft ??

Given the waste heat available from the reactor, keeping the gas bags *toasty* would seem to be a good move.

Uh, IMHO, the Zep' shape may not be the best shape, and a 'rounded rectangle' would provide more lift and cargo capacity for less structural weight. In effect, several skinny zeps', side by side within one envelope...

FWIW, putting vectored thrust pods on the corners would seem to give the best control moment...

[Dathi THorfinnsson]

As the other poster suggested, perhaps it is a hot-air craft ??

Given the waste heat available from the reactor, keeping the gas bags *toasty* would seem to be a good move.


??? read the comments re: H2 vs He. Warming the Helium (which is what I HOPE you meant) isn't going to help hardly at all.

If you meant warming air.... Well... the envelop would have to be 3-4 times BIGGER than for He (mental calculation), even if you heated the air to 300 degrees (~500F)

[MRig]

This is so 1950s US or Soviet military lunatic it is wonderful I can't believe nobody built one.

I am reminded at the space enthusiasts who dismissively scoff at the "political reasons" that ended Project Orion.

[Mnemorath]

"And then watch, Vasily. Watch the Americans over-engineer."


We may "over-engineer" But we have not had a reactor accident in over 50 years of operating Naval Nuclear Propulsion Plants (I know. I operate one every day, Yes, I willingly get irradiated for a living. Funny thing, you smokers get a higher annual dose then I do. Several times higher in fact.)

How many have the Russians had in that time frame? I lost count.

As a navy Nuke I find this idea AWESOME ME WANT!!:D

This must be made into a timeline.

[Hapsburg]

Instead of steampunk, perhaps a nukepunk world?

Isn't that kinda the realm world? :D

[TurkishCapybara]

Question: What advantage does nuclear power give it?:confused:

Death to alot of people when it gets blown out of the sky, hopefully the enemy.

[9 Fanged Hummingbird]

While I also like that design I strongly doubt that those rather small gasbags inside will create enough lift to get that thing airborne, although it's admittedly rather unclear with this cut-up view how much space is used for creating lift and how much for anything else.
I was making a joke, if you read the entire post... :confused:

[Laqueesha]

There'd be a British rock band by the name of Nuke Zeppelin.

The Zeppelin Race would begin.

[Telemond's_Lamb_Chop]

Two not four I was thinking atomic hydrogen muy bad.
PV =mRT/M
M(H2) = 2.016
M(He) = 4.002
PM/RT = m/V = rho
For const. P and T:
M(He)/M(H2) = 4.002/2.016
M(He)/M(H2) = rho(He)/rho(H2) = 1.994

[Telemond's_Lamb_Chop]

I am reminded at the space enthusiasts who dismissively scoff at the "political reasons" that ended Project Orion.


Good point about Project [I want to spead toxic poo all over the world] Orion. Can we not incorporate some of its concept into this airship? Why don't we do away with the nuclear reactor, put a pusher plate on the stern and throw small tac nukes out the back? It would be wizzy fast, a bit heavy perhaps but wizzy.

[Krall]

It sounds like an awesome name for a band:

"Ladies and Gentlemen! Give it up for.....NUCLEAR ZEPPELINS!"

"Nuclear Zeppelins" is my Abney Park cover band.

[Shevek23]

As the other poster suggested, perhaps it is a hot-air craft ??


For reasons I hope others have explained clearly enough by now, that would be dumb.

Hot air could in theory be heated up well enough to compete with helium. The necessary temperature, at sea level, would be--well, how high do we want to go?

With helium, the maximum altitude you want to reach without having to vent gas is your pressure height. As you rise, the gas expands; at pressure height your helium fills the available volume completely. Therefore that is the most helium you can load aboard down at sea level; any more and you will lose the excess if you ascend to pressure height. (Or, your pressure height with the extra gas is lower).

Blimps typically are filled 3/4 full at sea level, for a pressure height of 10,000 feet/3 kilometers. That is the altitude above which the FAA requires that passengers either be given oxygen masks or the cabin be pressurized.

The big US rigids operated by the Navy typically were filled for lower altitudes, giving them more lift but limiting their vertical range.

So let's say you want to compete with helium using hot air, and want as much lift as a 3/4 full at sea level helium ship can achieve. Well, 1 cubic meter of absolutely pure helium lifts a bit over 1 kilogram at sea level; allow for some helium impurity to make it exactly 1.

Air at sea level, in the "standard atmosphere," masses 1.224 kg/cubic meter. (Thus that, by the way, is the absolute upper limit of static lift available at sea level, even if you use a magic volume that is completely weightless and infinitely strong). To get .75 kg of lift by heating air, the air must mass 0.474, so you need to raise its temperature to 2.58 times the ambient; in the standard atmosphere this is assumed to be 285 degrees Kelvin. It comes to 734 Kelvin, which is 462 Celsius or 865 Fahrenheit.

That doesn't sound so bad, considering that it is after all air--it might not be inconceivable to make some kind of light structure that can stand that kind of heat and slow down heat losses enough that a good heat source can compensate, but we aren't done yet. The helium ship has the same lift all the way from the surface to pressure height; we need to match that. At 3 kilometers up, the temperature has fallen 19.5 degrees (Celsius or Kelvin) due to the adiabatic lapse rate--this will help. But density has fallen to 3/4--that will not! Now the density is 0.918; the hot air must be heated to lower its density to 0.168. So we have 255.5 degrees K * 5.46 = 1396 K, which is 1123 C or 2054 K.

That, I think you will agree, is darn hot.

(And by the way, to match the lift of helium with a very low pressure height helium cell--ie, one almost full at sea level--one needs to raise the temperature at least that much at sea level).

Trying to estimate just how what heat loss rate these temperatures imply is pretty far beyond me. Aside from the question of whether sufficiently lightweight materials can even hold air this hot without melting, burning, or failing for some other chemical reason, the fact is some heat will leak out, even if our structure includes a fair amount of insulation, and to keep it warm that heat needs to be constantly replaced. At what rate--depends on the inside temperature, outside temperature, surface area, and--here is the imponderable--the dynamic response of heated air to the heat itself. Wind conditions will presumably matter but it is hard to estimate just how.

It could well be that a hot air lift bag is still superior in power terms to using the same power you convert to heat to instead power some kind of dynamic thruster.

Going the other way--trying to get better lift than helium, even at sea level, is a mug's game. If you doubled the already-very-high temperature needed at sea level, you'd match the lift of hydrogen at 3/4 the volume sea level (that is, full at a pressure height of 3 kilometers). Which as pointed out is just an 8 percent improvement over helium.

You could moderate the temperatures by settling for a lesser lift. But that raises the necessary volume for a given payload, meaning more structural area to lose heat through and more structural mass too. It also raises drag if you propose to propel the thing.

Anyway, there is yet another lift gas available--steam. Water weighs 18 atomic mass units to the atmospheric gases (mainly nitrogen and oxygen) 29-30; also it must be hot to be a vapor, so there is an additional thermal reduction in density as well. The upshot is, at sea level saturated steam has 60 percent of the lift of helium. Also, you could carry some extra water to boil to get more lift if you need it, and allow it to condense to lower the lift. Actually, it will always be condensing anyway (but at a surprisingly low rate!) so to maintain lift, you would need to reboil it. Or enclose your steam cell in air heated above boiling temperature, but that heat will still leak away--however if you are propelling the airship the engines will put out waste heat anyway, so that heat might not cost anything extra. Meanwhile, if you do allow condensation, you not only remove the lift of the steam, you get back the weight of the water--so actually allowing 1 cubic meter of steam to condense is a net weight increase (loss of lift plus weight of water) of 1.225 kilograms.

The possible utility of hot air in a practical sense would be to get some variable lift; using steam for that purpose instead strikes me as more advantageous. There is the drawback that it is tricky to get steam to condense quickly.

If you want to learn more about steam for aerostation, here's your man. (http://flyingkettle.com/)

Given the waste heat available from the reactor, keeping the gas bags *toasty* would seem to be a good move.

The only move, if you are using hot air--"steamy" if you are using steam. The waste heat from these hypothetical reactors might be ideal for keeping steam vaporized.

Also, yet another traditional LTA buoyancy trick I forgot to mention is using "superheat" and "supercooling" to some advantage. The American naval airships would often try to time their flights so that the airship would pick up some extra heat from morning sunlight while the air was still cool, thus expanding their gas volume and gaining extra lift, which they would use to load on extra fuel, then as the temperatures of helium and air equalized, stay airborne on dynamic lift until they used up the extra fuel. There have been proposals--including by the Zeppelin works back when they were hoping to get helium for Hindenburg or Graf Zeppelin II--to artificially heat helium for extra launch lift. Any such maneuver, whether by natural or artificial means, lowers the pressure height until the gas cools again. In fact superheat is often the bane of any airship using helium--enough superheat can lower pressure height right to ground level, forcing that some helium be vented.

Uh, IMHO, the Zep' shape may not be the best shape, and a 'rounded rectangle' would provide more lift and cargo capacity for less structural weight. In effect, several skinny zeps', side by side within one envelope...

I really doubt this. Structurally, the ideal shape would be a sphere--minimum surface area to volume, and I don't think you can beat a sphere for static loadbearing efficiency either. Since a sphere is much more draggy than the elongated fish-shapes it isn't used, but the circular cross-section of the ellipsoidal ships is also hard to beat. I certainly don't think this proposal of yours is any improvement structurally; it clearly is a loser aerodynamically.

To be sure, minimizing drag is not quite everything; one might want better aerodynamic side forces, for dynamic lift or turning. You'd flatten it horizontally for the former, vertically for the latter. The "vertical airship" is yet another notion; the argument is that if the gas is kept in a symmetrical airfoil like a wing turned on its side, the structural forces are more in line with the load and so the structure can be lighter.

FWIW, putting vectored thrust pods on the corners would seem to give the best control moment...

Certainly at low airspeeds, yes. Better than the low to zero forces then available from the fin. But at high speeds they'd be quite inadequate, unless you are using such powerful thrusters one might ask why bother with static lift at all and just go for a flying bedstead!

[FlyingDutchman]

"a rigid aiship 980 feet long and 172 feet in diameter, with a gas capacity of 12,500,000 cubic feet. With a total lift of 380 tons and a disposable lift of 150 tons, it would be able to carry a ninety-ton payload of passengers and cargo. A four thousand-horsepower nuclear powered gas turbine would drive two slow-rotating, contrarotating sixty-foot propellers at the stern. Two additional one thousand-horsepower turbo-fan engines could be run on either nuclear or conventional fuel in case of reactor shutdown. With a top speed of ninety-five miles per hour, the ship would carry four-hundred first class passengers across the atlantic in thirty-five to forty hours,"(Payens 252.)
Make of this what you will.


I'm kind of disappointed for the time it lists needed for a Atlantic crossing.
Reminds me of the Blue Riband record crosses across the Atlantic.

Considering that the SS United States did a crossing in 82 hours in 1952 (40 mph) the advantage in speed over a fast liner isn't that big IMHO.
If speed was everything, you could just as well for military purposes fly the troops themselves by air (10 Boeing 747's ought to be able to transport the entire personnel of a brigade) and use RoRo-ships or preposition stores for their equipment.


"Nuclear Zeppelins" is my Abney Park cover band.


Kudos for the name.:)

[mailinutile2]

I've just went wet :D
here's the fundation for my Zeppelin-instead-of-submersibles nuclear strategic weapon idea.