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BrainGlutton
09-27-2004, 05:05 PM
I just saw a CNN piece on a military plan to use lighter-than-air dirigibles for aerial surveillance. There was a big white one flying over Washington. The advantage is that it's slower than an airplane, can stay up longer than a helicopter, and if it has to fly over a battlefield, it's above most fire and can be punctured by a lot of bullets and still maintain its integrity. Also, it's, believe it or not, "unobtrusive" -- huge, but quiet.

Makes me wonder -- in its day, which pretty much ended with the Hindenberg disaster in 1937, the passenger airship was a posh way to travel, like a flying ocean liner. Could it ever come back? For sheer speed, it could never compete with jet airplanes -- but is there some other market niche it could find? Some advantage it could offer?

Then there's freight. The Wikipedia -- http://en.wikipedia.org/wiki/Airship -- says "Recently, several companies have begun exploring the possibilities of airships with their potentially huge lifting capacities, near-VTOL capabilities, and potentially lower freight costs, though none has demonstrated the economic viability yet." If they did, how would that affect the world economy? Would it lower shipping costs for any commodity? In terms of capacity or speed or safety or fuel economy, would a freight airship offer any advantages over an oceangoing freighter?

Bosda Di'Chi of Tricor
09-27-2004, 05:18 PM
If a multiphase carbon composite with the right properties can be made, then yes.

Pump all the air out of an object without losing volume, & if the object is light enough, it will float in the air.

A multiphase carbon composite might be light enough to make a vaccum-lift zeppelin possible.

BrainGlutton
09-27-2004, 05:20 PM
If a multiphase carbon composite with the right properties can be made, then yes.

Pump all the air out of an object without losing volume, & if the object is light enough, it will float in the air.

A multiphase carbon composite might be light enough to make a vaccum-lift zeppelin possible.

What advantage would that offer over a helium-filled airship?

Bosda Di'Chi of Tricor
09-27-2004, 05:21 PM
Think: evacuation pumps".

BrainGlutton
09-27-2004, 05:24 PM
Think: evacuation pumps".

Unless you're trying to make some kind of nasty pun, which is what I'd be doing, I don't get it. Do you mean that such technology would make airships cheaper, because you wouldn't need to provide the helium? Maybe so, but that "multiphase carbon composite" wouldn't come cheap.

Bosda Di'Chi of Tricor
09-27-2004, 05:27 PM
Oh yeah--and tilt-rotor drive. To enhance maneauverability during take-off & landings.

A lifting-body shape for the upper structure would be nice, too. Electrical motors for drive, with, say, a liquified-propane fuel to run a generator, housed in a pod outside the body for safety.

And for keel ballast, we use batteries--doubling as backup power.

Bosda Di'Chi of Tricor
09-27-2004, 05:28 PM
Unless you're trying to make some kind of nasty pun, which is what I'd be doing, I don't get it. Do you mean that such technology would make airships cheaper, because you wouldn't need to provide the helium? Maybe so, but that "multiphase carbon composite" wouldn't come cheap.
With built in evacuation pumps, land-based storage of helium is unnecessary. Saving dough in airport construction. And run a power cable out to he Zep to restore lift at each end.

BrainGlutton
09-27-2004, 05:29 PM
Oh yeah--and tilt-rotor drive. To enhance maneauverability during take-off & landings.

A lifting-body shape for the upper structure would be nice, too. Electrical motors for drive, with, say, a liquified-propane fuel to run a generator, housed in a pod outside the body for safety.

And for keel ballast, we use batteries--doubling as backup power.

Seems to me that all that would be doable with current technology -- but I'm no engineer. Is it?

PaulFitzroy
09-27-2004, 05:37 PM
BrainGlutton, I think we finally agree on something. I have always been fascinated by the concept of airships and have wondered why you never really see them anymore. There have been threads on this subject before but I think it's time for a new one, anyway.

I would imagine the only problem with freight airships as opposed to cargo ships would be that should something happen to an airship causing it to drop its payload, tons and tons of crap would fall down all over the ground below, almost certainly destroying all the cargo and possibly destroying things below too, and the risk of lawsuits from anyone hit by said payload.

There's a smaller margin of error for aerial freight fuckups - the modern-day Coast Guard can often respond to emergencies before a ship can sink, should something happen; the same problems could be much larger thousands of feet above the air.

I think a better application for airships would be a ritzy way of traveling. You'd be able to see a lot of beautiful areas and have plenty of time to enjoy the scenery, take pictures, and whatnot. Since the trip would take a long time, airships would probably include cabins for people to stay in and upscale restaurants to eat at.

BrainGlutton
09-27-2004, 05:44 PM
I would imagine the only problem with freight airships as opposed to cargo ships would be that should something happen to an airship causing it to drop its payload, tons and tons of crap would fall down all over the ground below, almost certainly destroying all the cargo and possibly destroying things below too, and the risk of lawsuits from anyone hit by said payload.

Maybe Bosda, who seems to know a lot about the technical end of this, can correct me here; but I imagine if a disaster happened on an airship -- not a Hindenberg-scale explosion, but something that would cause a major puncture in the gas envelope -- the ship could be built with separate internal chambers so that, even if the puncture were huge and irreparable, the gas would leak out (or, in the case of an evacuated multiphase carbon composite envelope, the air would leak in) at a slow and manageable rate, and the ship would settle to the ground slowly instead of plummeting like a rock.

And it would be much simpler to build in safeguards to make sure the ship never "drops its payload" unintentionally.

BrainGlutton
09-27-2004, 05:45 PM
Of course, separate internal chambers did a lot for the Titanic . . .

Bryan Ekers
09-27-2004, 05:47 PM
Every now and then Popular Science or Popular Mechanics has blurbs about stuff like this, including airships that could deliver fifty tons of gear or some such. My guess is that if anyone picks up the idea, the American military will be the first, with shipping companies picking up the idea gradually for short hops into disaster-devastated areas. I don't see the idea competing with conventional container shipping or passenger travel, though.

Bosda Di'Chi of Tricor
09-27-2004, 06:04 PM
Maybe Bosda, who seems to know a lot about the technical end of this, can correct me here; but I imagine if a disaster happened on an airship -- not a Hindenberg-scale explosion, but something that would cause a major puncture in the gas envelope -- the ship could be built with separate internal chambers so that, even if the puncture were huge and irreparable, the gas would leak out (or, in the case of an evacuated multiphase carbon composite envelope, the air would leak in) at a slow and manageable rate, and the ship would settle to the ground slowly instead of plummeting like a rock.

And it would be much simpler to build in safeguards to make sure the ship never "drops its payload" unintentionally.Quite correct.
:)

Little Nemo
09-27-2004, 06:09 PM
Ships have always been the most efficient way to move cargo. The main advantage airships have over ships is the obvious one; they aren't limited to travel near water. But in terms of moving units of cargo per unit of energy, I doubt an airship is ever going to compete against a locomotive or even a truck. Now that the railroad and highway systems have been built, the incentive for shipping by airship is minimal. In terms of air travel, airplanes offer a huge advantage in speed. As for military use - airship's just another word for "big slow unarmored target".

GorillaMan
09-27-2004, 06:15 PM
Despite Wikipedia speculation, I doubt there's any viability in long-distance freight airships. Large ocean freighters and long-distance rail freight are the two most effecient forms of transporting goods, bar none. And this efficiency increases with every larger ship, with every longer train, with every improvement to track or to port infrastructure.

(Can anyone find a figure for the total weight of the load on a typical N American freight train?)

Bosda Di'Chi of Tricor
09-27-2004, 06:16 PM
Every now and then Popular Science or Popular Mechanics has blurbs about stuff like this, including airships that could deliver fifty tons of gear or some such. My guess is that if anyone picks up the idea, the American military will be the first, with shipping companies picking up the idea gradually for short hops into disaster-devastated areas. I don't see the idea competing with conventional container shipping or passenger travel, though.

The Navy could make good use of long-range, high capacity cargo airships--in supporting the Carrier Fleet at sea. Just lower cargo to the deck by cable/basket/winch.

Zeppelins would be ideal for shipping fruit from the tropics to the States or Europe. Faster than a ship, for that field-to-the-table freshness. It could pick up cargo from undeveloped areas. If the cargo bay is unpressurized, high altitude would act like a refridgerator, keeping the cargo fresh.

Bulk mail shippping might be very practical.

And think: Flying Cruise Ship. Wanna see Mount Everest--from above? From your stateroom?

BrainGlutton
09-27-2004, 06:33 PM
And think: Flying Cruise Ship. Wanna see Mount Everest--from above? From your stateroom?

That brings up another point. A dirigible looks big but most of that is the gasbag, not the gondola. I wonder, how many passengers could an airship carry? I mean, compared to an airliner? I think the Hindenberg only carried a few dozen. Of course, it inevitably reduces the number if you're going to give every passenger a stateroom. And what would a trip cost, compared to say, going an equivalent distance on the Queen Mary II?

PaulFitzroy
09-27-2004, 06:55 PM
And it would be much simpler to build in safeguards to make sure the ship never "drops its payload" unintentionally.

I don't even mean some kind of payload-dropping device being triggered accidentally. I mean: what if for some reason our airship exploded? If a ship explodes in the middle of the ocean, well, it's in the middle of the ocean. If a ship explodes over my house...

Polycarp
09-27-2004, 07:14 PM
You're mixing apples and oranges here.

First, a dirigible of any sort could function as a flying crane, carrying cargo suspended below it -- no problem with the concept, and the points already brought up about what happens if it is involved in an accident. But it would be my presumption that with very rare exceptions (moving big generators to rugged hydro sites, for example) you'd do interior cargo carrying, much like an airplane -- you don't sling the stuff beneath a C-5A, but load it inside it, in a cargo space.

Second, there are two (actually three) classes of dirigible, which are as different as a kayak and a hydrofoil. A blimp is a giant fusiform helium balloon with attached gondola -- you inflate the balloon, and ride in the gondola slung below it. You load the cargo into the gondola too -- and you need a relatively big gondola to hold everything.

But a rigid airship, like what the Navy flew in the 1930s and the Zeppelins, is a bunch of balloons inside an aluminum frame, which need not take up all the space inside the frame. Normally the bridge of a zeppelin was in a gondola in the normal location -- attached to the front underside of the hull -- but it need not be. And passenger and cargo space were located largely inside the frame, in areas where lifting cells were not mounted. The disadvantages of zeppelins were that 1920s and 1930s technology was not adequate to build a ship that would stand up under strong windshear (though the Graf Zeppelin and the Los Angeles, German-built, did better than any airplane of the time could, and never crashed), and that you do have the parasitic weight of the ship's frame to contend with. But in terms of added cargo and passenger capacity, the latter is far offset by the advantages, and I'm quite confident that 21st century metallurgical technology and engineeering can overcome the windshear problem.

The idea of a flying cruise liner capable of doing 100 knots or hovering and passing over either land or sea makes immense sense -- from the accounts of wealthy 1930s people, there was nothing comparable; it combined the best aspects of an airliner flight and a ocean cruise, with the added advantage of absolute stability -- nothing would disturb an airship in flight, unlike wave action or air turbulence (the latter of which it was large enough and slow enough not to be bothered by).

Cargo carrying, it's debatable whether it could compete economically with airliners -- at present. Although if the price of aviation fuel continues to rise, those who need to ship something relatively fast and inexpensively may think twice about their investments.

I'd say that technologically there are no dealbreakers, and economically it would make sense to build them -- but there's still a lingering memory of the Hindenburg as nearly the sole public knowledge of zeppelins -- and no recall of the long and nearly problem-free careers of the Graf and the Los Angeles.

BrainGlutton
09-27-2004, 07:29 PM
I don't even mean some kind of payload-dropping device being triggered accidentally. I mean: what if for some reason our airship exploded? If a ship explodes in the middle of the ocean, well, it's in the middle of the ocean. If a ship explodes over my house...

They don't use hydrogren for lift any more, only helium, which is a "noble gas" and can't burn. And the engines would be, you know, just engines -- maybe fueled by liquid propane as Bosda suggested, but in any case not by anything extraordinarily dangerous. So why would it explode?

Bosda Di'Chi of Tricor
09-27-2004, 07:35 PM
They don't use hydrogren for lift any more, only helium, which is a "noble gas" and can't burn. And the engines would be, you know, just engines -- maybe fueled by liquid propane as Bosda suggested, but in any case not by anything extraordinarily dangerous. So why would it explode?

No, I suggested that the liquid propane be used to run an electrical generator.

The voltage runs the motors that drive the propellors.

This approach keeps the fuel in a pod outside the hull, for peace of mind. Power can be transmitted by wire, which is especially helpful if we go the tilt rotor approach.

Fly by wire control.

Brutus
09-27-2004, 07:46 PM
The Army was/is funding a feasibility study by a German company, looking into building massive blimps that could transport several tanks or whatnot. The wisdom of paying the Hun to design his dread air-ships again aside, I believe the idea was shown to be unpracticle at todays level of technology (the cost of the materials used to make the skin, or something like that). I'll have to google for details.

BrainGlutton
09-27-2004, 08:17 PM
Apparently Zeppelin NT is running passenger flights -- here's a page with a photo gallery of modern airships: http://www.modern-airships.info/en/home.html See also http://www.myairship.com/ http://spot.colorado.edu/~dziadeck/airship.html, and http://www.aht.ndirect.co.uk/.

And here's a company called 21st Century Airships, Inc. Their ships, notably, are spherical, not cigar-shaped: http://www.21stcenturyairships.com/ I wonder why?

Lumpy
09-27-2004, 09:18 PM
For a dissentiing view, HERE'S (http://www.spacedaily.com/news/spacetravel-03j.html) a pessimistic article about the feasibility of airships. (Although the author is an infamous "naysayer" for what it's worth.)

Sevastopol
09-27-2004, 10:07 PM
What advantage would that offer over a helium-filled airship?

Hydrogen is fine. The "Hindenburg hydrogen-fire" thing is a recently debunked myth.

BrainGlutton
09-27-2004, 10:09 PM
Hydrogen is fine. The "Hindenburg hydrogen-fire" thing is a recently debunked myth.

How debunked? Cite?

Sevastopol
09-27-2004, 10:21 PM
Oh come on now, you can google.

Briefly, the pulverised aluminium based paints used on the balloon acted as accelerants on an electrical fire. I don't recall clearly but the fire may have been caused by static electricity or lightening, also aggravated by those paints.

That said, I think the reputation of the Hindenburg is the single impediment any such project faces. Not entirely rational, but real.

PaulFitzroy
09-27-2004, 10:27 PM
They don't use hydrogren for lift any more, only helium, which is a "noble gas" and can't burn. And the engines would be, you know, just engines -- maybe fueled by liquid propane as Bosda suggested, but in any case not by anything extraordinarily dangerous. So why would it explode?

If Sevastopol put a suitcase nuke on it.

JUST joking. Really.

Sevastopol
09-27-2004, 10:33 PM
Hilarious,

So, the things I do... Hindenburg and Hydrogen (http://www.abc.net.au/science/k2/moments/s1052864.htm)

...This bad reputation of hydrogen still bothers car manufacturers today, as they explore the use of hydrogen as a safe, non-polluting alternative to fossil fuels for powering cars. But it turns out that the extreme flammability of hydrogen is a mythconception...

As the Hindenburg came in to Lakehurst on May 6, 1937, there was a storm brewing, and so there was much static electricity in the air - which charged up the aircraft. When the crew dropped the mooring ropes down to the ground, the static electricity was earthed, which set off sparks on the Hindenburg.

The Hindenburg was covered with cotton fabric, that had to be waterproof. So it had been swabbed with cellulose acetate (which happened to be very inflammable) that was then covered with aluminium powder (which is used as rocket fuel to propel the Space Shuttle into orbit). Indeed, the aluminium powder was in tiny flakes, which made them very susceptible to sparking. It was inevitable that a charged atmosphere would ignite the flammable skin.

In all of this, the hydrogen was innocent...

Una Persson
09-27-2004, 10:58 PM
(Can anyone find a figure for the total weight of the load on a typical N American freight train?)
A typical American coal unit train, which is loaded about as heavy as one can get, has 100-115 cars of about 100-110 (short) tons each. This varies due to a variety of factors on each train, of course.

asterion
09-28-2004, 06:53 AM
A typical American coal unit train, which is loaded about as heavy as one can get, has 100-115 cars of about 100-110 (short) tons each. This varies due to a variety of factors on each train, of course.

So, about 20 million pounds? Dang.

BrotherCadfael
09-28-2004, 07:36 AM
This discussion is all futile. I remember well the articles in Popular Science back in the '60s and early '70s about how the future of industrial aviation would all be lighter-than-air craft of one sort or another.

As we all know, a glowing write-up about a future technology in PS is the Kiss of Death. Remember the Rotomat? Exoskeletons? Flying cars?

ralph124c
09-28-2004, 08:00 AM
If airships come back, will GIANT ROBOTS invade Manhattan? Check out "AIR COMMANDER and The World of Tomorrow"-GREAT flick!

fubbleskag
09-28-2004, 08:42 AM
Of course, separate internal chambers did a lot for the Titanic . . .how long did it take for the titanic to sink, though?

Aeschines
09-28-2004, 09:22 AM
I love the Hindenberg and have a big, beautiful book about it, but the passenger airship (on that scale) will never come back.

In the 20s and 30s, there was a market for such ships: wealthy people who wanted to get somewhere quick. The standard mode of travel across the oceans was, of course, the steamship.

Now the standard is the airliner, which can get you nearly anywhere within a day, usually a good deal sooner.

So the only thing that's left is the cruise idea. Of course, that would have to compete with ocean cruises. Now a first-class transoceanic flights costs more than $10k round trip; how much would an airship cruise cost? $20k? $50k? Still, the very rich might be willing to pay that. But the Hindenberg could only carry 50 persons transatlantic yet had a crew of 61. Cite. (http://en.wikipedia.org/wiki/Hindenburg_disaster)

As for profitability, my back-of-envelope goes like this. This (http://www.iht.com/IHT/MR/00/mr051700.html) has some helpful figures. The cost of developing a large aircraft is in the $10 billion + area. But let's say we can build and develop one craft for a cool $1B (about 5 times the price of a loaded 747). Let's say the company can squeeze $25k profit out of each passenger, and let's say that covers all the maintenance, G&A, everything. That requires 40,000 passengers to break even. At 75 persons per flight (25 better than the Hindenberg) and 1 flight a week (for a one-week cruise), that gives us a payback period of 10 years.

No one in Person's right mind would make such an investment.

kellner
09-28-2004, 10:15 AM
A while ago there was a German company, Cargolifter, that planned to build a large transport airship.

http://travel.howstuffworks.com/cargolifter.htm

Probably their most important selling point was that current heavy load transports (of individual heavy items, 100 tons+) are only as fast as a pedestrian over long distances and they offered significant advantages for that niche. It was never really intended for ordinary container cargo.

They are bankrupt now, but at the time they were supported by possible industrial clients like Siemens. Btw they really built that hangar, the largest self-supporting hall in the world and it is currently being converted into a "Tropical Island" theme park.

BrainGlutton
09-28-2004, 11:06 AM
Hilarious,

So, the things I do... Hindenburg and Hydrogen (http://www.abc.net.au/science/k2/moments/s1052864.htm)

So, if the Hindenburg had been filled with helium, it still would have exploded, because of the flammable stuff on the skin of the gasbag?

Little Nemo
09-28-2004, 11:26 AM
A typical American coal unit train, which is loaded about as heavy as one can get, has 100-115 cars of about 100-110 (short) tons each. This varies due to a variety of factors on each train, of course.
Most ship cargo is now packed in containers, which are basically the equivalent of a frieght car. A typical cargo ship will carry 1600 containers; a large one might carry over 6000.

Balle_M
09-28-2004, 11:50 AM
I'd say that technologically there are no dealbreakers, and economically it would make sense to build them -- but there's still a lingering memory of the Hindenburg as nearly the sole public knowledge of zeppelins --

And the Akron...
And the Macon...
And the Shenandoah...
And the R-101...

Bosda Di'Chi of Tricor
09-28-2004, 01:11 PM
If airships come back, will GIANT ROBOTS invade Manhattan? Check out "AIR COMMANDER and The World of Tomorrow"-GREAT flick!

That's Sky Captain And The World Of Tomorrow. Duh.

Sevastopol
09-28-2004, 08:14 PM
So, if the Hindenburg had been filled with helium, it still would have exploded, because of the flammable stuff on the skin of the gasbag?

'Exploded' doesn't appear to be a fair description of the Hindenburg disaster. So the question is a little misguided.

Would a helium filled airship have met with disaster in the same circumstances?

From the Link: (http://www.abc.net.au/science/k2/moments/s1052864.htm) In the terrible disaster, the Hindenburg burnt with a red flame. But hydrogen burns with an almost invisible bluish flame. In the Hindenburg disaster, as soon as the hydrogen bladders were opened by the flames, the hydrogen inside would have escaped up and away from the burning airship - and it would not have not contributed to the ensuing fire. The hydrogen was totally innocent. In fact, in 1935, a helium-filled airship with an acetate-aluminium skin burned near Point Sur in California with equal ferocity.

Xema
09-28-2004, 09:58 PM
Aeschines has it right.

The enormous difference between airships and airplanes in speed and passenger-miles per day means the former can't be competitive for human transportation. A small (and expensive) novelty tourist market might be possible.

And the enormous difference between airships and conventional freight carriers (ships and trains) in ton-miles per day means the former can only hope for very special cargoes (such as logs lifted out of remote forests).

tygerbryght
09-29-2004, 12:06 AM
I love the Hindenberg and have a big, beautiful book about it, but the passenger airship (on that scale) will never come back.
...
Now the standard is the airliner, which can get you nearly anywhere within a day, usually a good deal sooner.

<snip>
What about when the cost of petroleum products gets so high that nobody can afford jet travel except the very rich?? Some experts are proclaiming that the high point in barrels pumped will be ~Thanksgiving, 2005.

Aeschines
09-29-2004, 12:47 AM
What about when the cost of petroleum products gets so high that nobody can afford jet travel except the very rich?? Some experts are proclaiming that the high point in barrels pumped will be ~Thanksgiving, 2005.
I was talking about a cruise experience, which I, based on the numbers I gave, think will never work.

It's true that a Hindenburg-style airship is more fuel-efficient than a jumbo jet (I remember seeing a special on TV that such and such a [small] airship can fly for a week on what it takes a [big] airplane to taxi to the runway), but it's also a lot slower and, most important, carries a lot fewer people. So I doubt if ultimately it uses fuel much more efficiently.

It would take a large increase in petro prices to get people to stop flying. A reduction of some degree is likely, I guess. If worse comes to worse, I suppose we'll have to use sailing ships again.

t-bonham@scc.net
09-29-2004, 01:14 AM
Of course, separate internal chambers did a lot for the Titanic . . . Ah, but they were not actually separate, were they? The chambers were separately sealed at the bottom, but at the top (about 4th deck, I think) they were open to each other.

So the holed ones filled up with seawater, which eventually ran over the top and into the next one, and this continued until the whole ship sank.

Had they actually been separate sealed chambers, the Titanic would have stayed afloat much longer, at least enough to get the passengers off safely, possibly even long enough for them to have saved the ship.


P.S. The current Goodyear blimps are made this way. They have separate internal chambers where the helium gas is contained.

Polycarp
09-29-2004, 09:06 AM
Ah, but they were not actually separate, were they? The chambers were separately sealed at the bottom, but at the top (about 4th deck, I think) they were open to each other.

So the holed ones filled up with seawater, which eventually ran over the top and into the next one, and this continued until the whole ship sank.

Had they actually been separate sealed chambers, the Titanic would have stayed afloat much longer, at least enough to get the passengers off safely, possibly even long enough for them to have saved the ship.

That accords with what I read about the Titanic back in the day.


P.S. The current Goodyear blimps are made this way. They have separate internal chambers where the helium gas is contained.

I'd love to see a cite on this. I don't doubt your veracity for one moment, but that's a contradiction to the traditional concept of a blimp, though it makes far more sense from a safety standpoint than a single envelope, and I'd like very much to read more about it.

Brutus
09-29-2004, 09:31 AM
Anatomy of the Goodyear Blimp. (http://www.goodyearblimp.com/anatomy.html)

Multiple helium bags inside the blimp are used because the helium expands, and also helium is vented from the fore or aft 'ballonete' to trim pitch when not moving.

Polycarp
09-29-2004, 09:54 AM
Anatomy of the Goodyear Blimp. (http://www.goodyearblimp.com/anatomy.html)

Multiple helium bags inside the blimp are used because the helium expands, and also helium is vented from the fore or aft 'ballonete' to trim pitch when not moving.
Thanks, Brutus!

BrainGlutton
09-29-2004, 11:06 AM
It's true that a Hindenburg-style airship is more fuel-efficient than a jumbo jet (I remember seeing a special on TV that such and such a [small] airship can fly for a week on what it takes a [big] airplane to taxi to the runway), but it's also a lot slower and, most important, carries a lot fewer people. So I doubt if ultimately it uses fuel much more efficiently.

But a jet airplane runs on jet fuel -- which, I understand, is essentially the same thing as kerosene -- a petroleum derivative. According to Bosda, the best fuel for an airship would be propane (driving a generator, which would generate power for electric fan motors). I'm not sure where they get propane -- is it a natural gas? In terms of price and world reserves, how does it compare with petroleum fuels?

GomiBoy
09-29-2004, 11:27 AM
OK, so go super-green and use the skin of the airship as a solar panel... they have flexible ones now. That would power the batteries / motors / electrics...

I hate to be a naysayer, but aren't people forgetting about manufacturing costs? These things are made out of aluminum and plastics, right? Well, you can't make plastics without petrochemicals... unless someone has a different formula?

Santos L Halper
09-29-2004, 11:29 AM
Anatomy of the Goodyear Blimp. (http://www.goodyearblimp.com/anatomy.html)

Multiple helium bags inside the blimp are used because the helium expands, and also helium is vented from the fore or aft 'ballonete' to trim pitch when not moving.

I don't see where it says it has multiple helium bags. As far as I know, no blimps have more than one large helium compartment. The ballonets just have air in them. They increase or decrease the amount of air to keep the shape of the blimp as the helium in the main part of the envelope expands and contracts due to temperature and altitude.

There isn't much need to have separate compartments because a blimp isn't under much pressure. Getting a hole in it doesn't cause all the helium to shoot out like would happen with a child's toy balloon, you just get a slow leak.

Anyway, I think it's very unlikely we'll ever see large scale use of rigid airships for cargo or passenger use. As others have said, it's technically doable, but it would be more expensive then current methods without really having any advantages. I'd love to see it, though. I'd give anything to see something the size of the Hindenburg drifting across the skyline.

If some billionaire with a major airship fixation decided to built a couple modern flying cruise ships, it might make money if people were willing to pay the high ticket price for the novelty of a few day luxury flight from the US to Europe. But I think it's a lot more likely to happen because someone with the money to build them thinks it'd be cool than because it makes sense as a good investment.

Brutus
09-29-2004, 01:16 PM
I don't see where it says it has multiple helium bags...

Err, then you need to re-read it, and click on the pretty blimp picture. The Goodyear Blimp has two, fore and aft, and they are called 'ballonetes'.

Santos L Halper
09-29-2004, 01:49 PM
Err, then you need to re-read it, and click on the pretty blimp picture. The Goodyear Blimp has two, fore and aft, and they are called 'ballonetes'.

I'll see your "Err" and raise you a "harumph". :)

If you re-read that site, it says that the ballonets hold air, not helium, and describes what they're for.

Brutus
09-29-2004, 02:32 PM
I'll see your "Err" and raise you a "harumph". :)

If you re-read that site, it says that the ballonets hold air, not helium, and describes what they're for.

Look over there! BOBABOOEY! STERN RULES!


Damn, didn't throw you off...let's see... 'Air' is just scientific mumbo-jumbo for 'helium', heh, you know those crazy scientists with their goofy nomenclature! Don't feel bad, not too many people are as learned in science and alchemy as am I!

Still no? Well damn, it looks like I was wrong. DAMN. Thwarted, I was. Bested. Well, Mister Halper, you win this round!







;)

catsix
09-29-2004, 02:46 PM
GomiBoy said:
I'm not sure where they get propane -- is it a natural gas? In terms of price and world reserves, how does it compare with petroleum fuels?

Natural gas is also known as methane, chemical formula CH4. Propane has chemical formula C3H8.

It's similar to methane in that it is a hydrocarbon, but it uses a longer carbon chain and is much more easily liquified than methane. Two more carbons down the list, there's pentane, C5H12, which is from what I remember the base molecule for gasoline. If memory is serving me correctly, gasoline contains 2,2,4-trimethylpentane, as well as hydrocarbons containing carbon chains of 6 to 11 carbons, hexane, heptane, octane, nonane and decane are in there.

These things are all alkanes, and so are all part of the same hydrocarbon family having one bond between each carbon and being surrounded by hydrogen, for example:



H H H
| | |
H-C-C-C-H
| | |
H H H

is an example of the chain of carbons in propane.

Methane's commonly found in the same areas as petroluem deposits, and does burn cleaner than those hydrocarbons further up the chain. Propane burns fairly cleanly, as does butane (4 carbons). Beyond that I think they become liquid and you end up with more impurities and less efficient burns.

Either way, same chemical family.

catsix
09-29-2004, 02:50 PM
Gah. Shoulda previewed.

The code didn't come out quite right.

Each carbon has 4 bonds. The two carbons on the end have 3 hydrogens attached, and one carbon. The one in the middle has 2 carbons attached, and 2 hydrogens.

BrainGlutton
09-29-2004, 03:04 PM
Natural gas is also known as methane, chemical formula CH4. Propane has chemical formula C3H8.

It's similar to methane in that it is a hydrocarbon, but it uses a longer carbon chain and is much more easily liquified than methane. Two more carbons down the list, there's pentane, C5H12, which is from what I remember the base molecule for gasoline. If memory is serving me correctly, gasoline contains 2,2,4-trimethylpentane, as well as hydrocarbons containing carbon chains of 6 to 11 carbons, hexane, heptane, octane, nonane and decane are in there.

These things are all alkanes, and so are all part of the same hydrocarbon family having one bond between each carbon and being surrounded by hydrogen, for example:



H H H
| | |
H-C-C-C-H
| | |
H H H

is an example of the chain of carbons in propane.

Methane's commonly found in the same areas as petroluem deposits, and does burn cleaner than those hydrocarbons further up the chain. Propane burns fairly cleanly, as does butane (4 carbons). Beyond that I think they become liquid and you end up with more impurities and less efficient burns.

Either way, same chemical family.

OK, but what does propane cost, compared to kerosene? And where does propane come from? Is it a limited-supply, non-renewable resource like petroleum? Or is it something we could manufacture? These are crucial points when we're trying to determine whether a propane-powered airship is more or less fuel-efficient and economical than a kerosene-powered jet airplane.

BTW: On the subject of hydgrogen (not as fuel, but as lifting gas) vs. helium: Maybe hydrogen didn't really destroy the Hindenberg. But I still would stick with helium even though it's slighly less buoyant. Hydrogen might or might not be explosive, but it is definitely corrosive. It's a one-proton atom which will bond with anything. That's one of the reasons they haven't yet perfected a hydrogen-fueled car -- the fuel tends to corrode the parts. Helium will not bond with or corrode anything.

Polycarp
09-29-2004, 03:35 PM
Lovely job on bollixing chemistry and mineralogy here, folks.

Yes, monatomic hydrogen is extremely active, and will bond with nearly anything. Including itself. That is why it is not found in nature, save in rarefied gases in astronomical spectroscopy. Hydrogen itself is H2, a diatomic molecule, and is fairly stable, though quite combustible -- hence the idea of hydrogen-fueled cars, discussed in this space a few weeks past.

When organic matter is buried and decays, it is converted to a wide variety of chemicals, some of which are solid, black, principally carbon compounds -- called coal. Some of which are a thick, gooey mixture of liquids, called crude oil. And some of which are a mixture of the half dozen or so gaseous hydrocarbon compounds, with methane (CH4 as the principal component, and that mixture is called natural gas.

Propane (C3H8) can be extracted from natural gas and is easily liquefied at room temperature by being compressed to a certain easily-maintained pressure, hence LNG. It can also be produced from the more volatile components of crude oil by one of the innumerable "cracking" processes. As noted, butane (C4H10) is also gaseous, and even more easily liquefied -- your typical butane disposable lighter contains liquid butane, which vaporizes when the stopcock is held down and hence will combust when it encounters the spark of flint and steel from the roller flimdingie adjacent to the stopcock.

Gasoline is a mixture of liquid alkanes, including pentane and isooctane -- the "octane" rating of gasoline indicates how "knock-free" its combustion is compared to pure isooctane, which has an "octane rating" of 100.

For any lighter-than-air entity (hydrogen or helium plus load), the degree to which it ascends is defined by the amount of ballast (load) counteracting its buoyancy. Compressed air is used to "trim" airships; water is typically carried as ballast -- you may vent water to rise, or vent helium (or hydrogen) to descend.

In the absence of direct fire or spark, hydrogen is perfectly safe -- unlike a few unstable compounds, it will not spontaneously explode. However, an air-hydrogen mixture is dangerously explosive, requiring a flame or spark to ignite but then burning rapidly (and producing water vapor). In the Hindenburg fire, it's believed that the fabric burned rapidly, the hydrogen caught from it (but rose), and most of the severe burns suffered by the crew and passengers resulted from the burning fabric and accouterments, or from the frame (warped into structurally unstable shape and heated to high temperature by the fire surrounding it), not from the hydrogen, which was burning with an invisible flame above the collapsing Zeppelin.

BrainGlutton
09-29-2004, 03:42 PM
Propane (C3H8) can be extracted from natural gas and is easily liquefied at room temperature by being compressed to a certain easily-maintained pressure, hence LNG. It can also be produced from the more volatile components of crude oil by one of the innumerable "cracking" processes. As noted, butane (C4H10) is also gaseous, and even more easily liquefied -- your typical butane disposable lighter contains liquid butane, which vaporizes when the stopcock is held down and hence will combust when it encounters the spark of flint and steel from the roller flimdingie adjacent to the stopcock.

So, propane, like gasoline and kerosene, is made from stuff that's in the ground and of which we have a limited all-time supply and no way of renewing it, right?

So -- how do the world reserves of natural gas compare with the world's reserves of petroleum? I'm trying to figure out whether reviving airship travel might give us a fallback position for long-distance aviation, in the event of another fuel crisis.

Polycarp
09-29-2004, 03:55 PM
So, propane, like gasoline and kerosene, is made from stuff that's in the ground and of which we have a limited all-time supply and no way of renewing it, right?

So -- how do the world reserves of natural gas compare with the world's reserves of petroleum? I'm trying to figure out whether reviving airship travel might give us a fallback position for long-distance aviation, in the event of another fuel crisis.

According to a Montana university website (http://cse.cosm.sc.edu/hses/NatRes/pages/fossil.htm) which was the first source on Google with numbers, crude oil reserves will last 50 years or less (50 at current rate, which has been increasing annually), and natural gas reserves will last 125 years. This site shows coal reserves as good for 200-300 years; I was going to volunteer the 300 year figure, which I've seen cited numerous times, if I couldn't come up with numbers. Additional hydrocarbon sources are noted there which it is not economical to extract fuels from -- tar sands and oil shale. It might also be noted that a number of crops will produce quite plentiful and renewable oils -- the bottle of Puritan or Wesson Canola oil on your stove (you are using that rather than corn oil, right?) is an oil which is combustible under the right circumstances -- atomized by a jet, IIRC -- and produced from the rapeseed plant, which can be grown in fairly arid climates not suitable to most other crops.

BrainGlutton
09-29-2004, 04:12 PM
According to a Montana university website (http://cse.cosm.sc.edu/hses/NatRes/pages/fossil.htm) which was the first source on Google with numbers, crude oil reserves will last 50 years or less (50 at current rate, which has been increasing annually), and natural gas reserves will last 125 years.

Then it would appear we'll have to switch to airships sooner or later, for all air-travel needs but those where speed is of utmost importance. Unless somebody can figure out a way to fly a jumbo jet on propane, coal, hydrogen or plutonium.

Xema
09-29-2004, 11:15 PM
It's true that a Hindenburg-style airship is more fuel-efficient than a jumbo jet ... but it's also a lot slower and, most important, carries a lot fewer people. So I doubt if ultimately it uses fuel much more efficiently.

A full 747 delivers something like 40 passenger-miles per gallon. I doubt any current airship can match that.

Sam Stone
09-30-2004, 12:56 AM
The airship may make a comeback in a very unexpected way - as a spaceship (http://www.jpaerospace.com/). JP Aerospace is working on a design for a large V-shaped blimp called the 'Ascender' that will use bouyant lift to get it up very high (140,000 ft ). One proposal is to have a suborbital inflatable 'space station' at that altitude - above 99% of the atmosphere, out of the weather, and permanently stationed.

From there, an even larger airship (like, a mile long so that its density is low enough to be bouyant even in the hyper-thin air on the way to orbit) with electric engines would transition to orbit. The engines will begin to accelerate it through the thin atmosphere. The vehicle has a lifting body shape, so the combination of bouyant lift and aerodynamic lift takes it higher and higher, while it goes faster and faster, until eventually it's completely out of the atmosphere and in orbit.

To come back, it does the opposite. Very, very gradual deceleration (I think it takes days to get to orbit and days to get back), with a slow transition back to atmospheric flight. Since the transition happens very gradually, no heat shields are required, and the whole process is very safe. And it can haul a LOT of cargo.

It's a very cool idea, and I think they're already flying a prototype (non-space going). These guys are serious, and have big time funding from the U.S. Navy and private funds.

Santos L Halper
10-03-2004, 04:57 PM
A full 747 delivers something like 40 passenger-miles per gallon. I doubt any current airship can match that.

I've done some digging and found some info on rigid airship fuel consumption.

May 17-20 1937 the Hindenburg flew from Frankfurt Germany to Lakehurst, New Jersey. Total flight time was 78.5 hours and 4500 miles (7238 kilometers). They used a total of 41,110 kilograms (90632 pounds) of diesel fuel, which is about 12765 US gallons.

There were 41 passengers, so that works out to 14.45 passenger/miles per gallon. With a full load of 72 passengers, that would be about 25.4 passenger/miles per gallon.

The USS Macon was a US Navy airship, so it didn't carry passengers, but it was close to the same size (6,850,000 cubic feet to the Hindenburg's 7,062,000 cf). On the Macon's 110,000 pounds of fuel (15,500 US gallons), it's range was:

Speed in Knots...Hours....Range in Nautical Miles
........70................68..............4760
........65................75..............4855
........55................108............5940
........46................158............7268

So at it's cruise speed of 55 knots (63.3 mph), the range was 5940 Nautical miles (6819 miles).

These figures are for seventy year old aircraft. Presumably a modern airship built with 21st century technology could be a lot more efficient, but I don't know if it would equal the 747 numbers or not.

Figures are from the Airships Akron and Macon by Richard K. Smith and Graf Zeppelin & Hindenburg by Harold G. Dick and Douglas H. Robinson.

Kimstu
10-03-2004, 05:25 PM
Aeschines: I was talking about a cruise experience, which I, based on the numbers I gave, think will never work.

Depends on the scale you're talking about: what is a balloon ride (http://launch.net/rides.html) but a short, local, cheap airship cruise?

Spectre of Pithecanthropus
10-04-2004, 02:50 PM
Bulk mail shippping might be very practical.


See, now here is a case where a Hindenburg-type disaster might actually have been a positive boon. I can't imagine that Lowell Thomas would have cried out, "Oh, the slickly produced glossy catalogs! Oh, the Valpaks and Pennysavers!"

Xema
10-04-2004, 08:19 PM
what is a balloon ride but a short, local, cheap airship cruise?

Short - yes. Local - usually. Cheap - not very: typical cost of a balloon flight lasting 30-45 minutes is something like $150 - $200 / person.

BrainGlutton
10-04-2004, 08:25 PM
BTW -- does anybody know -- is it possible to design a jet airplane to run on some non-petroleum-derived fuel? Propane? Hydrogen? Coal?

Berkut
10-04-2004, 08:31 PM
Quite a few hobbyists run their homebuilt jet engines on propane.

BrainGlutton
10-04-2004, 08:33 PM
Quite a few hobbyists run their homebuilt jet engines on propane.

They do? I thought those little propane-powered model planes were all prop engines -- I've never seen a jet!

Xema
10-04-2004, 08:35 PM
is it possible to design a jet airplane to run on some non-petroleum-derived fuel? Propane? Hydrogen? Coal?

I can see no reason why it should be difficult to get a jet engine to run on any easily atomized fuel, so propane and hydrogen should be no problem. Coal would require some sort of gasification.

A thornier problem might be carrying suitable quantities of these fuels. Safe pressure vessels tend to be heavy, expensive or both.


(And is propane not petroleum-derived?)

Berkut
10-04-2004, 08:39 PM
They do? I thought those little propane-powered model planes were all prop engines -- I've never seen a jet!I'm not familiar with the model jet engines. I was referring to these turbocharger based engines that people like to build. It's a great deal easier to run one on propane than to properly inject diesel or gasoline.

BrainGlutton
10-04-2004, 08:41 PM
I'm not familiar with the model jet engines. I was referring to these turbocharger based engines that people like to build. It's a great deal easier to run one on propane than to properly inject diesel or gasoline.

Do these engines propel airplane? Or what?

asterion
10-04-2004, 09:25 PM
The airship may make a comeback in a very unexpected way - as a spaceship (http://www.jpaerospace.com/). JP Aerospace is working on a design for a large V-shaped blimp called the 'Ascender' that will use bouyant lift to get it up very high (140,000 ft ). One proposal is to have a suborbital inflatable 'space station' at that altitude - above 99% of the atmosphere, out of the weather, and permanently stationed.


Just out of curiosity, were they making an attempt for the X-Prize?

Berkut
10-04-2004, 09:55 PM
Do these engines propel airplane? Or what?None that I've seen. Most are mounted on runup stands and go-carts.

BrainGlutton
10-04-2004, 10:03 PM
None that I've seen. Most are mounted on runup stands and go-carts.

:confused: A jet-powered go-cart? What's the point?

Never mind -- is there any way one of these miniature propane-powered jet engines could be scaled up to propel an airliner?

Because if it can't be -- and if neither can an airliner be propelled by hydrogen, coal, plutonium, or anything else that we're not going to run out of within the next 50 years -- then, as I said above, sooner or later we are going to have to switch to airships (most likely powered by electric motors charged by propane-burning generators, as Bosda described) for all air-travel needs but those for which speed is of overriding importance.

BrainGlutton
10-04-2004, 10:04 PM
Just out of curiosity, were they making an attempt for the X-Prize?

Wouldn't that be sumpin'! :)

Sam Stone
10-04-2004, 10:52 PM
A jet engine can burn all sorts of stuff. Jet fuel is kerosene, similar to diesel fuel. In a pinch, different fuels can be used. The difficult part will be getting the fuels to work with the delivery system. Don't want to gum up the pipes. Some engines, like the GE CF6 are designed to be fed standard gasoline if necessary.

But you want to use a fuel that delivers lots of energy per unit weight, since this is an aircraft we're talking about.

Asterion asks:

Just out of curiosity, were they making an attempt for the X-Prize?


Nope. Their technology is not suitable for suborbital flight at all. Their smaller 'ascender' balloon can get up to about 140,000 feet, which is not quite halfway to space. From there, to get a balloon higher it needs to have ultra-low density and secondary propulsion. Such a balloon would have to be built in place, since it would never survive a trip through the atmosphere (it will be very light, and very large - a mile long). So they're not talking about doing this in a year, or even five.

I think the company's plan right now is to sell their permanent platforms at 140,000 feet which can be used for military purposes, weather reporting, communications relays, etc. But once they have such permanent floating platforms they can work on building the giant balloon that would float/fly to orbit.

I doubt if you'd see one within ten years. But it sounds like it's at least possible, and if it is, it would lower the cost to low earth orbit by a couple of orders of magnitude.

BrainGlutton
10-04-2004, 11:03 PM
But you want to use a fuel that delivers lots of energy per unit weight, since this is an aircraft we're talking about.

Does that rule out coal? Or hydrogen? Or propane?

Sam Stone
10-04-2004, 11:49 PM
I think coal would be ruled out for lots of reasons, unless you processed it into something else before you left the ground. I don't know about propane and hydrogen.

Broomstick
10-07-2004, 05:38 AM
Quite a few hobbyists run their homebuilt jet engines on propane.
They do?

I'm involved in the RC model crowd in this area (roughly defined as Indiana, Ohio, and Illinois) and all the model jet guys I've encountered run their machines on JetA, just like the big boys.

And that gent out in Ohio with the Part 103 jet-powered Mitchell Wing runs on JetA, too.

Wasn't aware there were propane powered jets.... [shrug]

Broomstick
10-07-2004, 05:43 AM
Short - yes. Local - usually. Cheap - not very: typical cost of a balloon flight lasting 30-45 minutes is something like $150 - $200 / person.
Last balloon ride I took was $135 for two full hours in the air, plus a muffin-and-champaign breakfast thrown in at no extra charge.

Shop wisely.





Heck, the airplanes I rent start at $140 for two hours AND I have to buy my own breakfast!

Ludovic
10-07-2004, 10:23 AM
These figures are for seventy year old aircraft. Presumably a modern airship built with 21st century technology could be a lot more efficient, but I don't know if it would equal the 747 numbers or not.
Even after base efficiency, we would also have to keep in mind the relative luxury involved.

Yeah, people have said that additional luxury would be a benefit of airships, but if that's not as important we can up the passenger miles/gallon even more. It might make it economically feasible, if petroleum products become the major expense in flight, versus labor costs.

On the other hand, you wouldnt want to cramp the conditions too much, since the flight would take much longer.

ExTank
10-07-2004, 02:23 PM
BG:

Of course, separate internal chambers did a lot for the Titanic . . .

Actually, those compartments did wonders for the Titanic. Without them, she would've sank a lot quicker than she did.

So..you proved your own point. :)

Polycarp
10-07-2004, 03:52 PM
Last balloon ride I took was $135 for two full hours in the air, plus a muffin-and-champaign breakfast thrown in at no extra charge.

For that price, I hope they threw in Urbana too! :p

Berkut
10-07-2004, 06:01 PM
Quite a few hobbyists run their homebuilt jet engines on propane.They do?Yes.
I'm involved in the RC model crowd in this area (roughly defined as Indiana, Ohio, and Illinois) and all the model jet guys I've encountered run their machines on JetA, just like the big boys.I didn't mention a single thing about model jet engines using propane. Where do you see that?

Did you read these previous posts?
I'm not familiar with the model jet engines. I was referring to these turbocharger based engines that people like to build. It's a great deal easier to run one on propane than to properly inject diesel or gasoline.Do these engines propel airplane? Or what?
None that I've seen. Most are mounted on runup stands and go-carts.

Xema
10-07-2004, 08:24 PM
Last balloon ride I took was $135 for two full hours in the air, plus a muffin-and-champaign breakfast thrown in at no extra charge.

You are obviously a savvy shopper.

Broomstick
10-07-2004, 09:40 PM
Did you read these previous posts?
Yeah - at 5:30 am, before my first morning dose of caffeine. Got a problem with that?

The "jet hobbyists" I know all happen to do RC models... maybe you know a different crowd. I'm a prop-plane hobbyist, as is my husband - the major difference being the size of the airplanes we fly, and if I crash mine it hurts a lot more. Next time you want to exclude a whole bunch of people from consideration it would help if you were more specific with your terms. "Hobbyist" is pretty broad.

Berkut
10-07-2004, 10:39 PM
I specifically excluded model jet engines.

I can't get any more specific than:I'm not familiar with the model jet engines. I was referring to these turbocharger based engines that people like to build. ... Most are mounted on runup stands and go-carts.Please take the time to read what I wrote before you take issue with it, and we can avoid the whole "being more specific" thing altogether.

Broomstick
10-08-2004, 04:30 AM
You said "I'm not famillar with", not "no one is allowed to mention". Lighten up.

BrainGlutton
10-08-2004, 11:26 AM
Just for giggles and why-nots, here's some pix of the incredible airships of the famous 19th-Century American inventor-adventurer, Frank Reade, Jr. (artists' conceptions based on the chronicles of the amazing Mr. Reade's adventures as told to Luis Senarens): http://www.bigredhair.com/airships/index.html

Saltire
10-08-2004, 12:36 PM
I'm not any kind of engineer, so don't beat me up too much about the exact facts and figures implied by this post. Instead, think about the possibilities. Call me an amateur futurist.

People on this thread have suggested light, ultra-rigid carbon composite tanks that could be drained down to vacuum. These would be more bouyant than the same tanks filled with helium or hydrogen, as well as saving the money needed to obtain and distribute these gasses. Of course, current tech cannot create such tanks, but it may be possible in the forseeable future.

Someone also suggested coating the hull with solar cells. Those are fairly expensive now, but should get cheaper every year.

It was also suggested that maneuvering props be run on electricity.

All of these ideas can come together. Imagine if the ship had multiple vacuum tanks and a photovoltaic coating. Then imagine that a couple of the tanks are instead filled with hydrogen. That hydrogen could be used to run a fuel cell to produce electricity. As the H2 is used up, the tank would actually start to provide extra lift, since the tank would slowly empty without adding in anything in place of the H2. Between the solar cells and the fuel cells, you'd have all the electrical power you need for maneuvering, the various pumps needed, and to run the passenger and crew areas of the ship. The main emission of the ship would be water vapor.

Another futurist thought I had while reading this thread is that the world may someday have much cheaper helium sources. Right now, He2 is pretty expensive, since it can only be mined in a few places worldwide. In the future, we may develop commercial fusion as an energy technology. This would produce a lot of waste helium.

So, as technology marches on, the economies of airships will shift. It isn't at all hard to imagine airships becoming cheap enough to build and run. It's just a question of how long that march will be.

matt
10-08-2004, 06:13 PM
I don't see the vacuum tank becoming a useful lifting body in the near or even distant future. The extreme strength levels found in carbon fibres or more recently in buckytubes apply to tensile loads, but it's hard to translate that strength into compressive situations such as a large evacuated shell.

You also have to consider how much extra lift you get from vacuum - a cubic metre of air weighs about 1.2 kg, so you get that much lift for each cubic metre displaced. A cubic metre of helium weighs 0.17kg and a cubic metre of hydrogen weighs 0.08g, so helium gives 1.03 kg lift per cubic metre, hydrogen gives 1.12kg, and vacuum gives 1.2 kg. It's a lot of trouble to go to for a fairly small lift advantage, and the weight of the rigid shell compared with a balloon canopy would probably more than offset it.

The suggestion of electric props powered by a motor-generator doesn't really make sense for airships. Essentially this is using electricity as a transmission. The system is used in locomotives and quarry trucks because it allows a large range of torque conversion (equivalent to gearbox with hundreds of gears) but it isn't necessary for airships and carries a weight and efficiency penalty. It would make more sense to put individual IC engines or turboprops in outboard cupolas, the way they used to in fact! (The petrol-electric cars coming onto the market now offset the efficiency penalty because the engine can is run at high output all the time, where it is most thermodynamically efficient. Unlike cars, an airship engine does not run at a fraction of its maximum output most of the time and so it wouldn't gain the same improvement.)

Solar electrical power is a neat idea, and there are some thin-film technologies that are lightweight and comparatively cheap. Their conversion effeciency isn't so great yet, but with all that collecting area they might well be viable. Another notion is to make the bottom half of the blimp internally reflective and the top half transparent, and focus the sunlight up onto a strip of solar cells running in a line across the top facing inwards. In eihercase electric props would of course be required.

I love the idea of hydrogen fuel cells running off the hydrogen in the balloon itself! Even without the vacuum tank concept, you can store a lot of extra hydrogen in a balloon that's at higher than atmospheric pressure, and in that situation the strength of carbon fibres and buckytubes can be easily exploited. Interestingly this is not a new idea - it was considered long ago as a fuel for the IC engines of airships but was never found to be reliable. These days we can build IC engines that will burn hydrogen but a fuel-cell electric-prop combo might well give better efficiency, and works very nicely to supplement solar electric power or be supplemented by it.

http://www.hq.nasa.gov/office/pao/History/SP-4404/part1.htm


Check out the solar powered airship with rechargable fuel cells at the end of this article! Don't know if the project ever got off the ground though.

http://wireless.iop.org/articles/feature/1/9/3/2

Personally I'd love to see airships come back, but then I also want flying boats and steam trains back so I can have a ride on them...

Aeschines
10-08-2004, 06:44 PM
Just get a fusion reaction going inside the dirigible and convert hydrogen to helium!

Bosda Di'Chi of Tricor
10-09-2004, 08:50 AM
matt --I was trying to link the 2 ideas of "tilt rotor control" and "electrical motors".

This obviously simplifies the problems of fuel lines.

matt
10-09-2004, 11:25 AM
matt --I was trying to link the 2 ideas of "tilt rotor control" and "electrical motors".

This obviously simplifies the problems of fuel lines.

It's a logical idea and quite elegant. It's becoming increasingly popular in large seagoing ships to use generator-motor transmission and house the motor and propeller in an external pod below the stern. The whole pod can be rotated to point the propeller in any direction, so you can dispense with the rudder and auxiliary thrusters and still turn on the spot.

For a large airship with a whole bunch of tilt-rotors all over it, a single engine-generator and a bunch of electrical motors might turn out to have more advantages than disadvantages - prop speeds down to zero, instant prop startup and of course the fuel line issue. Could be important when you're parking the thing or trying to hold it steady in gusty wind. If someone ever builds one, feel free to crow! I promise to accept it with bad grace to make it more satisfying.

Now I'm off to watch Sky Captain while eating enough toffee popcorn to make me hyper.