[IW] Zeppelins mean Alternate Timelines. So, how are they made feasible?

[DungeonCrawler]

High pressure air doesn't seem to cause too many problems, up to six atmospheres. Pure oxygen does require breaks to avoid oxygen poisoning, but is used.

Given that the proportion of oxygen to other gases generally determines how easily a substance sparks up, I don't think that the pressure alone would make much difference. However, it might make it tougher to keep air away from a fire via water. Now a gas system like CO2 or Halon should still be effective, just needing a lot more gas to fill the area at high pressure.

http://en.wikipedia.org/wiki/Hyperbaric_oxygen_therapy

[tshiggins]

Originally Posted by patrulje

Instead of looking at the past look to the future, say 30-40 years in the future when petro chemicals are running out or are sufficiently more difficult to aquire (say a war in the middle east in which nukes got used destoying all of the oil reserves there).

Would electro chemical powered Zepplins and coal fired trains become more feasible for transport than $50 a gallon gas?

J

I had thoughts along these lines, as well. Internal combustion engines need a chemical fuel source that has a high mass:energy ratio. For that, petroleum products are really, really tough to beat. That's why we use them.

So, what if there weren't any petroleum? You could use alcohol, but it's far less efficient. Stirling engines become pretty decent choices, as well, which somebody already mentioned.

Also, I think you can help address the hydrogen problem by using hot helium. David Morgan-Mar actually discussed this. Heated to 1500 degrees C, helium provides a lifting capability of about 97 percent of that of vacuum. You'd need a lightweight, flexible ceramic fabric to contain it (Would carbon fibers work?) plus an energy source to provide that heat.

However, even if you didn't go all the way up to superheated temperature, I think you'd see some measurable improvement in performance by heating the helium by even a few hundred degrees.

So, postulate a world in which petroleum doesn't exist, because all fossil fuels take the form of coal. Steam engines become vastly more efficient, but internal combustion never really goes anywhere, because it doesn't have a good fuel source. That just about forces aircraft into alternative forms, wouldn't it?

[maximara]

Originally Posted by Anthony

The basic problem with dirigibles is that they simply don't have the performance to compete with either ships or aircraft. A dirigible with basically equivalent performance to a 747 (same takeoff weight, same fuel consumption) would be about 1500' long with a cruise speed of less than 150 mph. The 747 is 231' long with a cruise speed of close to 600 mph.

This comparison is flawed on a key point: Dirigibles are lighter than air. This means that a lot of plane's fuel is spent getting and keeping the plane in the air. Also, for every 10 units of fuel you put on the plane you need another unit just to get the thing off the ground.

A 747 ranges from 128,730 to 398,780 pounds empty (64.36 to 199.39 standard tons). The Hindenburg by comparison weighted 130.1 tons empty but promotional of the time stated her fully fueled and crewed dead weight--430,956 lb (215.478 tons) As you can clearly see Hindenburg outweighs a 747-200 and is just slightly lighter than a 747-400 and she sure wasn't any 1500' long (she was in fact only 804' long.)

[malloyd]

Originally Posted by Joseph Paul

Ulzgoroth


Well you may not like the pace but you can’t beat the price.

Sure you can, just not with an airplane. Lighter than air vehicles operate in a middle regime - cheaper and potentially heavier capacity than airplanes but slower, more expensive and with less capacity than ships or railroads, but faster. This squeezes the market to stuff that wants that special combination of cost and speed (not very much) or applications where some secondary capability counts more than either cost or speed.

They're in much the same situation as passenger ships (which survive only for very short hops, not really an option at the higher cost of airships, or luxury cruises, which airships could do) or helicopters (which airships could compete with for hover ability and flexiblity of "landing" locations).

[Joseph Paul]

Originally Posted by malloyd

Sure you can, just not with an airplane. Lighter than air vehicles operate in a middle regime - cheaper and potentially heavier capacity than airplanes but slower, more expensive and with less capacity than ships or railroads, but faster. This squeezes the market to stuff that wants that special combination of cost and speed (not very much) or applications where some secondary capability counts more than either cost or speed.

They're in much the same situation as passenger ships (which survive only for very short hops, not really an option at the higher cost of airships, or luxury cruises, which airships could do) or helicopters (which airships could compete with for hover ability and flexiblity of "landing" locations).

It may have been hype but the SkyCat 1000 literature was claiming to be equal to sealift shipping and faster. If that is true then it may not matter to shippers that a sea vessel has greater capacity since many of them can't fill a vessel by themselves. If the cost is the same and going in a smaller load gets there faster it may squeeze sealift. There is also the added cost in sea lift of having to arrange transport further inland once it hits the coast. An airship may very well go direct or make stops on a route. Obviously if you are able to fill a 20,000+ ton vessel there may be financial incentives like taxbreaks etc in it for you even if it did cost more.

Then again there is always the possibility of the world having a drastically reduced hydrographic percentage. That would squueze sealift.

[Joseph Paul]

Originally Posted by Ulzgoroth
I doubt that's sufficient. If WWII is still in the cards, the Hindenburg not going down isn't going to prevent a huge wave of advancement in heavier-than-air craft.

Funny that. It is airships that pioneer the creation of duralumin alloys that allowed great advances in HTA aeronautical engineering. Huh.

[Joseph Paul]

Molokh- you might want to look for this book. It presents more information about why airships fail in the 30s.

"When Giants Roamed the Sky: Karl Arnstein and the Rise of Airships from Zeppelin to Goodyear. By Dale Topping, ed. by Eric Brothers. Akron, Ohio: University of Akron Press, 2001. illustrations. Photographs. Appendices. Bibliography. Pp. xiv, 276. $27.95 ISBN: 1-884836-704"

There are many more reasons besides crashes that made airships a difficult technology in the 1914-1937 time frame. Building a hanger for a 900 foot long airship was a challenge for instance. Changing the underlying assumptions may very make contiued use of airships plausible.

Also I have updated the thread "Damaging a TL10 Airship" with several posts fleshing out the ideas I had on a military application.

[Anthony]

Originally Posted by tshiggins

However, even if you didn't go all the way up to superheated temperature, I think you'd see some measurable improvement in performance by heating the helium by even a few hundred degrees.

Measurable, yes. Worth the effort, probably not. Helium is already at 86% the lift of vacuum, and the weight of the systems to keep the helium hot would probably consume any weight savings you might realize. If you have cheap power and expensive helium, heating the helium lets you use less of it to fill the bag, but probably also increases leakage rates, so not much advantage there either.

[Anthony]

Originally Posted by Joseph Paul

It may have been hype but the SkyCat 1000 literature was claiming to be equal to sealift shipping and faster.

That would be hype. The fact is, people have been looking at creating a new generation of dirigibles pretty much since the Hindenburg, and it hasn't happened. This is not a field with huge barriers to entry, so if dirigibles haven't returned, it's because no-one can make them good enough to compete.

[Erik_Nielsen]

Originally Posted by Anthony

That would be hype. The fact is, people have been looking at creating a new generation of dirigibles pretty much since the Hindenburg, and it hasn't happened. This is not a field with huge barriers to entry, so if dirigibles haven't returned, it's because no-one can make them good enough to compete.

The barriers to entry are raising capital, building whatever infrastructure is necessary (including hangars, docking technology, transference of cargo, training crew, etc.), convincing airports to allow airship traffic, and overcoming a legacy of bad PR. These are hardly insurmountable, but they're hardly negligible, and it's disingenuous to suggest that the lack of return of dirigibles in the sky is simply due to some economic Darwinian process.