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

[Joseph Paul]

Originally Posted by Kelly Pedersen

However, they probably can't land there. Airships need large ground crews to land safely and to load and unload. So airships might be able to overfly that sort of area, but they won't really be able to deliver to there. Plus, of course, the fact that there's often not much call for large cargo shipments to that sort of terrain anyway.
And it takes a very big detour before the airships taking the direct route over an area of rough terrain becomes more cost-effective than the trucks going around. And building a railway track through the region will probably still be a better idea than airships.

This no longer true. There are several schemes to improve the ground handling ability of airships. Some are: make a hybrid that is negatively buoyant. This means that it won't rise on it's own but instead uses dynamic lift from it's shape to provide that extra lift to fly. Set it on the ground and it stays on the ground. Lockheed's P-791 uses ground effect skirts to anchor itself to the ground. Literally it kisses the ground and sucks itself down. Another company clams to have a proprietary solution to offloading with out reballasting. I believe that it is the CL160 effort that had a cradle it deployed that acted as a crane/anchor. Once in place it kept the airship steady and allowed offloading of it's cargo container.

As for costs, the estimates I have seen claim costs per mass per distance that are competitive with trucks and sea freight.(caveat: provided by airship companies - if any one has an a more objective source please post it). I can certainly see that airships would enable a different settlement pattern. If you had a continent with a wide mountain range and lots of fertile valleys you might think twice about investing in a road net if airships are capable of getting there.

If we could have done an airship in the 1840s would it have made sense to spend money on driving railroads either?

In the US we have an interstate highway system only because Dwight Eisenhower, as a lieutenant colonel in the army, was appalled at how long it took the Transcontinental Motor Convoy to go coast-to-coast. It took 62 days over bad roads (There were no better alternatives) and averaged 6 mph. Lifting by airship is way faster even for the cruising speeds of the 20's and 30's.

[Phil Masters]

I suspect that a big problem with airships is that they really aren't that safe. Flammability of hydrogen and gasbag fabric aside, they don't like storms, at all. (As I recall, when someone asked one of the most successful airship captains in history how he managed a perfect safety record, he said "Simple - whenever I saw a storm, I went the long way round to avoid it", or words to that effect.) They'll always have a nagging accident rate (or a nagging delay problem, if all the pilots learn that lesson).

Britannica-6 manages to have its flight technology dominated by airships, partly because the local aristocracy enforces the rule of cool, but mostly by having a very rapid spurt of technological development (in all fields) starting in the early 19th century - when lighter-than-air flight was a known technology, and heavier-than-air was basically infeasible. So airships have appeared as internal combustion engines and suchlike have developed. In principle, local engineering would be capable of heavier-than-air flight, but the people who'd be able to finance the development are dangerously over-enthusiastic about everything.

If you look at the early history of aircraft development in our timeline, the fatality rate among pioneering aviators was pretty appalling. On Britannica-6, they've been in a bigger hurry, so it's been worse. The local potential counterparts to the Wrights and Santos Dumont are pretty well all dead, crippled, or being kept locked up by their concerned families. So you get airships armed with glide bombs as weapons. If I had to project the technological history of that timeline forward a few decades, I'd have to assume that heavier-than-air flight would appear eventually, and come to dominate fairly soon after, but it can be held back for a while by these factors.

[Running Wolf]

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. It might be theoretically possible to field an airship that wouldn't be utterly vulnerable to fighters of the era, but Germany didn't have the Helium and nobody else had much experience in the field. So airships would still get sidelined, and by the end of the war fixed wing planes have the range and lifting power to compete with them in a great many roles. Airships might see more use than they do, but they would lose a lot of ground when large, safe, fast, powerful intercontinental heavier-than-air craft are available.

On the other hand, a British failure to develop effective incendiary bullets in 1915-1916, or some viable countermeasure, might go a long way.

Oh, if you've got really vast tracts of generally low-value land, airships can potentially serve a useful role as aircraft carriers. That was proved workable historically, but is a bit harder to justify in a world dominated by sea when non-air ships can also carry aircraft. On a plain too vast or inhospitable to set up lots of ground bases, a flying airbase might be viable.

I'm not sure there could be a logical reason for it.... but if the fixed wing aircraft could only support a single engine there might be the need for the longer range aircraft to be lighter than air.

I'm also not sure of the radar image of a zep/blimp. The LTA craft would be slow as bombers but also might be high enough and quiet enough, and stealthy enough to not be noticed until the bombs start exploding on the cities and bases.... But than again the Japanese made a mess of Pearl Harbor with the smaller fighter/bomber.

[Mgellis]

Why use airships?

* Twist of history...accidents are just less common or less horrifying, so the airship does not suffer from bad publicity

* Twist of physics/engineering...there's a little more helium in the atmosphere, some genius invents a way to store it more efficiently, etc. so the price drops, and all airships use helium, which doesn't burn and/or blow up the way that hydrogen does

* Twist of technology...various minor changes in physical laws in an alternate universe could make it easy to develop the specific technologies needed for airships a little early, so airships in the 1850s and maybe even earlier aren't so crazy.

* Twist of culture...until jets come along, and even after, long distance travel by air is somewhat uncomfortable. Ever travel in one of those little 19-seat puddle jumpers with the engine buzzing in your ear for an hour? Okay, now do it for twelve hours. Or twenty. Suddenly, even though it takes longer to get where you're going, the experience of an airship might look like a pretty good idea! Maybe there's enough cultural emphasis on "anything that needs to be done quickly can be done by phone; anything that needs to be done in person should be done with elegance" to make aircraft something you use for military purposes but not passenger travel. During the days of propeller airliners, the difference wasn't that huge; a zeppelin can cruise at about 50 mph, a C-47 only does about 160.

Suffice that there's no reason airships couldn't dominate the skies of an Alternate Earth at any time from Age of Napoleon to the Age of Elvis. They probably aren't practical without some kind of magic before TL 5 and jets probably supersede them by TL 8, but a dirigible-based air economy in any TL 5 to TL 7 world could be made plausible very easily, I think.

I hope this helps.

Mark

[Joseph Paul]

Ulzgoroth

The problem on the bulk freight side is that the CL160, which didn't actually manage to get built, would have lifted slightly more mass than the soon-to-be released 747-8F...and cruised at one-tenth the speed. It was supposed to be able to operate with little infrastructure, but moving at modest highway speeds is a significant drawback.

I'd love for heavy-lift airships to work out, but I'm not convinced they can beat the existing technology. So I'm looking for ways they could have preempted that technology's being developed in the first place.

Well you may not like the pace but you can’t beat the price. A significant fraction of freight charges is the fuel consumed. An example from here http://www.armada.ch/08-2/02_Morphing.pdf will suffice- Airlifting an Mrap vehicle to Iraq runs $130,000 while sealifting it is $16,000 dollars. The time difference is, of course, substantial. Most sealift will take 4-6 weeks. What if you could do this in a week at sealift prices?

There are other designs that beat the heck out of the 156 ton load of the 747-8 and could do 100-125 knots. If they can do that at sealift prices do you think that shippers will ignore the cost savings?

BTW the CL160 is rated for 160 metric tons so it actually caries 20 tons more than the 747-8.

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.

Except that airships have substantially less fuel consumption, have a better payload fraction, and certainly don’t need to be 1500 feet long to do so. There are designs that should cruise at 125 kts/143 mph so they are not far below that 150 mph limit. So lets look at transcontinental shipping with those figures. Mapquest says LA to New York is 2787 miles and 42 hours to drive. An airship cruising at 150 mph will make that in 18.58 hours. A ship going through the Panama canal is going more than twice as far at 22-30 knots. That is going to take a while. If it doesn’t need to be there in 4 hours why pay for it to go airfreight? If you want it in less than 4 days why go seafreight if the airship is cost competitive? Point to point over the ocean the airship is 4-5 times faster. Yes freighters carry more but there is a wide niche between 30 and 600 mph and 150 tons and 20,000 tons to be filled.

Phil's point about storms is the most telling argument for me in this. Mitigating the danger from storms would be a serious boost and worth pursuing.

[Joseph Paul]

Originally Posted by Ulzgoroth

Which airship designs lift in the neighborhood of 300 tons? I thought the CL160 was about as big as had been seriously proposed so far, and 22 tons out of 160 does not make 'a couple of times'.

Walrus HULA, Aerocraft, and Skycat 1000 are all in the 400-1000 tons of cargo range. Walrus HULA is on hold for more funding from DARPA and SkyCat has plans to take their SkyCat20 model on a world tour to get interest in producing the 220 ton and 1000 ton models. That was supposed to start in late 2008 but I have not found any thing more current on it. Aeroscraft is planning a scaled down model to fly in 08 and a passenger model in 2010.

Additionally I came across a paper on using two airship hulls conected by an inboard wing to good effect.

[Nosforontu]

They could have the potential for usefulness in places like Africa which has large interior sections well away from the coast line and historically large sections of its rivers were unnavigable. Toss in generally poor road infrastructure frequent internal political turmoil which makes developing that road structure dangerous, and the rising price of Gas overall, and I think a case could be made at least for fictional purposes for Air ships to see a resurgence in the region fulfilling the niche their that truck/train transport fulfills elsewhere, with the additional caveat that such airships are marketed externally as "preserving Africa's natural beauty" for tourist and other eco groups encouraging them to spend money on the "African Experiment"

[Luke Bunyip]

Originally Posted by Anthony

Not unless the air density is absurdly low. Let's ponder a world with, say, 10x normal air density.

FYI the setting in question had an atmospheric density of times 6. Above that I believe there are issues with breathing, but I am prepared to be corrected on that.

[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

[Anthony]

Originally Posted by Luke Bunyip

FYI the setting in question had an atmospheric density of times 6. Above that I believe there are issues with breathing, but I am prepared to be corrected on that.

You can't have more than about half an atmosphere partial pressure of oxygen, or more than 2-3 of nitrogen. You can toss in other gases, though, if you want to go beyond that point, though most of them have some sort of bad effect at high pressure. Also, large quantities of buffer gases will cause fires to not burn.