Why Dirigibles?

[Fred Brackin]

Originally Posted by dcarson

Geoffrey A. Landis has done work for NASA on floating cities on Venus.. The Clouds of Saturn by Michael McCollum has them on Saturn.

I've read the McCollum and in re this discussion it should be noted that the cities are balloons rather than dirigibles but the vehicles used for general travel are heavier than air types powered by fusion air-rams.

[johndallman]

Originally Posted by AlexanderHowl

Since they can go very high, that means that they can benefit from very fast winds, which would allow them to travel with practically no fuel.

Changing altitude allows a choice of the available wind directions, like any lighter-than-air vehicle, but tends to require discarding ballast to rise and gas to sink.

Both of those are very finite resources, and you tend to have to discard gas to make up for the loss of weight as you burn off fuel. Advanced airship designs include tricks like using a combustible gas of about the same density as air for fuel, and condensing water from the engine exhaust gasses to reduce weight loss.

Being able to heat the lifting gas helps with that. In Roger_BW's Victorian Atoms setting, it's normal to do that with heat from the nuclear reactor, which is far safer than burning fuel for the job.

However, there are several problems with going very high. Powerful winds are fine if they're very stable. If they're gusty, or there is wind shear, they're a risk to the airship's structural integrity. Going high can readily start the gas cells leaking, as happened to the USS Macon. Icing on the envelope can easily destroy all your lift (in Victorian Atoms, that is something else you can do with reactor heat).

[Icelander]

If the ever-frisky Antarctic Space Nazis had managed to discover some way to travel the multiverse and were preparing to claim vast amounts of Lebensraum conveniently occupied only by TL3 or lower primitives, would zeppelins have been a reasonable choice for exploration, as opposed to conventional trucks, planes, ships and so forth?

What kind of infrastructure does a TL3 world have to have so that these Intrepid (but Evil) Nazis can traipse all around it by zeppelin while they map it for conquest?

Assuming that these Antarctic Space Nazis were of the Last Redoubt kind and had all the technology of 1945, but unfortunately accompanied by only what resources a creative team of foresighted Nazi scientists could save during the frantic last months of the Reich, what kind of vehicles would be most plausible as the scout vessels launched from their Hidden Base?

Am I way off track in even imagining that zeppelins would be considered for the role of exploring other worlds?

[Ulzgoroth]

The hovering, passable speed, ability to cross both land and water, and freedom from prepared landing fields are highly attractive features.

The low payload and vulnerability to weather are much less attractive, though.

Zeppelins need fuel sources just as much as any other TL6 powered vehicle, and in particular are almost certainly going to need refined petroleum. Which is going to be a major problem if they're trying to traipse all over a TL3 world that really isn't going to have any sources for that.

[Icelander]

Originally Posted by Ulzgoroth

Zeppelins need fuel sources just as much as any other TL6 powered vehicle, and in particular are almost certainly going to need refined petroleum. Which is going to be a major problem if they're trying to traipse all over a TL3 world that really isn't going to have any sources for that.

Yes.

That's a major problem, of course. On the other hand, it's not necessary to match the performance of the passenger zeppelins of the 1930s, only to be able to scout the vast and dangerous world in a safer and faster manner than walking or using animal transport.

The TL3 world has vast coal reserves at hand near the Last Redoubt and I imagine that the Antarctic Space Nazis, not having neglected a good supply of TL6-7 weaponry in their pioneer kit, will quickly arrange for some slaves to work those.

I imagine that trading for coal could be done in several places around the TL3 world, as the ASNs would (somewhat uncharacteristically) manage to avoid actually declaring war on the entire world at once.

What kind of zeppelin can you power with coal?

[Ulzgoroth]

Probably not a happy one. Steam engines are heavy.

You could perhaps make burnable liquids suitable for some kind of diesel engine out of coal? I don't know about coal liquefaction as opposed to gassification.

[Phil Masters]

If your world-jumping technology involves any sort of uncertainty about the kind of terrain you'll be moving to, minor uncertainty about how high the ground will be, or worries about hostile locals, then jumping while at aviation altitudes rather than on the ground makes a lot of sense. Airships then at least mean that you can hover and needn't find yourself heading for a mountain at high speeds. But they have other issues as previously discussed.

[Fred Brackin]

Originally Posted by Ulzgoroth

Probably not a happy one. Steam engines are heavy.

You could perhaps make burnable liquids suitable for some kind of diesel engine out of coal? I don't know about coal liquefaction as opposed to gassification.

Yes, you have to have coal gassification. Coal and coal-burning engines are too heavy.

Structural weight and power-to-weight ratios are important for all vehicles but they are life-and-death matters for vertol flight and then even more critical for lighter-than-air vehicles.

If you're actually facing terrain that a JU-57 can't land in then a LTA won't be able to land there either. In particular, an LTA 's ground crew needs to be waiting for it at it's landing site whether that's the hundreds of people that were there for Hindenburg or the 7 man crew a Goodyear advertising blimp used.

If LTA's have an advantage anywhere it's in there ability to remain airborne without expending energy. You want an actual dirigible rather than just a balloon so you can avoid going wherever it is the wind wants you to.

The problem is that once you start thinking about travelling from point A to point B a fixed wing aircraft does that more efficintly than any LTA at any speed above the fixed wing's stall speed (and very low stall speeds are possible).

The most successful LTAs in real world history in any particular niche (besides Goodyear's advertsing blimps) would be the US Navy's radar picket blimps in service from the end of WWII to the early 60s. Those were eventually repalced with fixed wing aircraft of course but if you can come up with some sort of medium altitude, low speed and long duration eye-in-the-sky mission then for some (improbable) level of tech small-ish blimps might be the answer.

On the gripping hand, if you want Zeppelins for the Rule of Kewl then you want enormous ones with swastikas on their sides. Paint the swastikas in arow like shields on the side of (ciinematic) Viking longship is you want to. Sheilds and Zeppelins might even lead you back to a gripe post I made about 4e Shield rules long ago.

[RogerBW]

Originally Posted by Ulzgoroth

Zeppelins need fuel sources just as much as any other TL6 powered vehicle, and in particular are almost certainly going to need refined petroleum. Which is going to be a major problem if they're trying to traipse all over a TL3 world that really isn't going to have any sources for that.

Really, the ideal fuel source for a zeppelin is a lightweight nuclear reactor. Refuelling isn't a problem, the vehicle mass stays constant (in the real world the use of Blaugas on Graf Zeppelin was an attempt to fix that), and you have plenty of spare power for e.g. de-icing, death rays, etc.

The easiest way to make the reactor lightweight is to minimise shielding; I favour a BWR design for minimum mechanical complexity.

[Black Leviathan]

Maybe it's not about Air travel at all.

Maybe the early Helecopter attempts were sabotaged or just not well engineered in this reality and the image of "whirlybirds" exploding into flinging propeller blades doomed their development at the beginning. As the Airplane overtook the dirigible for travel there was still a need to view things from the air at a slow speed so the blimp remained in service as a way of getting good clean areal photos, getting an overview of traffic, viewing the unspoiled natural Majesty of tropical islands or even pursuing criminals from overhead. Perhaps they were even instrumental in the war for their ability to land troops without an airfield. Wealthy businessmen that can't wait for traffic bought personal airships to land on the roofs of their skyscrapers. VTOL craft are now overtaking the dirigible but because they're so much a part of the culture you still see them around everywhere.