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Old 05-11-2018, 10:07 PM   #11
AlexanderHowl
 
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Default Re: Why Dirigibles?

Vacuum dirigibles are an interesting idea, though I think they are really only feasible with TL9+ smart materials. At that point, smart structures would also allow for sufficient flexibility to survive the worst weather, so dirigibles might have a comeback at TL9.
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Old 05-12-2018, 12:48 AM   #12
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Vacuum dirigibles are an interesting idea, though I think they are really only feasible with TL9+ smart materials.
Nah, vacuum is only sensible if you have unobtanium materials it takes too much strength to prevent it from collapsing.
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Old 05-12-2018, 01:25 AM   #13
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Nah, vacuum is only sensible if you have unobtanium materials it takes too much strength to prevent it from collapsing.
The materials only have to resist a pressure differential of one atmosphere, and we've been doing much more than that with submarines for decades.
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Old 05-12-2018, 01:45 AM   #14
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The materials only have to resist a pressure differential of one atmosphere, and we've been doing much more than that with submarines for decades.
Submarines that don't fly.
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Old 05-12-2018, 01:53 AM   #15
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The materials only have to resist a pressure differential of one atmosphere, and we've been doing much more than that with submarines for decades.
Oh, we can do it. We just can't do it for less weight than filling it with helium.
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Old 05-12-2018, 02:04 AM   #16
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Default Re: Why Dirigibles?

I guess it depends on what you meant by unobtanium. I read it to mean a material that can't possibly exist or has purely fictional properties, whereas vacuum dirigible shells would have to be something that's only an order of magnitude or two better than what we can do now. That's either TL9 or some slightly divergent X-punk.
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Old 05-12-2018, 03:22 AM   #17
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Default Re: Why Dirigibles?

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Early discovery of aluminum, titanium, Kevlar and Nomex.
Aluminum and titanium were both eighteenth-century discoveries. The problem was production. You need to use magnesium to extract titanium from its ores, and magnesium and aluminum are both produced by large-scale electrolysis. That needs the development of large-scale electricity generation.

Large dirigibles weren't built until aluminum was available in bulk; the first Zeppelin had an aluminum frame.
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Old 05-12-2018, 05:14 AM   #18
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Default Re: Why Dirigibles?

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Originally Posted by Daigoro View Post
I guess it depends on what you meant by unobtanium. I read it to mean a material that can't possibly exist or has purely fictional properties, whereas vacuum dirigible shells would have to be something that's only an order of magnitude or two better than what we can do now. That's either TL9 or some slightly divergent X-punk.
Something like an aerogel, except that the expansion during production produces vacuum pockets (instead of air pockets) for some reason, and it's impermeable and non-fragile enough that it doesn't let air in until significantly damaged (and it's Diffuse). Definitely TL^, but perhaps TL6^?

Probably not as cool in terms of actual aeronautical usefulness as it is in explanation too. Also wonder if it'll be misused for military purposes (such as lightweight armour)?
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Old 05-12-2018, 06:33 AM   #19
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Default Re: Why Dirigibles?

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Airships would be even better for cargo... cheaper than trains overall, and faster than ships.
Even in the 1930s an airship wasn't cheaper then a train; it required a large crew in both the ship and on the ground for operation. Then there was the special mooring mast and hanger. Finally the cargo capacity was minuscule compared to a train. This all cost and was reflected in the cost of a ticket ($450 equivalent to get on the Hindenburg for example)

While ships were slower they could carry far more cargo. In fact even though airplanes are faster ships are still the go to for long distance cargo transport even in our modern day.
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Old 05-12-2018, 08:32 AM   #20
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Default Re: Why Dirigibles?

You can construct vacuum bubbles from modern steel alloys, the problem is the expense of constructing a vacuum facility large enough to produce the steel alloy bubble in a vacuum. Paradoxically, it is only affordable at TL9+, when you can use LEO production techniques to construct steel alloy bubbles in the vacuum of space (the steel also benefits from the lack of atmospheric contamination and gravitational defects).

The key thing is to reduce the density to 178.5 grams per cubic meter. A 10 m radius sphere possesses a volume of 4,188.8 cubic meters, meaning that your mass budget is 747.7 kilograms, or 545 grams per square meter, which is tin foil thickness. Your only choice is to go bigger. A 1 km radius sphere can afford 59.5 kg per square meter, which is 7.4 mm, which is sufficient for submarines Of course, more advanced materials could do it better, but you would probably need an advanced metallic laminate to create a vacuum bubble small enough for an airship.
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