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Warhammer Fantasy: Divided Loyalties - an Advisor's Quest

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Sculpt0r said:
Then with standard atmosphere hot-air balloons, they would just need enough liftgas to cancel out their normal weight, and they could adjust altitude by venting (easily replaceable) heated air instead of the liftgas.

(I am not an aeronautics engineer)
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Well, you did succeed in independently re-inventing the Roziere balloon, which was first created by Jean-François Pilâtre de Rozier in 1785, shortly before his dead in a ballooning incident where his balloon caught fire and crashed.

Abhorsen said:
I don't think there can be a gas better at lifting than hydrogen? It's the lightest possible stable molecule. Unless it's pure magic, which doesn't seem to be the dwarven way.
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By the same logic, there can not exist a metal as strong yet light as gromril, yet that hasn't stopped the dwarves from using it.

Warhammer physics don't need to be our own.
 
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LightLan said:
Clearly this world's background level of magical winds has physics slightly more loose in general even if you aren't actively casting spells :p
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If you start a fire, it attracts Aqshy. If you put Aqshy into a fire, it burns hotter for longer.

So simply by being in a place where Aqshy exists, a fire will naturally burn hotter for longer than its fuel allows.
 
LightLan said:
Clearly this world's background level of magical winds has physics slightly more loose in general even if you aren't actively casting spells
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Given the amounts of improbably large monsters and beings that exist in this world, I think that's a safe bet. The Square-Cube Law, at least, is probably crying in some corner of reality.
 
10ebbor10 said:
The problem is that the gas forge is in one location, as I understand it.

This makes airship operation rather hard. Just look at a regular voyage.

1) Take-off, carrying a certain amount of cargo, fuel and the lifting gas to cancel out that mass.
2) As the airship flies, it maintains it's altitude by alternatingly venting lifting gas and ballast to account for temperature changes, and the slow of lifting gas to deal with the burning of the fuel.
3) Arriving at its destination, the airship vents whatever gas it needs to descent, gets tethered, unloads, loads new fuel and so on.
4) The now heavier airship can no longer take-off, because it has gained additional fuel mass but it's source of lifting gas is a thousand miles away.

Now, what kind of gas is used by the gas forge is not specificied, afaik. Maybe it's a special gas that is far, far better at lifting than hydrogen, in which case it could be useful.
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Why do you have to vent the gas? Can't you compress it to reduce the aircraft's bouyancy while retaining the lifting gas for later use?

A wackier, warhammery solution might be to winch an airship to the ground with grappling hooks or to have the gondola descend separately from the gas envelope.
 
Or, honestly, since this is fantasy, it might just be that the gasbag means it can fly, and it goes up or down when you point it up or down and give it a bit of throttle.
 
Draz said:
Why do you have to vent the gas? Can't you compress it to reduce the aircraft's bouyancy while retaining the lifting gas for later use?
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If warhammer has some kind of magical gas compression pump, then maybe.

In practice however, this would require a large and complex pumping system, especially since airships tend to operate with many gasbags for redundancy reasons. So you need to make sure that all those are hooked up to leak free pumps.
 
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HungryHamadryad said:
If spells like Transmutation of Lead exist, then I'd imagine there are some creative means of altering density/mass which could be used for buoyancy control.
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This 1m^3 block of wood (Density < 900 kg/m^3 ) is now lead (Density 11400kg/m^3)

Just make sure the structure can support the Lead block, and you can use a wooden block as Ballast.

Hell, Rune of the Unknown would probably work even better :V
 
10ebbor10 said:
If warhammer has some kind of magical gas compression pump, then maybe.

In practice however, this would require a large and complex pumping system, especially since airships tend to operate with many gasbags for redundancy reasons. So you need to make sure that all those are hooked up to leak free pumps.
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This was interesting to me, so I looked into it. Turns out that real blimps and zeppelins have relied on compressing the lift gas to descend and allowing it to expand to ascend.

aviation.stackexchange.com

Am I correct about how airships control their altitude?

I have read about how airships work, especially about how they control their altitude. Because what I understand from readings about the Zeppelin airships is that they were able to perform long range
aviation.stackexchange.com aviation.stackexchange.com

When an airship ascends, it's envelope will want to expand anyway because of lower atmospheric pressure. This doesn't increase lift, but it means if you fly it up or down then it will tend to stay at the altitude you put it at, if your weight remains constant.

Burning fuel does represent an issue, though: you lose the weight of the fuel as you burn it. You can compensate for this by capturing the exhaust (later zeppelins captured water from their exhaust to use as ballast) or you could do as blimps do and use a compressor to vary the pressure of the lift gas in the envelope, as I suggested.

You don't need to connect the compressor to the gas cells: you can vary the pressure of the air in the envelope that the gas cells sit in and that will cause the sealed gas cells to expand or compress. Zeppelins didn't do this, but blimps do something similar by adjusting air pressure in their ballonets to affect lift gas pressure in the envelope.
 
Draz said:
(later zeppelins captured water from their exhaust to use as ballast)
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Minor nitpick, but no Zepellin ever had the recapture systems. US airships used them, because the helium they used was so expensive, but for hydrogen airships the recovery tech was not considered to be worth it. You just valve it.

Draz said:
or you could do as blimps do and use a compressor to vary the pressure of the lift gas in the envelope, as I suggested.

You don't need to connect the compressor to the gas cells: you can vary the pressure of the air in the envelope that the gas cells sit in and that will cause the sealed gas cells to expand or compress. Zeppelins didn't do this, but blimps do something similar by adjusting air pressure in their ballonets to affect lift gas pressure in the envelope.
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There's one big problem with this solution. It sacrifices the entire redundancy principle behind the gas bags. As soon as your outer covering develops a leak, you lose the pressurization, and thereby lose altitude control, and then you're back to venting.
This kinda thing isn't even rare, many airships developed small tears during flight and had crews to fix stuff in the air.

This (and the practicality of atmospherically sealing an entire airship hull) are some of the reasons why this was never done on any major airship IRL, only on much smaller blimps (and a few tiny, early airships).
 
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