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Old 12-06-2017, 08:44 AM   #1
Fred Brackin
 
Join Date: Aug 2007
Default A new magical airship scheme

This one centers around the Atmospheric Dome spell. the rules text for that one _should_ say "As for Weather Dome except that air pressure is maintained as well" but it doesn't.

Instead, it has a complicated mechanism where the caster sets desired composition and pressure and the dome barrier pushes out or pulls in gasses as desired. If this was a spirit-maintained magic system I'd say it worked that way because Maxwell's Demon had a brother-in-law who needed work.

At any rate there doesn't seem to be anything preventing you from setting composition and pressure to "none" and having the spell produce a sphere of hard vacuum for you. Vacuum gives you about 10% more lift than hydrogen but the real advantage is durability. With no balloon walls or much of anything else it will be hard to damage the vacuum spheres at all. Leaks certainly won't be an issue,

One drawback is the lack of a standard Enchantment version. that would require a Spell Engine from Magic Items III or other general spellcasting device. Use of the Ensorcerel Spell might also be an option. There's also a general issue of cost to cast which is relatively high at 4 per hex.

Ramping up to lifting "gasses" with even more lift it might be possible to contain pure Celestial Ether in your vacuum bubbles. You obviously can't do that with ordinary matter. The Celestial Ether would degrade upon contact with mundane stuff. Everybody knows that. :)

Lifting power of Celestial Ether is uncertain but at least 10x hydrogen is a common estimate. It might also be possible to use "compressed" Celestial Ether and do away with bulky containers. I believe this might be the system in use upon (or actually above) Barsoom.
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Old 12-07-2017, 08:06 AM   #2
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Default Re: A new magical airship scheme

Of course, doesn't it made a dome rather than a sphere? you've got to worry about the bottom of your balloon. Though it is nice to have a magic pump driving it.
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Old 12-07-2017, 09:41 AM   #3
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Default Re: A new magical airship scheme

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Originally Posted by ericthered View Post
Of course, doesn't it made a dome rather than a sphere? you've got to worry about the bottom of your balloon. Though it is nice to have a magic pump driving it.
If that's the case (Magic isn't really my thing), you could easily contain it within a hemispherical lifting chamber, rather than a spherical one. Or, you know, just have some hemispheres of vacuum somewhere within the ship, and clearly mark them with explosive decompression warning signs (while inaccurate, a warning sign of a stick figure's head exploding would be a pretty good one).
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Old 12-07-2017, 09:51 AM   #4
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Default Re: A new magical airship scheme

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Originally Posted by Varyon View Post
If that's the case (Magic isn't really my thing), you could easily contain it within a hemispherical lifting chamber, rather than a spherical one.
IIRC the dome closes with the ground, Physically, the under-pressure in the dome would let the ground emit gases ... if you try to have the dome without a bottom, it would just fill in from the bottom.

You would have to explain, how to close the bottom ... and how pressure resistant the bottom is: for instance: a metal plate, a glass plate ... or, if you can "reverse" the dome, you could close it with the dome, that extends to the bottom: two half-spheres making a full sphere. That, of course, means also double cost ...
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Old 12-07-2017, 10:45 AM   #5
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Default Re: A new magical airship scheme

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Originally Posted by ericthered View Post
Of course, doesn't it made a dome rather than a sphere? you've got to worry about the bottom of your balloon. Though it is nice to have a magic pump driving it.
According to the FAQ, it's a sphere. It does have to be wholly anchored inside a solid surface, but we could postulate a variation for this purpose.
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Old 12-07-2017, 11:55 AM   #6
Fred Brackin
 
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Default Re: A new magical airship scheme

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Originally Posted by Daigoro View Post
According to the FAQ, it's a sphere. It does have to be wholly anchored inside a solid surface, but we could postulate a variation for this purpose.
From ancient lore (i.e 3e) revolving around use and abuse of Force Domes mostly this type of spell is a sphere and that sphere can be anchored to a vehicle of sufficient size.
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Old 12-07-2017, 05:11 PM   #7
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Default Re: A new magical airship scheme

But can such an anchoring impart force on the vehicle, or does it just mean the dome moves where the vehicle does (if a hot air balloon basket with no balloon, not at all)?
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Old 12-07-2017, 08:23 PM   #8
Fred Brackin
 
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Default Re: A new magical airship scheme

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But can such an anchoring impart force on the vehicle, or does it just mean the dome moves where the vehicle does (if a hot air balloon basket with no balloon, not at all)?
<shrug> The dome is a part of the vehicle and adds to the vehicle's volume while not adding to its' mass. The resulting buoyancy should affect the vehicle as a whole.
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Old 12-07-2017, 10:17 PM   #9
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Default Re: A new magical airship scheme

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Originally Posted by Fred Brackin View Post
From ancient lore (i.e 3e) revolving around use and abuse of Force Domes mostly this type of spell is a sphere and that sphere can be anchored to a vehicle of sufficient size.
So the lift deck is covered with domes extending above and below it? How substantial does the deck have to be? Presumably it'd need enough structural strength to transmit the lift force to the airship load, but would the spell demand anything?
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Old 12-08-2017, 09:22 AM   #10
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Default Re: A new magical airship scheme

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So the lift deck is covered with domes extending above and below it? How substantial does the deck have to be? Presumably it'd need enough structural strength to transmit the lift force to the airship load, but would the spell demand anything?
You need something (cables I guess) to transfer lift from the balloonets in a conventional airship so you're probably not losing anything that way.

I don't think there are any huge structural requirements for the deck from the spell. You might make the deck strong enough that a caster could stand at the center of the spell area just to be safe.
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