Water Treatment Spells

[Vebyast]

Why Prismatic Wall? What about a windowless cell form Forcecage, with gate effects as doors. You could conceivably create two force cages, one inside the other, with vacuum between, and the inner force cage being the passenger cavity. Though I don't know how that'd affect what you're trying to do.

Can't permanency Forcecage. I forgot about Wall of Force, though, and it turns out that it gives you about 10% more surface area per XP.

On the other hand, using Prismatic Wall turns your airship into a stupidly powerful weapon if you're wiling to remove some of the cladding. Just leave the first foot of the airship uncovered and ram anything you want gone.

[fectin]

"Impermeable" is the difficult part. There is basically nothing that is explictly air-tight. Vebyast spotted prismatic sphere, which actually is impermeable to gas, though it's too small to be really great.

Prismatic wall is explicitly airtight and eligible for permenacy. Forcecage is neither. It also scales in size with level, and encloses much, much more area than forcecage.
I assumed the walls had to be flat. Either way, a circle isn't that advantageous over a hexagon, though better endcaps would be.

You can't stack forcecages; the volume is fixed.

Anything that actually is impermeable to gas you can wrap in material that's full of gas bubbles, then mount a superstructure to. You already want it completely lead-lined, to block dispel effects.



On efreeti and undead, I'd rather either table the discussion, or move it to a new thread. For the purposes of this thread (or at least for this thread hijack/expansion), I'm going to consider undead as operating without any variant or extended rules. Your "undead cause disease" variant is genuinely cool, but it's also a bit hard to plan around, since it's not codified yet.

[Ice9]

Do undead with diseases even change anything?
If they're just normally virulent, then seal your skeletons inside full-body suits and you're good - you might want to do that anyway because they'll look less disturbing.
Even if they're supernaturally virulent, you just designate an "industrial zone", keep your undead in the industrial zone, and make sure the supervisors/repairmen have protection from disease.
And if they're so ultra-virulent that they can spread plague from a long distance, then thank your MC for the WMD he just gave you and go crush some enemy kingdoms with your plague-machine.

I'm not sure that undead are the best components for a computer though - Magic Mouth traps are only 40xp each and can fit into a much smaller area. Also the triggers for them can explicitly be as complex as you want.

[Endovior]

So...

How exactly are you making a lead flying machine? The basic idea of 'lead-line so nobody can dispel the structure' makes sort of sense, but a lead blimp literally doesn't fly.

Also, all it really does is mean that your enemies have to throw a disintegrate or something before they throw a dispel... heck, even a humble fireball or something might melt enough lead to put a dispel through.

[DSMatticus]

you might want to do that anyway because they'll look less disturbing.

Put them in a suit and tie. Nothing snazzier, people'll love that shit.

Magic Mouth traps are only 40xp each and can fit into a much smaller area. Also the triggers for them can explicitly be as complex as you want.

That actually works. They can respond to visual stumuli (does magic mouth A have his mouth open? does magic mouth B have his mouth open?) and then you just have them say things that cause them to open or close their mouths (say 'ah,' say 'hm'). Except, of course, the XP cost. I believe Vebyast started with the tome of necromancy's playing with fire rules, where you could animate a theoretically infinite number of undead and they'd follow the last instructions issued on loop even after they were uncontrolled. So you could have an arbitrarily large amount of skeletons using gold, and not XP. XP makes things unpleasant, because such a device would take a lot of magic mouths.

But yeah, there are totally easier ways to do a D&D computer. You certainly don't need skeletons, we just ended up talking about that because it came up and it was sort of hilarious.

[K]

The real question about various spheres and walls is if you can make movable objects out of them at all (only Telekinetic Sphere explicitly moves). I mean, there has always been an assumption that if you put a Wall of Force on a ship deck or something it will move with the ship, but there are no rules to handle a case where you cast the wall on an object and then remove that object.

It makes the most sense that it simply freezes in place when the supporting material is taken away, even if that means it's hanging unsupported in the air. That ruins most airship designs right off.

Using prismatic anything as a building material seems impossible since anything touching it is taking massive amounts of damage and might get shifted to another plane of existence or turned to stone.

As for undead, I think you'd take the DM fiat disease rules and just generally have people get diseases over prolonged periods of time like they would in the presence of several hundred corpses over prolonged periods of time. This means that mixing your living and undead workforces together is bad idea, and making hazmat suits will be hard in a world without plastics or industrial rubber.

[fectin]

You're correct. Prismatic wall is explicitly vertical and explicitly immobile. That's pretty clear; the zeplin fails. Darn.

For the other objections (because I hope there's another use of this):
Lead foil at 10 mils is about 0.65 lb/foot^2. That comes to... a bit under 19 tons. That's eating nearly all of your lift, so you'd need to fix that. Probably you can just keep adding sections, but that's expensive.

The spell description is pretty specific about only damaging characters who try to go through it, and "stops mundane weapons". What that means for inanimate objects is not really clear.

[Vebyast]

The real question about various spheres and walls is if you can make movable objects out of them at all (only Telekinetic Sphere explicitly moves). I mean, there has always been an assumption that if you put a Wall of Force on a ship deck or something it will move with the ship, but there are no rules to handle a case where you cast the wall on an object and then remove that object.

It makes the most sense that it simply freezes in place when the supporting material is taken away, even if that means it's hanging unsupported in the air. That ruins most airship designs right off.

What does "immovable" mean? When you cast Prismatic Wall on a rotating plane or an airship, does it go CLANG! and destroy everything standing directly west of it? If not, at what point does an anchor become too small for the wall to be considered to be "immobile" relative to that object? Can you start with something big enough to anchor a wall to and then steadily shave bits off until it's the right size?

Additionally, if the Wall is immobile, what happens when you anchor a wall to a cart or a floating rock and then push really really really really hard on the wall? Fectin's Prismatic Wall airships, for example, are 80 feet long and more than 50 feet tall, and displace a bit over 10 tons; if you've anchored all of those walls to a one-ton metal framework, what happens when you cut the tether and the atmospheric pressure differential exerts a net force of over ten tons on something that doesn't weigh very much at all?

You're correct. Prismatic wall is explicitly vertical and explicitly immobile. That's pretty clear; the zeplin fails. Darn.

Darn is right. We can still make the vertical sides of the zeppelin out of it, though. We just need to build floor and ceiling sturdy enough to support a vacuum.

Also, what does "vertical" mean when you're somewhere with nonstandard gravity? Could we redefine vertical by having the wizard in the Astral casting through a planar portal or similar?

Edit: we don't need permanency except for reliability. Breaks the custom-items restriction, but command-word item of Wall of Force and command-word item of Forcecage, then recast as necessary. Build a tall cylinder with flat top and bottom; use walls of force for the cylinder walls and forcecage for the floor and ceiling. Also significantly reduces XP costs.

---

Edit: use permanent Walls of Force as sails. Spectacular sail area; easily reef sails by temporarily suppressing them with Dispels. Only works on square-riggers, unfortunately; on the other hand, you could get some seriously amazing sail area without weighing down your ship at all, which means you'd be able to run with the wind like nothing in real life.

[Prak]

Ok, what specifically is trying to be accomplished? I'm not up on physics, but it seems that you are attempting to create an air ship through lift generated by a contained vacuum, is this correct? How does this work, in vaguely laymen's terms? Once I understand it, I might be able to suggest some things.

[Vebyast]

Ok, what specifically is trying to be accomplished? I'm not up on physics, but it seems that you are attempting to create an air ship through lift generated by a contained vacuum, is this correct? How does this work, in vaguely laymen's terms? Once I understand it, I might be able to suggest some things.

We're building a vacuum airship. Wiki pages: Buoyancy and Vacuum Airship.

[DSMatticus]

Blimps 'float' by maintaining some store of material inside them that is less dense than the surrounding air (hydrogen gas, helium, or heated air). A vacuum is also less dense than the surrounding air, because it's just an empty space, not a space filled with something light. A blimp using a vacuum would be something like 14% more effective than a blimp using helium, which isn't a lot, and maintaining a vacuum is hard because the outside pressure usually collapses the container. So in the real world, you don't see vacuum-driven blimps.

But in D&D-land, we can build containers that don't collapse (force and prismatic effects) that also have zero weight, and use magic mumbo jumbo to get a vacuum inside them (creation spell, wait for it to disappear). Not to mention, harvesting helium is probably super hard because nobody understands chemistry, so in D&D land a vacuum airship is probably actually easier than anything else. Except heated air blimps, but those things suck. You have a giant balloon for one tiny little cabin.

[fectin]

You need something rigid, air-tight, and near weightless. You need to be able to seamlessly contain a very large area with it, because you need about 14 cubic feet of vacuum to lift 1 pound.

The upsides are that it has no moving parts, and can't really fall out of the sky. The downsides are that it basically has to be massive like the Hindenberg, and if someone ever pops your vaccuum balloon, you will fall instantly.

I don't think use-activated works here. Your walls would continuously migrate out, and you'd eventually lose your seal. Also, 200 minutes isn't that long; you'd have to renew these things all the time.

I think the real gold standard is going to be steamcopters. You can make an autogiro run off a lawnmower engine, the steamballs from earlier should cover that fine, and also scale to hovercarriers. To do that though, you need a core method for constantly generating heat. Cheaper is better: you could constantly Major Creation thermite into a pool of water, but tgat is expensive and not very stable. Ideally, you'd want a version of Continusl flame rhat was actually hot. Any thoughts?

[Grek]

Mage Hand. It can move an object weighing 5 pounds or less up to 15 feet as a move action. At two move actions per round, that's 25 pound-feet per second of force for under 500 gold.

[Vebyast]

To do that though, you need a core method for constantly generating heat. Cheaper is better: you could constantly Major Creation thermite into a pool of water, but tgat is expensive and not very stable. Ideally, you'd want a version of Continusl flame rhat was actually hot. Any thoughts?

Brainstorming:

Heat Metal on a heavily-equipped fire giant or a bunch of stretched-out chicken wire. Casting on the fire giant lets you warm up hundreds or thousands of pounds of metal with a SL2/CL3 spell, while casting on the chicken wire exploits: "If cast underwater, heat metal deals half damage and boils the surrounding water." Depending on the definition of "surrounding", your 75 lbs of metal could boil a really amazing amount of water in a hurry.

Wall of Fire can boil entire swimming pools, since it deals the same fire damage as Heat Metal but in a large area. It can also be made permanent and partially suppressed using cold spells, which makes it good for controlling a boiler (not perfect, though, since it's fail-deadly).

[K]

Some notes:

-Wall of Force can't be dispelled. It's one of it's more interesting properties.

-I read somewhere that the lift from vacuum is not much better than hydrogen.

-Wall of Fire can be made permanent and probably would be quite good at keeping a hot air balloon up, but I'd be interested in what that much heated air would be capable of in terms of thrust, assuming you had a good design that took advantage of stuff like Walls of Force that were manipulated by people like archmages.

Gust of Wind can also be made permanent, so starting an air flow that you heat could be pretty neat.

Either should be good at turning a propeller, so airplanes are not bad.

[Prak]

What about an adamantine skin over a framework? I mean, we're basically talking ultra-titanium here, then we leave the magic to forming the vacuum inside, and you have an adamant-foil balloon. Granted, it'll be huge, but what if you then use shrink object? Is there any reason to believe that a shrunken vacuum sphere will produce any less lift? Conceivably, you could float a battleship with a vacuum sphere shrunk down to the size of basketball.

Failing that, I don't see any reason why we couldn't bring some bullshitium into this and make lightweight, or weightless, "force weave" by basically enchanting a bolt of fabric with wall of force to create a new magic item.

[Vebyast]

Here's a fun target for Major Creation: hydrazine. One casting every six seconds at CL9 gives you a bit more than 40 liters per second, which is comparable to the flow rates of some small, but serious, rocket engines. Six items running at full blast through a well-engineered engine will put you, and something like 50 tons of cargo, into space. Alternatively, if you thrust sideways, you will briefly be a fireball screaming across the sky at mach 14 before you melt from atmospheric friction.

What about an adamantine skin over a framework? I mean, we're basically talking ultra-titanium here, then we leave the magic to forming the vacuum inside, and you have an adamant-foil balloon.

Adamantine simply isn't strong and light enough. Atmospheric pressure is about 15 pounds per square inch, and atmospheric pressure in a vacuum is zero. The force on a plate like that is equal to the pressure differential, so for every square inch of surface area on the vacuum airship you have 16 pounds of force trying to collapse the airship. If you work better in metric, that's about 100,000 newtons per square meter. Then consider the surface area of this thing we want to build.

Granted, it'll be huge, but what if you then use shrink object? Is there any reason to believe that a shrunken vacuum sphere will produce any less lift? Conceivably, you could float a battleship with a vacuum sphere shrunk down to the size of basketball.

Buoyancy is equal to the mass of fluid displaced minus the mass of the thing doing the displacing. Shrinking your object decreases the amount of fluid it displaces and therefore decreased buoyancy.

Shrink Object has to be useful for something, though.

[Chamomile]

Shrink Object has to be useful for something, though.

Paint army of eight-inch miniatures, shrink down to 1/4 their previous size, your army is now painted with incredible accuracy with no need for concentration or a steady hand.

[Prak]

Here's a fun target for Major Creation: hydrazine. One casting every six seconds at CL9 gives you a bit more than 40 liters per second, which is comparable to the flow rates of some small, but serious, rocket engines. Six items running at full blast through a well-engineered engine will put you, and something like 50 tons of cargo, into space. Alternatively, if you thrust sideways, you will briefly be a fireball screaming across the sky at mach 14 before you melt from atmospheric friction.

What about an adamantine skin over a framework? I mean, we're basically talking ultra-titanium here, then we leave the magic to forming the vacuum inside, and you have an adamant-foil balloon.

Adamantine simply isn't strong and light enough. Atmospheric pressure is about 15 pounds per square inch, and atmospheric pressure in a vacuum is zero. The force on a plate like that is equal to the pressure differential, so for every square inch of surface area on the vacuum airship you have 16 pounds of force trying to collapse the airship. If you work better in metric, that's about 100,000 newtons per square meter. Then consider the surface area of this thing we want to build.

Um... Adamantine isn't strong enough? Then what is? (other than force and prismatic walls, which are currently up in the air as to whether they're functional for ...being in the air).
How would you figure the "damage" for this kind of pressure? I looked up the pressure exerted by deep water, since I can't imagine it'd be too out of line from that, and that's only (1d6/100')/min. You can submerge up to 300' before you even need to worry about an adamantine submersible taking any damage. Looking a few things up on Wikipedia, that means that Adamantine can reasonably withstand about 60 atmospheres, while 16 pounds of pressure per square inch is only slightly higher than 1 atm. So, I think adamantine foil would more than suffice.

Granted, it'll be huge, but what if you then use shrink object? Is there any reason to believe that a shrunken vacuum sphere will produce any less lift? Conceivably, you could float a battleship with a vacuum sphere shrunk down to the size of basketball.

Buoyancy is equal to the mass of fluid displaced minus the mass of the thing doing the displacing. Shrinking your object decreases the amount of fluid it displaces and therefore decreased buoyancy.

Shrink Object has to be useful for something, though.

Ok, yeah, you're right, I was thinking... well, wrong. Basically I was thinking "This volume of (substance) provides this much lift, even if it's shrunk down." and that vacuum counted as a substance. I'm an artist, not a physicist...

[Vebyast]

Um... Adamantine isn't strong enough? Then what is? (other than force and prismatic walls, which are currently up in the air as to whether they're functional for ...being in the air).
How would you figure the "damage" for this kind of pressure? I looked up the pressure exerted by deep water, since I can't imagine it'd be too out of line from that, and that's only (1d6/100')/min. You can submerge up to 300' before you even need to worry about an adamantine submersible taking any damage. Looking a few things up on Wikipedia, that means that Adamantine can reasonably withstand about 60 atmospheres, while 16 pounds of pressure per square inch is only slightly higher than 1 atm. So, I think adamantine foil would more than suffice.

Go grab a sheet of aluminum foil. Poke a finger through it. Steel has a hardness of 10 or so; how did you do that without a hammer or a giant metal spike? Similarly, take a chunk of adamantine light enough to be carried by this airship (20 tons, so 80 cubic feet, a cube about 4 feet on a side), spread it out over an area equal to surface of the airship (about the size of a football turf, so you have adamantine foil and no more), then cram 15 thousand hippos onto your football-field-sized sheet of foil.

So, to answer your question: basically nothing is strong enough. Some people *think* that, with a big enough airship (to minimize the surface-area-to-lifting-capacity ratio), super-light and super-strong nanotech materials might work. We're talking about perfect, building-sized crystals of fullerene here, though, so I kind of doubt it's going to happen.

I'm an artist, not a physicist...

Not a problem. Keep going like this and you'll turn into a physicist in no time. =P

[Prak]

Well, failing that, one could, conceivably, slay and animate as a zombie a prismatic or force dragon, and order to "Fly to these locations at these times (or when these signals are given)" and you have Zom-dragon Air, D&D's first commercial airliner.

The entrepreneur needs to be fairly high level, unfortunately.

[Quantumboost]

Shrink Object has to be useful for something, though.

Retractable landing gear?

[RadiantPhoenix]

How has nobody mentioned putting temporal stasis on building materials?

[Chamomile]

Dammit, Jim, I'm an artist, not a doctor!

[Vebyast]

How has nobody mentioned putting temporal stasis on building materials?

That's brilliant, except that it only targets creatures and it's 5kgp per cast. Build a foil airship cover, turn it into a creature somehow (in stages?), freeze it with temporal stasis, vacuum it out, and done.