Spelljammer Banestorm

[David Johnston2]

Originally Posted by johndallman

"They do this because it's the way the world works" is an answer to how they move, as is "They ride on the backs of invisible turtles". But you have to abandon the idea that Newtonian gravity is involved, which means you have to look carefully at any existing information about Yrth's solar system.

No prob. There is no existing information about Yrth's solar system. We don't know whether Yrth revolves around it's sun or vice versa. Heck, we've never been definitely told that Yrth is a sphere.

You can have less fantastic physics if you assume that the gravity and the air envelope are produced by the spelljamming drive, but you then have the problem that if the drive goes off-line (and it works by having a magician sit on it and draining his spell energy)

Me, I gave my helm an internal reservoir of energy. Mages were just needed to steer it. (Because mages are generally needed to command powerful magic items.)

[Astromancer]

Originally Posted by Delvidian

I love your suggestions, especially the Counterearth idea, which is more fantastical.

And you do hit on a key element to consider, namely the Elven Question. We do have to somehow explain why they live on a silvery body and not a green one. Perhaps what you're seeing on Yrth's moon aren't craters but grand citadels or bubble-cities?

What if the forests of Far Luna have silver leaves?

[Tyneras]

A few notes on from my own Spelljammer conversion (literally handwritten notes on the back of a lab report). They might be good for inspiration.

Air envelopes:
*As described, they are much too small and the crew would asphyxiate in less than a day. An operational spelljamming helm also refreshes the air.
*Adventure note: Kill the wizard, see how they escape with only hours of air and a panicking crew to deal with.

Gravity and planets:
*Things with a "point" gravity source follow a path controlled by the nature of the crystal sphere and will not deviate from that course unless smashed into parts so small they have "gravity planes".
*Things with gravity planes can be moved around. Consequences unexplored, think on this more.
*Atmosphere extends to the edge of a "gravity envelope" which is where gravity goes from 1 to 0 and the air stops. Size of gravity envelope variable and controlled by crystal sphere handwavium just like point gravity paths. If GE is smaller than objects physical size, you have airless object with zero G on surface.

Space Travel:
*Make all those sails and oars and stuff relevant somehow. Check ether sails and oars and drives from GURPS Spaceships.
*Figure out how to make Magery, ER and FP consumption, and SJ speed interact in a meaningful way.
*Maybe a SJ Helm can use non-mages, but it kills them quickly? Possible "decide who lives and dies" adventure point.

[Astromancer]

Originally Posted by sir_pudding

The only real problem is that parachronic travel and interstellar travel don't really work well together in the same setting. I think I'd go back to the 3e Yrth as another planet rather than an alternate Earth and eliminate the White Star/Infinity elements from the setting.

Why not say that their is more than one Infinity, and that some are arranged by physical law and others by mythic patterns? Then drop strict rationalists into the mythic worlds and steal plots from De Camp.

[Astromancer]

Originally Posted by johndallman

I'd say the Moon Elves are shielding the rest of the universe from Yrth. It has a dangerously busted world-aura which causes all sorts of incursions from other realities; some dangerous disease, species, or idea could pop up any time and make the place uninhabitable. And anywhere else that it can infect. Of course, this means you need a reason for the Moon Elves to not kill the adventurers.

Another issue you need to think about is Spelljammer physics. Are you going to have Spelljammer gravity and air envelopes? If so, that makes space travel much safer, but you need some idea of why the planets orbit the sun, moons orbit planets, and so on. The idea of having a spelljamming drive retain the ship's air envelope is dangerous - if the drive ever goes off, everyone dies. You also need to decide how operating a spelljamming helm interfaces with GURPS magic.

Are you going to have a crystal sphere, and a Flow outside it, or will you limit the setting to a single solar system?

Reread Out of the Silent Planet. The description of space flight on the first voyage to Mars is wonderful. C.S. Lewis has a whole theology of why spaceflight isn't allowable. Lift big chunks for your Luna Elves.

Random thought, to make the Luna Elves less like Yrth's Elves, why not give them wings like Luna Moths? These could be like the wings like the people of Thanagar in the 1960's Hawkman stories. Or they could living parts of them. The Luna Moth also offers a color sceme for the Moon folk.

Reread Tolkien's man in the Moon pomes for atmosphere details about moon palaces and citadels.

[johndallman]

Originally Posted by Tyneras

If GE is smaller than objects physical size, you have airless object with zero G on surface.

Try to keed the PCs from landing on those. As they go close enough, the "air envelopes" mix ... so their air all leaves.

*Make all those sails and oars and stuff relevant somehow. Check ether sails and oars and drives from GURPS Spaceships.

My first Spelljammer GM figured that one out. They help with maneuverability; this is even supported by some of the ship statistics. Of course, you need crew to operate them. That leads you to variable-geometry ships, with great big hinges and winches. A PC of mine designed a variant of a Great Bombard ship that uses this trick to speed up reloading dramatically. He gave the plans to a bunch of Giff, and sneaked away.

[Tyneras]

Originally Posted by johndallman

Try to keed the PCs from landing on those. As they go close enough, the "air envelopes" mix ... so their air all leaves.

Sounds like a great adventuring hazard to me, thanks! *adds to list of "How to make the PCs die horribly"* Sounds like a great "Why is that valuable ship sitting on that world with a dead crew and no damage?" type of mystery adventure.

On a slightly less homicidal note, if the space between the surface and the planetoids actual gravity envelope is large enough, they shouldn't touch, and thus should be fine.

Originally Posted by johndallman

My first Spelljammer GM figured that one out. They help with maneuverability; this is even supported by some of the ship statistics. Of course, you need crew to operate them. That leads you to variable-geometry ships, with great big hinges and winches. A PC of mine designed a variant of a Great Bombard ship that uses this trick to speed up reloading dramatically. He gave the plans to a bunch of Giff, and sneaked away.

I'm the first GM (or even person) in our group to hear the name "Spelljammer" and the actual crunch of the system doesn't really make any sense to me, so I'm just rolling with the fluff (with a "as described by a pre-scientific society" bend to it) and turning it into GURPS as best I can.

[johndallman]

Originally Posted by Tyneras

On a slightly less homicidal note, if the space between the surface and the planetoids actual gravity envelope is large enough, they shouldn't touch, and thus should be fine.

In canon Spelljammer, this is (probably) impossible. Gravity is not related to mass. At all. It is controlled by size and shape.

"Spelljammer" and the actual crunch of the system doesn't really make any sense to me

Actually, you can drop "to me" from that statement. When you start digging into it hard, its aparent internal consistency becomes dubious.

[Tyneras]

Originally Posted by johndallman

In canon Spelljammer, this is (probably) impossible. Gravity is not related to mass. At all. It is controlled by size and shape.

I know, I just used the gravity envelope to explain why an earth sized planet has an atmosphere only a few hundred miles thick and a gas giant is basically nothing but air, and both have 1 gravity. My solution is that the envelope is a set size, a gas giant has a tiny core and is mostly atmosphere, while an earth-like world is mostly rock with only a tiny bit of envelope left for the air to fill. Then I just rolled with the idea that you could have a rock bigger than the gravity envelope, and thus no air and no gravity (on the surface, dig down and you might find something interesting) but still in a set orbit.

Originally Posted by johndallman

Actually, you can drop "to me" from that statement. When you start digging into it hard, its aparent internal consistency becomes dubious.

Good to know I wasn't just being dense.

[Delvidian]

Wonderful ideas and inspiration here, especially on the Luna Elves. Re mechanics, I like the suggestion that the helm also provides basic atmosphere. And no doubt at some point someone will knock out the helm and send the PCs gasping.

I do have the original Spelljammer rules. I'm torn between wanting to keep it simple -- bodies have 1g gravity or none -- and wanting to play with different gravities. I'm tempted to go for the easiest solution (gravity or not) and find ways to hand-wave other gravities as the mood strikes.

The way I have it outlined, the party will find the helm in the treasure trove of a Djinn (Elven Banestorm variety). They already have allies with a cog from a previous series of adventures in Araterre: Captain Magnus Fromage and his wife Dominique. She has Magery and also will fit better in the Elf-sized helm. These were such popular NPCs I brought them back for a later story arc in Sahud. So the party will have "chauffeurs" to begin with, so no character gets stuck in the chair. Not too big an issue, anyway, since they play multiple characters.