Planetary requirements for Dragons to fly?

[SCAR]

Thanks to everyone for the feedback and ideas so far. I need to go and read the relevant parts of Biotech, Space and Dragons for some base figures, and play with some of the ideas see where they lead.

I also did a google search and found that the question of flying creatures on other worlds (with different gravity and atmospheres!) has been asked a couple of times in non-gaming forums!

[Anthony]

There are two major factors preventing large flying animals: the tensile strength of muscles is too low for long wings holding up large weights, and the metabolic power density of living creatures is too low for powered flight above a fairly modest scale. Acquire super-materials for muscles and give it the power density of an airplane and you can have flying dragons on earth (and they will probably be crazy-fast on the ground as well). If that's not an option, your easiest choice is to reduce gravity -- broadly speaking, you can take a terrestrial bird design and multiply its linear scale by 1/gravity (multiply mass by 1/g^3) and it should still fly in lower gravity. Increasing air density will also allow larger creatures to fly, but the effect is much smaller (double density will get you flying that are maybe 20% bigger).

[Agemegos]

Originally Posted by rasimus

I understand CO2 can make an atmosphere heavier in a hurry, with a bonus that it's opaque to infrared and makes things warmer.

Also, it provokes hyperventilation. And if you get enough breathing it produces acidosis.

[Agemegos]

Originally Posted by StevenH

Lastly, hydrogen is pretty easy biologically to produce, so H2 gasbags are at least plausible..

Yes, but it diffuses like a bastard, and it's unstable in the presence of oxygen, which would mean that you'd have to constantly replenish it if it were in contact with oxygenated (living) tissue.

[StevenH]

Originally Posted by Brett

Yes, but it diffuses like a bastard, and it's unstable in the presence of oxygen, which would mean that you'd have to constantly replenish it if it were in contact with oxygenated (living) tissue.

Very good point. I wonder if there are any natural membranes that are "dense" enough to not allow the H2 molecule to diffuse through. While I don't know of any (not being a biologist), some might exist. Or, the metabolism would need to be stepped up to counteract the diffusion by creating more. As for instability, either the tissues in contact would have to be very alien to keep the oxygenated bits away from the hydrogen bits, or something even more esoteric would have to be invoked.

In any case, gasbags would be very undragonlike, and aren't really designed for the high velocities we all like to see in flying reptile-like critters. :-)

(I still think that Vermithrax from Dragonslayer rocks!)

[Anthony]

Originally Posted by Brett

Yes, but it diffuses like a bastard, and it's unstable in the presence of oxygen, which would mean that you'd have to constantly replenish it if it were in contact with oxygenated (living) tissue.

Unlikely the gas bag would be living tissue, though; too heavy that way. Methane might be easier, though; it's only got half the lift of hydrogen, but it's a lot easier to work with and can be readily generated by biological procedures.

[Refplace]

Electric organs to generate Hydrogen from water might be another option.
My fav though is just a toxic acid, possibly one that ignites when it starts to dissolve most substances.

[Pragmatic]

Let's see if there's a profanity filter:

Ass Blasters

[Crakkerjakk]

Circumventing the profanity filters is a ban-able offense. You may want to reword your link.

[Pragmatic]

But I didn't circumvent anything. I gave it one shot, to see if the link would work. It did. Apparently, "ass" is not a banned word.

And it IS a concept that MIGHT work. A beast with a digestive system that provides rocket fuel for powered flight. Not exactly a traditional dragon, but...

It's from the Tremors film series. I don't like the fact that they used vulgarity in naming the third life-stage of the graboids, but that's what it's called.