concept

Aerostat

Any flying body held up by buoyancy rather than by motion — balloons, powered airships, weather sondes, and on Pandora the Medusoid. The essential difference from an aircraft or a bird is the cost structure: an aerostat pays once, in volume, and then floats almost free for months, while a wing pays every second and falls the moment it stops. The price of that cheapness is that it drifts with the surrounding air, so it feels no relative wind and has nothing for a rudder to push against — a free aerostat can barely choose its own direction.