A few internal wires/cables might allow the final inflated structure to be roughly parabolic. All sorts of wacky shapes can be made with internal stays. Also, at low pressures the outer shape of the balloon could be made parabolic. Not every balloon need be perfectly round. When inflated a balance occures between internal pressure and outer structure. Just look at any birthday baloon. They arent spheres. And perfection isnt needed for a radio antenna. It just needs to be better than one of the same mass.
> Just look at any birthday baloon. They arent spheres.
Yeah, I wondered about that. I guess a birthday balloon is a pretty complicated curve; but I doubt it comes closer to a paraboloid than it does to a sphere or a plane, anywhere on its surface.
But this thing isn't a telescope, it doesn't have to focus an image; it doesn't need to be a parabola, a sphere is fine for achieving highly-directional gain.
