[lkm]

Don't hold me to this, but I think if you heat it to 500K or so you halve the density of helium. Of course you then have to start thinking about materials, and insulation, maybe a thin shell of aluminium covered by aerogel and then a composite shell, but it all adds weight. A further thought is that you can do much the same by halving the internal pressure and having a stronger shell, which with modern composites might be possible, wiht the added benefit of slowing disfusion. It may be that best compromise between energy mass and lift is a combination of a lower pressure and a hotter gas.
Finally either of thes ideas is going to require air bladders of some form.

[NoMoreLies]

How far can we heat it? Say we make it 50% less dense, that would be reaching 1kg/m3

[lkm]

Still, I think it might be safer to do that with Helium, especiallly as it's much more suceptable to electric fields.
Secondly, what do you think of heating the helium for extra lift? It's not something you could do with hydrogen but helium is so inert you could easily exceed hydrogen's lift capacity.

[NoMoreLies]

Not really. I'm not suggesting Ionising it all the way to a Plasma, I'm suggesting making it into a bag full of H- atoms, Ionised with an electron gun.

[lkm]

That sounds dangerous.