What I really need to have explained to me (and I've spent quite a while on Wiki) is why you run out of Helium buoyancy at relatively low altitude.
Hi
What you are referring to is pressure height. An airship consists of (amongst others) an envellope containing helium, and a ballonet (or more) containing ambient air. As you climb or as helium heats (superheat) the ballonet contracts due to helium expanding. There comes a height when there is no air in the ballonet. This is pressure height. The only way to climb further is to valve helium. Obviously this comes at the expense static lift.
I believe they are looking at using hydrogen.
Google the 'exploding glider' about ten years ago. Lightning strike on a carbon fibre airframe!