One thing I've thought about, when thinking about airships, is the problem of expendable stores, like lift gas or ballast. Solar might well be the solution! One

One thing I've thought about, when thinking about airships, is the problem of expendable stores, like lift gas or ballast. Solar might well be the solution! One approach being taken is re-liquefying of the lift gas. Another approach might be the condensation of water from the air. Both might be combined. Either way, the problem is made simpler by the availability of power. Airships have a lot of surface area for solar power!