The goal is a lighter than air vehicle, using Hydrogen as a lifting gas, which modulates altitude with ducted fans, and more importantly, by the movement of lifting gas from tank to balloon and from balloon to fuel cell, storing the fuel cell's output water in ballast tank, which can be emptied as necessary to maintain buoyancy(or pilot hydration), or, in the event of insanity, decomposed via electrolysis to make the whole thing go BOOM! (in which case the whole thing becomes a hot air balloon, complete with oxyhydrogen burner, but this aspect requires Stanley Meyers' 'water fracturing' technology)