My grandmother had a bundt cake pan that looked a lot like that.....
Flying buttocks. Figures.
About 20 years ago Lockheed was proposing a lighter-than-air ASW vehicle that was hydrogen gas based, capable of cruising from a base in California to the North Atlantic area around Iceland, then taking station at around 60,000 feet altitude to observe Soviet submarines. It would be fueled by the hydrogen providing lift, with engines driving propellers capable of maintaining station or cruising as required. I think it was probably much the same craft as your picture shows.