This is not really accurate. Submarines maintain roughly neutral buoyancy and use a motor for propulsion. They can use lifting surfaces for buoyancy control, bu

This is not really accurate. Submarines maintain roughly neutral buoyancy and use a motor for propulsion. They can use lifting surfaces for buoyancy control, but they need the motor to move forward. Airships operate on essentially the same principle--- airships are closer to "air submarines" than "air ships." This device is an air-equivalent of an underwater glider.[0]* It establishes positive buoyancy to rise through the fluid (air, in this case, rather than water) and then establishes negative buoyancy to enter a dive, after which it glides just like any other glider. The difference between this thing and a 'normal' glider is that it uses buoyancy to rise in altitude rather than needing to be towed by a conventional airplane. [0]https://en.wikipedia.org/wiki/Underwater_glider https://en.wikipedia.org/wiki/Underwater_glider * An underwater glider being the water equivalent of a... glider.