New??? They call this new???
Christ. I don't remember who the author was, but I remember reading a story about adjusting the density of a human-transport balloon using mechanical compressors, when I was a child. And I don't mind saying that not only was that long ago, but the story had been written long before that. Verne maybe? I don't recall off-hand.
If they can pull it off with modern technology, great. But the suggestion that this is a "new' idea is just plain ludicrous.