Keith Breazeal Video Productions

The common structure to all of the California UFO Drone photos is the center circular structure with the "Staves" protruding upward. There are some interesting features protruding from the center of the hub that I will call "Loops". There are seventeen of these "Loops" on this particular "Drone". Earlier photos had sixteen of them, an interesting fact. These "Loops" appear to be directly related to the "Staves" because they are directly in line with and have the same number count. At this point in time, I think the "Loops" are a means of controlling the energy(of whatever type) that flows between the "Staves" and the center "Hub". The shape of the "Staves" leads me to believe that the energy is being funneled into or out of the top of the "Staves". The "Loops" may play a part in controlling the energy flow in such a way as to balance the "Drone" in the horizontal plane. The other function of the "Loops" may also be to control the flow of energy in a circular "race track" around the inside of the "Hub". The actual form of propulsion is still a mystery, but my best guess is a form of rotating plasma within the "Hub".
The long arm-type structures that extend from the "Hub" may be part of some type of sensor system. These extensions vary between different "Drones" photographed, so seem to be related to mission oriented design versus propulsion. One thing to note is the smaller extensions appear to be hinged in a way that they fold up to the vertical position. If These are "Drones", they need to be stored upon retrieval. The fact that they fold upward leads me to think that the center "Hub" produces an energy field in the downward direction. The nine "Tabs" that extend down from the "Hub" may be a part of a docking mechanism. The "Tabs" don't appear on all the different "versions" of the "Drones" photographed.
The variation in the number of "Staves" could be related to the amount of energy required by a particular version of the "Drone", or a hoaxer got the count wrong. Real or not, the reports seem to keep trickling in. Since nobody has taken credit from the initial appearance, the mystery deepens. Video games and movie hype are out of the window now, so that leaves fewer options if it's a hoax.