Due to the shape, and it's location it's quite possible that internal shutters or ducts can be configured so as to allow partially disrupting the coanda effect on either side by selectively allowing air to exit through the slit. Possibly, but not necessarily ducted in from the fans high pressure zone.
This would likely cause a rather strong vectoring of the thrust as it would also almost certainly lower the lift on the detached side due to interactions with the fans.
If that isn't how its done, I'm quite positive it can be done in this way. I'll be happy to be named inventor in any thusly aquired patent and collect a very modest licensing fee, if only that would be how the world works...
I wonder if this maybe has two contra rotating single blade props that they can control quickly enough to be able to speed them up for half a revolution to generate asymmetric thrust to provide pitch and roll?
But it could still be based on the same idea: if the blades are not flexing in the same way under acceleration, any asymmetry might do it, if it can be properly controlled.
Which brings us to how I thought this thing does pitch/roll until I noticed that I just got hung up on a difference between a prototype in the picture and a later iteration in the video: contrarotating propellers will influence each other when blades meet, creating nonuniform efficiency over the duration of a rotation. Three peaks and three troughs, like the legs of miniscule of pressure differential. I don't know where the peaks would be relative to the meeting points, but given the general fickleness of aerodynamics thrust of contrarotating propellers just can't be perfectly even all around the rotation. But that's still three-symmetric. It could become a control option when overlapped it with e.g. an n-symmetric grid where n is not a multiple of three, even if not a good one (mixing it with yaw would be a wobbly mess). The prototype picture shows five arms which is how I got the idea, but in the video it seems to be six/three, so this candidate is out (unless the specifically made a misleading dummy for the video, which I don't think, even though the video is cut in a way that it might be).
Seems expensive and tricky though.
Paper is not free but video conveys the idea well: https://www.youtube.com/watch?v=KZe7l5_LfoA
Likely with clever two-material molding you could do away with the hinge and it would look similar to the prototype shown in the article.
> The main motor directly drives the propeller hub, which is itself connected to the propeller blades by two inclined hinges. The hinge geometry couples blade lead-and-lag oscillations to a change in blade pitch. Instead of only driving the motor with a steady torque, we add a sinusoidal component in phase with the rotation of the rotor to induce a cyclic pitch variation. The amplitude and phase of this control signal determines the magnitude and direction of the vehicle response.
Maybe shifting the battery?
I can't remember the details but as you shift weight and begin moving laterally, when you pick up lateral speed it interferes with the ducting effect or enhances it in some way can counter reacts against the movement, giving dynamic stability.
For some definition of useful. Batteries really are the worst thing ever. We got dense energy from oil so early, and then nada.
I doubt that, because in "stacked propellers" configuration the second propeller gets very turbulent air, causing extra noise and vibration, i.e. loss of efficiency.
EDIT: link to patent.
To make a real co-axial vehicle, you'll need to handle changes in the 3 translational axes (forward/backward, strafe left/right and up/down) as well as the rotational axes. Despite being a complicated movement, it's pretty well understood and Kamov has been making coaxial helicopters for many years.
My best guess based on the video is that there are two contra-rotating fixed pitch props in the middle. This gives you up/down and by varying the speed of the props gives you yaw right/left. A couple of clever ducts forward, aft, left and right on the duct give you stability forward/backwards and left/right.
I look forward to actually learning how they did it. It certainly looks cool.
A boring solution will be fins operated by micro servo/