If they have done their arithmetic properly, lift off should be easy, and enough should be known by now about power and lift to do the sums. On a smaller scale, there have been autonomous models that work well, so scaling up should not have presented any problems. I am left wondering exactly how crazy the driver has to be to sit upright between those spinning blades. For any practical use, the amount of power that can be stored puts a solid limit on flight duration, so its going to need something pretty radical to happen before it becomes in some way useful.
