We are still talking about an inclined ramp? If "smooth" is describing just the shape of the curve of the ramp and notsaying that it's frictionless, i.e. we assume no slip, then the rotation just depends on the final speed, and the final speed just depends on the initial height from which you start. (i.e. the potential energy). The exact shape of the inclined path is not important.

You mean a frictionless inclined plane like Teflon? No, indeed not, it would just slide and accelerate, but not pick up rotation. Indeed the angle of the force acting through the point where roll and plane would touch would be different. So, indeed concerning your original wording, if the plane is not frictionless, the force acting in this point is not normal, i.e. not going through the center of the roll. If the plane is Teflon, then the force is normal. The difference between those two forces is indeed the friction.

The first part of my question refers to an MIT device and the second one to a Stanford device. "Pseudoscience" and downvote?? I am simply not comfortable with posting commercial links, but that's something different than pseudoscience.

thanks, the paper referenced is interesting, since it supports slingshots of WIMPS at black holes. It seems to care only about supermassive black holes, I have to think whether it is plausible that they dominate in this question.

Hi, I mean it as in: en.wikipedia.org/wiki/Compact_star