Imagine a children's roundabout, with vertical wheels around the circumference, pointing towards the centre. Each wheel has a weight on it's outside edge making each wheel unbalanced. If we spin all these wheels together in synchronisation, and the weights go up on the outside and the down nearer the centre, would there be a slight upward lift when the weights are moving up on the outside, and a slight downward pressure when they are going down towards the centre.
If the answer is yes, then my thought is that if we could keep the unbalanced weight on the outside, always going up then we would have a slight lift.
So, if remove the weights so the wheels are balanced, spin the wheels, then we spin the roundabout really fast, the outside edge of all the wheels would be heavier than than the inside edge of the wheels due to the fact that the linear velocity on the outside is greater than towards the centre and this would cause it to be heavier because relativity says faster things get heavier. This would give a constant lift.
The lift would only be small, but any non propellant thrust in space is really useful.
Also, apart from overcoming friction, it does not need any energy, once it is up to speed.