I've been playing with the concept of zero gravity in my mind for a bit and I think it's not as hard as they make it sound.
If we line up 4 unbalanced wheels, make NR 1 and 3 spin in one direction, NR 2 and 4 spin in the other. We have the final mass moving horizontally. Now we accelerate the wheel half of the spin and decelerate it the other half.
behold! Both the acceleration and deceleration create opposed reaction forces in the same direction!

momentum of the wheel

balancing gyro momentum

quantumfork

art of the apparatus

stay in the air

combine momentum change

conversion to linear rotation
discussionsuggested readinggabydewilde - gde wilde anti gravity