I'm a scientific/technological natural philosopher, so although I don't have formal training, the internet has quite enough information that if there are leads to follow, I'd find 'em.

But honestly, the subject of gravity manipulation is saturated with fraud, and actual information on gravity is difficult to even find, and if you can find it, it's either the most obvious aspects, like on Wikipedia, or it's just not testable with modern equipment.

For instance, it is not easy to test gravitational speed or force. We can't just create an orb that produces or reduces gravity, and then turn it on and off at will, to test what REALLY happens to objects in a gravitational field. We can't even test miniature gravitational orbits like that. No way to test black holes either.

It feels like looking at the difference between a useless crystal made from sand, a drinking glass made from sand, a glass seeing-lens made of sand, and a silicone computer chip made from sand.

With gravity, we are still at the "We are lost in the desert, and we thirst" stage. 

The sand is something to choke on, a desert of heat, oppression, and confusion.

Mirages abound.