Tesla used the "veritable ropes" to describe the lines of force running around the earth, so I am not sure he meant an actual mechanism.
stan deyo has done a lot of research on anti grav and UFO propulsion https://www.youtube.com/watch?v=_HW6wY60dJI
Boyd bushman worked for the skunkworks and did some experiments in this area https://www.youtube.com/watch?v=hNPBYtJyfZo
and here https://www.youtube.com/watch?v=xPt6LU1ZKk8
anti gravity machines are already a reality, have been for 50 years. majestic 12 has been using them for years, as well as naval space command, it was one of the first transfers of technology given by the Nephilim in the last contact phase.