Scientists who have since studied Brown’s devices have not found any anti-gravity effect, and have attributed the noticed motive force to the more well-understood phenomenon of ionic drift or “ion wind” from the air particles, some of which remained even when Brown put his device inside a vacuum chamber. More recent studies at NASA, held at high voltages and proper vacuum conditions, showed no generated force.

Ion thrusters are real (and neat), but they are not anti-gravity tech.