EHD 'ionic wind' propulsion (MIT 2018).
documentedresearch_programConjecture Layer (hypotheses)
Solid-state electroaerodynamic propulsion: high-voltage electrodes ionize air and push it (ionic wind) with no moving parts - MIT's 2018 aircraft was the first heavier-than-air solid-state-propelled flight.
Real and demonstrated - but only as a lightweight winged aircraft (~5 m span, 40 kV, aerodynamic lift, ~60 m indoors, very low thrust density; MIT flagged efficiency/thrust-density as needing major improvement). Scaling to a silent Walmart-sized hovering sphere is undemonstrated and speculative. The often-cited 'plasma-skin drive' for UFO spheres is this real mechanism extrapolated far past its demonstrated envelope.