Asymmetric Gravitational Coupling: A Theoretical Framework and Testable Protocol for Directional Propellantless Propulsion

We propose a mechanism for propellantless propulsion through local, controllable asym-metry in the gravitational coupling coefficient α(x) between a vehicle’s mass elements and an external gravitational field (here, Earth’s). By differentially modulating the effective gravitational mass along the craft’s length, a net directional force can arise. We derive the net thrust, the internal structural stresses induced in a rigid body, and the thrust-to-mass ratio. We explicitly acknowledge the severe theoretical challenges—including potential structural failure for significant asymmetries and a local violation of the weak equivalence principle—and present a concrete, falsifiable experimental protocol using a torsion balance or sensitive accelerometer. The concept requires new physics but is testable with current laboratory equipment.