Theoretical Framework for Spacetime Metric Swap Propulsion and Fluid-Vacuum Displacements

The Metric Swap Engine is a speculative propulsion concept that treats spacetime and vacuum as an effective fluid that can be reshaped rather than pushed against. Instead of expelling reaction mass, the engine locally “swaps” the metric inside a spacecraft’s engine volume with a different metric configuration in the surrounding vacuum, creating pressure‑like gradients in the spacetime fabric itself. In this framework, acceleration arises from controlled fluid‑vacuum displacements: regions of compressed and rarefied metric behave analogously to pressure fronts in a fluid, guiding the craft along geodesics that are dynamically sculpted rather than passively followed. The theory formalises these effects using modified field equations and conservation laws, aiming to remain compatible with relativistic causality while exploring how engineered metric differentials could, in principle, produce thrust or effective superluminal transit without locally breaking lightspeed.