EmDrive

The EmDrive is a theoretical propulsion device that claims to produce thrust without expelling propellant, using microwaves inside a specially shaped cavity. It works on the idea that reflecting microwaves within the cavity creates a small imbalance of radiation pressure, potentially generating a force. While some experiments have reported tiny results, the physics behind it conflicts with established principles of conservation of momentum, and mainstream scientists remain skeptical. As of now, the EmDrive has not been conclusively demonstrated as a viable propulsion technology, and its existence remains controversial.