Reactionless drive

Common card · No. 395106

Reactionless drive refers to hypothetical and unproven forms of spacecraft propulsion that would generate thrust without the expelling of propellant or otherwise exchanging momentum. A propellantless drive is not necessarily reactionless if it functions as an open system interacting with external fields, but a reactionless drive is generally conceived as a self-contained or closed-system device, which is why such claims are commonly treated as conflicting with Newton's third law and the conservation of momentum. Reactionless-drive claims are therefore often compared to perpetual motion machines or other impossible-energy schemes if their reported performance is taken at face value. The expression has been in English-language newspaper use since at least 1963 and later became a recurring public label for alleged no-propellant engines. Concepts described this way have included the Dean drive, electrogravitics and lifters, gyroscopic and oscillation devices, microwave-cavity thrusters such...

Read on Wikipedia · Image Norman Rockwell, Public domain