A big news story has been making the rounds about a new and potentially game changing space propulsion technology, which was recently tested by NASA scientists in a vacuum chamber at the Manned Space Flight Center in Houston Texas. The system, called the EM Drive, is based on microwaves bouncing around a specially shaped cavity. These aledgedly create thrust, thus making it possible for the EM drive to be used as a propulsion system, if attached to a spacecraft.
What makes the EM drive so much different than any previous propulsion technology is that it does so without expelling any propellant. All existing rocket engines use some kind of material, known as reaction mass, in order to produce thrust. Even highly efficient ion engines require a gas of some sort to be used as the reactionary mass. The need for propellant is a major limiting factor in spaceflight. It means that propellant must be launched with the spacecraft, often constituting a large percentage of the spacecraft’s mass. It also limits the duration of the spaceflight. Eventually the propellant runs out. However, the EM drive uses only energy, which can be provided almost without limits by solar panels or a nuclear power source, which could provide energy for decades.
The only problem with this is that the whole concept seems to violate the law of conservation of momentum. Our current understanding of physics would seem to indicate that this is impossible. You can’t add momentum to something without pushing off of something else. Every action has an equal and opposite reaction, and that’s why rockets need to shoot propellant in one direction to go in the other.
New Test Suggests NASA’s “Impossible” EM Drive Will Work In Space
[T]he EM Drive’s thrust was due to the Quantum Vacuum (the quantum state with the lowest possible energy) behaving like propellant ions behave in a MagnetoHydroDynamics drive (a method electrifying propellant and then directing it with magnetic fields to push a spacecraft in the opposite direction) for spacecraft propulsion.
Last year, NASA’s advanced propulsion research wing made headlines by announcing the successful test of a physics-defying electromagnetic drive, or EM drive. Now, this futuristic engine, which could in theory propel objects to near-relativistic speeds, has been shown to work inside a space-like vacuum.
NASA Eagleworks made the announcement quite unassumingly via NASASpaceFlight.com. There’s also a major discussion going on about the engine and the physics that drives it at the site’s forum.
The EM drive is controversial in that it appears to violate conventional physics and the law of conservation of momentum; the engine, invented by British scientist Roger Sawyer, converts electric power to thrust without the need for any propellant by bouncing microwaves within a closed container. So, with no expulsion of propellant, there’s nothing to balance the change in the spacecraft’s momentum during acceleration. Hence the skepticism. But as stated by NASA Eagleworks scientist Harold White:
The trouble with this theory, however, is that it might not work in a closed vacuum. After last year’s tests of the engine, which weren’t performed in a vacuum, skeptics argued that the measured thrust was attributable to environmental conditions external to the drive, such as natural thermal convection currents arising from microwave heating.
The recent experiment, however, addressed this concern head-on, while also demonstrating the engine’s potential to work in space. (Image: NASA Eagleworks.)