EmDrive

The EmDrive of 2070

The fictional world of 2070 presented in Robot Dawn: The Mazzy Nova Chronicles is much different from the world of today primarily because of supposed advances of propulsion and energy generation.

The principle of the electromagnetic thruster, also known as radio frequency resonant cavity thruster, and designated here as the EmDrive, is a fictional means of propulsion that uses no reaction mass or propellant. It was first proposed at the turn of the 21st Century and was not taken seriously by scientists for the first three decades as inventors struggled to provide a compatible theory of its operation. But experiments, particularly those of the US National Astronautical and Space Administration (NASA), showed the concept’s viability early on. The purpose of this short dissertation is to provide a short description of the (fictional) science behind the EmDrive’s functionality.

The scientific skepticism of the EmDrive originates in Newton’s law of conservation of momentum. The momentum of a body is defined as its mass multiplied by its velocity:

momentum = mass x velocity

Newton’s law states that the momentum of an object remains constant unless acted upon by an external force. That is to say, unless acted upon by another object. This is usually explained by introducing a second object and having it collide elastically with the first object. The momentum of the two-object system before and after the collision must remain constant even though the masses and velocities (which are vector quantities) of each body may have been changed by the collision. In that case:

m1 x v1 + m2 x v2 = constant

This concept was used for rocketry by having the first object designated as the rocket itself and the second object being the onboard propellant as it is expelled by great force from the aft end of the rocket. The ejected propellant and the rocket are then both variable mass objects, but still taken together, the momentum is constant although both objects travel at greater velocity but away from each other. The combined momentum of both objects remains constant and satisfies Newton’s law. The propellant contains the energy that is released in a burning process that pushes the mass of propellant and the rocket apart and enables the rocket to obtain tremendous velocity. This concept and theory of operation was used and found remarkably accurate for predicting rocket trajectories. The theory of rocket and spacecraft dynamics that developed and expanded through the decades was found to be extraordinarily accurate and was used by engineers and scientists (including the author) to propel cars, trains, airplanes and spacecraft around planet Earth and about the Solar System.

Then (fictionally) came the EmDrive that required no propellant to act as the second object and provide a reaction force to propel the rocket forward. The explanation (fictional) of the science behind the EmDrive is quite short and stems from the fact that scientists initially misunderstood the device. Essentially, it is not a propulsion device. It never develops thrust. It is an energy exchange or transfer device; therefore, the principle of conservation of momentum should never be applied. The EmDrive’s resonant cavity converts electromagnetic energy directly into kinetic energy. The law of conservation of energy is not violated because a second body does not act on the first body, no forces are created, and no propellant is ejected.

In support of this is the associated fact that forces in nature do not exist. No one has ever found a force lying around on the ground. The concept of  the force, as proposed by Newton and others before and after, has never been, and never will be, proven to exist. It is an abstraction, an artifice and convenient fiction that assists in calculating end results. It should be remembered that first and foremost, Sir Isaac Newton was an alchemist. He wrote many more words on alchemy than he ever thought about writing on science. The concept of force and action at a distance (gravity) are fabrications that enable scientists and engineers to work with physical phenomena that are currently beyond human understanding. (The force of gravity was and still is a convenient fiction used for computation that was exposed by Einstein’s General Theory of Relativity as being the result of a curvature of the space-time continuum.) This concept of force came to Newton, an extraordinarily religious man, as an act of faith, a revelation. As such, he didn’t question it, and neither have all but a few engineers and scientists through the hundreds of years since Newton published his theories of motion.

Since no propellant (second object) exists within the EmDrive, no force can act on the object (the rocket), no force is generated, and the electromagnetic energy in the magnetron is transferred directly to the rocket as kinetic energy. The law of conservation of energy, which requires no force fictions, holds for the EmDrive.

What is the means of energy transfer? That is, how does the electromagnetic energy metamorphosis into vehicle kinetic energy? That is an excellent question and not one that will or can be answered here. We’ll have to accept the fact that it does on faith. My own perspective on the matter is that the transfer of energy from electromagnetic to kinetic occurs at the atomic or subatomic level and is a macroscopic manifestation of quantum physics. Of course, you are welcome to perform an Internet search to stay up to date on current EmDrive research and development that is ongoing throughout the world.

So what if the EmDrive proves to be an impossible form of propulsion? I believe the concept is still useful because it helps to expose the true nature and function of gravity and gravity wells within the Solar System and what it would be like navigating within it. Even if a propulsionless kinetic energy supplying device isn’t possible, we will one day in the future have something that approximates it, and this little story, Robot Dawn, illustrates what that future could be like. That is the purpose of science fiction.