Electromagnetic Propulsion Explained

Electromagnetic Propulsion System

The electromagnetic propulsion system is a simple system in concept with no moving parts. I will try to explain how it works in order from simplest explanation to advanced that way you have the choice on what to read.


Simple Conceptual Explanation:


An electromagnetic propulsion system is an engine of sorts that creates thrust by means of using the properties that tie electricity and magnetism together. In analyzing the simple diagram I drew above we first notice that it is a cross sectional view of the device and that I have numbered the main components necessary for electromagnetic propulsion to take place:


1. Cathode - Electrode
2. Anode - Opposite electrode
3. Insulator (with inlets) - Non-conducting material


*The Cathode can take the place of the Anode and vise-versa. It will still operate correctly.


Now that we know what everything is lets talk about how it works step by step. Neutral gases from the inlets are passed by the electrodes. The two electrodes have such a large potential difference between them it creates a strong electric field, so strong it forces electrons to shoot across from cathode to anode colliding into the neutral gas particles, breaking down the gas into a plasma. The particles now carry a charge and like the electrons will want move in the direction of the electric field (but opposite direction of the electrons). We now have current because we have charges in motion. The positively charged particles cannot enter the conducting electrodes and move around inside, but the electrons can and its this motion of electrons inside the cathode that induce a magnetic field in a circular direction around the center. Now here comes the propulsion part, we have ions in the chamber (surrounding the cathode and inside the anode) and we have electrons passing through the inside electrode inducing magnetic fields, colliding into particles, and then passing through the outside electrode back to the power source. These induced magnetic fields are pointing perpendicular to the motion of the ions and that creates a force on the ions in the direction to the right in the diagram. And that is your thrust. What I just explained happens instantly and is continuous.


More Advanced Explanation (for those that know about basic electric and magnetic principles):


The diagram drawn about shows a cross sectional view of the propulsion system. The main operating components are numbered:


1. Cathode
2. Anode
3. Insulator (with inlets)


An electromagnetic propulsion system uses a strong electric field between an outer tubular electrode and an inner cylindrical electrode to break down the gas that enters the chamber into a plasma and propel that plasma by using the current of electrons passing through the cathode to induce a magnetic field thats direction is perpendicular to the motion of ions. This cross product of vectors creates a force that accelerates the ions and produces thrust.


Design Notes:


1. The system needs not only a strong voltage to be applied across the electrodes but also must be able to supply great power in order to maintain a strong enough current in the cathode to provide a sufficient magnetic field.


If lets say the power source was from a Tesla coil which produces 50,000 volts and holds a natural resistance due to length of wire and impedance. When in open circuit conditions (like shown below)the V1 (load voltage) will equal the PSV voltage no matter the impedance, which can be applied to our electromagnetic propulsion system as our power source, but when our propulsion system is operating correctly it has a steady current because the gas is maintained in plasma form which means our circuit is not an open circuit. Now assuming the electrodes are perfect conductors and the plasma offers a good conducting media to transport electrons then we have almost a wire connection from electrode to electrode. So our V1 becomes zero and the current is our PSV divided by our natural impedance in the Tesla coil. The resistance and impedance of Tesla coils are tremendous which is why they produce so little current. And here's our problem, "so little current." Yeah, we might be able to maintain sufficient voltage and current to keep our ions charged but it means nothing if we can't produce enough current to induce a strong enough magnetic field to provide a thrusting force. So this might be a problem someone may overlook if they were to make a small propulsion system. Even a thruster the size of a thumbnail would require quite a bit of power to produce measurable thrust. I would estimate that a small thruster the size of a thumbnail would require at least a 50 kW power source to provide 1 N of thrust. (really quick estimate I feel like it could be lower) but makes sense for two reasons:
1. Electromagnetic propulsion systems get more efficient the bigger and more powerful they are.
2. These systems are meant for space travel (*Small thrust with high exhaust velocity)

2. The curved shape inside the outer electrode allows for an electric field to be produced in such a way that it acts like a nozzle when expelling the plasma so that none of the ions are forced back and outward from center. This is one of the reasons we have nozzles on rockets and turbomachinery. It's to make sure all of our particles are going straight back. and not out from center. "Out from center" is a waste of energy and doesn't provide optimal thrust. Only the velocity in the x-direction is provides forward thrust.
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Spraying Without Nozzle

* Space propulsion should have high exhaust velocities because when your vehicle is traveling through space you want it to go fast and you ideally want your exhaust speed to match your desired max speed so your being as efficient as possible. (you want the particles to contain no kinetic energy after being exhausted)






I try my best to make the information provided as accurate as possible. If you spot a mistake or disagree with what I have wrote please let me know. Thank You.