# Cyclotron engines as a means of thrust for interplanetary travel?

How feasible is it to use a cyclotron in this manner for space propulsion?

Inject small amounts (aliquots) of ionized matter into cyclotron at some high integer multiple n of the cyclotron frequency $\omega=qB/m$ so that there are n aliquots at each radius in the cyclotron. Since the time it takes to complete one revolution is the same for all of these aliquots, one could use the frequency $2n\omega$ of the alternating electric field to accelerate all these aliquots in a synchronous manner. This would give essentially a continuous stream of very high speed plasma or material to accelerate spacecraft. Of course, the aliquots could move at relativistic speeds which would affect the cyclotron frequency by $\gamma$. But one could design a magnetic field that gets stronger with increasing radius especially toward outer portions where relativistic effects would be more prominent. There would also be electrostatic repulsions between aliquots that would need to be taken into account. The spacecraft would likely need nuclear power source. Is this a feasible idea? Has this been thought of already?

• aaaand we have a very efficient propulsion for an orbital torus-shaped station, to keep it spinning. The problem with cyclotrons is that they eject the particles far off center. You'd need two, or one working with bidirectional streams, or some way to turn the stream 90 degrees. Plus energy requirements and mass. So far we use just linear accelerators AKA ion engines.
– SF.
Commented Dec 7, 2015 at 7:31
• Nah, you just need to install it with its thrust line going through the CoG. You end up with an asymmetry (the entire cyclotron on one side of the ship) but if the ship is large enough you can install enough mass on the other side to balance things. Commented Dec 7, 2015 at 11:31
• @Hobbes: It won't be sufficient. The force of propulsion in this case isn't applied the moment the propellant leaves the nozzle, at the point of the nozzle - it's applied along the whole route of acceleration, tangent to the acceleration trajectory at all its points - in this case generating a genuine torque with the center in the middle of the cyclotron, completely regardless of what and where you attach to its circumference. Even my suggestion ("turn the stream 90 degrees") wouldn't suffice.
– SF.
Commented Dec 7, 2015 at 14:04
• Ah, I see what you mean now. Commented Dec 7, 2015 at 16:01
• This would work very well for something that lived at the pace of the continents. The ISP (assuming solar power) would be phenomenal. The flight time would also be phenomenal, though. Commented Apr 19, 2017 at 22:49