Magnetic Propulsion

[JackDugan]

I was just thinking about how magnets repel and wondered if permanent magnets could be used as a propellant-less source of delta-V in space. If there is something completely wrong with this idea or this is a stupid question, please correct me.

[Nibb31]

I was just thinking about how magnets repel and wondered if permanent magnets could be used as a propellant-less source of delta-V in space. If there is something completely wrong with this idea or this is a stupid question, please correct me.

No. To propell, they would need to repel something.

[Newt]

One thing that might interest you is the idea of magnet based orientation controll for (mostly) small LEO satellites. A magnet close enoguht to the Earth can be pulled around like the magnet on a compass, to orient and stabilize the vehicle. This provides no thrust, of course, but it is vaugley on the same lines.

[architeuthis]

No. To propell, they would need to repel something.

You can use the magnetic field to repel charged particles from the sun (or if you have a really powerful static particle accelerator you can point that at the magnetic field to accelerate the spacecraft). I believe this concept is called a magsail, and is the basis of a delightful hard-SF novel, 'Permanence', by Karl Schroeder. Here is a brief synopsis.

[peadar1987]

I had a think about this. Obviously you need something to push against.

What if you threw out some sort of pusher plate and repelled against that? Hmm... The force would drop off quite quickly, wouldn't justify the mass.

Okay, maybe you don't just use one pusher plate, you can keep dropping them after you when the force from the previous one has diminished. This is looking a little better.

Now how about we miniaturise the pusher plates as much as we can, until they're basically just charged partic... Oh wait, I've just spent the last ten minutes reinventing an ion drive with a magnetic nozzle. *facepalm*

[SargeRho]

What you're thinking of is called a Magnetic Sail, or an Electrodynamic Tether.

[shynung]

This is an electrodynamic tether.

It pushes off a planetary/stellar magnetic field, and consumes only electricity.