Magnetic Orbit

[MinerEdgar]

Would it be possible in a true Zero-g environment to orbit a metal sphere around a magnetized Metal sphere?

I've had the idea of this for a while now. I just want to know, would it work?

[supermap]

i can only guess it should work,

i mean magnetism works like gravity in that it gets weaker by the square of the distance.

however things get odd since in magnetism you can have positive and negative charges, and it is hard to have a positive and a negative object floating around.

however it would be extremely odd since... for gravity as force is proportional to the mass then acceleration is constant for all objects at the same spot.

This is not the case however for magnetism since charge does not depend on mass directly.

This would make an odd system since closer objects may orbit slower than objects further away since the first have a lower charge.

Im sure it would mess up with many ksp players´ minds, but would be a nice thing to see

[MinerEdgar]

Hm interesting ,but sorry please fix your grammar.

But, yeah a slower closer orbit hm.

[stupid_chris]

I really doubt so, the object would crash into the other object it's orbiting before completing a single orbit.

The thing with magnetic force is that it follows the magnetic field, and that field is not a circle around the object, its some sort of closed loops that take root at the core of the object, like this:

You can't "orbit" the magnetic field sideways, magnetic force will always follow the field's direction, so really, that's not possible because the magnetic force is not a force that just attracts the other body but it creates a field that can interact with the other one's field.

[KOCOUR]

Hm interesting ,but sorry please fix your grammar.

.

Interesting how people still think, that something as unimportant as english grammar still matters in international forum, where most people have english as second or maybe third language.

[tek_604]

The two objects would orbit each other anyway (or a common barycenter, depending upon mass), as they both have mass and therefore gravity themselves.

[Inspector Gadget]

The metal objects would need to be EXTREMELY magnetised before they would have a greater magnetic pull then the gravitational pull.

[Brabbit1987]

It would be pretty cool to run some experiments in space with magnets and the forces of gravity. How magnetic fields will alter objects rotating a mass, and how much of a magnetic field would be needed to cause a collision.

[DerekL1963]

Interesting how people still think, that something as unimportant as english grammar still matters in international forum, where most people have english as second or maybe third language.

Since we're communicating in English - how can it not be important?

[KOCOUR]

Since we're communicating in English - how can it not be important?

Since we seem to be only two people here who (each in his own way) cares, how it can be?

[Mr Shifty]

http://www.phy.olemiss.edu/~berti/colloquia/PTE000460.pdf

[Themohawkninja]

Since we seem to be only two people here who (each in his own way) cares, how it can be?

Third actually. If you are going to learn a language, it's worth learning it correctly (which I do understand will take a lot of time, especially for English).

OT: Since, as people pointed out, it would be difficult, due to the fact that magnetism works with two poles, and not just a given density, would this mean that the two bodies would be tidally locked to each other?

[Brabbit1987]

Third actually. If you are going to learn a language, it's worth learning it correctly (which I do understand will take a lot of time, especially for English).

OT: Since, as people pointed out, it would be difficult, due to the fact that magnetism works with two poles, and not just a given density, would this mean that the two bodies would be tidally locked to each other?

First of all, even if you learn a language correctly that doesn't mean people do not make grammar and spelling mistakes. Let me think, English is my first language and spent my entire life in school with English classes, and yet here I am today and still have grammar and spelling mistakes. Keep in mind I have an IQ of about 130. So it is certainly not like I am stupid either. It's simply just not my thing.

[Bunsen]

Short answer: I don't think so. It's possible for certain mathematically ideal starting conditions (particular alignment of the magnet's field and a perfectly circular orbit), but the one case I know of is unstable and I suspect the other options are worse.

The big difference between this and a gravitational or electrostatic orbit is the fact that magnetic dipole fields fall off as 1/r³, not 1/r², and the force on a dipole is not proportional to the field strength. Two permanent dipoles (think two fridge magnets) will exert a force on each other proportional to 1/r⁴. A magnetic, but not permanently magnetized, object (think a little iron ball near a permanent magnet) feels a force that falls off even faster -- 1/r⁷ if you approximate its magnetization as linear in the external field. That force also depends on how the magnetic moment is aligned relative to the external field -- it's attractive if they're parallel, repulsive if they're antiparallel, and zero if they're perpendicular.

Even if we take the simplest version of this situation -- two permanent magnets, aligned so as to produce maximum attraction (and zero torque), starting in a perfectly circular orbit so the magnetic force provides the centripetal acceleration -- it falls apart as soon as you breathe on it. The perfectly circular orbit works, but the tiniest deviation from circularity causes the orbit's eccentricity to grow exponentially (it also quits being elliptical, so eccentricity is a crappy term to use, but whatever), until the periapsis goes low enough for a collision. That happens for any central force that falls off as 1/r³ or faster, and we have 1/r⁴. Here's a reasonable description of why if you're not afraid of calculus.

The more complicated versions, where the magnets don't stay at a fixed relative alignment, are probably unstable in more complicated ways. Rotation of the magnets comes into play, because they exert large torques on each other and can exchange spin angular momentum for orbital angular momentum, and now you have more degrees of freedom to worry about. Somebody with too much time on his hands could probably solve for a few example cases, but I'm not that bored right now.

You can't "orbit" the magnetic field sideways, magnetic force will always follow the field's direction, so really, that's not possible because the magnetic force is not a force that just attracts the other body but it creates a field that can interact with the other one's field.

That's not true. The force on a magnetic dipole isn't along the field -- it's along the gradient of the field. A magnet that's aligned parallel to an external field will be attracted to regions where that field is stronger. If it's aligned antiparallel to the external field, it'll be repelled from strong fields. If it's perpendicular to the external field, it will feel no net force.

The metal objects would need to be EXTREMELY magnetised before they would have a greater magnetic pull then the gravitational pull.

Really? I've got some little chunks of neodymium/iron/boron mix on my desk here whose magnetic interactions, when they're close together, are 12 or 13 orders of magnitude stronger than their mutual gravitational interactions. It all depends on the scale.

http://www.phy.olemiss.edu/~berti/colloquia/PTE000460.pdf

That's electrostatics, not magnetics. It's still (mostly) monopole fields, so it follows very nearly the same math as gravitation. It's interesting to see how far it deviates from ideal 1/r² behavior due to some fairly small influences, though.

[Themohawkninja]

First of all, even if you learn a language correctly that doesn't mean people do not make grammar and spelling mistakes. Let me think, English is my first language and spent my entire life in school with English classes, and yet here I am today and still have grammar and spelling mistakes. Keep in mind I have an IQ of about 130. So it is certainly not like I am stupid either. It's simply just not my thing.

No need to get so hostile, I said I understand it takes a lot of time. English is my native language, and I still have a lot of grammar questions.

[Brabbit1987]

No need to get so hostile, I said I understand it takes a lot of time. English is my native language, and I still have a lot of grammar questions.

lol XD, wasn't getting hostile, was just making a bit of a point.

[Bunsen]

Can we try focusing on the physics thing here? There's a perfectly appropriate place for useless debates about who should be how grammatically correct in which language, and it's about three forums that way: ↓

[Brabbit1987]

Can we try focusing on the physics thing here? There's a perfectly appropriate place for useless debates about who should be how grammatically correct in which language, and it's about three forums that way: ↓

Would have been better to not of said anything since I am pretty sure we where done. I really don't know why people get their feathers all roughed up when the topic goes a little off. Only makes things worse, not better.

However, yes, back on topic.

Really do not have much to add to it to be honest. Nor do I think many others do either. Which I think is the main problem.

[MinerEdgar]

Interesting how people still think, that something as unimportant as english grammar still matters in international forum, where most people have english as second or maybe third language.

I'm sorry it it just bothered me.

[Cheebsta]

I really doubt so, the object would crash into the other object it's orbiting before completing a single orbit.

This. Unless maybe said orbiting object also has a very effective way to rotate itself 180 degrees in place and use repulsion, and probably some acceleration, to travel to the other side of the field?

Also, interesting how people think that matters at all, international forum or not. If a post is understood by 95% of the people who read it, and you complain about it, you're making yourself look dumb, not the other way around.

[Natsarugiy]

Thanks to the International Space Station and the curious astronauts on board, we have an example of magnetic orbits that you can watch by

. Now this is not a sphere, so unfortunately it doesn't completely answer your question, but it is an orbit that exists thanks to electromagnetic forces acting on the satellite by the parent body. The system is even experiencing zero g-forces thanks to it being in orbit. Orbits like this can exist (although they seem to be highly unstable) in a controlled environment. However, such an event would be nearly impossible to find in nature as gravity would quickly destroy the balance between momentum and the electromagnetic forces in the system and it would either end as a satellite guided by gravity, or a solid object bound together by electromagnetic forces.

[Brabbit1987]

Thanks to the International Space Station and the curious astronauts on board, we have an example of magnetic orbits that you can watch by

. Now this is not a sphere, so unfortunately it doesn't completely answer your question, but it is an orbit that exists thanks to electromagnetic forces acting on the satellite by the parent body. The system is even experiencing zero g-forces thanks to it being in orbit. Orbits like this can exist (although they seem to be highly unstable) in a controlled environment. However, such an event would be nearly impossible to find in nature as gravity would quickly destroy the balance between momentum and the electromagnetic forces in the system and it would either end as a satellite guided by gravity, or a solid object bound together by electromagnetic forces.

Thanks, pretty neat video.

[Bunsen]

Thanks to the International Space Station and the curious astronauts on board, we have an example of magnetic orbits that you can watch by

. Now this is not a sphere, so unfortunately it doesn't completely answer your question, but it is an orbit that exists thanks to electromagnetic forces acting on the satellite by the parent body. The system is even experiencing zero g-forces thanks to it being in orbit. Orbits like this can exist (although they seem to be highly unstable) in a controlled environment. However, such an event would be nearly impossible to find in nature as gravity would quickly destroy the balance between momentum and the electromagnetic forces in the system and it would either end as a satellite guided by gravity, or a solid object bound together by electromagnetic forces.

Cool video, but that's also electrostatics, not magnets. Some similar physics applies, particularly since the attractive force is mostly due to the water droplet being polarized by the rod's electric field, which gives you 1/r^>=3 behavior for the force (depending on whether it's near a uniformly-charged section of rod, or closer to the end or some other nonuniformity) and unstable orbits. You don't get to see the alignment dependence that magnets would give you, though.

It would have been cool if they had also done it with a strongly charged droplet (which you could get just by squirting it out of a grounded conductive tube near the charged rod). You'd be able to get stable orbits that way, and see lots of strange orbital mechanics that we don't usually see because all our central bodies are more or less spherical.

[Kmuster]

You can't really talk about ferromagnetism the same way as gravity because you can't have a monopole. The metal sphere would be pulled more strongly to the poles than to the equator, so the orbit wouldn't just be elliptical, it might be peanut shaped. But I think it's doable, probably not stable though.

[Mr Shifty]

You can't really talk about ferromagnetism the same way as gravity because you can't have a monopole. The metal sphere would be pulled more strongly to the poles than to the equator, so the orbit wouldn't just be elliptical, it might be peanut shaped. But I think it's doable, probably not stable though.

I don't think you could get a stable orbit around a ferro-magnet simply because of induced currents in the orbiting object.