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/sci/ - Science & Math

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3904550 No.3904550 [Reply] [Original]

Question for /sci/:

How much power would it take to produce a magnetic field as powerful as Earth's, strong enough to repel cosmic rays, over a colony that's about 1 mile in diameter?

>> No.3904557
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3904557

hahahahahahaha oooooooowh

>> No.3904562

With a permanent magnet, none.

>> No.3904563

A lot.


fucking "jiggawatts" for sure.

>> No.3904566

>>3904562

1)

>strong enough to _______


2)

>2011
>believes that a bigger magnet == stronger field

nope.

>> No.3904571
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3904571

>How much power would it take to produce a magnetic field as powerful as Earth's

mother fuck

>> No.3904573

Hey at least the OP didn't ask for a Jupiter-strength field

>> No.3904580

>>3904566
>Implying permanent magnets aren't capable of producing fields as or more intense than Earth's magnetic field
http://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Intensity
>The intensity of the field is greatest near the poles and weaker near the Equator. It is generally reported in nanoteslas (nT) or gauss, with 1 gauss = 100,000 nT. It ranges from about 25,000–65,000 nT, or 0.25–0.65 gauss.[8][9] By comparison, a strong refrigerator magnet has a field of about 100 gauss.

>> No.3904587

>>3904550
>>3904550


long term, it would be cheaper (economically) to just bring/manufacture a skin/wall/shield around this hypothetical (I assume orbiting or space-born) colony made out of the following materials:

boron
lead
carbon
oxygen


those all do a pretty good job of stopping or slowing most massive cosmic radiation, which is all that matters anyway.


the boron/carbon will even slow down neutrons (which a magnetic field will not)

>> No.3904593

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/solenoid.html

Magnetic Field strength of earth minimum = 30 microteslas

You're going to have to find out the materials used for the solenoid and other factors yourself.

>> No.3904596

Also the strength of a magnetic field at increasing distances is 1/d³

>> No.3904605

>>3904580

you don't get it: A boulder sized magnet does not produce a STRONGER field than a tiny magnet made out of the same material (neglecting "tiny" enough for molecular/atomic issues to come into play)


the only difference is that the field created by either magnet occupies more/less space.


Earth's field is as strong as it is in the atmosphere because the spinning iron at the core is fucking gigantic.

its the size of a small moon or a big fucking asteroid..


much much bigger than 1 mile in diameter.
in order to get a field as strong as the earth's, outside of a structure that is 1 mile in diameter, with the magnet situated at the center....

here comes the key:

from a magnet that is not gi-fucking-gantic

you will need a fuck ass powerful magnetic field emanating from a fuck ass powerful electromagnet.


either that or some kind of specialized halbach array as the "skin" of this hypothetical structure.

>> No.3904630

>>3904605
>from a magnet that is not gi-fucking-gantic
That was not one of OP's premises. Your whole argument is invalid.

>> No.3904647
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3904647

Hhmm, you'd need to inject the core of Mars with liquid iron, then get it rotating.

Maybe you could use a different metal for a different outcome..

>> No.3904651

>>3904647
dumb bitch
doesn't even have an integrand

>> No.3904652

>>3904605
Couldn't we just Faraday cage the station?

>> No.3904654
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3904654

>>3904651

>> No.3904657

>>3904630


I was never referring to OP in that part of the argument.

i was referring to the guy who said you would not need "power" because you could use a permanant magnet.


to create a magnetic field that is 30 microtesla when measured outside of a 1 mile diameter sphere....


you would need

1) a gi-fucking gantic permanent magnet that fills up most of the volume of this hypothetical 1 mile diameter sphere

2) a reee-fucking-diculously powerful electromagnet, which is much much much smaller than the gigantic permanent magnet from 1.


THAT was the issue:


if you wanted to mimic the strength of the earth's field, you need a big magnet.


Earth has a big magnet at its core. its a big fucking magnet, and yet it only produces 30 microtesla in the atmosphere.

that is because its both far away, yet big enough to maintain a field of microtesla even many thousands of miles away (eg: thousands of miles from the surface to the center of the earth).


if you wanted to do this with a 1 mile diameter sphere, the permanent magnet would need to be very very big to produce that field outside of the sphere's surface.

it would take up the majority of the space inside the sphere and it would weigh hundreds of thousands of tons.

>> No.3904663

>>3904654


I saw that exponential of an integral way over there in the bottom right corner.... and I thought maybe we were doing some path integrals.


then i realize it was just an integrating factor and I relaxed.

>inb4 path integral is an integrating factor

>> No.3904671

Wait, if we wanted to make the station safe, wouldn't we take the intergral of the field from the centre to infinity away, to find how much work it can impart upon a particle moving in the path that is the hardest to deflect, i.e. moving directly to the centre of the magnet?

Then again, I am a biom student, so I may be wrong here.

>> No.3904684

>>3904657
so if we compressed the earths magnetic core to say a sphere of radius 1 meter, what would the field strength at the surface of the sphere be?

for reference rare earth magnets hit about 1.5T at their surface.

>> No.3904713

>>3904652
A Faraday cage wouldn't stop charged particles.

>> No.3904774

>colony that's about 1 mile in diameter?

a superconducting ring of about the same diameter

>> No.3904891

>>3904550
none. if you use superconducting wire, your loss will be near zero.

>> No.3906208

I'm a completely laymen here, can any a you eggheads spell it out for me? can we live in space without having mutie kids or not? I'd really love to think we could.

>> No.3906223

>>3906208
Of course it's possible. We even know what to do.
We just don't have the funding or patience to colonize space, which I find to be ridiculous.

>> No.3906233

>>3904891
how does it not violaste conservation of energy that you can make any arbitrary large field (well, up to the critical field of a superconductor) from like a 1mV voltage source

>> No.3906266 [DELETED] 

>>3904654
>exp(-ln(something))
>not 1/something
ISHYGDDT

>> No.3906882

>>3906233

the voltage between any two points on the superconductor is exactly zero. you cannot extract energy from a static magnetic field. the current in the superconducting ring is induced in the same way you magnetize a permanent magnet.

>> No.3907664

>>3906882
i can extract a fuck ton of energy from a magnetic field. take any ferrous or other magnetized material by it and it will gain kinetic energy for free.

you lose "magnetic potential energy" - analog of graviational potential energy, but this magnetic potential energy comes from nowhere. free energy

>> No.3907747

>>3907664
how much energy does it cost to put it there?

>> No.3907775

>>3907747
nothing.

1. have large mumetal/high permeability object
2. have superconductor in large radius coil (field lines through he middle)
3. turn on superconductor (basically zero energy with r=0.0000000000001, typically small non-superconductor wire is used to control current)
4. metal gains energy from field for free
5. turn off superconductor

moving the metal back requires less energy then you gained from magnetic acceleration.

>> No.3907783

>>3907775
altneratively just turn superconductor back on, and reverse the direction and you'll gain energy in the object as it accelerates the other way.

>> No.3907799

>>3907775
>>3907783
the reason this is different from typical magnet energy schemes is because you can't gain energy from a permenant magnet as you wil have to use energy to move backwards AGAINST the field, but with electromagnets (esp superconducting ones) we can turn off the field and we can make the field as large as we want just by increasing the # of turns (concept of magnetic multiplication by geometric allignment of wires defys the laws of conversation of energy)

>> No.3908201

>how much energy does it cost to put it there?
>nothing.
>3. turn on superconductor
>5. turn off superconductor
Is that something you plug in like an electromagnet or are you saying we already have freestanding super conductors?

>> No.3908434

>>3908201
Every single 1.5/3T MRI has that super conductor setup..