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If not for the earth's magnetic field our atmosphere would be bombarded by high energy plasma (ionized gas) from the sun and other space sources. At very high altitudes and orbital altitudes this protection is less and when space travel takes astronauts out of range of earth's magnetic field there is no protection.

Does the International Space Station or other craft have an artificial magnetic field to protect its astronauts? If not are there plans for implementation?

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    $\begingroup$ You may have better luck with this question on Space.SE or even Physics.SE, since you are asking about a theoretical technology. I'm sure that somebody has considered it, but the actual implementation I think is outside the scope of this site. $\endgroup$ – Ron Beyer Jul 11 '17 at 20:38
  • $\begingroup$ The ISS is not shielded because it is below (300/400 km altitude) the Van Allen belts. A shield would be needed if you go out of the magnetosphere, or more accurately, at some altitude before the magnetopause. The latter is not a sphere, but on the Sun side it's about 10 Earth radii, more than the geostationary orbit. If needed, it would require only about 2 or 3 kW to create a protective magnetic field around a spacecraft (Earth field is only 50,000 nT). See this question on Space.SE. $\endgroup$ – mins Jul 11 '17 at 22:08
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This won't work.

What to shield

Most of the cosmic radiation has quite low energies and can easily be shielded by the hull of an aircraft, spaceship or spacesuit. This would also be shielded by the atmosphere, but it would also burn/blow it away over time due to the intensity of the radiation. For luck, the magnetic field of the earth shields us from this radiation before it reaches the atmosphere.

And then there is the nasty stuff. Particles with energies which can easily punch through several centimeters of iron, lead or whatever. This stuff can not really be shielded by the magnetic field of the earth, nor could it be by artificial fields. Even worse, when this stuff hits a nucleus in the hull of a spaceship, it would smash it into many pieces, which will then fly along the direction of the original particle. Yes, this means radiation can be even higher behind a too thin shield! And since this happens in the hull or in the spaceship, one can't shield that by fields outside the ship.

In fact, most of the radiation in aviation is not made of the primary particles from space, but of secondary particles created in collisions between the primary particles and atoms of the atmosphere.

Field strength

The most important factor of field strength of a magnetic dipole is

$$B(r) \sim m/r^3$$

(Yes, to the power of three)

$m$ is the magnetic dipole strength, which for a simple conductor loop is given by current times area enclosed by the conductor.

So, if we build a coil of several thousand windings, resulting in a total current of several thousands of amperes, and an area of some ten squaremeters, we end up with an $m$ of several 10000Am². In contrast, earths magnetic field has about $8\cdot10^{22}$Am², which is a totally different order of magnitude.

Earths field strength might not be high - only about 40µT at the surface, but it reaches far, far into space. So, the time / distance the field acts on a particle is quite long, an can deflect it easily. In contrast, a human-made field will decrease to near zero within just a very few meters, and that's not enough.

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