# How strong would a magnetic field have to be to protect interplanetary craft?

The following suggests that this is a possible idea to protect crew on interstellar space flight: Is NASA doing research on "mini-magnetospheres" to protect crew from radiation in space?

The strength of the Earth's magnetic field is 25-65 micro-Teslas at the surface according to wikipedia, but it is projected across the entire planet, so requires a lot of energy to create.

My hypothesis is that creating a similar magnetic field over a smaller craft, even just for the crew quarters, would require far less energy, and possibly be able to be created by extending solar panels during flight. Would this be enough to protect a craft during interplanetary flight from the radiation of the Sun?

I ask this also because another question was answered suggesting that you'd need a much weaker field at the source: How much power would a spacecraft's magnetic shield require?

Of course, this is at the source and not the surface of the craft, but by my estimation a 0.1 Tesla field at the source would be .0000001 tesla or only 1 micro tesla at 100 meters away. I would have thought it to be 2.5 Tesla at the source for proper protection.

How powerful should it actually be to get the same protection that we have on Earth, and how much power would that take to produce on a craft? Could it be solar powered?

• Field strength is not the only consideration. The extent of the field matters. The strength determines how much it curves the trajectory of incoming charged particles, but the extent determines whether the curve goes on long enough to divert particles away from the spacecraft. Oct 10, 2019 at 9:34
• Possible duplicate of How much power would a spacecraft's magnetic shield require? Oct 11, 2019 at 5:48
• Thank you for the comments, let me have some time to think about how my question differs from the one you posted as I did in fact post that myself as having got information from it. It didn't satisfy my curiosity, and I would like to properly clarify how it did not. I'll be back to this in a few days once I've collected my thoughts on the matter. Oct 12, 2019 at 0:58
• @ChthonicOne a good way to make this even less-answered by the linked answers, and to make it more specific, would be to specify a scale or size. As SteveLinton points out charged particles have a radius of curvature at a given field strength. It's written $B \rho$ and called magnetic rigidity. A giant Earth-sized ship with an Earth-sized dipole-generating coil might get away with 1 gauss since the field drops off over thousands of kilometers, but a tiny 3 meter capsule might need a field of many kilogauss or over 1 Tesla.
– uhoh
Oct 12, 2019 at 4:57
• So if you specify a size, I'll write a specific answer!
– uhoh
Oct 12, 2019 at 4:58