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A superconducting shield for astronauts

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"Captain, magnetic shields at 50%! We've got to pull back." -- some future space traveler.

I remember some interesting discussions about magnetic shields in the NASA technical journal, but there were issues with things like electronics inside the shield and conductive cabling going through it to sensors outside of it. Even in the more detailed site (http://www.sr2s.eu/2013-08-01-15-34-14) I didn't see a lot of info on those sorts of "known" issues.

This appears to be merely a mag-sail, but used as a radiation shield.

It seems to be in every way inferior to the m2p2 concept, which uses a mini-magnetosphere (instead of just a magnetic field) for the same purpose [1]. The advantage being that we could build and field such systems using existing technology at reasonable cost.

1: http://earthweb.ess.washington.edu/space/M2P2/rad.shielding....

Just out of curiosity, I wonder if it would be possible to embed the superconducting magnets in a spaceship's liquid hydrogen tank. This would eliminate the need for "exotic" high temperature superconductors.

It's plausible, but cryogenic fuels are currently only used on takeoff. This is because there's no way to keep your fuel cold; that plume of vapour you see from the top of rockets on the launch pad? That's fuel being vented because as the temperature slowly rises and the fuel boils. Once you reach orbit you typically switch to a different fuel, which will keep. Deep-space vehicles tend to use hydrazine. Voyager 1 still has hydrazine in its tanks which is 38 years old and it still works fine.

If you're capable of keeping cryogenic fuels cold in, say, the rings of Jupiter where such a shield would be useful, then you've probably got power to burn and don't need to resort to that sort of hack.

Hydrogen as well as methane and propane etc were looked at for Constellation's lunar module Altair some years ago. You save a lot of weight since it's much more efficient than hydrazine.

At least for the lunar descent you could use hydrogen, that's the most mass anyway and you don't need to worry about heat management at the surface anymore.

https://en.wikipedia.org/wiki/Constellation_program#Altair

Lockheed Martin has been working on lots of technologies for long term flights with Centaur stages. You could have onboard refrigerators etc.. It's not so strange nowadays as it was in the sixties.

A long-range spacecraft would probably not have LH2 on board. It evaporates quite quickly unless you want to install cryo cooling systems and the power to run them.

Boil-off is a bigger problem with LH2 than with liquid oxygen or liquid methane. However, I'm under the impression that it's a tractable problem out to months or maybe even years. Apparently the Spitzer Space Telescope maintained a supply of liquid helium for about five years [1][2].

A lot of Mars manned-mission proposals (starting with Zubrin's Mars Direct plan) depend on the use of a Sabatier reaction which would convert hydrogen brought from Earth into Methane and Oxygen. So the experts must think they can at least minimize boil-off over at least 8 or 9 months. [3]

[1] https://en.wikipedia.org/wiki/Spitzer_Space_Telescope

[2] http://www.spitzer.caltech.edu/news/436-ssc2009-12-NASA-s-Sp...

[3] https://en.wikipedia.org/wiki/In-situ_resource_utilization#M...

Mars Direct uses suspiciously low boil-off rates for LH2. Certainly well past current state of the art. Best achievable (not flown, but could be) is 0.1%/day, and Mars Direct wants 0.1%/month. You don't lose a lot at 0.1%/day, but it adds up.

At 0.1% per day, I get 30% boil-off in 1 year (0.999 ^ 365 ==> 0.694), which is expensive but probably still a net win. I don't think boil-off is a problem once you're on Mars because you can probably just use the hydrogen gas as feedstock into the Sabatier process.

Which is not to say that Mars Direct isn't overly optimistic, possibly about many other things as well.

That reminds me of the Arthur C Clarke story 2010, where he says they used ammonia instead to avoid the boil off.

Now, if you would please strip your spacestation of all metalls and arrange for propulsion to counter the small drag of earths magnetosphere upon the system...

Or are the magnetic fields generated and the corresponding heat from induced eddys not so strong? The sceptic in me wants to know more before feeling optimistic..

Supraconducting magnets allready exist in Magnetic Resonance Tomography and the idea of a cookoff in space after a micro asteroid impact...

Is power consumption a problem here? It seems like power production on a space craft would be quite limited (solar, plutonium?) and this thing would consume a lot of it. Is the idea that this would always be on or only on in an emergency? Also, is interference w/ electronics on the craft a problem?

It's easier to supply power than mass in space, and mass shielding is the alternative.

Solar is problematic on Earth but is actually quite good in space. Lots of reliable energy right there, especially if you're not in Earth orbit (where the shadow occasionally gets you).

If you're in deep space then you're not near any particular star. That's going to reduce the available starlight by several orders of magnitude, right?

Sure, but if humans are going into deep space (beyond Mars in this case) then we're talking about nuclear propulsion at least which means you've got lots of power.

When people designing real spaceships say "deep space" they mean "beyond Earth orbit", but usually not past Mars.

In sci-fi deep space, yes, you'd have next to no solar power. (In fact, it's minimally useful in the solar system past Jupiter.) But if you can get there at all, you're probably not worried about that.

Makes sense, thanks

You only lose power when you deflect particles, and maybe when you radiate some photons as you move through space. Intuitively, both effects seems like they would be fairly small.

Given how little shielding would be required to protect the astronauts, nuclear power would be quite effective.

Is it possible to make a magnetic configuration that will repel all charged particles?

Won't particles moving in the right direction be attracted and you'll irradiate everyone inside when they slam into the shield, with some extra energy from it?

I'm guessing there would be multiple shields in a configuration to funnel any radiation away from the crew sections. But I still think you would need to harden the ship with some material like water to impede the fastest particles or something even more dense.

The nice thing about magnetic fields is that all charged particles are deflected: the positive ones bend one way, and the negative ones bend the other.

In a lot of situations, the particles will actually spin along helical paths whose net motion is along the magnetic field lines. In the case of Earth, that means that the charged particles eventually make their way to one or the other pole... and as the field lines descend into the atmosphere, those particles create auroras. Neat stuff!

That's why the comment you've replied to says "particles with the right direction", not "particles with the right charge".

Well the planet Earth has a nice shield with exactly this issue. Particles are channeled to the north and south poles, where they hit the atmosphere and generate the colourful aurora in the sky :)

So perhaps there's going to be a cool spaceship with it's own aurora?! Or you could try and channel the particles into a collecting device, bombard them into a fluid, trigger muon generation and try to catalyse a fusion reaction. Probably wouldn't break even but it'd be fun to try.

Though on Earth it's our atmosphere that stops the high energy particles.

I wonder how much cooling superconductors need in space.

Basically, how warm is the interior of a satellite with a high albedo (gold foil?) in the inner solar system?

Thermal management in space is a big issue. The ISS has big radiators on the long truss, and lots of plumbing for cooling.

For a superconducting magnetic shield, it depends how much power is used to maintain it. MgB2 supports high currents compared to cuprates, so I guess once it's turned on it doesn't need much?

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