Radiation shields in space

17 June 2014

Interview with

Ruth Bamford, Rutherford Appleton Laboratory

Looking heavenwards now, one of the biggest dangers while travelling in space is Cosmic Raysexposure to potentially lethal bursts of radiation from the sun. These can flare up during periods of increased solar activity known as solar storms.

Currently, we have no way of protecting astronauts. The Apollo moon missions in the 60s and 70s avoided them purely by chance.

But now, the moon may have provided us with an answer: dark patches on the surface - known as lunar swirls' - have given physicists an idea for a way to shield our spaceships in the future. Ruth Bamford is heading this work at Oxford's Rutherford Appleton Laboratory, and explains why this radiation is such a problem...

Ruth - Well, this particular type of radiation consists of energetic particles that are more akin to what you would see in a particle accelerator. And they are so fast they can go through the hole of a spaceship and smash the DNA of the astronauts. During a storm, so many of these can occur that it's beyond the body's capabilities to repair.

Chris - When you say there can be so many of them, what's the likelihood of someone on a space journey coming into contact with these sorts of levels of radiation?

Ruth - The levels occur during a storm and those storms are intermittent in their occurrence. So on average, the sun will give out two or three of these big events a day during solar maximum and about the same during solar minimum a week. They don't all come our way, but if you are in the way and you're on a long journey for a year and a half to Mars then the chances of one passing through the spacecraft are too high to be acceptable for the astronaut's safety.

Chris - Why can we stop this radiation because we can do that on Earth?

Ruth - Well, we have the Earth's magnetic field producing a barrier, a first line of defence and then we have the Earth's atmosphere. We can't put large quantities of material on a spacecraft because it would be too heavy. So, things like lead or concrete which is what you might consider make a good shelter on the Earth won't work in space.

Chris - We obviously can't cart those up into space because they're far too heavy. So, what could we do instead?

Ruth - Well, we have to get smarter and this is where the examples of what nature has offered us comes into play. We start with a magnetic field, but if you just use a magnetic field to deflect charged particles, because they're so fast, you'd need an enormous magnetic field to do the job. So, what we do in fact is, we're proposing you gather the substance called plasma from the solar wind and use it, captured by the magnetic field to help hold back the charged particles by adding an electric field to your magnetic f ield.

Chris - Okay, well let's unpick this a little bit. So, you've your spacecraft going around in space. Talk us through the first thing you'd have to create to create this shield you have in mind? What's the first thing you got to do?

Ruth - Like the Earth, we start off with the magnetic field. So, the Earth has a magnetic field. It's very low intensity magnetic field even here on the surface of the Earth, but it's still capable of holding back this radiation from space. The way it does it and the way we're proposing to be able to put one on the spacecraft is by gathering the solar wind particles which are in the vacuum of space. So, between here and Mars, it isn't really a vacuum. In that sense, there's a sparse number of protons and electrons, the component parts of hydrogen atoms are coming naturally from the sun, that are flying off in the solar wind. And we're suggesting that you capture these and hold and control them by the magnetic field that you bring on-board with you.

Chris - So, you have a spacecraft which has its own magnetic field. It's generating a bit like the Earth's magnetic field, this will capture some of these particles that are natively floating around in space, these protons and electrons, and once you've got them stuck into this magnetic aura around your spacecraft, then what do you do?

Ruth - Then you've got an electric field helping the magnetic field and you'll produce a narrow electric field some distance from the spacecraft. So, the spacecraft is safe from this electric field. The idea is that, much like you would deflect a charging rugby player with an ankle tap or push to touch, what you need is enough of an electric field that will deflect rather than stop these hazardous energetic particles that would otherwise go through the spacecraft.

Chris - I see. So, the capture of the charge particles in space gives you that electric field which then extends the reach of the protection you've got around your spacecraft so any more stuff that comes flying past gets enough of a push so it's off course and it misses or swerves around your spaceship. It doesn't go through your astronauts inside.

Ruth - Yes, that's the idea. During a really big storm, you can release some of this plasma yourself from the spacecraft, from a gas canister and even for a mission to Mars, the quantity of gas you would need, being no bigger than say, a fire extinguisher. So you wouldn't need vast quantities.

Chris - How would you power the magnetic field in the first place? Would that be solar or a nuclear or something to give some source of magnetism to start the process off in the first place?

Ruth - You would need a magnetic field on-board the spacecraft and the suggestions are that the superconducting magnet would be the most practical. It would be powered by whatever is powering a manned spacecraft which currently, they suggest it wouldn't have to be a nuclear power source because with a manned mission, you're going to require quite a lot of power in general.

Chris - This is theoretical at this stage, isn't it? Have you got any plans to - or anywhere you can test this?

Ruth - Well, we have tested it in small scale in the laboratory and we've also been looking at natural mini-magnetospheres - as they're called - on the moon. This has shown that it does actually work in space and at the dimensions that we needed to. There's a little feature on the moon, on the eye of the man in the moon, his left eye, a bit like a tear. It looks like a patch of white on the dark area of the moon, and that little patch of white is called Reiner gamma. It is being protected by a small patch of magnetic field that naturally occurs on the moon because the moon doesn't have an overall magnetic field of its own. It would appear that for the eons that it is being there, that little magnetic anomaly. It's been able to keep away all these hazardous particles sufficiently to change the colour of the moon.

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