Protecting astronauts from radiation
One of the main obstacles we currently face in sending people to Mars is cosmic radiation. How will we protect the astronauts on board from these potentially deadly rays? Ruth Bamford from the Science and Technology Facilities Council thinks she may have the answer and it's not all that dissimilar from how the Earth protects us from radiation, as she explained to Chris Smith...
Ruth - Out in space, there are lots of small particles that are accelerated at very high energies and can penetrate deep within the body and cause lots of damage.
Chris - What sorts of particles are there, what are they called?
Ruth - Well, they're protons and electrons, the substance of the sun and they're accelerated by the explosions on the sun.
Chris - I suppose then that you get these particles, they're going at very high energies and given that they're very small, they're capable of penetrating the skin of say, your spacecraft and then if you happen to be in the way, they're going to go through your body and they could well interact with the cells in your body and act a bit like a microscopic missile.
Ruth - Yes, that's exactly right. They go through the whole of the spaceship and then they're able to penetrate deep inside the body just like microscopic bullets and can damage nerve tissue and cells and cause organ failure ultimately if they're in very high numbers.
Chris - Are you saying then that it's not such a risk of getting cancer because of damage to your DNA that you might not even live long enough to get cancer. If you had a big dose of these things, they could just wreck your cells and all your tissues and make you acutely unwell just during your space journey.
Ruth - Yes, that's right. They reckon that the general quiet time solar wind is sufficiently low for you to be able to survive a trip to Mars. So long as there isn't a big storm that produces a large of number of particles at very high energies and if that happens the human body can't deal with it and you get acutely sick, and potentially could die. But even acutely sick is threatening for the entire crew to be in that state.
Chris - Obviously, we can't take that chance. We want to come up with some kind of way of dealing with this. But given that the Earth is effectively a spacecraft, it's in orbit around the sun, the Earth must be being hit with these streams of particles all the time. So, why aren't we seeing them here at the surface?
Ruth - Well, we do see a small fraction of them but we have a couple of lines of defence. The first of which is the Earth's magnetic field that helps to slow down the particles and deflect a lot of them. Then after that, we've got the Earth's atmosphere which does a good job of cutting out a good fraction of the particles that otherwise would hit us.
Chris - What about when we put things into space then? If you look at the International Space Station for example, are the astronauts there subject to more radiation?
Ruth - The astronauts in the International Space Station encounter about 200 times the radiation we do on the ground, but the Space Station is still within the Earth's atmosphere, right at the edge. So, they are still partly protected by the Earth's magnetic field in any event. But even so, they do have like a panic room, which they have had to use on occasion when there have been big storms.
Chris - And such a room wouldn't be practical for our craft that we want to send to Mars?
Ruth - I would expect that a Mars ship would have an extra shielded room but it can be because you don't have the Earth's magnetic field and the Earth's magnetosphere protecting you that the energy and the particles you're encountering will go through that because we believe it goes through meters of concrete.
Chris - So that being the case, what approach can we take then in order to protect our astronauts so that if there is a storm, they're not fried in their spacecraft?
Ruth - What we would like to do is take a leaf out of nature's book and try and put an artificial magnetosphere around the spacecraft.
Chris - How do you intend to make the field?
Ruth - What we'd expect to do is make a very large loop of superconducting material and energise that if it's needed for a storm, using the power that the rest of the time is being used to power the spacecraft systems.
Chris - I see and you use the fact that you have a coil to create the field you need.
Ruth - Yes, that's right.
Chris - How strong would the field need to be because that doesn't sound like a very big solution? It sounds pretty simple really.
Ruth - Well, it's simple in concept but in fact, the interaction is immensely complicated. From our study, it's looking much more credible level of power for a manned spacecraft. So, you're talking about a few tesla for a magnetic field.
Chris - To put that into perspective, that's sort of roughly on par with the intensity that you get in a hospital MRI machine, isn't it?
Ruth - It's even less.
Chris - Once you create that field, what does it then do to the spacecraft in order to mean that these particles with formally the ability to penetrate meters of concrete are suddenly tamed?
Ruth - Well the magnetic field acts on the two charges in the solar wind. You have your negatively charged electrons which are very light, and you have a positively charged protons which are the hazard that you're concerned about. So, a magnetic field will pick up the electrons very quickly and redirect them because they're so light. The ions, the protons would normally find it quite difficult to follow the magnetic field lines. But they notice if they've lost their electrons because that sets up a space charge, an electric field and it's that electric field that then pulls back on the ions and will redirect them, hopefully away from the spacecraft.
Chris - One therefore thinks that were you to transplant this approach to an interplanetary vessel, it could work then.
Ruth - We're very hopeful that it could.