Electrostatic Radiation Shielding
Published on Oct 23, 2009 at 7:23 pm.
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Filed under space exploration, space radiation.
Clearly carrying heavy shielding to protect astronauts from radiation in space is expensive. If you havent’ been reading my space radiation series as I’ve been posting, then you can look over the last several of my postings about space radiation to see some of the problems. So, some other strategy may be the way to go to shield against radiation. One idea that I ran across a while ago was electrostatic shielding. Space.com did a good article on that a few years ago.
The basic idea is that like electric charges repel. So, an object with a very large positive charge would repel incoming positively charged particles, like protons. The idea sounds really good at first glance. However, as with many ideas, further study shows that there are some considerable difficulties that need to be worked out before it is truly a viable shield. Working out those difficulties, though, means a lot of time, effort, and hours from scientists and engineers. They need to be paid a salary. It also means experimentation, building simulations, computing, etc. All that requires money, too. Unfortunately, I think that far too little money is being spent at this time on working out all of the problems any time soon. Of course, so little money is being spent on extending space exploration in the US that it will be a very long time before we even need an effective radiation shield.
So, what are the problems with an electrostatic shield idea? Well, the first problem is that it would do nothing to shield against X-rays or gamma rays. Also, if positive charged bodies are used, they would only repel positive particles, like protons. They would even pull in negative particles, such as electrons! So, one strategy would be to have a multiple layer shield. One layer of the shield would deflect protons, and the other would deal with the electrons. Depending upon who you ask, the outer layer might be negative to repel electrons (they are easier to deal with than the heavier protons), and the inner layer would repel the protons. Conversely, the outer layer could be a strong positive charge to repel the protons, and the inner layer negative to handle the electrons that were accelerated by the outer shield. There are advantages and disadvantages to each approach, of course, and I don’t want to go into all of the technical details of each.
But, there are some more serious matters to contend with. First, what sort of charge and voltage would be needed to repel the charged particles? Well, that depends upon the energy of the incoming particles. Solar particles are much slower than galactic cosmic rays, and are thus easier to deal with. Also, solar radiation is almost entirely protons and electrons, while galactic cosmic rays have a higher percentage of heavier nuclei. The voltage required to shield against the particle increases roughly as the weight of the particle. But, the really big problem is that galactic cosmic rays move much faster than solar radiation particles. Galactic cosmic ray particles often move at very near the speed of light. The voltage needed increases roughly as the square of the velocity, so it would take a very high voltage to block the galactic cosmic rays. The charge on the deflectors is related to the voltage, so that means a very large charge would be needed, and that requires a very big power source. The power requirements of the shield are another issue that has to be dealt with. It may be that electrostatic shielding simply won’t be effective with galactic cosmic rays. But, I think that it could certainly be made to work for solar radiation. It may even work for the most common forms of galactic cosmic rays, but if so, then that’s OK. The heavier particles are far less common, and radiation exposure due to them alone during a mission might be within acceptable limits. Further work is needed.
-Astroprof
Image Credit: NASA/ASRD Aerospace Corp./ Charles Buhler
