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Sunday, August 19, 2012

Cosmic Pollution

    We are getting pretty good at sending probes to other planets. Voyager, Cassiopia, and now Curiosity, have shown we can build complex devices, launch them into space, have them survive for long periods of time and  function reliably.
   Sending a probe to another star is another matter.  The main problem is having a rocket engine that can provide thrust for a long period of time. Today's rocket engines burn out in a matter of minutes, or even seconds. They are designed to generate large amounts of thrust for short periods of time, which is necessary to get out of Earth's gravity well. But once you are in orbit, that is no longer a requirement.
    In order to to provide thrust for a long period of time, you need to meter out the mass you are expelling as a propellant, and in order to get any appreciable acceleration out of such a small amount of mass you need a very high exhaust velocity. Rockets are very impressive: they make a great big roar and shoot out huge flames and clouds of smoke, but their exhaust velocity, in cosmic terms, is pitiful. What we need is something that can accelerate matter to very high velocities. What we need is a particle accelerator. I mean they accelerate particles to pert near the speed of light. You really couldn't ask for anything faster. Of course they are big, cumbersome, heavy and have some kind of unknowable power requirements, but if we are operating in space and on a scale of years, I think we could manage.
    One of the draw backs of particle accelerators is that they only accelerate sub-atomic particles, in particular protons and/or electrons, because the magnets they use only act on charged particles. So you would have to be making a continuous supply of charged particles to feed them. And if you making protons (from hydrogen, say) where do all the electrons go? Wouldn't they leak out, and be drawn to the protons so they could recombine to make hydrogen? And what would that to your carefully created thrust? Hmmm.
    Then I had another thought. There are basically two kinds of cosmic rays: various sub-atomic particles, and very high velocity iron particles. Wait a minute! Iron is magnetic. Couldn't we feed our particle accelerator iron particles? Iron is heavy. We could generate a boat load of thrust from hardly any mass, providing we can get it going fast enough, and in a vacuum with enough electromagnets, we should be able to do that. Granted our linear accelerator might need to be really long. The ones here on Earth are sometimes miles in length, and they are only accelerating tiny bits of stuff. Building one to use for propulsion might need to be, I dunno, ten miles long?
    We have all the science we need to do this. We know how to build nuclear reactors that generate electricity, we know how to build linear accelerators, we know how to make little particles of iron, we know how to build really big things (like bridges and damns) and we know how to put stuff in orbit. All we need is the determination.
    As a bonus, I've figured out we aren't alone. All those cosmic rays I was talking about earlier? The ultra-high velocity iron particles? They are the exhaust from alien intersteller space craft!

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