15 Jul 08
Originally posted by Andrew HamiltonThere is a ratio of anti to our kind of particles, 10 billion regular to 1 anti.
[b]"But it has already been discovered there is a huge supply of anti-matter already present in the solar system"
I simply cannot believe this....
Yes; and you have good reason to not believe it! Any antimatter particles in interstellar space would be gradually annihilate by collisions with particles of protons and electrons in the solar w ...[text shortened]... uld be serious problems if some of that vast amount of antimatter made contact with the Earth![/b]
That is the present abundance of antimatter right now. There was an article in Scientific American about this about a year ago. So if you have a gas cloud with 10 billion pounds of mass in it, 1 pound is going to be antimatter. The reason they don't just collide and make a nice gamma ray pulse is the vacuum of space provides plenty of space for both types to co-exist side by side and never touching. When the average distance between particles is over a meter in outer space, its easy to see how antimatter could be floating around just waiting to be collected. Of course some of the stuff hits the top of our atmosphere all the time but in such small quantities you would be hard pressed to register a hit on a scintillation counter but you can be sure SOME of those hits are directly from an antimatter particle colliding with our type and one by one going ballistic. That leaves a very large volume of space between here and the moon where clouds of matter and antimatter mix with no interaction. So the gist of the article was to make a mesh like chickenwire and charge it up opposite to the antimatter ions and thus preferentially attract the stuff into the mesh where an inner trap awaits that keeps the stuff perpetually out of reach of ordinary matter, concentrating it billions of times. That is the idea and it's for real. Anti and regular matter co-exists in the vacuum of space, since they are always a meter apart between particles of any type.
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16 Jul 08
Sticking with Physics of the known possible...
Interstellar flight is possible but very slow.
Propulsion would be by some kind of reaction drive, (Mass driver, ion, plasma, Nuclear pulse...) powered either by fusion or antimatter annihilation (antimatter is produced by certain nuclear reactions which happen naturally in space, a good place to collect it would be in the Van Allen belts of Jupiter.
The type used will depend on the desired objective, If you want to move a large number of people and not have them sat in stasis pods (or similar) then you need a VERY large spacecraft (dimensions in the hundreds of kilometres) with internal biosphere which wont be able to accelerate very fast (a small fraction of g top). this would probably use nuclear powered mass drivers or ion drive, and accelerate for the vast majority of the journey. If you want to send a small number of people in stasis pods or similar (if floating in pressurised fluid with fluid in the lungs you could withstand greater g forces) then you would have a small ship with either fusion or AM powered plasma drive, which would accelerate hard at either end of the journey. both would take many years to reach there objective (and would not expect to return) so they would have to take the tools required to build a new world with them. I say build because finding a suitable planet is likely to be exceedingly difficult and is likely to be a long way off, whereas a constructed space habitat would be much faster to be habitable and could be built in the optimum location in almost any star system.
On the radiation front, the increase in energy of radiation in the direction of travel is going to be trivial for anything under 99.9 or so light speed, the energy of cosmic radiation is vastly higher than even the new LHC particle accelerator due to be turned on this year which will achieve speeds of 99.99999.. % C.
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16 Jul 08
Originally posted by WheelyThe fusion going on in stars is complicated and depends on the stars mass, this is the proton proton chain which dominates in our Sun. The vast majority of nuclei in the suns core are Hydrogen (H) or single protons. these are continually colliding and a certain proportion do so with enough energy to combine (fuse) at which point one turns into a neutron and kicks out a positron (anti electron) and a neutrino, and becomes deuterium (D) a proton and a neutron. now the logical next step for making He4 is to add two deuterium atoms together however these are so rare (in proportion) that they hardly ever hit. however there is lots of lone protons around which bang into the newly formed Deuterium nuclei and every so often they fuse to form He3 (giving of a Gamma ray), two protons and one neutron. The He3 nuclei could then react with a single proton but the energy required to make that reaction happen is quite high and so is very rare. so rare that the last reaction in the step is that two He3 nuclei collide, kick out 2 protons (or normal Hydrogen nuclei) and form He4 (which is too hard to fuse in the sun during main sequence)
I thought deuterium was fused in many stars instead of hydrogen. If so, there must be a fair bit of it around!
Other reactions will occur but be relatively rare and any unstable products (like tritium) will be rapidly destroyed. Deuterium is found all around you (in water for example) and is a preferred fusion reactor fuel. The most popular choice of reaction for terrestrial fusion reactors is the deuterium - Tritium reaction. (as this has the lowest initial energy input to make the reaction work) the deuterium is extracted from heavy water (one oxygen two deuterium) and the tritium (in a Tokamak reactor) is made in the reactor by coating the reactor walls with an isotope of lithium which releases tritium when exposed to the radiation the reaction produces (obviously an initial primer of tritium is needed to get the thing going).
I hope this overly verbose posting has helped answer your question without being unduly confusing. If so I would recommend having a look at Wiki's fusion page and moving on from there.
16 Jul 08
Originally posted by googlefudgeGranted you would need something large, an asteroid probably, like in the book 'the sparrow' by Mary Doria Russell. You would still need significant shielding which would be provided by an asteroid. An ice comet would be nice! All that water just heat it up and serve! But any interstellar voyage would not go out blind. Telescopes are getting exponentially stronger year by year so in another 30 years or so we should have a handle on nearby stars, what planets there are, and are they in a habital region of the star and what kind of atmosphere, is there methane, oxygen, nitrogen, etc.
Sticking with Physics of the known possible...
Interstellar flight is possible but very slow.
Propulsion would be by some kind of reaction drive, (Mass driver, ion, plasma, Nuclear pulse...) powered either by fusion or antimatter annihilation (antimatter is produced by certain nuclear reactions which happen naturally in space, a good place to collect ...[text shortened]... particle accelerator due to be turned on this year which will achieve speeds of 99.99999.. % C.
It would be incredible if such a planet were to be found in the Alpha Centauri triple system. It could happen on either of the three stars there, the big ones most like our sun of course. But there are something like 100 stars within 20 light years so maybe one of those will show a suitable planet. We should also know in another 30 years if there are any signs of civilization on anything within a couple hundred light years also, radio noise, anomalous IR or some such. From a human POV the ideal planet would be one with an oxygen atmosphere, primitive life and no intelligence, easy to terraform. And hopefully, around one of the stars in Alpha Centauri!
16 Jul 08
1 edit
Originally posted by googlefudgeSure but finding a planet with O2 would make it a lot simpler. I have read stories where they thought about this and ended up building habitats and terraforming at the same time, say living on a moon or asteroid and continuing to terraform the nearby planet in whatever star system you are in. There are 33 stars within 12 light years of earth so maybe we would get lucky. Probably not but I think we will know in the normal progression of science in the next 30 or 40 years. By that time maybe we will be preparing a robot probe to some star system. There are designs that use microwave beams to accelerate basically a mesh with sensors, not a spacecraft as we know it, but a mesh miles wide with little optical or radio sensors by the thousands and very light weight to reach very close to C and it just goes by some system at that speed taking high speed readings as it goes by and transmitting the data back to earth. Practically no hardware, no steering, etc. All done with the microwave beam. That's only one technique I see discussed.
The probability of finding a potentially habitable planet aside. It is far more practical to build your habitat from scratch. The resources and time needed to terraform a planet are much greater than building a from scratch habitat and then terraforming that.
16 Jul 08
1 edit
Originally posted by sonhouse"When the average distance between particles is over a meter in outer space"
There is a ratio of anti to our kind of particles, 10 billion regular to 1 anti.
That is the present abundance of antimatter right now. There was an article in Scientific American about this about a year ago. So if you have a gas cloud with 10 billion pounds of mass in it, 1 pound is going to be antimatter. The reason they don't just collide and make a nic sts in the vacuum of space, since they are always a meter apart between particles of any type.
If you by outer space mean intergalactic space, then I don't object much. In our solar system there is one particle in every qube centimetre. The suns solar wind sees to that.
If the concentration is one antiproton to 1 billion normal proton, even in solar system (not!), doesn't seems very huge to me. ("But it has already been discovered there is a huge supply of anti-matter already present in the solar system"/sonhouse) What will the tecnique be to harvest all these antimatter particles? And how to store them?
16 Jul 08
Originally posted by sonhouseStop drinking.
What do you think will be the most significant problem going to even the nearest star?
In my opinion, based on reading a lot of articles about the issue, my prognostication is this: in the coming century or two, I think we will be surprised by the power of future space drives, mainly in the area of anti-matter drives. Here is my reasoning: while the idea o ...[text shortened]... auri, surviving the coming climate battle with our technology for spaceflight still intact.
16 Jul 08
Originally posted by FabianFnasThe plan is to use a giant mesh, maybe a klick wide, like a giant football but open mesh. The mesh is metal. So its an open mesh like an electric fence, and in fact would be charged up the opposite of the anti particles so would preferentially attract them into the mesh. Then a smaller collector would trap them in a magnetic field keeping them in motion around a magnetic trap so they won't touch regular matter.
"When the average distance between particles is over a meter in outer space"
If you by outer space mean intergalactic space, then I don't object much. In our solar system there is one particle in every qube centimetre. The suns solar wind sees to that.
If the concentration is one antiproton to 1 billion normal proton, even in solar system (not!), do ...[text shortened]... hat will the tecnique be to harvest all these antimatter particles? And how to store them?
I would imagine those magnets would have to be permenant magnets so the thing wouldn't explode if you lost power🙂
The guy who thought of this scheme is presently hawking it to NASA and others. If it works it would be a great boon to spaceflight, forget interstellar! An anti matter rocket could launch the space shuttle with about 30 MILLIgrams of the stuff. It would open up the solar system like roads opened up America.
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16 Jul 08
Originally posted by FabianFnasAs I stated in a previous post. certain nuclear reactions emit anti-particles. These charged particles will float around until they decay or hit their ordinary matter equivalent. These particles being charged will be effected by magnetic fields, such as those generated by planets, these will concentrate charged particles in specific regions (Van Allen belts), the collection method is to place a large magnetic trap in one of these belts which will guide charged particles to a central collector which will then use the particles mass and charge to identify and separate out anti-particles from ordinary matter and then store these particles in magnetic bottles. to collect any kind of significant amount of AM would require numerous collectors of significant size and plenty of patience, but is possible.
If the concentration is one antiproton to 1 billion normal proton, even in solar system (not!), doesn't seems very huge to me. ("But it has already been discovered there is a huge supply of anti-matter already present in the solar system"/sonhouse) What will the tecnique be to harvest all these antimatter particles? And how to store them?
16 Jul 08
Originally posted by googlefudgeNo, I found it all rather interesting. Thanks.
The fusion going on in stars is complicated and depends on the stars mass, this is the proton proton chain which dominates in our Sun. The vast majority of nuclei in the suns core are Hydrogen (H) or single protons. these are continually colliding and a certain proportion do so with enough energy to combine (fuse) at which point one turns into a neutron ...[text shortened]... onfusing. If so I would recommend having a look at Wiki's fusion page and moving on from there.
I remember reading about the larger brown dwarf stars not having the mass to fuse hydrogen but were massive enough to fuse deuterium. Your post was much more informative.
16 Jul 08
Originally posted by sonhouseBut antimatter is not collectable with magnets if they are not charged. In order to charge antimatter, you have to ionize it. How do yyou do that?
The plan is to use a giant mesh, maybe a klick wide, like a giant football but open mesh. The mesh is metal. So its an open mesh like an electric fence, and in fact would be charged up the opposite of the anti particles so would preferentially attract them into the mesh. Then a smaller collector would trap them in a magnetic field keeping them in motion aro ...[text shortened]... ut 30 MILLIgrams of the stuff. It would open up the solar system like roads opened up America.
Or do we talk about antiprotons only?
16 Jul 08
2 edits
Originally posted by FabianFnasI think that is correct, anti-protons, maybe even anti-electrons, but they would have opposite charges.
But antimatter is not collectable with magnets if they are not charged. In order to charge antimatter, you have to ionize it. How do yyou do that?
Or do we talk about antiprotons only?
Anti-protons and protons have the same electrical charge, that doesn't change.
So a negative charged mesh would preferentially attract anti-protons and protons alike, I don't know how you would separate them, I assume the mass would be the same, maybe the velocities would be different, not sure.
I'll see if I can recover the Scientific American article about the issue and re-read it. Have to find an index for that though.
Wait a minute. Is the anti-electron and the positron the same particle?
Not sure about that one. I know positrons are like electrons but with positive charges. I am assuming protons and anti-protons have the same charge but maybe I'm wrong.
Ok, I found a wiki:
http://en.wikipedia.org/wiki/Antiprotons
The gist of it is anti protons have exactly the opposite charge as a proton, and magnetic moment is opposite also, so it has a negative charge and the north south alignment is the opposite of protons too.
So they would curve in the opposite direction in response to a magnetic field and would be attracted to any proton in its vicinity.
So the mesh would have to be charged POSITIVE to attract anti-protons.
So that positive charge would REPEL protons. Neat.