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Nuclear fusion

Posted by: Dr_Keith_H - Sun Jun 06, 2004 1:26 pm
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Nuclear fusion 
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Post    Posted on: Mon Jun 07, 2004 2:04 pm
Alright till the last point, Fusion reactors are the key component to fusion drives. These use the plasma created by the process and expel it out of the back, think of an ion drive but a hell of a lot faster! The fusion reactor in the case of propulsion is used in a similar way to if it were a combustion chamber in a conventional rocket. So you see that's exactly why i was talking about it.


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Post    Posted on: Mon Jun 07, 2004 2:36 pm
don't you think that for practical purposes their designs are radically different?


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Post    Posted on: Mon Jun 07, 2004 2:46 pm
No, simply because tokamaks, at the moment, are one of the few ways in which we know that containment can be retained (they use a complex toroidal electromagnetic field to contain the plasma). If this stuff was to touch the tokamak it would vapourise, it's at around a million degrees! There are a couple of reactor designs but the tokamak has been used for some time as it's seen as the most feasible method. Of course there would be differences, for example the releasing of the plasma but fusion drives for some time I think would be designed at least along similar lines.


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Post    Posted on: Mon Jun 07, 2004 8:40 pm
fusion is the second most efficient energy conversion, behind antimatter, the fusion in the sun uses normal Hydrogen-1, as opposed to Deuterium or Tritium, which are H-2 and 3 respectively. H-1 fusion produces the least radiation, but the others still don't produce alot. Fission is about .01% efficient i think, and makes tons more radiation. Until we have efficient antimatter production, and after we work it out, fusion will be the main source of energy for just about everything.

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Post    Posted on: Mon Jun 07, 2004 9:36 pm
well i simply disagree with you there nova: any tokamaks i've seen have been toroidal because of the containment issues while any fusion drive designs i've seen are openended linear designs for expelling mass in one direction

that's a radically different design for me, and after all they have very different purposes so it's not a surprise really

edit: to be more precise in explaining my opinion:
- the primary aim of a fusion reactor is generating energy
- the primary aim of a fusion drive is generating thrust
that's what i mean by having very different purposes and alas different designs


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Post    Posted on: Mon Jun 07, 2004 10:23 pm
TerraMrs, that's exactly what i've been saying all along, read my posts! Yes antimatter is a brilliant source of energy and I have seen many articles concering it's use. In the end even this will not be the holy grail of propulsion though as like practically all the current propulsion designs so far you still need to waste energy propelling the extra mass of the fuel required. This makes me interested in another form of propulsion, Solar sails, but more on that in a minute.

n54, I do apologise. This conversation made me remember one fact about the tokamaks being currently developed. So as to have a better chance of reaching sustainable fusion the most efficient tokamaks are those with the smallest angle of the chamber, I.e almost spherical. This would not allow for the channeling of the plasma from the reactor so I suppose linear reactors would need to be used. however I still insist that with a toroidal tokamak the plamsa produced could be channelled linearly i.e. out of the reactor in one direction.

moving on, hopefully sometime soon there will be the first ever launch of a solar sail vehicle, Cosmos 1, being developed by the Planetary Society. When i first looked up on solar sail propulsion I found some interesting things about it such as apparently it is believed (using lasers as well probably) that they could reach speeds of around 13% the speed of light! :shock:

What do others think of this?

P.S. Here's the Cosmos 1 site: http://www.planetary.org/solarsail/index2.html

Edit adressing n54's edit: Is not a linear fusion drive a form of fusion reactor? They a practically one in the same thing. A fusion drive is simply a fusion reactor that releases it's plasma in a stream instead of using it to produce electricity. As I said before, capitulating, linear reactors/drives would be more appropriate than the spherical tokamaks being developed. I had to clear all this up before we move on.


Last edited by Nova on Tue Jun 08, 2004 12:07 pm, edited 2 times in total.



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Post    Posted on: Mon Jun 07, 2004 11:36 pm
i did some lab work with solar sail materials at the local univeristy, and they're really awesome things. barring FTL travel (a long ways in the future if it ever comes around i think), solar sails will be the only form of long range propulsion (long range == neptune or >), possibly barring fusion ramjets, which are very theoretical and basically run off of free-floating hydrogen, because they require no fuel and can be propelled by lasers situated near a major power source (the sun). however, they are really too massive and slow for close distances, ergo antimatter will be used for merely interplanetary hops. this is also barring efficient antigravity, which would redefine propulsion as we know it, but antimatter would still be the best way of getting energy for that probably.

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Post    Posted on: Mon Jun 14, 2004 2:30 am
For anyone interested, a good web source on the intricacies of controlled fusion is the Princeton Plasma Physics Laboratory site: http://www.pppl.gov.


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Post    Posted on: Mon Jun 14, 2004 5:19 pm
nuclearspace.com did an interesting article (that's not available now) about a gas-core nuclear rocket. That was a fission concept that had a torrid of nuclear material that was used to heat hydrogen I believe that was passed through the center of the torrid and then ejected. That way none of the nuclear material was ejected. Maybe something along those lines would be a good possibility for a fusion drive.


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Post    Posted on: Tue Jan 31, 2006 12:44 pm
I thought that I would revive this old thread as this article in Spacedaily suggests that the Russians are 35 years ahead of the US on nuclear drive technology and wondered if that was a realistic statement.

http://www.spacedaily.com/reports/Could ... clear.html

The article covers an interview with Paul A. Czysz who says that a mission to Pluto would take about a month compared to 9 years that New Horizons is going to take. He also makes some interesting points about the effects of weightlessness on the human body and that some of these could be permanent.

Any thoughts, could the Russians be that far ahead in the field? I find it difficult to believe personally.

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Post    Posted on: Tue Jan 31, 2006 2:17 pm
Mr. Czysz has his facts all mixed up. He only uses the word "fusion" twice in the whole article while giving examples of past fission technology (Rover and Pluto are just other names for Nerva). His only evidence that they are ahead of us is
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A guy I know at the Keldysh Institute (for Applied Mathematics, in Moscow) who is working on this claims that by 2050 there will be such as device.
Wow, what an accurate source! If we could just find a guy in the US who would say we could have it by 2040, we could be 10 years ahead! :roll:


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Post    Posted on: Tue Jan 31, 2006 8:04 pm
I thought it was a bit light on evidence but if the Russians had continued to work on Nuclear propulsion when the US had more or less abandoned it (this assumes that there hasn't been a secret military program going on all the time in the states) it would be interesting to see how far they've got.

Not very if they are talking about another 50 years before we see something fly.

I was more interested in what he said about body functions not returning once cosmonauts returned to Earth after long stays in space, I had always assumed that things eventually returned to normal after a period of time. If what he says is true it makes a 7 month trip to Mars pretty hard on human physiology.

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Post    Posted on: Tue Jan 31, 2006 8:31 pm
Andy Hill wrote:
I was more interested in what he said about body functions not returning once cosmonauts returned to Earth after long stays in space, I had always assumed that things eventually returned to normal after a period of time. If what he says is true it makes a 7 month trip to Mars pretty hard on human physiology.
Well he doesn't really cite any good sources, but the information at least sounds plausible. All except the plan to send a man back to space for the rest of his life. :roll:

Anyway, I am not too bummed out by the effects of 7 months 0 g. Plenty of people have been in space for that long and recovered. Mars gravity is 1/3 g and he is saying you only need 1/4 g to prevent problems. I do agree though that we don't really know that. What if the crew, after 7 months 0g, 1 year 1/3g and another 7 months 0g, cannot recover on Earth? We really need some way to find out before risking a crew. What kind of things could we do to find out? Extended stays on the Moon comes to mind. Maybe a 1/3 g spinning space station would come in handy, both as a tourist destination and a long term low g research facility.


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Post    Posted on: Tue Jan 31, 2006 9:03 pm
grr i was just gonna post that link haha :)

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