Ive been thinking about this recently. I understand how much energy it would take to creat plasma-initiated propultion, but with a efficient nuclear reactor, there would be an abundance of energy. The concept would be much like a jet engin, but not using fuel. I thought i had seen something of the sorts in experimental stages some time ago in an article, or tv.

Am i just losing my mind? or is this an actuall idea thats under development?

Mostly plasma engines are under development for use in space at the moment.

if you mean plasma propulsion in a direct way (fusion propulsion), we are probably a couple centries away.


there are sooooo many things that have to be developed before this can be possible and practicle

first of course is controlled fusion...

Originally posted by white_raven0
if you mean plasma propulsion in a direct way (fusion propulsion), we are probably a couple centries away.


there are sooooo many things that have to be developed before this can be possible and practicle

first of course is controlled fusion...

We have controlled fusion. The JET (Joint European Torus) in the UK has sustained a fusion reaction for 12 minutes. Unfortunately the reaction was not self sustaining because the reactor wasnt big enough, which is why the International Torus is being built (and the big arguement over that!*). They expect the IT to be self sustaining from practically the moment its turned on, due to the advances in the area under the JET and its size.

Its looking very unlikely that in the near future we will have the ability to build a size of reactor that can be fitted to an aircraft. Indeed, even the B-52 couldnt carry the JET.

*The current proposed locations for the IT are Japan and Europe (CERN). The US doesnt want it to be positioned in Europe because of its antiFrench stance, but Japan is a poor location because of the enhanced risk of earthquakes etc. Europe has said it is more than willing to go it alone, with Russia and China (the other major members of the IT team), and its pretty much only the US currently opposed to having it positioned in Europe. With only less than 20% of funding coming in from the US for the project, its completely feasable that the US can be left out of this. Its interesting to note that the JET is currently the only fusion reactor that has sustained a reaction for a long period of time.

indeed that is correct. Its a shame because in my highschool we were taught controled fusion was impossible... at the same time they were doing tests with the Tokamak fusion reactor at princeton plasma physics department... and it wasnt a secret.

BTW: try to find pictures of the reaction, it looks awesome. Its a bright pink coil that goes around the donut shaped reactor... bright pink cause thats hydrogen's emition spectrum.

I was just wondering, but I played some video games with plasma guns in them, could something like that be possible, and what do they exely fire?

Originally posted by DJFiyaaBl8
I was just wondering, but I played some video games with plasma guns in them, could something like that be possible, and what do they exely fire?

Don’t they shoot out ionized plasma particles?

I know short timed controlled fusion has been achieved, however it give negative energy returns (more energy is needed to enter than what you get back).

So first we need to achieve controlled fusion that gives positive returns


there are sooo many things required before a fusion engine can really become practical tho...

Originally posted by white_raven0
I know short timed controlled fusion has been achieved, however it give negative energy returns (more energy is needed to enter than what you get back).

So first we need to achieve controlled fusion that gives positive returns


there are sooo many things required before a fusion engine can really become practical tho...

As I said in my post, the *only* reason the JET tokamak reactor is a negative energy reaction is because the actual reactor is physically too small to produce a self sustaining fusion reaction. This was *always* known to be the case, and the JET was only ever to be an experimental reactor. The International Torus will use exactly the same principles but on a larger scale, and is expected to produce sustained positive energy reactions right from the start. Its the next step in fusion reactor development, and many think its the last step before commercial fusion reactors become a reality.

I do agree that we will probably never see a miniaturised fusion reactor for propulsion within our lifetime. The physics involved just arent there at the moment, getting it to selfsustain in the JET is beyond us currently, so forget anything smaller unless we make some fairly major breakthroughs.

Im just waiting for someone to mention 'cold fusion' in this thread

I wonder.. how great is the input source to creat the self controlled fusion?

That article is nicely worded, what it means is *if* Japan withdraws its bid, then the US would conceed the French bid. While the Japanese bid stands, the US prefers it

Oh well, even if they prefer the Japan site, and Japan sticks to its guns, we'll go ahead and build it anyway, and Japan and the US can build there own. Russia and China back the EU site too.

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[edit on 22-11-2004 by DEADSTEVE]

Thank you, I figured id make it somewhat apparent what my studies are for.

Ive been looking for the energy source for the fusion. So far as i can gather, after the initial reaction, the fusion becomes somewhat self relient.... is this correct?

correction, i think ive found the source. But i came to wonder, fusion can only hold place for so long with the supply of hydrogen first used to initiate the reaction. How is more hydrogen introduced, and also introduced in a way that doesnt disrupt the reaction?

After reading one article, one thing poped into my head.. mr fusion from back to the future.

Nuclear fusion mainly depends on the temperature that the fuel is at, and that depends on what fuel is being used.

The fuel needs to reach a temperature where the forces repelling protons can be overcome. Within Dueterium or Tritium (common fusion fuels - both are isotopes of hydrogen), this energy barrier is 0.1MeV. Once the fusion reaction is complete, the new nucleus drops to a lower-energy configuration and gives up additional energy by ejecting a neutron with 17.59 MeV, considerably more than what was needed to fuse them in the first place. This means that the D-T fusion reaction is very highly exothermic, making it a powerful energy source.

Normally the temperature required is in excess of 1Giga Kelvins (999 999 727 degrees Celsius), but this initial temperature is only required to initiate the fusion reaction, as once fusion has occured, the temperature where this reaction becomes self-sustaining is about 45 MK, still a very high temperature, but about 1/10th the energy of the Coulomb barrier itself (the point at which you need to overcome the proton repulsion force).

Plasmas tend to be leaky in terms of energy; the neutrons that carry away the energy often simply leave the reaction. However, their energy is so high that if even a small fraction of them are "captured" in the plasma, they will heat the plasma back up, allowing other nuclei to undergo fusion. This allows the critical ignition point to be reached, at which the reaction becomes self sufficient, with a sufficient number of fusion reactions occuring which gives enough energy back to the overall reaction.


Because the reaction is highly exothermic, you can harness energy from the reaction while still sustaining a self sustaining reaction. This is the beauty of the system.

I havent got time to go into how they feed the reaction, but when I get back later, I shall post some more on it.

thank you, this is pretty informative, i actually hadn't researched any of this previously.