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Fusion Powered Spacecraft, not far away?

Posted by: WannabeSpaceCadet - Tue Feb 06, 2007 1:04 pm
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Fusion Powered Spacecraft, not far away? 
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Post    Posted on: Tue Mar 06, 2007 6:39 pm
The recent space show that had Jim Benson as the guest pointed me to this video of Bussard giving a talk at google. An hour and 32 minutes jam packed with way more information that I could take in.
http://video.google.com/videoplay?docid ... 6673788606


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Post    Posted on: Wed Mar 07, 2007 2:50 am
Did Benson say much about what he's going to do with the EMC2 lab equipment? I haven't had a chance to listen to the show yet.

I watched the Google video before I started this thread, but I figured the paper was easier to understand.


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Post    Posted on: Wed Mar 07, 2007 1:42 pm
He only said that he had several of Bussard's people on the SpaceDev payroll and that he was trying to get funding for Bussard.


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Post    Posted on: Thu Mar 08, 2007 5:32 pm
campbelp2002 wrote:
He only said that he had several of Bussard's people on the SpaceDev payroll and that he was trying to get funding for Bussard.


Didn't Benson resign from the SpaceDev management and sell his shares in the company?

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Post    Posted on: Thu Mar 08, 2007 8:28 pm
Benson hired 3 of Bussard's employees before he left SpaceDev, and they are still there. He is still working with Bussard to help him raise money, but only as an aside.

He needed to raise more money and wanted to avoid diluting the stock of SpaceDev, so he started a new company called Benson Space Company which contracts vehicle construction back to SpaceDev. The following month he did leave SpaceDev but he didn't say anything about selling his shares. He talks about it early in the program, which you can listen to here:
http://thespaceshow.com/detail.asp?q=680


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Post    Posted on: Mon Jun 25, 2007 11:35 am
I am still doubting if the energy balance really allows for economical vehicles powered this way.

It has been said that the huge energies required to ignite a fusion power plant are need only once. While this may be correct regarding a power plant to provide electricity only this is NOT valid regarding space vehicles.

Space vehicles start their engines and shut down them later when they have reached their destination. Then they have to fire their engines oince more and so on. This also holds for expendables.

This means that the huge amount of energy required to ignite the fusion(s) would be needed very often.

...



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Post    Posted on: Mon Jun 25, 2007 5:42 pm
Ekkehard Augustin wrote:
This means that the huge amount of energy required to ignite the fusion(s) would be needed very often.


Not sure it follows that just because the engines are switched off it is necessary to power the fusion power plant down. It might be OK to keep it running but with its output disconnected or powering something else.

This would only work for a reactor producing electricity rather than superheated gases expelled as thrust. I have seen designs where a gas is used to cool a nuclear core and then expelled to give thrust, obviously in such engines turning the gas supply off would cause the engine to overheat.

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Post Fusion is ALWAYS 20 years away.....   Posted on: Sun Jul 01, 2007 10:24 am
Buzzards fusor disregards a few fundamental problems. A PhD submitted quite a while ago is interesting reading:

T. H. Rider, Fundamental Limitations on Plasma
Fusion Systems Not in Thermodynamic Equilibrium
(Ph.D. thesis, 306 pp., MIT, 1995).

I have a copy of this from MIT in PDF format. For strictly personal use you could PM me. Be warned its reasonably mathematical. (Fokker-Plank and all that)
And a presentation from the same person:Warning PDF!
http://www.fusor.net/board/getfile.php?bn=fusor_future&att_id=3717

All electrostatic confinement methods are non thermal equilibrium plasmas. Without Addressing these issues then its hard to take seriously. Note that I have run though the calculations, its very hard to discount out of hand. At the very least you would expect some supporting calculations or why his method will work when others have shown it won't.

To sum up, the fusion cross sections are just too low. To keep the plasma out of thermal equilibrium means you need to pump in large amounts of energy. And thats more than you get out. Unless you can convince me that scattering won't push the energy distribution of the ions closer to equilibrium I just won't buy it.

There are other problems too. If it will scale so well then the Russians should have seen better yields in there large systems. Hes no crack pot, but hes just been out of the loop for too long. But i do agree with his views on ITER however.

ITER scales so badly that the smallest size is likely to be rather uneconomic. So that approach does not impress me that much either. Not to mention the massive high energy neutron flux that is produced.

At any rate, its easy to produce fusion. Its hard to get useful fusion.

There is one interesting thing about the above papers etc. It considers steady state. Inertial confinement or non steady may be away around the problem. And we have a working example: Fusion weapons.

Unfortunately I think that beamed energy may be a better way to go. Or fission.


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Post    Posted on: Sun Jul 01, 2007 10:56 am
delt0r wrote:
Unless you can convince me that scattering won't push the energy distribution of the ions closer to equilibrium I just won't buy it.

The fact that the development of the magnet insulation was in my view inexplicably and agonizingly slow, statements to the effect that it can't be simulated (directly or indirectly?) and that there are (yet to be explained) reasons why it won't thermalize etc. also leave me thinking it's actually a rather unlikely prospect.


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Post    Posted on: Wed Apr 08, 2009 6:57 pm
According to the article "Friendly 'Death Star' Laser to Recreate Sun's Power" an experiment wil start in the nearby future at Lawrence Livermore National Laboratory in California in the National Ignition Facility.

Obviously inertial confinement fusion (ICF) will be applied instead of magnetic insulation or electromagnetism.

But have a look to this link Reaction Chamber - I am seriously doubting that such largers chambers might alow for fusion powering space vehicles.



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Post    Posted on: Wed Apr 08, 2009 7:43 pm
The "large" chamber isn't the problem in my opinion, but the enormous facility that generates the lasers certainly is ;).
take a look at this video:
http://www.livescience.com/common/media ... 8_RideBeam

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Post    Posted on: Thu Apr 09, 2009 12:33 pm
I wonder if a fusor could be adapted for a propulsion unit? They require alot less power. http://www.kronjaeger.com/hv-old/fusor/construction/

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Post    Posted on: Thu Apr 09, 2009 12:57 pm
Oops! Should have read this before posting. I intend to build one and test this out in the future. I belive this will work in the short term believe it or not. I think this is the right path for now. Hopefully we will find out!

Monroe

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Post    Posted on: Thu Apr 09, 2009 4:08 pm
Hello, Marcus.

the large chamber will be of large mass - compared to a smaler chamber.

The chamber to be seen in the image is significantly larger than the F-1 and the walls ae much more massive than those of the F-1.

This will be a problem.

Next there might be another problem too - to propell a vehicle the products of the fusion must leave the chamber as a jet of exhaust. How to that without contact between the exhaust and the walls? Because the event of fusion takes place only seconds before leaving any contact to the walls wil be destructive because of the extreme temperatures.



What about it?



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Post    Posted on: Fri Apr 10, 2009 2:53 am
I have seen jets of particules fly out of a fusor in star mode. There for there must be a way to induce the jet where you want it. I dont really know yet but I think there may be a way to get lower power fusor to work for low impulse long duration.

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