Talk:Fission-fragment rocket

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How could this be possible that it would get an ISP close to that of an antimatter rocket? In antimatter, all of the mass gets converted to energy. In fission, only a very small percentage of the mass in the reactants gets converted to energy. Sounds like someone misread their source.

Hmm, looking some more, I found the problem: There's one extra zero in that ISP  :) Check out http://www.batse.msfc.nasa.gov/colloquia/abstracts_summer05/rsheldon2.html for a reference. 129.255.141.196 (ISP is roughly 1/10th MN/kg) 16:29, 15 Jun 2005 (UTC)

[edit] Project 242

Is this someway related to the fission-fragment motor by Carlo Rubbia named "PROGETTO 242" (project 242), from Italian Space Agency? See http://www.crs4.it/Areas/cfd/P242.pdf and http://www.rai.it/Contents/eventi/600/ASIProgetto242.ram.

It does seems similar but I'm not sure if it's the exact same thing as in this article. Whatever it is, this "Project 242" probably deserves its own article.--Hibernian 18:57, 3 August 2006 (UTC)

[edit] Clean up

Well written article. Organizing into distinct components and starting reference section. --Rev Prez 14:34, 15 April 2007 (UTC)

[edit] A Few Silly (and non-technical) comments

I have a few (obvious) questions concerning the fission-fragment idea :

1) What are the "Numerous technological challenges" referred to within the "design considerations" section?

2) Is the Specific Impulse of the device impeded by the fact that the nuclear reactions which are considered for the fission-fragment design are forced to rely upon the fissioning of HEAVY nuclear materials (I suspect that, if a way were found to utilise nuclear fusion, it might actually be possible to obtain a higher specific impulse than with even the fission-fragment design - my calculations on this point are probably going to be rusty, though they assume that a nuclear fusion reactor would have to rely on a lower mass of reactants in order to release the same amount of energy that a nuclear fission reaction would, with the obvious proviso that a nuclear fusion reactor would be of comparable mass to a nuclear fission reactor at some point in the future).

3) Does anyone with more experience than myself envision that the separation of highly energetic heavy nuclear materials from the fissioning masses used in this engine decision could somehow be used in order to `catalyse'/speed-up or act as a sufficient source of energy to initiate a D-T nuclear fusion reaction (I suspect that, as you are planning to use magnetic confinement techniques anyhow, and it is possible that some nuclear fission reactions will produce the kinds of temperatures needed to initiate and maintain nuclear fusion, then it should be reasonable to assume that a `mixed' fission-fusion nuclear reaction would actually increase the specific impulse to an even higher amount - but, as any good blagger, I haven't actually done the maths, yet).

4) " The axial magnetic field is too weak to affect the motions of the dust particles but strong enough to channel the fragments into a beam which can be decelerated for power, allowed to be emitted for thrust, or a combination of the two. "

Obviously, just use a feedback system to channel the `low-grade' output from the initial nuclear suspension reaction (for those particles which are travelling in the wrong direction and can only be used for power generation via some sort of magnetic deceleration/heating process) in order to yield more energy from the those particles that are travelling in the `right' direction (that way, further `secondary' and tertiary nuclear nuclear reactions could be made to occur at the exhaust possibly increasing the specific impulse a little amount here dependent upon the fission fuel reaction that is being dealt with >).

> I think that the secondary nuclear reactants can be fed in at the exhaust stage for the nanoparticle design (without comprising thrust via, say, reducing the exhaust temperature or inducing reactions which could somehow induce `negative momentum change' due to the fact that the momentum transfer occurs at the `point of fuel fission'. I am uncertain as to whether this is correct).

ConcernedScientist 13:58, 25 August 2007 (UTC)

1) has this been removed?

2) absolutely; a fusion design will outperform the FFR, especially in terms of overall spacecraft performance. However, we actually know how to build a FFR.

3) hmmm. well I can't say for sure, but my guess would be "no" based on poisoning of the fuel load (quenching). The last thing you want is high-z materials entering the fuel anywhere, the effect on radiative cooling is overwhelming.

4) I think a system like this would be used on any such design, not just this "new" one. Neutrons will be unaffected (well, polarized maybe) and continue the reaction within the reactor, but the small chunks of fuel and carbon that break off are highly ionized and suitable for magnetic direction (well, that's basically the whole idea!). Of course they have actually tried this in the "real world", and last time I checked there are still no operational MHD generators in commercial use...

Maury 22:47, 1 December 2007 (UTC)