Robert Lucky and old news
on
Reflections
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· Score: 2, Interesting
First and foremost, this was developed at Bell Labs. (People I knew when I was a Bell Labs were doing on the research.)
Robert Lucky was at Telcordia, not Bell Labs. The New Yorks Times articles notes this. So, editors, please do a vague glance in the general direction of the article and the article summary before posting..
Second, this is old news. Here is a general scientific article on the underlying basis for the technology from September 2001:
Enjoy... a paper proposing a colliding beam fusion reactor. Protons and boron ions are injected via oppositely directed beams into an FRC (Field Reversed Configuration---a solenoid with a reversed coil in the middle). Power is extracted with inverse cyclotron generators at the ends. Its a pretty cool magnetic confinement idea but its feasibility is a matter of some controversy. But, the economics of the device (if it works) look better than tokamak D-T fusion based systems.
P.S. My undergrad was at Purdue. I can vouch that virtual cathodes aren't taught in first-year physics. Actually, they generally aren't taught in graduate-level physics classes either. Typically you learn about them if you are doing research in high powered microwave devices. (My Ph.D. advisor studied virtual cathode oscillations in the 1960s which is how I came to know about them.)
I know my plasma physics and E&M. I hate to do this as the egaltarian attitudes of the web hate when people pull a credential, but check out my home page and decide for yourself whether or not I am qualified to talk about plasma physics and electromagnetics.
Now for your objection: If you have a charge uniformly distributed over the outside of a spherical region, oppositely charged particles exterior to the sphere will be attracted towards the center of the sphere. However, inside the sphere the field is zero---from Gauss's law (I don't need a review).
Suppose the particle can pass through the sphere of charge (IEC approximates this using a grid electrode). The particle will not be confined to the inside of the sphere. The particle will oscillate radially about the grid (this was what I was talking about with dynamic virtual cathode / anode effects).
You could argue than that the particle is confined. However, you have a charged grid in the confinement region, so you have not achieved a purely electrostatic confining potential. In IEC, eventually, the particle will interact with the grid---if something doesn't kick it out of the trap first. So it is not confined. Maybe you could argue quasi-confinement.
Furthermore, potential well setup by the presence of the grid is (in the Hirsch Meek patent for instance) on the order of 6KV. It will not confine particles of sufficient energy to fuse readily. So, if you want a lot of fusion, you better have a high density. IEC doesn't.
Suppose you were able to get a MV (there are significant technical challenges to achieving this). How long do you think your inner electrode grid, which is directly exposed to your fusion plasma, will last? One of the show-stoppers for magnetic confinement fusion is that walls (which are not directly exposed to the plasma) won't hold up very long. For IEC, you have even tougher demands on your materials.
Geez... still getting responses. I would have thought this thread dead and buried by now.
In any case, here is a web site on a light weight space power sources (I saw a lengthy talk on it recently from the head of the institute). This is not to advocate this technology; this is just to give a flavor of the competition.
http://www.inspi.ufl.edu/research/gcr/index.html
This does generate power and could be tighly integrated with a VASIMR style propulsion system. A fair amount of the systems engineering has been worked out and they were estimating power / weight ratios sufficient for Mars quick trip (for a large system, better than 1 kW / kg --- including shielding).
The approach has other benefits (such as being unable to melt down; you need actively drive the system). The biggest issue they were foreseeing was MHD electrode lifetime.
Maybe I've missed the point and the fusion part of IEC isn't relevant to IEC as a propulsion system. If so, why use IEC as opposed to VASIMR, MPD, Hall thrusters,...
I've seen some talks on IEC as a propulsion source. (I've seen similar talks about using distorted Tokamaks and the Spheromaks.) It's not out of the question but there are lots of means of accelerating your propellant once you've made the decision that chemical rockets aren't going to cut it.
Once you've moved away from chemical propellants, one of the big questions is: where are you going to get your power for the propulsion system? For a chemical rocket, the energy is largely liberated from the reactants themselves.
If IEC isn't going to give you the energy from fusion, then you still have to carry the weight of some other power source. The talks I've seen proposing IEC as a propulsion source assume the propulsion power would be generated from the fusion reactions themselves (and the IEC produces directed propellant flow by using electrodes distorted from their gridded spherical shape).
However, IEC's fusion yield, for reasons discussed at length previously, is presently infinitesimal. So, if you want to use IEC as a propulsion device, you still need to lug around some other power supply. In such a configuration it isn't clear that IEC is competitive with any of the other advanced propulsion schemes out there.
If you could get IEC's fusion yield up several orders of magnitude, IEC could be a promising fusion based propellant system.
Kevin
P.S. I'm not clear what you are considering as the propellant. If the fusion products are the propellent (which would be nice as the fusion reaction liberate energy), then choice of fusion fuel is very important; I doubt you can make fast neutrons a useful propellant. However, if you are just planning to use the energy liberated from IEC fusion reactions to heat your propellant, then IEC is really just acting as a power supply. (Possibly a compact one though if the unreacted fusion fuel and the propellant are one and the same---using the fusion energy to heat the plasma for thrust purposes... needless to say, but it would be very difficult to make this work.)
If you look at the the general tenor of comments about the story and the submitter of the story, they are talking about a fusion power supply---not a low flux isotropic radiographic neutron source. My original comment was directed at them and I stand by it.
Your original reply to the my post was hostile, implied I didn't know my butt from a hole in the ground (that remains to be seen), that I was implicitly accusing researchers of scientific fraud. So, don't be too surprised when you get a curt response.
Okay. I stand by those statements though I should have elaborated on the Lawson criteria. It would have better exaplained about the "confining" issue. The fusing ions aren't trapped and since the plasma density is low, the vast majority fusion capable ions (which took much energy to make in the first place) zip right though the plasma without doing anything useful.
As far as "right minds" is concerned, there are people claiming IEC as a power supply that will be ready "real-soon-now" and these people do sometimes pop up at conferences or in the national media. It is unfortunate because they make legitimate research in the field more difficult.
The slashdot story summary was written just like that and gives this conspiratorial impression that fusion is easy but "The Man" is holding it down.
Controlled fusion power is tough and a long way off. The fusion research community shot itself in the foot long ago when they grossly underestimated how difficult it would be---leading to the recurrent quip that fusion is always just 20 years away. There have been several recent breakthroughs but history should teach people not to get their hopes up. IEC is a long shot for a power supply.
I'm not sure you understand the meaning of "ad hominmen". The question was a legitmate one. The link you provided supported my argument that IEC is not a power supply as claimed by the slashdot summary.
In your original post, you quote a fusion rate, that while still miniscule, is a thousand times higher than what is actually claimed by your own link:
"Clearly, the fact that these systems produce neutrons in substantial quantities seems unassailable - whether the exact results or numbers Hirsch and Meeks reported or claims (billions of neutrons per second or whatever)"
If the fusing ions are not trapped, that is equivalent to a short-confinement time strategy. For that to work you need a high density plasma so the fusing ion has a respectable chance of actually fusing. This device lacks that. If you are doing low density, you want the ion trapped to that its chance of fusing is much higher (it stay in the plasma much longer).
"All you need is some basic engineering skills, this site and the inspiration necessary to make your very own 'fusor' produce more energy than it consumes."
They are talking about a power supply. IEC is not one and to get to be one would require addressing the objections in my original post.
Also in my original post that I noted I've seen talks about the technology before at plasma physics conferences. So, once again, I don't doubt you can make such a device but I doubt that you can make one a power supply (as was stated by the story summary).
As far as proving a statement weaking than my original, I quote myself:
"To confine a plasma with sufficient energy to have respectable amounts of fusion..."
I didn't deny there was any fusion. Just not enough to get excited about as a power supply. Get the confining potential up to several MV and I'll start getting excited.
The flux rate is 5e6 n/s (presumably isotropically) according to their web site. Roughly one fusion reaction is happening every microsecond. It is not a power supply.
Hmmm... seem to hit a nerve with some people. I'm not too surprised. Before I reply specifically to your post, see my reply to the other poster. Once again, it would not rock my world if a _miniscule_ amount of fusion was going on in these devices.
Now from your Intel Science Contest:
"EN031: Design, Construction and Test of a Portable Nuclear Fusion Reactor. Adam Lee Parker, 18, Bradshaw High School, Florence, Alabama
Hmmm... no link to the results of the test. And this prize is in the engineering category. So, I don't consider this a proof-of-concept. A high school student building a high energy plasma source is a pretty big achievement in and of itself. What if the test was negative? It would still be worthy of the award.
From your wisc.edu link:
"The gridded IEC approach possesses the significant advantage that ions can be accelerated to high voltages (tens of keV) with relative ease."
Tens of keV isn't enough for a fusion reactor as a power supply. (Tens of keV is consistent with the Hirsch / Meeks patent.) And the goals of the project aren't a commercial reactor. Instead they looks like they are trying to produce a proton/neutron radiographic source (though the third goal of the project sounds like a round-a-bout way of saying "fusion power supply").
I don't deny the existence of the device. There is a guy in my research group at Los Alamos who had some grant money for investigating electrostatic fusion concepts. But, I don't think you'll see your home powered by it anytime soon for the reasons stated in my previous email. (Now, if you could get the confining potentials much much higher than shown in your wisc.edu page and in the Hirsh and Meeks patent, the idea is much more plausible.)
Well... mistaking the natural background neutron flux for fusion has been a recurring theme in exotic fusion research. (A recent example is the controversy over claims by Oak Ridge scientists that miniscule amounts of fusion were being produced by sonoluminescene.)
I have no doubt that you can make a glowing ball of plasma with this technique. It wouldn't rock my world if there was an infinitesimal amount of fusion going on. But, I don't see any reason to believe this will be the next generation power source or could be developed into one.
This isn't an out of hand dismissal of the exotic techniques; I'm much more open to wacky ideas than many of my colleagues. And I don't have a whole lot of faith in mainstream techniques for fusion becoming viable power sources either (but that is another issue).
However, the mainstream techniques have calculated the requirements needed to make a viable fusion reactor. It is neatly summarized by the Lawson criteria. By looking at Lawson criteria, you can develop different strategies for designing a fusion reactor. The strategies amount to trade offs between plasma density, plasma temperature or duration of confinement. Laser and heavy-ion inertial confinement aim for high-density but short confinement time. Magnetic confinement uses a long confinement time but a low density. And so forth...
I don't see anything here to indicate this is competitive with mainstreams techniques (which are themselves already lacking) and there are obvious problems with the physics in making the reactor more practical.
So I read through the patent and I've seen talks on electrostatic confinement fusion at plasma physics conferences (plasma physics is once again my day job).
I'm quite doubtful. My objection can be explained by looking at Figure 2 of the Hirsch and Meeks patent linked to through the fusor.net site.
You need accelerate the ions to high energy (or equivalently heat the ions to high temperatures) so that they will collide and fuse. If the energy is too low, electrostatic repulsion will prevent the nuclei from getting close enough to let the strong force do its work.
So what is my objection with Figure 2?
To confine a plasma with sufficient energy to have respectable amounts of fusion requires very high potentials (think many mega-volt DC potentials) to trap the ions if you are doing it electrostatically. If the potential barrier isn't high enough, the ions will escape the reactor without fusing---you dump all this energy into the ions and they just leave, taking your energy with them...
For an electrostatic confinement system, you would need confining potentials comparable to the height of the nuclear electrostatic repulsion barrier (for the ions to fuse, they need to have energies higher than the nuclear electrostatic repulsion barrier but below the reactor electrostatic confinement barrier).
Figure 2 is the potential distribution for the reactor. The potentials are a couple _thousand_ times too small to have any chance of confining fusion capable ions. At no point in the patent was it explained (clearly... legalese is not good science writing) why high energy ions would be trapped and fuse in such a modest potential well.
Kevin
P.S. Furthermore, a purely electrostatic confining potential is not allowed by Poisson's equation (the equation governing electrostatics), as is taught in any first year college physics class. The quick explanation is that Gauss's law implies the existance of a charge in the potential well. But if you are trying to make a trap to isolate a particle, that is exactly what you don't want in your well. For example, Penning traps use a combination of electrostatic confinement (confinement at the end-caps) and magnetic fields (radial confinement). However, I'll give them the benefit of the doubt as this appears to be relying on dynamic effects virtual cathode/anode effects. (Actually, much of the initial modeling of virtual cathodes was done by my thesis advisor in the 1960s.)
Optical fibers don't work that way, at least at the high end.
High end optical fiber equipment uses light on several different carrier frequencies (or wavelengths or "channels" or "colors"---it all means the same thing). This is not unlike your analog car radio or TV. However, each of these channels tends to be a digital data stream.
For example, a state-of-the-art DWDM (dense wavelength division multiplexing) system could have a single optical fiber carrying 128 channels in the 1500nm to 1600nm band where each channel is separated by 50GHz. Each channel contains a stream modulated at somewhere in the range of 10-40Gbs. The modulation scheme for the channels tends to be some kind of digital scheme (NRZ and RZ are two common methods).
To put things in perspective, the net bandwidth of current (but not necessarily deployed) optical fiber equipment:
128ch * 40 Gb/s ~ 5 Tb/s
Research results at faster speed have been demonstrated but nobody is buying equipment right now. (See the whole dark fiber problem... the technology has outpaced the demand.)
Kevin
(P.S. I have a Ph.D. and I work in the same building.)
A couple of brief comments... people claiming several different effects (and possibly mixing things up)... I am trying to put together a coherent picture.
Ion wind: accelerate ions to use charge exchange collisions to accelerate a neutral gas. There is a fair amount of mainstream research into this for fusion applications (look for papers on neutral beam injection). My intuition says that this is probably not a great way to generate thrust, but, after all, these lifters are made of tin foil and balsa wood. Furthermore, this is not an area where I would trust my intuition.
Assuming ion wind, the lifters should not operate in vacuum. Some people are claiming that these do. I doubt it these claims are coherent or tested sufficiently, especially because making a really large ultra high vacuum chamber is well outside what even moderately sized organizations have the means to do.
A historical side note: many early plasma experiments were completely misinterpreted because the experimentalists didn't have sufficiently good vacuum chambers (the technology didn't yet exist) and they assumed that the effects (glowing discharge chambers and what not) were occuring in regions of hard vacuum.
Induced dipole: a number of people have made me roughly aware of the frequency conditions (DC to tens of Hz sometimes with pulsed operation modes). Thus, I would guess that an induced dipole effect like I proposed is not operating. That is not to say that it still isn't some type of induced dipole effect / just that the phase lag mechanism I proposed is likely not the mode of operation. The frequencies are way too low.
If you are spitting off electrons, you are building up a large positive charge. Eventually, the positive charge will overcome any thrust you got from the electrons.
Thrust charge neutralize is a _big_ issue in ion thrusters.
So, go back to the 8th grade and pay more careful attention.
Sorry to respond to my own (once again typographically challenged) post.
However, thinking about it, assuming the lifter is using the AC from the horizontal monitor sweep, what you are probably seeing is an induced dipole effect.
This is nothing new. Take a balloon. Rub it against the carpet (charge it up statically). Stick it to the wall.
Why does the balloon stick?
The static electricity induceds dipoles in the wall. These dipoles attract the balloon.
In the case of the lifter, the + wire on top and the grounded foil forms a dipole. This dipole induces a mirror image dipole in the ground beneath it. However, if the AC is near at frequency that is in the general vicinity of the horizontal sweep frequency of the monitor, the induced dipole in the surroudings (table/ground/floor) will be out of phase with the regular dipole. This will cause a repulsive force.
As it stands though, the lifter is highly not optimized. The frequencies could be optimized which in turn would give you a stronger force (or conversely require a lower voltage power supply). The lifter layout could be redone to for a strong dpole moment or made out of studier materials (as the system currently is put together, the force would be very very weak).
Here is the difference between science and pseudo-science. The above is _testable_.
- The device should exhibit power supply frequency dependent characteristics. Notably there should be frequencies ranges exhibiting repulsive and attractive forces and these the ranges are dictated by the speed of light and the effective distance of the induced dipole.
- The device should be sensitive to the surroundings. i.e. it would have different operational characteristics if you operated it starting from a wooden table or a metal table.
I skimmed through the the NASA patent in question.
It's not a reactionless drive. The propellant photons. The patent proposal seems to be a variant of an end-fire phased array antenna. (Or a less sophisticated version of laser propulsion system.)
However, if you have a background in propulsion, you are probably aware that photons are terrible for thrusters. It you want to spit off directed momentum, photons give you the _least_ bang for your buck. Photons are classically massless and only give you h_bar omega / c momentum. Only if your are talking about hard gamma do photons even start to compete with propellants of current rockets.
As far as the lifter page is concerned:
What is the damn frequency of the power supply? Heck, I have all the equipment (even a dead 14" monitor for salvage). I would build it for fun.
Monitors use both a high DC voltage for acceleration of electron beams and an two sawtooth-ish AC components for sweeping the beam (vertical at 70Hz and horizontal at 100KHz). Is this a purely DC phenomena or should I tap the sweep signals?
All in all, he didn't give sufficient details to replicate his work so it sets my BS detector humming. Or more likely, if I replicate it and it doesn't work, I'll probably be told that only magical NEC monitors from the mysterious Hokkaido forest manufacturing plant work... not my crappy dead 14" CTX.
Last time I looked, pdflatex doesn't handle EPS pictures. Only gifs. Of course, EPS is superior for printed documents.
The problem with ps to pdf conversion is that ghostscript and Adobe don't see eye to eye about fonts.
You can fix it. Here is the script I use to compile all my LaTeX documents in pdf with nice looking fonts.
You should be using ghostscript 6.0 or higher.
Enjoy, Kevin
#!/bin/sh # # Usage: texit [article] # # article is the name of the article to compile. # article should have an article.tex and article.bib file in the current # directory # # pdfit compiles the LaTeX file from scratch and # produces a dvi, a ps file and a pdf file from it. # # Important errors and warnings (usually) from the compile are dumped to # screen # (important = something that is your problem and you should fix...) # (not important = the whiny TeX errors about inability to hypenate a # word such that the pagination agrees with the principles # of Feng-Shui or other such typographical nit-picking) # # article.lof,.lot,.log,.toc,.aux,.bbl,.blg,.dvi,.ps.gz and.ps # in the current directory will be overwritten # # Details about the errors can be found in the log files
To bring a piece of matter to absolute zero in the sense you remove all random energy from it: the short answer is no. Heisenberg uncertainty / random fluctuations in background fields prevent you from achieving this.
You are quite perceptive about accreation disks. A class of supernovae is thought to be due to surface fusion in a neutron star binary system (the regular star is eaten by the neutron star and fusion of spiraling cannablized material occurs on the neutron star surface... after a while the arrangement becomes unstable and boom). Look in 1999 Scientific American for a general reader article about soft X-ray stars about this... don't remember the month.
Some chirped pulse tabletop laser experiments have achieved miniscule amounts of fusion. Basically, if you hit anything with 10^20 W/cm2 weird stuff will happen.
It is possible for a couple of random H's to slap into each other to fuse. At low temperatures and densities though is it exceedingly unlikely (wait the lifetime of the universe kind of thing).
Muon catalyzed fusion was experimentally shown to make fusion easier to do at lower temperatures in the 1960s. Muons are just like electrons but 207x more massive. In muonium (i.e. a hydrogen atom with the electron replaced by a muon), the muon has a much tigher orbit than regular hydrogen. The muon shields out much of the proton's electrical charge... making it easier to fuse. Of course, muons are unstable and hard to make. So it is more a curosity.
Tomamaks get some fusion but it is still quite a ways off. Depending on how optimistic you are about electrical power extraction and economic feasibility, we currently have reactors near breakeven (I've seen technical articles indicating if you fusion as a breeder for fission, we are beyond breakeven). I could speak at length about various forms for controlled fusion, but I have some old slashdot posts that talk about the matter a bit (look up the one called "Ass-talking").
Sorry to reply to my own post. However, given its typographically challenged nature (three out of four sentences in a paragraph started with "However"... ugh... difficult to think with a toddler screaming nearby), I have to make this correction:
The surface of the sun is about 6,000 kelvin. See my other reply about K as in thousands versus K as in Kelvin.
0 Kelvin is absolute zero under common definitions of temperature.
Since you asked, temperature is usually a measure of the random energy. That is, if I know the temperature of gas, I can say the average molecule has such and such energy, the molecules have such and such a velocity distribution and as a result chemical reactions proceed at this rate...
However, temperature is a tricky concept in both plasma physics and quantum statistical mechanics. In plasmas far from thermal equilibrium (most are), temperature can actually be pretty meaningless. In quantum statistical mechanics temperature has to do with how the number of microscopic states available to the system changes with changes in total system energy (as a result, some spin magnetic systems can actually have a negative temperature). However, mostly physics grad students really worry about those technicalities.
I didn't mean to insult. However, if people were reading the temperatures though that K was an abbreviation for thousands, they might either:
- Go running around telling people that The Man is fusion down... after all, it can be done with household objects.
- Think I have no clue (which remains to be seen).
See my reply to the previous poster for most of the answer. The electrons are hot, the ions aren't. The electrons are at about 40,000K.
To keep things on topic, sonolumenscence typically gets temperatures of 100,000K to 1,000,000K.
Also, the surface of the sun isn't hot compared to the core of the sun (6,000K with a near vacuum mass density at the surface versus about 15,000,000K in the core with a mass density greater than lead). Fusion only happens in the core. Fusion requires a hell of a lot more energy that fluorescence.
By the way, the K here is for Kelvin (not for thousands). Plasma physicists measure temperature in electron volts (eV) or Kelvin. Here are the conversions off the top of my head:
Slashdot Mirror
First and foremost, this was developed at Bell Labs. (People I knew when I was a Bell Labs were doing on the research.)
Robert Lucky was at Telcordia, not Bell Labs. The New Yorks Times articles notes this. So, editors, please do a vague glance in the general direction of the article and the article summary before posting..
Second, this is old news. Here is a general scientific article on the underlying basis for the technology from September 2001:
http://www.aip.org/pt/vol-54/iss-9/p38.html
Kevin
Thanks
Enjoy ... a paper proposing a colliding beam fusion reactor. Protons and boron ions are injected via oppositely directed beams into an FRC (Field Reversed Configuration---a solenoid with a reversed coil in the middle). Power is extracted with inverse cyclotron generators at the ends. Its a pretty cool magnetic confinement idea but its feasibility is a matter of some controversy. But, the economics of the device (if it works) look better than tokamak D-T fusion based systems.
1 41 9.pdf?ijkey=A.zNwOzIwyrKA
http://www.sciencemag.org/cgi/reprint/278/5342/
Kevin
P.S. My undergrad was at Purdue. I can vouch that virtual cathodes aren't taught in first-year physics. Actually, they generally aren't taught in graduate-level physics classes either. Typically you learn about them if you are doing research in high powered microwave devices. (My Ph.D. advisor studied virtual cathode oscillations in the 1960s which is how I came to know about them.)
I know my plasma physics and E&M. I hate to do this as the egaltarian attitudes of the web hate when people pull a credential, but check out my home page and decide for yourself whether or not I am qualified to talk about plasma physics and electromagnetics.
Now for your objection: If you have a charge uniformly distributed over the outside of a spherical region, oppositely charged particles exterior to the sphere will be attracted towards the center of the sphere. However, inside the sphere the field is zero---from Gauss's law (I don't need a review).
Suppose the particle can pass through the sphere of charge (IEC approximates this using a grid electrode). The particle will not be confined to the inside of the sphere. The particle will oscillate radially about the grid (this was what I was talking about with dynamic virtual cathode / anode effects).
You could argue than that the particle is confined. However, you have a charged grid in the confinement region, so you have not achieved a purely electrostatic confining potential.
In IEC, eventually, the particle will interact with the grid---if something doesn't kick it out of the trap first. So it is not confined. Maybe you could argue quasi-confinement.
Furthermore, potential well setup by the presence of the grid is (in the Hirsch Meek patent for instance) on the order of 6KV. It will not confine particles of sufficient energy to fuse readily. So, if you want a lot of fusion, you better have a high density. IEC doesn't.
Suppose you were able to get a MV (there are significant technical challenges to achieving this). How long do you think your inner electrode grid, which is directly exposed to your fusion plasma, will last? One of the show-stoppers for magnetic confinement fusion is that walls (which are not directly exposed to the plasma) won't hold up very long. For IEC, you have even tougher demands on your materials.
Kevin
Geez ... still getting responses. I would have thought this thread dead and buried by now.
l
In any case, here is a web site on a light weight space power sources (I saw a lengthy talk on it recently from the head of the institute). This is not to advocate this technology; this is just to give a flavor of the competition.
http://www.inspi.ufl.edu/research/gcr/index.htm
This does generate power and could be tighly integrated with a VASIMR style propulsion system. A fair amount of the systems engineering has been worked out and they were estimating power / weight ratios sufficient for Mars quick trip (for a large system, better than 1 kW / kg --- including shielding).
The approach has other benefits (such as being unable to melt down; you need actively drive the system). The biggest issue they were foreseeing was MHD electrode lifetime.
Enjoy,
Kevin
Maybe I've missed the point and the fusion part of IEC isn't relevant to IEC as a propulsion system. If so, why use IEC as opposed to VASIMR, MPD, Hall thrusters, ...
... needless to say, but it would be very difficult to make this work.)
I've seen some talks on IEC as a propulsion source. (I've seen similar talks about using distorted Tokamaks and the Spheromaks.) It's not out of the question but there are lots of means of accelerating your propellant once you've made the decision that chemical rockets aren't going to cut it.
Once you've moved away from chemical propellants, one of the big questions is: where are you going to get your power for the propulsion system? For a chemical rocket, the energy is largely liberated from the reactants themselves.
If IEC isn't going to give you the energy from fusion, then you still have to carry the weight of some other power source. The talks I've seen proposing IEC as a propulsion source assume the propulsion power would be generated from the fusion reactions themselves (and the IEC produces directed propellant flow by using electrodes distorted from their gridded spherical shape).
However, IEC's fusion yield, for reasons discussed at length previously, is presently infinitesimal. So, if you want to use IEC as a propulsion device, you still need to lug around some other power supply. In such a configuration it isn't clear that IEC is competitive with any of the other advanced propulsion schemes out there.
If you could get IEC's fusion yield up several orders of magnitude, IEC could be a promising fusion based propellant system.
Kevin
P.S. I'm not clear what you are considering as the propellant. If the fusion products are the propellent (which would be nice as the fusion reaction liberate energy), then choice of fusion fuel is very important; I doubt you can make fast neutrons a useful propellant. However, if you are just planning to use the energy liberated from IEC fusion reactions to heat your propellant, then IEC is really just acting as a power supply. (Possibly a compact one though if the unreacted fusion fuel and the propellant are one and the same---using the fusion energy to heat the plasma for thrust purposes
If you look at the the general tenor of comments about the story and the submitter of the story, they are talking about a fusion power supply---not a low flux isotropic radiographic neutron source. My original comment was directed at them and I stand by it.
Your original reply to the my post was hostile, implied I didn't know my butt from a hole in the ground (that remains to be seen), that I was implicitly accusing researchers of scientific fraud. So, don't be too surprised when you get a curt response.
Kevin
Okay. I stand by those statements though I should have elaborated on the Lawson criteria. It would have better exaplained about the "confining" issue. The fusing ions aren't trapped and since the plasma density is low, the vast majority fusion capable ions (which took much energy to make in the first place) zip right though the plasma without doing anything useful.
As far as "right minds" is concerned, there are people claiming IEC as a power supply that will be ready "real-soon-now" and these people do sometimes pop up at conferences or in the national media. It is unfortunate because they make legitimate research in the field more difficult.
The slashdot story summary was written just like that and gives this conspiratorial impression that fusion is easy but "The Man" is holding it down.
Controlled fusion power is tough and a long way off. The fusion research community shot itself in the foot long ago when they grossly underestimated how difficult it would be---leading to the recurrent quip that fusion is always just 20 years away. There have been several recent breakthroughs but history should teach people not to get their hopes up. IEC is a long shot for a power supply.
Kevin
I'm not sure you understand the meaning of "ad hominmen". The question was a legitmate one. The link you provided supported my argument that IEC is not a power supply as claimed by the slashdot summary.
In your original post, you quote a fusion rate, that while still miniscule, is a thousand times higher than what is actually claimed by your own link:
"Clearly, the fact that these systems produce neutrons in substantial quantities seems unassailable - whether the exact results or numbers Hirsch and Meeks reported or claims (billions of neutrons per second or whatever)"
So, do you read your own links?
Kevin
See my post about the Lawson criterion.
If the fusing ions are not trapped, that is equivalent to a short-confinement time strategy. For that to work you need a high density plasma so the fusing ion has a respectable chance of actually fusing. This device lacks that. If you are doing low density, you want the ion trapped to that its chance of fusing is much higher (it stay in the plasma much longer).
Kevin
From the slashdot summary:
..."
"All you need is some basic engineering skills, this site and the inspiration necessary to make your very own 'fusor' produce more energy than it consumes."
They are talking about a power supply. IEC is not one and to get to be one would require addressing the objections in my original post.
Also in my original post that I noted I've seen talks about the technology before at plasma physics conferences. So, once again, I don't doubt you can make such a device but I doubt that you can make one a power supply (as was stated by the story summary).
As far as proving a statement weaking than my original, I quote myself:
"To confine a plasma with sufficient energy to have respectable amounts of fusion
I didn't deny there was any fusion. Just not enough to get excited about as a power supply. Get the confining potential up to several MV and I'll start getting excited.
Kevin
Do you even read your own links?
The flux rate is 5e6 n/s (presumably isotropically) according to their web site. Roughly one fusion reaction is happening every microsecond. It is not a power supply.
Hmmm ... seem to hit a nerve with some people. I'm not too surprised. Before I reply specifically to your post, see my reply to the other poster. Once again, it would not rock my world if a _miniscule_ amount of fusion was going on in these devices.
... no link to the results of the test. And this prize is in the engineering category. So, I don't consider this a proof-of-concept. A high school student building a high energy plasma source is a pretty big achievement in and of itself. What if the test was negative? It would still be worthy of the award.
Now from your Intel Science Contest:
"EN031: Design, Construction and Test of a Portable Nuclear Fusion Reactor. Adam Lee Parker, 18, Bradshaw High School, Florence, Alabama
Hmmm
From your wisc.edu link:
"The gridded IEC approach possesses the significant advantage that ions can be accelerated to high voltages (tens of keV) with relative ease."
Tens of keV isn't enough for a fusion reactor as a power supply. (Tens of keV is consistent with the Hirsch / Meeks patent.) And the goals of the project aren't a commercial reactor. Instead they looks like they are trying to produce a proton/neutron radiographic source (though the third goal of the project sounds like a round-a-bout way of saying "fusion power supply").
I don't deny the existence of the device. There is a guy in my research group at Los Alamos who had some grant money for investigating electrostatic fusion concepts. But, I don't think you'll see your home powered by it anytime soon for the reasons stated in my previous email. (Now, if you could get the confining potentials much much higher than shown in your wisc.edu page and in the Hirsh and Meeks patent, the idea is much more plausible.)
Kevin
Well ... mistaking the natural background neutron flux for fusion has been a recurring theme in exotic fusion research. (A recent example is the controversy over claims by Oak Ridge scientists that miniscule amounts of fusion were being produced by sonoluminescene.)
...
I have no doubt that you can make a glowing ball of plasma with this technique. It wouldn't rock my world if there was an infinitesimal amount of fusion going on. But, I don't see any reason to believe this will be the next generation power source or could be developed into one.
This isn't an out of hand dismissal of the exotic techniques; I'm much more open to wacky ideas than many of my colleagues. And I don't have a whole lot of faith in mainstream techniques for fusion becoming viable power sources either (but that is another issue).
However, the mainstream techniques have calculated the requirements needed to make a viable fusion reactor. It is neatly summarized by the Lawson criteria. By looking at Lawson criteria, you can develop different strategies for designing a fusion reactor. The strategies amount to trade offs between plasma density, plasma temperature or duration of confinement. Laser and heavy-ion inertial confinement aim for high-density but short confinement time. Magnetic confinement uses a long confinement time but a low density. And so forth
I don't see anything here to indicate this is competitive with mainstreams techniques (which are themselves already lacking) and there are obvious problems with the physics in making the reactor more practical.
But I could be wrong.
Kevin
So I read through the patent and I've seen talks on electrostatic confinement fusion at plasma physics conferences (plasma physics is once again my day job).
...
... legalese is not good science writing) why high energy ions would be trapped and fuse in such a modest potential well.
I'm quite doubtful. My objection can be explained by looking at Figure 2 of the Hirsch and Meeks patent linked to through the fusor.net site.
You need accelerate the ions to high energy (or equivalently heat the ions to high temperatures) so that they will collide and fuse. If the energy is too low, electrostatic repulsion will prevent the nuclei from getting close enough to let the strong force do its work.
So what is my objection with Figure 2?
To confine a plasma with sufficient energy to have respectable amounts of fusion requires very high potentials (think many mega-volt DC potentials) to trap the ions if you are doing it electrostatically. If the potential barrier isn't high enough, the ions will escape the reactor without fusing---you dump all this energy into the ions and they just leave, taking your energy with them
For an electrostatic confinement system, you would need confining potentials comparable to the height of the nuclear electrostatic repulsion barrier (for the ions to fuse, they need to have energies higher than the nuclear electrostatic repulsion barrier but below the reactor electrostatic confinement barrier).
Figure 2 is the potential distribution for the reactor. The potentials are a couple _thousand_ times too small to have any chance of confining fusion capable ions. At no point in the patent was it explained (clearly
Kevin
P.S. Furthermore, a purely electrostatic confining potential is not allowed by Poisson's equation (the equation governing electrostatics), as is taught in any first year college physics class. The quick explanation is that Gauss's law implies the existance of a charge in the potential well. But if you are trying to make a trap to isolate a particle, that is exactly what you don't want in your well. For example, Penning traps use a combination of electrostatic confinement (confinement at the end-caps) and magnetic fields (radial confinement). However, I'll give them the benefit of the doubt as this appears to be relying on dynamic effects virtual cathode/anode effects. (Actually, much of the initial modeling of virtual cathodes was done by my thesis advisor in the 1960s.)
Hi,
... the technology has outpaced the demand.)
Optical fibers don't work that way, at least at the high end.
High end optical fiber equipment uses light on several different carrier frequencies (or wavelengths or "channels" or "colors"---it all means the same thing). This is not unlike your analog car radio or TV. However, each of these channels tends to be a digital data stream.
For example, a state-of-the-art DWDM (dense wavelength division multiplexing) system could have a single optical fiber carrying 128 channels in the 1500nm to 1600nm band where each channel is separated by 50GHz. Each channel contains a stream modulated at somewhere in the range of 10-40Gbs. The modulation scheme for the channels tends to be some kind of digital scheme (NRZ and RZ are two common methods).
To put things in perspective, the net bandwidth of current (but not necessarily deployed) optical fiber equipment:
128ch * 40 Gb/s ~ 5 Tb/s
Research results at faster speed have been demonstrated but nobody is buying equipment right now. (See the whole dark fiber problem
Kevin
(P.S. I have a Ph.D. and I work in the same building.)
A couple of brief comments ... people claiming several different effects (and possibly mixing things up) ... I am trying to put together a coherent picture.
Ion wind: accelerate ions to use charge exchange collisions to accelerate a neutral gas. There is a fair amount of mainstream research into this for fusion applications (look for papers on neutral beam injection). My intuition says that this is probably not a great way to generate thrust, but, after all, these lifters are made of tin foil and balsa wood. Furthermore, this is not an area where I would trust my intuition.
Assuming ion wind, the lifters should not operate in vacuum. Some people are claiming that these do. I doubt it these claims are coherent or tested sufficiently, especially because making a really large ultra high vacuum chamber is well outside what even moderately sized organizations have the means to do.
A historical side note: many early plasma experiments were completely misinterpreted because the experimentalists didn't have sufficiently good vacuum chambers (the technology didn't yet exist) and they assumed that the effects (glowing discharge chambers and what not) were occuring in regions of hard vacuum.
Induced dipole: a number of people have made me roughly aware of the frequency conditions (DC to tens of Hz sometimes with pulsed operation modes). Thus, I would guess that an induced dipole effect like I proposed is not operating. That is not to say that it still isn't some type of induced dipole effect / just that the phase lag mechanism I proposed is likely not the mode of operation. The frequencies are way too low.
Kevin
A standard exam question is why that won't work.
If you are spitting off electrons, you are building up a large positive charge. Eventually, the positive charge will overcome any thrust you got from the electrons.
Thrust charge neutralize is a _big_ issue in ion thrusters.
So, go back to the 8th grade and pay more careful attention.
Kevin
Sorry to respond to my own (once again typographically challenged) post.
However, thinking about it, assuming the lifter is using the AC from the horizontal monitor sweep, what you are probably seeing is an induced dipole effect.
This is nothing new. Take a balloon. Rub it against the carpet (charge it up statically). Stick it to the wall.
Why does the balloon stick?
The static electricity induceds dipoles in the wall. These dipoles attract the balloon.
In the case of the lifter, the + wire on top and the grounded foil forms a dipole. This dipole induces a mirror image dipole in the ground beneath it. However, if the AC is near at frequency that is in the general vicinity of the horizontal sweep frequency of the monitor, the induced dipole in the surroudings (table/ground/floor) will be out of phase with the regular dipole. This will cause a repulsive force.
As it stands though, the lifter is highly not optimized. The frequencies could be optimized which in turn would give you a stronger force (or conversely require a lower voltage power supply). The lifter layout could be redone to for a strong dpole moment or made out of studier materials (as the system currently is put together, the force would be very very weak).
Here is the difference between science and pseudo-science. The above is _testable_.
- The device should exhibit power supply frequency dependent characteristics. Notably there should be frequencies ranges exhibiting repulsive and attractive forces and these the ranges are dictated by the speed of light and the effective distance of the induced dipole.
- The device should be sensitive to the surroundings. i.e. it would have different operational characteristics if you operated it starting from a wooden table or a metal table.
No dubious "electrogravitics" required.
Kevin
I skimmed through the the NASA patent in question.
... not my crappy dead 14" CTX.
It's not a reactionless drive. The propellant photons. The patent proposal seems to be a variant of an end-fire phased array antenna. (Or a less sophisticated version of laser propulsion system.)
However, if you have a background in propulsion, you are probably aware that photons are terrible for thrusters. It you want to spit off directed momentum, photons give you the _least_ bang for your buck. Photons are classically massless and only give you h_bar omega / c momentum. Only if your are talking about hard gamma do photons even start to compete with propellants of current rockets.
As far as the lifter page is concerned:
What is the damn frequency of the power supply? Heck, I have all the equipment (even a dead 14" monitor for salvage). I would build it for fun.
Monitors use both a high DC voltage for acceleration of electron beams and an two sawtooth-ish AC components for sweeping the beam (vertical at 70Hz and horizontal at 100KHz). Is this a purely DC phenomena or should I tap the sweep signals?
All in all, he didn't give sufficient details to replicate his work so it sets my BS detector humming. Or more likely, if I replicate it and it doesn't work, I'll probably be told that only magical NEC monitors from the mysterious Hokkaido forest manufacturing plant work
Kevin
Last time I looked, pdflatex doesn't handle EPS pictures. Only gifs. Of course, EPS is superior for printed documents.
...) .lot, .log, .toc, .aux, .bbl, .blg, .dvi, .ps.gz and .ps
The problem with ps to pdf conversion is that ghostscript and Adobe don't see eye to eye about fonts.
You can fix it. Here is the script I use to compile all my LaTeX documents in pdf with nice looking fonts.
You should be using ghostscript 6.0 or higher.
Enjoy,
Kevin
#!/bin/sh
#
# Usage: texit [article]
#
# article is the name of the article to compile.
# article should have an article.tex and article.bib file in the current
# directory
#
# pdfit compiles the LaTeX file from scratch and
# produces a dvi, a ps file and a pdf file from it.
#
# Important errors and warnings (usually) from the compile are dumped to
# screen
# (important = something that is your problem and you should fix
# (not important = the whiny TeX errors about inability to hypenate a
# word such that the pagination agrees with the principles
# of Feng-Shui or other such typographical nit-picking)
#
# article.lof,
# in the current directory will be overwritten
#
# Details about the errors can be found in the log files
rm -rf $1.lof $1.lot $1.log $1.toc $1.aux $1.bbl $1.blg $1.fgx $1.tbx $1.end
latex '\scrollmode\input ' $1.tex
bibtex $1
latex '\scrollmode\input ' $1.tex
latex '\scrollmode\input ' $1.tex
latex '\scrollmode\input ' $1.tex
dvips -Ppdf -j0 -o $1.ps $1.dvi
ps2pdf13 $1.ps $1.pdf
clear
grep -n ! $1.log
grep -n arning $1.log
To bring a piece of matter to absolute zero in the sense you remove all random energy from it: the short answer is no. Heisenberg uncertainty / random fluctuations in background fields prevent you from achieving this.
... after a while the arrangement becomes unstable and boom). Look in 1999 Scientific American for a general reader article about soft X-ray stars about this ... don't remember the month.
... making it easier to fuse. Of course, muons are unstable and hard to make. So it is more a curosity.
You are quite perceptive about accreation disks. A class of supernovae is thought to be due to surface fusion in a neutron star binary system (the regular star is eaten by the neutron star and fusion of spiraling cannablized material occurs on the neutron star surface
Some chirped pulse tabletop laser experiments have achieved miniscule amounts of fusion. Basically, if you hit anything with 10^20 W/cm2 weird stuff will happen.
It is possible for a couple of random H's to slap into each other to fuse. At low temperatures and densities though is it exceedingly unlikely (wait the lifetime of the universe kind of thing).
Muon catalyzed fusion was experimentally shown to make fusion easier to do at lower temperatures in the 1960s. Muons are just like electrons but 207x more massive. In muonium (i.e. a hydrogen atom with the electron replaced by a muon), the muon has a much tigher orbit than regular hydrogen. The muon shields out much of the proton's electrical charge
Tomamaks get some fusion but it is still quite a ways off. Depending on how optimistic you are about electrical power extraction and economic feasibility, we currently have reactors near breakeven (I've seen technical articles indicating if you fusion as a breeder for fission, we are beyond breakeven). I could speak at length about various forms for controlled fusion, but I have some old slashdot posts that talk about the matter a bit (look up the one called "Ass-talking").
Kevin
Sorry to reply to my own post. However, given its typographically challenged nature (three out of four sentences in a paragraph started with "However" ... ugh ... difficult to think with a toddler screaming nearby), I have to make this correction:
The surface of the sun is about 6,000 kelvin. See my other reply about K as in thousands versus K as in Kelvin.
Kevin
0 Kelvin is absolute zero under common definitions of temperature.
...
... after all, it can be done with household objects.
Since you asked, temperature is usually a measure of the random energy. That is, if I know the temperature of gas, I can say the average molecule has such and such energy, the molecules have such and such a velocity distribution and as a result chemical reactions proceed at this rate
However, temperature is a tricky concept in both plasma physics and quantum statistical mechanics. In plasmas far from thermal equilibrium (most are), temperature can actually be pretty meaningless. In quantum statistical mechanics temperature has to do with how the number of microscopic states available to the system changes with changes in total system energy (as a result, some spin magnetic systems can actually have a negative temperature). However, mostly physics grad students really worry about those technicalities.
I didn't mean to insult. However, if people were reading the temperatures though that K was an abbreviation for thousands, they might either:
- Go running around telling people that The Man is fusion down
- Think I have no clue (which remains to be seen).
Kevin
See my reply to the previous poster for most of the answer. The electrons are hot, the ions aren't. The electrons are at about 40,000K.
To keep things on topic, sonolumenscence typically gets temperatures of 100,000K to 1,000,000K.
Also, the surface of the sun isn't hot compared to the core of the sun (6,000K with a near vacuum mass density at the surface versus about 15,000,000K in the core with a mass density greater than lead). Fusion only happens in the core. Fusion requires a hell of a lot more energy that fluorescence.
By the way, the K here is for Kelvin (not for thousands). Plasma physicists measure temperature in electron volts (eV) or Kelvin. Here are the conversions off the top of my head:
[eV] = 11,600 [K]
[C] = [K] + 273.16
[C] = 5 * ( [F]-32 ) / 9
Enjoy,
Kevin