warfare, strategical and tactical implications

If polywell fusion is developed, in what ways will the world change for better or worse? Discuss.

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Indrek
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warfare, strategical and tactical implications

Postby Indrek » Fri Nov 16, 2007 1:41 am

I spent a few minutes thinking about the strategic and tactic implications polywell could have on warfare. Now I'm a complete amateur here as well so don't take me too seriously :)

With an energy source like polywell available directed energy weapons become a practical reality and one can shoot down almost anything (be it missiles or simple artillery shells or even bows&arrows) currently in use. I can see two ways for weapons to adapt: either by stealth (to make them harder to detect) or by employment of speed and mass (as impact weapons or to shield the warheads). I don't think reliable stealth in the atmosphere can be done.

Polywell based weapons can be put on mobile platforms (easy for ships, harder for land-based units, very hard for airplanes). As those can be moved around specific attacks from very far (to gain the speed-mass) would not work well.

Someone mentioned orbital death-rays. Unless the force building them already dominates the earth - those are tactically sitting targets - won't work. Also I assume hidden surprise buildup on the moon is unlikely (that's why everyone is going there now to make sure others don't get to dominate it), that means the main dissipators of attacks will be earth-based.

What about the MAD? All the superpowers have to do is to build stealthy launch platforms and place them in high earth or probably solar orbits. Retaliation will take couple of days or maybe even weeks, but the enemy cities will be leveled one way or another.

So how will the "conventional" warfare look like? I predict doom to high-flying warplanes in most situations. Helicopters might still have a chance as they can use the terrain better to hide from the direct view of the enemy death-rays. As for the big guns. Overwhelm the enemy. Mobility matters. Nothing that new here I guess. We'll see death-ray against death-ray battles between mobile units.

So what do you think, does that make sense, what could really happen?

- Indrek

Keegan
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Postby Keegan » Fri Nov 16, 2007 5:19 am

It was once said imagination is more important than knowledge. Truly infinite possibilities come with our new insights into fusion technology.

A polywell powered free electron laser space based platform is Dr Strangelove's wet dream. I doubt we will ever see such an evil weapon that has the scale to destroy entire cities, as conventional fission/fusion based weapons are more suited and economical for that task.

However a space based platform that provides a surgical capability to destroy missiles, planes, tanks, ships and crucial infrastructure from mouse click on a google earth type interface is a disturbing reality we must face.

A land based polywell powered directed energy beam is also a possibility i can see the US pursuing in the near future. This upsets me greatly as it will no doubt be used for missile defense and undermine the MAD doctrine. A lot of people dislike the insanity that is MAD, but it has worked hasnt it ? Shit on me and ill shit back on you before your shit has even hit me. We will be in the shit together and no one likes the smell of shit.

These are all possibilites, but now the reality.

Alot of people are getting excited about the polywell. Im one of them, but it seems to me alot of people aren't looking at the facts. Its been over 20 years since Dr Bussard filled his first patents. After all that time they finally got workable magrid that lasted 5 briefly pulsed tests to produce a appreciable number of neutrons. Its as almost people forget that we arent aiming to produce a few neutrons here, we are aiming to produce mass quantities of POWER. WB6 magrid coils used 4000 amps over half a millisecond. Ignoring the scaling issues, we need to extract a continuous 4000 amps from fusion reaction products just to power the coils. Without accounting for other systems, without even making excess power we are facing some formidable engineering challenges. I cant wait to contribute, but even with funding its going to be a long road, and im an optimist.

There are currently about 2 or 3 Free electron lasers in the world. They are still in the early stages of research and development and i cant say when one would have the capability to knock down missiles or pierce through the atmosphere, Much less be able to be transported.

The space program needs a massive kick in the butt, which may happen soon considering the U.S. has some competition again. Even still a new heavy launch vehicle yet to be developed will be needed to get objects the scale of polywells and FELS into orbit unless they adopt an ingenious modular design.

I see a strong parallel between the polywell today and other technologies when they were in their infancy. Rockets had an efficiency of 2% before Robert Goddard came along in 1920 and applied the De Laval nozel to the combustion chamber increasing their efficiency up to 50-70%. I would equate this to the EMC2 team discovering the conformal toroid magnet geometry. Even with the industrial might of WW2 it was still 40 years before rockets entered space.

The future is shaping up to be pretty interesting again, new technology will change the face of warfare, but im thinking we wont have to be worrying about the things mentioned here for 20-40 years.
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Indrek
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Postby Indrek » Fri Nov 16, 2007 8:00 pm

About orbital death-rays burning individual insurgents. I suggest you watch this video to see some of the tactics:

http://www.youtube.com/watch?v=afv5el1-nhg

Your best bet is to play dead.

- Indrek

JohnP
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Postby JohnP » Fri Nov 16, 2007 9:16 pm

WB6 magrid coils used 4000 amps over half a millisecond. Ignoring the scaling issues, we need to extract a continuous 4000 amps


If you can use superconducting coils and can keep those babies cold with all the fusion going on, you won't need to power them continuously.

Keegan
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Postby Keegan » Sat Nov 17, 2007 9:47 am

You said it best John, we are going to have to keep those babies cool. That is going to require mass amounts of coolant or energy from refrigeration systems. Im still trying to get my head around the whole superconductor thing. Superconductors allow current to flow unimpeded. So in a super conducting magnet the mass amount of circulating current creates a strong, lasting magnetic field. Im a little confused as to how it circulates. I also read superconductors screen out external magnetic fields.

It just seems too good to be true. I just programed myself to believe that magnetic fields collapse, that it takes energy to maintain a field at a certain strength

Also MRI machines are a singular magnet. The field is uninterrupted to a great extent. In the pollywell magrid the fields are all pinched together. Something just doesnt seem right, i feel it may take more juice than people think. Plus i also read that superconductors don't like oscillating current. That means we cant modulate the magnetic fields. Bummer.
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MSimon
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Postby MSimon » Sat Nov 17, 2007 10:56 am

MRIs use a set of coils.

They cool with LHe cooling the super conductors. Then a vacuum space then LN2 cooling around the LHe.

For a high powered unit we add 1 more vacuum space and circulating water.

Coil currents decay because of resistance. No resistance no decay.

Keegan
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Postby Keegan » Sat Nov 17, 2007 12:26 pm

Its still doing my head in. Take a coil of wire (an inductor). Put some dc current through it. A magnetic field rises with time. When the current stops, the magnetic field collapses which induces current back out of the inductor the exact reverse it entered it. The magnetic field is mathematically like a spring, you apply force and unless you keep applying the force it will snap back.

All the literature i have been reading on superconductors says when you generate a magnetic field with superconductors you need little to no power to maintain the magnetic field. Say you put current through a superconducting coil of wire. You have this energy circulating with no resistance which is cool, but i thought you were still fighting a magnetic spring that wanted to snap back. This would suck energy from the system. I can understand if it needed less power to maintain a magnetic field, but a magnetic field with no extra power ? it seems like i am missing some physics here.


The coil geometry of MRI coils seems fairly basic (its a toroid more or less). I have read up on the geometry of accelerator cavities (quadrapole etc). But i haven't seen anything that squishes the field lines up against each other like the polygedral cusp. Even though the coils are simple toroids the overall geometry is fairly complex. Why should we assume that it will work just the same as the simpler stuff ?

cheers -k
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dch24
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Postby dch24 » Sat Nov 17, 2007 7:29 pm

Keegan,

The force from a spring is F=K*x, right? And the voltage from an inductor (following your analogy) is V=L*dI/dt, right? Resistance is not a term in the inductor equation. Now, everyone knows that real inductors have non-zero resistance. But it's typically so small that it's not a factor.

Running 4000A through an inductor is going to produce a significant amount of heat from the resistance in the wires. But that energy loss to heat will I think still be insignificant for the inductor equation.

So what I'm getting at is -- if I remember right from when I took the class -- an inductor is typically modelled without any resistance anyway. Even superconducting coils behave like plain vanilla inductors. So creating an oscillating magnetic field still requires a transfer of energy into and out of the inductor.

The only difference (AFAICS) between a superconducting coil and a copper coil would be the energy lost due to resistance: E=I^2*R.

dnavas
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Postby dnavas » Sat Nov 17, 2007 7:38 pm

Keegan wrote:Its still doing my head in. Take a coil of wire (an inductor). Put some dc current through it. A magnetic field rises with time. When the current stops, the magnetic field collapses which induces current back out of the inductor the exact reverse it entered it. The magnetic field is mathematically like a spring, you apply force and unless you keep applying the force it will snap back.


Isn't it more like the magnetic field in an inductor is stored energy? The only way to deplete it would be to perform work. The induced current in a superconductor meets no resistance, no electrical potential develops, no work is done. ??

Edit: err, also, don't inductors resist changes in current? Wouldn't the induced current be in the same (not opposite) direction?

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Postby tonybarry » Sat Nov 17, 2007 9:15 pm

Keegan, you are correct here. When you energise the superconducting ring by closing the switch, the magnetic field exists "forever" but only as long as you don't push against it. If electrons subsequently travel through the hole in the ring (i.e. free electrons as part of the polywell, or electrons confined in the exciting wire) then the magnetic field will react against that current change, and change the circulating current in the ring, and hence change the magnetic field, either increasing its strength or decreasing its strength according to whether the magnetic field does work on the electron, or the electron does work on the field.

If an electron is orbiting in the magnetic field of the ring, looping through the centre of the ring and then out around the outside of the ring and then back through the centre, no work is done on the electron (it's just in an orbit) so it can remain in the loop forever. If however a charged species (e.g. a helium nucleus) possessed of great kinetic energy flies through the centre of the ring and off forever, this corresponds to a current, and it will either augment the magnetic field or reduce it according to its direction and charge. I suspect the canny Dr. Bussard has arranged things so that liberated He nuclei (alphas) will augment the magnetic field as they speed away, slowing the nuclei down (slightly) as they zoom out.

Moral of the story - superconductors are great, but there is no free lunch. If work has to be done, then someone has to sweat.

Image

MSimon
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Postby MSimon » Sun Nov 18, 2007 4:25 am

Fixed magnetic fields do no work on charged particles.

You can't charge superconductors by induction. They don't like changing fields. (It is being worked on)

Some currently in use take minutes to charge up. MgB can be charged in a few seconds.

Here is how you do it:

Heat a very small section so it is not superconducting. Input your current across that section. Once your current is up to the final level let that section cool and you then have your circulating current.

Keegan
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Postby Keegan » Sun Nov 18, 2007 4:34 am

^^Your right dnavas. It seems i a had a brain meltdown after a few beers. I was thinking of what happens in an LCR circuit. With just a plain inductor the energy is stored in the magnetic field and the induced current of the collapsing field flows in the same direction.

Thanks for the picture Tony. It helps illustrate my point. In that picture those magnetic field lines are nice unimpeded loops. In the polywell they are pinched 45 degrees at the centre and flowing in opposite directions. Just wondering if this could be seen as a sort of friction to the magnetic flywheels, an energy loss.

Super conductors are sexy, but a big slice of the 200mil Dr Bussard was asking for would be required to forge them. Thats why i have been largely ignorant of them. I have just been focusing on how much one could achieve with good ol copper in a DIY reactor.
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dnavas
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Postby dnavas » Sun Nov 18, 2007 6:56 am

MSimon wrote:Fixed magnetic fields do no work on charged particles.

You can't charge superconductors by induction. They don't like changing fields. (It is being worked on)
...
Heat a very small section so it is not superconducting. Input your current across that section. Once your current is up to the final level let that section cool and you then have your circulating current.


Yeah, I didn't know that, but I was kind of concerned by it. If the field doesn't collapse, it stands to reason that it would be hard to put one there in the first place. Can you induce a current across the non-superconducting section, or does that not work either?

I am kind of surprised, though, as I thought that a very thin layer at the top of the superconductor does react/intersect magnetic fields, and I would have thought one could use that effect to jump-start/charge. Ah well.

I'd be very concerned about quenching in the dynamic Polywell environment, but that's probably because I don't know what I'm talking about. Seems likely that all of these high temperature He+ ions flying around would cause a bit of a snag here and there, and snags are kind of contagious....

Anyway, thanks for the info! Learning lots....

tonybarry
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Postby tonybarry » Sun Nov 18, 2007 8:10 am

Hello Simon,
I feel intuitively that a fast moving charged particle passing through a magnetic field in such a way as to cut across lines of force will have work done on it to change its direction.
I may be in error here, but if this were not the case, then there would be no advantage to using electrons in the polywell to contain positively charged species. The electrons have a much lower mass, so are more easily worked on by a magnetic field.
However my knowledge base is limited to elementary electrical theory, and I may be incorrect.

Regards,
Tony Barry

MSimon
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Postby MSimon » Sun Nov 18, 2007 4:20 pm

tonybarry wrote:Hello Simon,
I feel intuitively that a fast moving charged particle passing through a magnetic field in such a way as to cut across lines of force will have work done on it to change its direction.
I may be in error here, but if this were not the case, then there would be no advantage to using electrons in the polywell to contain positively charged species. The electrons have a much lower mass, so are more easily worked on by a magnetic field.
However my knowledge base is limited to elementary electrical theory, and I may be incorrect.

Regards,
Tony Barry


Tony,

You are confusing acceleration with work. As long as mv (momentum) scalar value does not change - no work is done.

Think of the earth moon system. The moon is constantly being accelerated by the earths grav field. No work is being done (except that minuscule fraction lost to tidal friction).


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