More reasons for the Navy to have polywell reactors

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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MSimon
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Post by MSimon »

I'm absolutely convinced that theoretical physicists try to make magnetic fields too simple.
Feynman was of the opinion that magnetics was the most difficult part of basic physics. Esp. when you start throwing iron at problems. Very non-linear.
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hanelyp
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Post by hanelyp »

Another question is, what of antennae? A typical antenna is an open circuit, and deleting the term might be invalid in that case.
The basic dipole antenna is an open circuit at DC, but very much a closed circuit at resonance due to capacitance.

Nik
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Like a ferrous / non-ferrous magnetic separator...

Post by Nik »

I'm very surprised Graneau had that reaction, for industrial-scale recyclers use DC fields to attract ferrous alloys and AC to repel non-ferrous metals...

So, while a soft-iron 'rider' would be pulled *into* rising field intensity, a copper or alumin(i)um rider would be repelled by the eddy currents.

Similar phenomena permit Maglev motors, trains etc...

QED ??

MSimon
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Post by MSimon »

A mixture of ions and diagmagnetic materials partially ionized?
Please give exact proportions.
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GIThruster
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Post by GIThruster »

Anyone know what that is on the muzzle? Are they using a plasma window to evacuate the barrel?

D Tibbets
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Post by D Tibbets »

GIThruster wrote:Anyone know what that is on the muzzle? Are they using a plasma window to evacuate the barrel?
Perhaps a stupid observation, but if the research rail gun used a vacuum with a fragile end cap at the muzzle to keep the air out, this would explain why there is such an impressive muzzle flash. Otherwise, I suspect little would be seen at the muzzle other than perhaps shock wave distortions. Would a deployed rail gun utilize a vacuum with the complexity of a new end cap for each firing, or would it push against the air in the barrel, or would it predetinate a chemical charge in front of the projectile to mostly evacuate the tube...?
[EDIT] Actually, with a rail gun there should be no need for a seal behind the projectile (to contain the expanding gas from the charge detonation). So the projectile could be sliding past the air in the 'open barrel'. Still this would offer some resistance and would result in a longer (or more powerful) rail length to reach the same muzzle velocity.

Dan Tibbets
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GIThruster
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Post by GIThruster »

Yes well, no need to use a solid end cap. A plasma window ought to suffice if it can be engineered to not interfere with the operation of the gun.

http://en.wikipedia.org/wiki/Plasma_window

Certainly, pressing a hypersonic projectile through air while in the barrel has serious consequences. You'd either need to port the barrel all over (and there's no sign of this in the photo) or you need to evacuate it and keep it evacuated between shots--perfect app for the plasma window.

ladajo
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Post by ladajo »

There are no current plans for military application railguns to be evacuated of air.

Test devices have been fired with multiple consecutive shots, and work is being done on lightweight barrels, and none have a requirement to have a vacuum. It does not effect the firing at all.
As I understand the muzzle blast is an artifact of the armature to rail interface during firing creating a plasma.
The bigger issue being faced is pulsed power supply density in a package suitable for mobile applications. Ships, no problem. Tanks and vehicles, big problem. Aircarft, a problem.

krenshala
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Post by krenshala »

My understanding was that the muzzle-flash is a combination of vaporized armature and compressed air built up in front of the armature as it travels down the rails. The compression gets high enough to "ignite" the air.

A test I saw video of a few years ago (firing into a ballistic pendulum for early version of the navy's rail gun) they had the railgun peel itself open about 1/3 of the length due to the air pressure in the barrel exceeding the strength of the steel used for the rail frame and the bolts holding it together. The air holes along the barrel length were apparently insufficient for the task of reducing built up air in front of the armature. I don't remember the power used, but the armature was a 4" Lucite block with a band of aluminum around it.

Unfortunately I saw the video on TV (Discovery Channel, IIRC) but don't remember what show it was, and have not been able to find it online.

ladajo
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Post by ladajo »

Yes, the armature scheds material, as well as the rails, as I understand, it turns to plasma and then pops the fireball at the end of the barrell. There has been some research on how to control this, and I think they have a better handle on it, but that did not include creation of a vacuum in the weapon. I would also think the the transition shock for a hypersonic object from vacuum to instant sea level air density would be impressive. Brickwall comes to mind. Kind of like falling into the water from 200 feet up.
Rail containment is a big issue. There are obviously significant pressures/forces at work. The most spectacular I know about launched the upper containment through the roof in Texas. But as I understand this is all Lorentz force based.
In order to weaponize, the issue is size and wieght. The army has had success in a lightweight raligun barrell. I think it is 3 meters long. The unit is an all-in-one. This is important because mounting the system on a platform requires a sensible field barrell, vice a lab test barrell. The Blitzer test video is a good run on what a mountable larger scale weapon will look like. It was built along ship installable gudielines. Look at it, and then the graphics on the Navy's DD(X) website. Purdy darn similar...

hanelyp
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Post by hanelyp »

Given the immense currents used in firing a railgun, I wouldn't be surprised if an arc was struck as the projectile left the end of the rails. Similar in some ways to scratch starting an arc for welding.

GIThruster
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Post by GIThruster »

I'd love to see the stats on the cryogenic ceramic caps that DARPA and ONR have been working on the last decade for these guns. ONR is paying MTEC and General Atomics for years and MTEC has an affiliate with all sorts of cryo-goodies, Cryo-Circuits. If you look at the 2006 link you'll see the original contracts and the 2010 link shows the news at C-C.

I've been wanting to see this stuff for 4 years now but they don't even publish the simplest stats. Might one day make a good M-E thruster core.

http://www.mtechlabs.com/about/news?year=2006

Essentially though, they're looking at integrating the entire power systems in a cryo environment, both for man portable systems, ostensibly for compact communications (DARPA) and larger systems for the electric fleet. MTEC is even working with NASA a little on their superconducting ducted fans for future aircraft.

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