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Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
Ive been researching about railguns recently, and I keep coming across B-dot probes. It seems that they measure magnetic fields produced by plasma. This would be very usefull in collecting Data. Does anyone know anything about these? the only articles i can find are ones on IEEE and i dont have a subscription.
As for velocity skin affect, it seems that it can be prevented by using a conductive lubricant (indium) with a resistive coating on the armeture. The coating should be 10x the resistance of the armeture. For those of you that dont know what velocity skin affect is: as a projectile gains velocity, the current begins to flow primarily in the back of the projectile, increasing resistance greatly. Think of it as a water bottle (armeture) with some water in it (electricity). When you move it fast, the water moves and collects at the back. My question is which would be better: 1) have the higher initial circuit resistance, and eliminate velocity skin affect 2) dont use the resistive layer and have low resistance, that climbs up
I would post the technical paper's, but there from a paid subscription database (ebscohost) my school has (would i still be able to post it since the copyright is expired? 2001)
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
There are members on the forum that can get ieee papers so if you post its information it might mysteriously appear in your inbox.
In any case a b-probe seems like just an ordinary coil of wire that is stuck to the gun that should react to the fields present (and by carefully picking what planes you put everything you can use it to find when the rails are shorted together by the projectile). It is useful for a plasma armature since you cant use a chrono to detect plasma for obvious reasons. I suppose that it would also be useful for normal copper slugs since it would give you an idea of the projectile is being accelerated over the whole length of the gun or not...
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
*cough* "http://ieeexplore.ieee.org/Xplore/login.jsp?url=/
iel1/20/10395/00486539.pdf?arnumber=486539 and *cough*
thanks for the articles! And if anyone wants to see a 3 series technical paper on railgun lubrication (indium), or a permanent magnet agumentation, or self agumented (shunt) papers.....
Edit
another question: what is a shunt?
Im hoping to get some pressure sensors to moniter the pressure, but the ones that i picked (specifically designed for military rocket engines) cost $3k each (i need 3), so the guy im talking to is seeing if there are any that can be donated.
anyone know good resources on articles on rogowski coils? ide like to build my own.
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B-dot Probe and velocity skin affect
