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Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
My theory thread here got mostly ignored, but I think I learned an important lesson from it: Railguns have problems because the inductance gradient is tiny, and induction coilguns are expensive to make because the pulse has to be very short necessitating the use of low capacitance, high voltage capacitors.
Combining the advantages of both would be a railgun with external iron that brings the inductance (and therefore the gradient) up by a factor of 100 or so, so I have been pondering whether a MOT core could be wrapped around my 5cm mini railgun (mind you 5cm is the length, not the caliber). Using the approximate formula from Sulaiman
For small airgaps you can use L=Mu x (Nsquared) x A/d L is inductance in Henries Mu is the permeability of free space (air) = 4 x pi x 1E-7 A is the cross-sectional area of the airgap in square meters d is the length of the gap in meters. Nsquared is the number of turns, squared.
it seems that a reasonable inductance could be obtained even with a rather large air-gap of 1cm or so. I don't think that saturation of the core would be a problem either, since the area of the core is much larger than the bore of the railgun, so the field in the bore can be significantly higher than the 2T saturation field of silicon steel.
Of course this would be a major undertaking in terms of machining, not only would I have to cut the middle leg from the MOT core, but ideally it should get some kind of dome shape to focus the field into the bore. So before I start grinding, I wonder if there are any opinions on how worthwhile this would be?
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Feasibility study for a railgun with external iron
