Re: [FT] Railgun Goals

On Fri, 27 Nov 1998, Andrew & Alex wrote:
> A short, large diameter barrel is
> easier to manufacture and aim than a long, thin barrel.

one of the problems with big powerful electromagnets is this:
electromagnets use a coil of wire with current in it it generate a 
magnetic field. a current flowing in a magnetic field experiences a
force.
in the case of coils, this force is outwards. hence, at large fields,
electromagnets tend to explode. the research group down the road here at
oxfurd builds such things, and half of the coil is carbon fibre for
strength. they still have to run the tests at night in case the
explosion
annoys other labs.

if you use a smaller diameter coil, you have less length of wire
per turn (and it is turns which determine field strength), and so less
outward force. i'm not sure exactly how the physics work out (and i'm
not
inclined to figure it out right now, i have DNA to macerate back in the
lab), you might find that smaller diameter barrels have less radial
force
per unit field strength, and so can operate at higher field levels. of
course, you might also find that larger barrels spread the stress wider
and so it makes no difference. unless someone wants to run the algebra
on
this, we'll leave it as PSBable.

just my 20 m$

Tom