On 25 Aug 2016 at 9:29, DED [Traveller wrote:
> Given examples from other things Traveller capacitor tech should be
> able to keep the bulk down even with the capacitors as part of the
> "bomb".
>
> So depending on how good the tech is, you may have anything from
> briefcase sized (sort of an EMP satchel charge) to grenade sized.
>
> ===============
> Great! Didn't think it could be scaled down that small. Makes for a
> better delivery system. ===============
Well, the capacitors can be smaller (after all, k=look at what the
capacitors a Black Globe* uses can store! Or "jump capacitors for
those versions of Traveller that have them as part of the drive.
But now that I think about it, the physical size of the coil in the
EMP unoit is probably going to limit the strength of the field and
thus the strength of the EMP effect.
Remember, the basic design works like this:
Have a coil that'll produce a strong magnetic field.
Dump a *lot* of current into it fast.
As the field strength peaks detonate an explosive charge that
compresses the coil which spikes the field density even higher.
High current requires thicker wires (for lower resistance). You can't
use superconductors (even if they are available in your TU, because
superconductors revert to being fairly lousty conductors when any of
three things are exceeded:
Critical temperature. Not only do they quit superconducting when the
temp exceeds this, but since there's now a significant amount of
resistance, you get termal runaway as the current makes it even
hotter, which increases the resistance which makes it even hotter
which...
Can you say postive feedback loop?
Critical current. Above a certain number of amps, supercondoctors
revert as well. Again, you get a feedback loop as the now high
resistance causes heating which leads to the critical temp problems.
Critical field strength. If the ambient magnetic field strength gets
too high, superconductors revert to high resistance. You may not get
a feedback loop because the reversion won't affect the field
strength.
The values of critical temp, current and field strength will be
different for different superconducting materials. But they seem to
nbe an inherent part of the physics that makes superconductors work.
Since a coil for an EMP uniot will be subjected to high current *and*
high magnetic fields, superconductors are right out.
So, with regular conductors, the thickness of the wires limits the
current. Given that you only need them to handle it for a second or
less, helps, but only so much.
Field strength depends on three things. Number of turns in the coil,
size of the coil, and what it is using for a "core".
More turns is good. But "bigger" (length and width) are bad. But
smaller coils mean fewr turns for the same size wire...
So, with the same materials, in general a bigger coil will give you a
bigger spike.
Capacitors ability to store power depends opn size (all else being
equal). So the bigger the capacitors the more current they can dump
into the coil.
So a briefcase sized unit can probably kill unshielded electronics
within a dozen meters, but a grenade sized one may be lucky to do it
to something a foot away.
I'm guessing that "power" of the unit depends on volume, so a unit
twice as big (ie 2 times as high, wide and deep) will be 8 times as
strong.
Size matters <eg>
--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com
> Given examples from other things Traveller capacitor tech should be
> able to keep the bulk down even with the capacitors as part of the
> "bomb".
>
> So depending on how good the tech is, you may have anything from
> briefcase sized (sort of an EMP satchel charge) to grenade sized.
>
> ===============
> Great! Didn't think it could be scaled down that small. Makes for a
> better delivery system. ===============
Well, the capacitors can be smaller (after all, k=look at what the
capacitors a Black Globe* uses can store! Or "jump capacitors for
those versions of Traveller that have them as part of the drive.
But now that I think about it, the physical size of the coil in the
EMP unoit is probably going to limit the strength of the field and
thus the strength of the EMP effect.
Remember, the basic design works like this:
Have a coil that'll produce a strong magnetic field.
Dump a *lot* of current into it fast.
As the field strength peaks detonate an explosive charge that
compresses the coil which spikes the field density even higher.
High current requires thicker wires (for lower resistance). You can't
use superconductors (even if they are available in your TU, because
superconductors revert to being fairly lousty conductors when any of
three things are exceeded:
Critical temperature. Not only do they quit superconducting when the
temp exceeds this, but since there's now a significant amount of
resistance, you get termal runaway as the current makes it even
hotter, which increases the resistance which makes it even hotter
which...
Can you say postive feedback loop?
Critical current. Above a certain number of amps, supercondoctors
revert as well. Again, you get a feedback loop as the now high
resistance causes heating which leads to the critical temp problems.
Critical field strength. If the ambient magnetic field strength gets
too high, superconductors revert to high resistance. You may not get
a feedback loop because the reversion won't affect the field
strength.
The values of critical temp, current and field strength will be
different for different superconducting materials. But they seem to
nbe an inherent part of the physics that makes superconductors work.
Since a coil for an EMP uniot will be subjected to high current *and*
high magnetic fields, superconductors are right out.
So, with regular conductors, the thickness of the wires limits the
current. Given that you only need them to handle it for a second or
less, helps, but only so much.
Field strength depends on three things. Number of turns in the coil,
size of the coil, and what it is using for a "core".
More turns is good. But "bigger" (length and width) are bad. But
smaller coils mean fewr turns for the same size wire...
So, with the same materials, in general a bigger coil will give you a
bigger spike.
Capacitors ability to store power depends opn size (all else being
equal). So the bigger the capacitors the more current they can dump
into the coil.
So a briefcase sized unit can probably kill unshielded electronics
within a dozen meters, but a grenade sized one may be lucky to do it
to something a foot away.
I'm guessing that "power" of the unit depends on volume, so a unit
twice as big (ie 2 times as high, wide and deep) will be 8 times as
strong.
Size matters <eg>
--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com