On 9 Mar 2012 at 6:42, Tim O'Reilly wrote:
> in military vehicles that get slammed by EMP they have a
> "battle-over-ride" switch that bypasses the fuses etc so that they
> can get operational again. I suspect that there's something similar
> in navy ships as well although there they have a full up maintenance
> capability. The overall idea being to get some capability back as
> soon as possible, and then, of course, work on getting the rest of
> it back while getting ready for the enemy's follow on assault...
Thing is, EMP won't blow *fuses* except at *insane* levels.
Fuses protect against excessive *current*. EMP induces excessive
*voltage*. Which blows diodes, transistors and all sorts of ICs.
> With a starship and its inherent shielding hmmm I suspect that would
> be like the difference between a fuze and a lightning arrestor (its
> been nearly 30 years so I may have the wrong term on the latter)
> basically the former may blow, and blow quickly but the surge its
> intended to counter is still relatively small and slow to build
> compared to lightning, and so the special build types used there.
> Something built to withstand (hardened) EMP would have to be faster,
> much faster still. And to be truly effective it would have to be
> able to self-recover within a short period of time, its insane to
> expect a crewman to suit up and go out on the hull to change fuzes
> when something like that is happening.
Lightning arrestors try to divert the lightning by providing an
"easier" path than the house (or whatever) wiring.
BUT EMP damage and lightning damage are very different. Lightning is
huge voltages *and* huge current.
EMP is high voltages (how high depends on the length *and
orientation* of the conductor the EMP is inducing the voltage in. But
is generally fairly miniscule current.
That's why EMP kills semiconductor based electronics so easily. A
mere 50 volts at **millamps* of current is enough to fry junctions
inside an IC.
You can *literally* kill an IC by touching it after scuffing your
shoes across the carpet. And withouit having built enough voltage to
even feel the resulting static "shock".
So it doesn't take much of an EMP to kill something that uses ICs or
even transistors or diodes.
There's a gizmo some folks like to play with called a "violet wand".
Originally a quack healing gadget, but stil sold for use by beauty
salons and the like. And for "kinky" uses.
It creates really high voltages (100kV or more) and they go thru a
glass tbe filed with krypton and other gases (which makes the tube
glow purple, hence the "violet wand".
ou some nice sparks (maybe a millimeter or so) and a shock from it.
But the current is *way* microscopic. Like I said, milliamps.
A violet wand will kill (woithout leaving any marks) digital watches,
cell phones, PDas, pocket calculators etc if used "too close" to
them.
But it can't "burn out" a hair fine wire used as a fuse. Not enough
power/current.
> Another comment in this thread was self-defeating/contradictory ...
> at one point it was mentioned that EMP would by virtue of the
> atmosphere be directed downward to the planet only and not toward
> satellites or ships in orbit, shortly later in the comment he
> mentions that EMP is 360 degree effect. The latter statement is
> more accurate, while the EMP is greatly enhanced by the interaction
> between a nuke and the atmosphere, it remains a 360 (globally)
> effect. (until or unless they've determined a way to focus the
> energy) so within the constraints of the energy being disperssed by
> range satellites could be affected.
You misread what I said. I said that to get *widespread* EMP, you had
to detonate a nuke in a planet's ionisphere. And that it'd affect a
moderate sized chunk opf the planet under it (that's how we
*discovered* EMP, when a high altitude nuclear test took out stuff in
Hawaii.
It may or may bot affect stuff farther out (in orbit) as well. I'm
not certain.
But the same nuke detonated farther out *won't* create an EMP as big.
The "full sphere" effects is a *seperate* factor. If was noting that
you can't *focus* the effects.
Detonating n the ionisphere create a huge EMP because the bomb is
surrounding by charged particles, and they are somewhat trapped in
the planetary magnetic field.
Probably get similar results up in the Val Allen belts (and this is
why solar storms like the one the other day can disrupt
communications, because a lot of communications rely on either
reflecting off the ionisphere, or being able to pass *thru* it. Which
the changes disrupt)
TLDR: setting off a nuke in the ionisphere magnifies the EMP a *lot*.
And EMP effects are generally full sphere, not focused.
> Another point in the thread revealed that a nuke is not required to
> generate an EMP, I didn't know how they did that, only that it had
> been achieved - interesting, thanks for the info
Yeah, but the EMP bombs are fairly limited effect. A briefcase sized
unit might take out stuff within a few hundred feet (if you are
lucky). A few *dozen* feet is more likely)
--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com