OT: EMP and Equipment

[Allison]

>
>Subject: Re: OT: EMP and Equipment
>   From: jim stephens <jwstephens at msm.umr.edu>
>EMP as related to an atmospheric nuclear explosion is caused because
>of the release of energy from the atmosphere ionized by the radiation
>pulse sent by the blast.

Radiation as in Energetic Particles or as Waves like EM?

>when the ionized gases recombine, they release a huge amount of radio
>frequency radiation in a pulse.  This causes any junctions to have
>induced a potential across them, unrelated to being plugged into anything.

That pulse wouldn't happen to be ELECTROMAGNETIC would it?

>This is similar to the damage from static electricity, but is not related
>to >direct conduction and release of potential to ground, which static
>usually is, but is rather induced potentially deep inside any devices 
>however well shielded.

Your confusing netrons and gamma particles that go through most 
everything to Electromagnetic waves that don't.  Faraday shield
will stop or suffifiently attenuate EM waves.


>The only way to guard against this is to engineer all junctions and
>circuits to withstand and survive this potential.

That makes stuff resistant.


>This is also the reason that vacumn tube circuits recover faster or at
>least they should, if the circuits don't get damaged by a sudden jump
>in potential passing thru them and settle back down.  They don't have
>solid state junctions to be damaged permanently in such an event, and
>in theory should settle back to original function.

Wrong in part.  Tubes are more resistant as anything that nominally 
operates with hundreds of volts is less likely to be terminally 
affected by a 20V spike.  However a piece of logic that runs on 5V
will be totaled with even a 1V spike.

>note that satellites in orbit, or airborne aircraft can be equally at
>risk to EMP.

Yes they are.  At least the electronics will be.  A C150 flying behind 
a real honest to dog Slick magneto won't even notice it.
However Sats die not only from the EM fields from solar storms they
also suffer from the ionizing radiation that literally posions the
silicon and it's doping.


>Note that the high potential caused by lighting is mostly caused by
>conduction, not by the field of the bolt.  It is an excess of electrons
>looking for a path that cause the damage there.

Really wrong!  While that is the primary damage path it is far from
the only path.  Near hits are a danger due to the EM field resulting.

I have a computer that was damaged by EMP from a direct hit to the 
house I was in at the time.  It was not connected to power or terminal.
The damaged chips were near the physical edges close to openings as 
the case (NS* horizon with wood cover) was not 100% enclosure.
The terminal (an H19) was totaled.  It too was no cables connected
and line cord laying on the ground. Another machine in the house 
that was connected was totaled. A portable battery operated common
6 transistor AM radio was cooked, mixer/osc transistor connected 
to internal loopstick antenna was shorted(that's a magnetic loop!).

Remember in an intense EM field any wire is the load side of a 
transformer (or field of a generator) and the connected circuits
have to dissipate the power induced in that winding.

>  Nuke EMP is from the radiation pulse and is effective far from 
>the point of the blast, which is why it could be an effective 
>threat over hundreds of miles distant.

Even then inverse square law says no, not that far.  Check the 
various studies done with the Nevada desert blasts and out in 
the Pacific.  

Military field radios are EMP resistant.  Ever look at field radios?
They have everything going in or out through connectors, when 
connectors are unplugged there are conductive caps placed over 
the connector and the cases are all continous conductive including
closeable covers on things like speakers. This is partially to protect 
against handeling and environment but also EMP.  If "you" a user are 
far enough away to survive without ill effects likely those radios
will.  The key is anything too close is at risk.  Distance is safety.
For known cases, Hiroshima, Nagasaki, Pacific Islands that safe
distance only a few miles from ground zero.  This does not include
radioactive fallout and it's longer term poisoning.

Further in the desert where thy did underground blasts for years 
at the top of the hole were older computers with CORE memory that 
were subjected to both EMP and physical shock waves.  Usually the
system was trashed due to the trailier being tossed around but, 
the cores would be pulled and read if the machines were too 
mechanically damaged.

Fact, bombs are bad.  Being close to them is very bad. 


Allison