On Fri, 18 Jul 2003 00:20:51 -0500, David L Peterson wrote:
On Thu, 17 Jul 2003 22:12:06 -0700, "Richard W."
wrote:
The old magneto or point distributor would be the way to go. I would want to
stay away from any type of electronic ignition system. We are talking
survival here and if it came to nuclear weapons then everything with an
electronic ignition wouldn't work. Also it wouldn't help to go down to the
parts store, because the magnetic flux would have ruined all the new parts
sitting on the shelf. Any pre 1972 car with points would quit when the blast
went off, but all you would have to do is restart the engine. Anything newer
would need a tow truck to get it home. Assuming you could find a tow truck
that still ran.
I'm thinking that if I was close enough for this to be a problem I
wouldn't be worrying about power for very long. 
Actually, I'm not
certain, but I'm thinking that using a power transistor driven by the
points to drive the coil (I've seen schematics of this kind of thing
for a hotter spark) would be robust enough to survive. What blows?
Any diode type junction rectify the too much power and blow? you just
talking normal nuclear bombs or EMP weapons? I'm not sure any coils
or condensors would survive an EMP event. Anyone know the details of
this stuff?
EMP is the induced surge that causes a static crash in an AM radio
when there is a nearby lightning strike (or other high current arc event).
If the lightning strike is very nearby, the EMP will induce a surge on any
long exposed wiring (antenna) large enough to possibly puncture solid
state device junctions.
Just think of nuclear EMP (NEMP) as a very large lightning bolt.
If a 1 MT device is detonated nearby, the NEMP will be similar, though
on the order of about 10 times larger, to an ordinary nearby lightning
strike. For ground bursts and low altitude bursts, the destructive
magnitude NEMP effects will be limited to a radius not much larger
than the blast radius, so worrying about NEMP effects is pretty much
moot.
However, a high altitude burst is a bit different. Because the mean
free path of the Compton electrons generated by the detonation
is *much* longer at high altitudes, the magnitude of the pulse
only decreases inversely linearly with distance instead of inverely
to the square of distance (line coupling instead of point coupling).
That means much longer range effects are possible. In other words,
a detonation at a 200 km altitude will produce NEMP effects on the
ground similar to those of a low altitude or ground burst device of
similar magnitude 1.41 km away.
Still, the receiving antenna (exposed wiring) has to have enough
capture area to gather significant energy from the NEMP. The Navy
operates (or did operate in 1988) a NEMP simulator to test whole
ship naval electronic systems. The ARRL (amateur radio organization)
got permission to test some typical amateur radio installations in the
simulator. They found damage to the front ends of HF transceivers
when connected to 80 m halfwave dipole antennas (about 136 feet),
but no damage at all to handheld transceivers and auto mounted
VHF mobile rigs when the exposed wiring lengths did not exceed
1 meter.
What this says to us is that unless the equipment is connected to
exposed wiring of significant length, the chance of damage, outside
the blast radius of the generating detonation, is slight. The scare stories
about every auto, and every stored electronic auto part, being destroyed
by NEMP are just scare stories based on ignorance of the physics of
NEMP (and electromagnetic waves in general).
Note, though, that the possibility of damage to the power grid, and the
telecommunications networks, is very real. That's because they have
a huge amount of exposed wiring to act as antennas, so their capture
area for the NEMP energy is also huge. So they have to take extraordinary
measures to protect connected equipment against EMP. These measures
include wiring practices, use of single point grounds, gas discharge shunt
protectors, etc.
None of that is a concern for electronics which is not connected to exposed
wiring which can form an antenna with a large capture area, however. It simply
intercepts too little energy from the pulse to do any damage.
Gary