Emp flashlight and battery question – survivalist forum gas variables pogil worksheet answers


I have done some studying up on EMP’s, as an electrical engineer that I am, when it come to semiconductors (and yes LED’s fall in this as well). Anything that has a semiconductor in it will fail. what happens is the semiconductor will heat up to the point the the die melts, shorting out the device. So batteries will be fine but the LED’s are toast, but if you are using an incandescent bulb in your flashlight you will not have any problems.

First off, semiconductors aren’t particularly susceptible to EMP by them selves. Millions if not billions of semiconductors have been been exposed to EMP without damage, The few that get damaged are the ones that are connected to wires that act as antennas. I’ve seen the USAF lab in Warner Robbins AFB hit semiconductors with pulses thousands of times more powerful than EMP (I think they were running fields 10-20x as strong (500-800 V/m is what I think were zapping them with), and pulses much, much longer), without inducing damage (which is the military goal, electronics that can survive in front of a fire control radar- and in their WRAFB’s case, they want to induces the failure so they can take the chip apart and find the failure point.)

Second if you knew anything about nuclear electromagnetic pulse, it’s not the power that causes the problem, it’s the voltage- there really isn’t that much power. In a high altitude nuclear detonation, most (99%) of the energy isn’t released as gammas. Most of gammas (75%) don’t travel towards the earth. Very little of the energy is turned into non ionizing radiation. SO there isn’t enough power to be melting silicon across the entire united states. What does happen if you couple enough of the nanosecond pulse into a semiconductor, it hits a high impedance junction and the voltage can blow a hole in the microscopic junction layer (in CMOS, you get reversible effects first.). Under any normal conditions that takes a conductor feet or inches long to collect enough energy, especially under real world conditions.

BTW, a 50,000 V/m EMP pulse is is 663W/ cm^2. That’s a lot of power. But it only lasts for 100 nS or so at that level. That’s ten millionth’s of a second. So our energy is .63 mW-S/cm, or .63 mJ/cm^2. Not melting a semiconductor die at that power level. Over a second, that’s less power than from a cell phone. And that’s assuming the chip somehow focused the energy from a full square cm on the die, and the die absorbed all of the energy.

And you realize EMP peaks in the HF band. What hams call the 160 meter to 30 meter bands. They are called that due to the wavelength. You need antennas 1/2 of that wavelength to efficiently capture energy. so an antenna about 20 to 80 meters is going get the strongest signal per foot. And the leads on your semiconductor are millimeters, and the ones in a flashlight are centimeters long (also in a coaxial (metal shell) or parallel (plastic body)arrangement which makes for a really poor antenna arrangement.) But they are also hundreds of times too short. Or put another way, the frequency they might couple well (say 500 Mhz) is where EMP has dropped 1/50 of it’s levels at low frequencies. (I’m thinking 1/50 works for a 6 CELL Maglite, for a surefire sized light, maybe 1/200 the power)

While it’s a wild guess what EMP would do to our society, or even the power grid, it’s not had to know what it does to a cell phone, laptop, electronic lock, watch, flashlight, etc (assuming non of the above is connected to a power or data cable- that’s makes it hard to make generalizations.)

Lots of small electronics (such as the Ultra radaic plus radiation meter I have in my desk) are certified to be EMP resistant. I’m sure the same tests were done before the military picked aimpoints or PVS14s, or whatever. I know for a fact they did it on the MAS Hamilton X-07 lock, the DOD "electronic" safe lock.

EMP is a Electro Magnetic Pulse. its just a pulse of electromagnetic radiation. You could describe sending morse code, or radar as strings of EMPs. Pulse implies something of short duration so a solar storm (or the sun rising) is not properly described as a pulse (and the sun is a hell of a generator of electromagnetic radiation- next month through march, it’s going to jam every stationary (geosynchronious) satellite link in the northern hemisphere, and do the same in the southern hemisphere in late march and april- but that’s still not EMP.)

When emergency management, or the military, or a well informed pepper, uses the term EMP, they are usually referring to a Nuclear EMP (NEMP), typically a high altitude EMP (HEMP). It could also mean directed energy weapons which can be used to disable electronics at short distances.

If it’s not clear, if a nuclear device goes off at ground level it will free Compton electrons just like at high altitude, but with billions of trillions of gas molecules per cubic foot, they aren’t going far, and the EMP will be insignificant compared to the blast damage (again unless done right outside a hardened shelter, where you MIGHT be able to damage something that doesn’t get destroyed seconds latter. For a high altitude NEMP (30km is a figure of merit), the atmosphere is 1000 times thinner, so an electron will travel 1000 times farther, more or less making the current density 1000 times higher. There are other effects that make the pulse stronger, and more coherent also. There’s tons of classified and unclassified work on source region EMP, and I’ve ignored most of it, because unless you design battle ships, tanks, or something similar, it’s not particularly relevant.. For a battle ship (OK, they don’t exist anymore, so a capital ship of some sort) that might be attacked with a nuclear torpedo or depth charge (subs, I guess), it’s relevant.

BTW the above description of high altitude EMP, should make it clear than any ballistic missile can cause an EMP. If it doesn’t get in to the ultra thin air, then it’s not much of a ballistic missile. The problem is the technology of building a lightweight nuclear device is challenging, and a much simpler bomb, is going to tend to weight tons, and be incompatible with the likely available ballistic missile technology (A Saturn-5 rocket could put Fat Man (5 tons) past 30 miles, but a SCUD ain’t gonna get off the ground. A scud missile will carry a Russian designed modern nuclear weapon.)