EMP - Page 1
Forum section: electronics / projects

author: Delta labs
author_rank: Newbie
timestamp: April 30, 2014, 11:42:41 am
content: Do any body know how explosion inside copper tube around it thick copper wire would generate high frequency and volts ?This how they generate the high volts and frequency inside EMP rocket

author: richard.cs
author_rank: Super Contributor
timestamp: April 30, 2014, 11:55:55 am
content: Try searching for "flux compression generator" but essentially expanding the tube does work against the field.

author: Delta labs
author_rank: Newbie
timestamp: April 30, 2014, 02:43:08 pm
content: Yes i know the pulse only takes microsecond to generate this high energy which is enough to destroy most of our electronics

author: TerraHertz
author_rank: Super Contributor
timestamp: May 01, 2014, 02:38:23 am
content: Not sure if these links are still current. But you can search for the titles.http://www.spectrum.ieee.org/biomedical/devices/the-dawn-of-the-ebomb/020100715Fromhttp://www.helium.com/items/1889648-bp-preparing-super-weapon-to-avert-escalating-gulf-nightmare?page=2Explosively pumped flux compression generator (EPFCG)http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator"Scientific Collaborations Between Los Alamos and Arzamas-16 Using Explosive-Driven Flux Compression Generators" - PDFhttp://www.fas.org/sgp/othergov/doe/lanl/pubs/00326620.pdf"An Introduction to Explosive Magnetic Flux Compression Generators" - PDF[‘Stamped; DO NOT CIRCULATE’]http://www.fas.org/sgp/othergov/doe/lanl/docs1/00374018.pdf

author: ejeffrey
author_rank: Super Contributor
timestamp: May 01, 2014, 04:32:35 am
content: The way flux compression works is that you have a pre-existing magnetic field (generated by a large electromagnet) that threads a conducting pipe. And explosive charge outside the pipe causes it to collapse. However, it is "hard" for magnetic field lines to move through conductors at high speed. Therefore, as the conducting shell collapses, the flux (flux = magnetic field * area) has to stay constant but be compressed to a much smaller area, so the field strength goes up. This creates a very large dB/dt, which can in turn induce large currents in other conductors, i.e., an EMP.This is a localized and relatively weak affect compared to the 'traditional' EMP generated by detonating a nuclear weapon outside the earths atmosphere. In this case, the nuclear blast creates a wave of high speed electrons which simultaneously impact the atmosphere and suddenly decelerate. Because this happens coherently over a large area, it creates a powerful EMP over an enormous area.

author: madshaman
author_rank: Frequent Contributor
timestamp: May 01, 2014, 04:52:34 am
content: OT: why do they always depict EMPs in movies as if they will effect *all* electronics, even if they're RF shielded?

author: ejeffrey
author_rank: Super Contributor
timestamp: May 01, 2014, 05:47:33 am
content: Obviously there is a significant element of dramatization, but the field strength of an EMP can be enormous (10s of kilovolts / meter), and thus can overwhelm protections designed for smaller fields, for instance by causing breakdown of insulators and arcs that then cause secondary damage.

author: madshaman
author_rank: Frequent Contributor
timestamp: May 01, 2014, 01:18:35 pm
content: Quote from: ejeffrey on May 01, 2014, 05:47:33 amI'm really just using my intuition, but 10-90KV/m seems pretty small; it would seem the majority of "damage" would occur to the power grid (and possibly hose anything plugged into a wall socket before a bunch of giant breakers fire), I'm pretty sure most vehicles and portable electronics would survive, but I'm totally eager to see what I might be missing :-)Sent from my iPad using Tapatalk

author: Tinkerer
author_rank: Frequent Contributor
timestamp: May 01, 2014, 04:51:13 pm
content: The above is correct. Explosively pumped flux compression generator is the proper name to such a device that use an explosive.Power will vary according to a number of factors. Some research in regards to vehicles suggests that it takes above 20kV before they start malfunctioning, but once you have hit 30kV that is enough to kill them.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 01, 2014, 07:03:11 pm
content: Quote from: madshaman on May 01, 2014, 01:18:35 pmIt isn't high compared to, say, the field strength in a capacitor, or the breakdown voltage of air (typically quoted as 3 MV/m), but it is also covers a large area. This means you don't need very big conductors before you can start generating huge voltages, and the currents induced in large shields can also be quite high. The upshot is that small devices can be shielded pretty effectively, but as soon as you start adding wires going in or out, or the device gets bigger, the shielding gets much harder.