The Straight Dope

Go Back   Straight Dope Message Board > Main > General Questions

Reply
 
Thread Tools Display Modes
  #1  
Old 12-04-2009, 02:01 PM
AllFreedomUnlessDefyingScience AllFreedomUnlessDefyingScience is offline
Guest
 
Join Date: Sep 2009
EMP prevention

Being convinced of mankind's upcoming doom, I'm looking for a way to prevent EMP damage. Would one of the fire-safes used for storing documents serve as a Faraday cage to insulate a computer or digital media from Electromagnetic Pulse? What about a real safe? Will the precautions like special paint and windows with special film used to isolate an area from cellphone and radio communications allow you to insulate against EMP? To anyone who can give me answers I offer a warm cookie and my deepest thanks.

AllFree
__________________
If you are the only sane person in the room, everyone else says you are crazy. Have you ever noticed that the world is just one big room?

Last edited by AllFreedomUnlessDefyingScience; 12-04-2009 at 02:02 PM.. Reason: incomplete
Reply With Quote
Advertisements  
  #2  
Old 12-04-2009, 02:23 PM
butler1850 butler1850 is offline
Guest
 
Join Date: Nov 2001
Digital media stored in optical form (CD/DVD) should be fairly immune.

Electronics stored in a faraday cage should be secure. Properly built, and grounded of course.

Rooms/buildings can essentially be built as a faraday cage, which would prevent/limit damage to the devices.

Personally, If an EMP device is set off over Con-US, your cell phone, or MP3 player (or computer) is likely to be useless in the first place... you won't be able to charge it, and if it "should" connect to anything, they likely will be affected by the EMP at t=0 (if you agree time exists. )
Reply With Quote
  #3  
Old 12-04-2009, 02:43 PM
capeo capeo is offline
Guest
 
Join Date: Aug 2009
What's the use of protecting digital media when you'll have no way to use it after an EMP anyway? To the point though, CDs and DVDs won't be effected by an EMP unless it somehow heats the reflective coating to its melting point (upwards of 1800 F). RW type CDs and DVDs can survive close to 400F. Optical media is not effected by magnetism. Tape media will be effected/destroyed if not shielded as would just about any complex electronic device. I don't think a fire safe would protect them in every instance but I'm not sure. A properly built and grounded Faraday cage, as has been mentioned, should work.
Reply With Quote
  #4  
Old 12-04-2009, 02:53 PM
AllFreedomUnlessDefyingScience AllFreedomUnlessDefyingScience is offline
Guest
 
Join Date: Sep 2009
I have solar power and batteries that can be charged by it, which will be stored inside the Faraday cage of course, so my electronics will function to some degree (more when I buy more portable solar panels and batteries). I feel that should there be people left after the EMP, the stored electronics, along with the stored data like encyclopedias, dictionaries, translation software, entertainment like e-books, video, audio and ect. would be a better bargaining item then something like say gold. Anyone have any ideas about the specific items I mentioned? Especially the things like paint and window film? I could strip the walls, floors and ceiling and layer tinfoil inside, and install steel shutters and doors but this will of course be very expensive remodeling. I'd also like to know if I can afford to have any holes at all in the insulation, like small ones from nails, etc. As I understand it the size of the hole must be smaller in relation to the wavelengths to be stopped, does anyone have any idea how that works? Also, can someone point me to a better description of a Faraday cage than Wikipedia?

Thanks,
AllFree
__________________
If you are the only sane person in the room, everyone else says you are crazy. Have you ever noticed that the world is just one big room?
Reply With Quote
  #5  
Old 12-04-2009, 03:04 PM
Machine Elf Machine Elf is offline
Guest
 
Join Date: Feb 2007
Quote:
Originally Posted by capeo View Post
What's the use of protecting digital media when you'll have no way to use it after an EMP anyway? To the point though, CDs and DVDs won't be effected by an EMP unless it somehow heats the reflective coating to its melting point (upwards of 1800 F). RW type CDs and DVDs can survive close to 400F.
The problem of the EMP is the generation of large voltages in conductive media. A microwave oven makes this happen in CD's/DVD's. Granted, if you leave them in long enough they actually get thermally cooked, but the initial effect is pretty sparks that eat up your data.

I'd think that without shielding, the same might be possible due to EMP.
Reply With Quote
  #6  
Old 12-04-2009, 10:44 PM
Little Nemo Little Nemo is offline
Charter Member
 
Join Date: Dec 1999
Location: Western New York
Posts: 55,067
IIRC, vacuum tubes are unaffected by EMP so electronic devices using them will function.
Reply With Quote
  #7  
Old 12-05-2009, 05:37 AM
engineer_comp_geek engineer_comp_geek is offline
Robot mod in beta testing
Moderator
 
Join Date: Mar 2001
Location: Pennsylvania
Posts: 7,523
EMP weapons get a lot of hype these days, but it's mostly Hollywood hype. The real weapons don't live up to their reputation.

There are two main problems with EMP weapons. The first is that it's very difficult to generate a powerful EMP. You pretty much need a nuke to make an effective EMP weapon. Without a nuke, you are limited to teeny tiny EMP weapons that are only effective over a very small range.

The second problem is the inverse square law. Your EMP drops off at a rate equal to the square of the distance. In other words, at 2 feet away it has 1/4th the power it had at 1 foot away, at 3 feet it's 1/9th, at 4 feet it is 1/16th, etc. Because the power level drops off so quickly, EMP weapons, even with a nuke, don't have a huge area of effect.

One consequence of this is possibly a fatal flaw in your plan. You are thinking that electronic devices will be valuable because of scarcity after the big EMP attack. Even with a massive EMP attack all over the world, you are going to have so many devices in areas that aren't affected that your electronic devices aren't going to really be all that rare or valuable.

That said, you may still want to protect your own devices from EMP just because they are your own devices.

As you suspected, you need a Faraday cage. Any completely enclosed conductive metal box will act as a Faraday cage. You may need to check something like a fire safe or other types of metal boxes (like a tool box) because sometimes holes for things like the lock will let certain frequencies in.

You need to take special precautions for any cables and such that might go in and out of your Faraday cage as well. If you have some electronic device that you are trying to keep powered up, just drilling a hole in the side of your Faraday cage and shoving the power cable through there is just asking for trouble.

You might want to move into some sort of steel frame building too. Steel frame buildings with metal roofs make excellent natural Faraday cages. They will shelter you from much of the EMP even if the building has windows and such in it. If you know of some building that is really annoying because your cell phone never works inside of it, that's perfect.

I poked around on the net and didn't find anything that I would call a good article on Faraday cages, unfortunately. The concept is pretty simple, though. The energy is going to flow around the surface of the box, leaving everything inside unharmed. Basically, a Faraday cage keeps everything from outside from getting in. It also works to keep anything inside the box from getting out. Your computer case, for example, is required to act like a Faraday cage of sorts, so that radio waves generated by your computer (caused by things like sharp square waves on clock signals on your motherboard) don't radiate out and cause interference to other stuff in your home.

Quote:
Originally Posted by Little Nemo View Post
IIRC, vacuum tubes are unaffected by EMP so electronic devices using them will function.
Vacuum tubes work with higher voltages internally, so if you zap one with some high voltages across its conductive materials it won't be damaged anywhere near as easily as something like a silicon transistor. However, vacuum tubes are not completely immune to EMP. Zap a vacuum tube with a big enough EMP and you will fry it.

Vacuum tube devices are getting pretty rare these days. Unfortunately, this also means that the audio whackos who think that vacuum tubes make the sound better are going to be the only folks with a working stereo system after the big EMP blast.
Reply With Quote
  #8  
Old 12-05-2009, 06:01 AM
Cubsfan Cubsfan is offline
Guest
 
Join Date: Jul 2002
On a related but different note do Faraday cages have a rating? Like can they only handle X amount of current/mag field strength? Is the rating related more to the material the cage is made of, coarseness of the mesh or any other design aspect of the cage?
Reply With Quote
  #9  
Old 12-05-2009, 08:32 AM
Little Nemo Little Nemo is offline
Charter Member
 
Join Date: Dec 1999
Location: Western New York
Posts: 55,067
Quote:
Vacuum tube devices are getting pretty rare these days. Unfortunately, this also means that the audio whackos who think that vacuum tubes make the sound better are going to be the only folks with a working stereo system after the big EMP blast.
That and people with old Soviet military equipment. The Soviets kept using vacuum tubes long after the technology had been replaced in the west. Some commentators mocked this as evidence that Soviet science was primitive compared to its western counterparts. Others felt that it was a conscious choice made by the Soviets to "harden" their military equipment to work in nuclear battlefield conditions.
Reply With Quote
  #10  
Old 12-05-2009, 01:44 PM
Kevbo Kevbo is offline
Guest
 
Join Date: May 2005
For a safe to be an effective faraday cage, the door needs to be conductively bonded to the body of the safe...not just one wire, or at the hinges, but pretty much continuosly, so you'd need to scrape off any paint down to bare metal and apply RF gasket, finger stock, or similar.

Steel will work to make a Faraday cage, but aluminum is better (as long as you can weld the joints) but copper is best.

Effectively filtering/protecting any data or power lines running to the equipment is a serious concern. Best to run on battery or a generator inside the cage, and feed the data via optical fiber.
Reply With Quote
  #11  
Old 12-05-2009, 01:49 PM
msmith537 msmith537 is offline
Guest
 
Join Date: Jan 2001
Leave it in the trunk of your car. It acts like a Faraday cage.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 04:26 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright 2013 Sun-Times Media, LLC.