EMP and water

hal · 01-20-2021, 09:16 AM

Hello Folks,
Dumb question time:

How effective does water shield against an EMP strong enough to disable computers an other electronics as far away as 6 light years?

Anyone got an answer?

Thanks.

whswhs · 01-20-2021, 09:26 AM

How far away is the water from the source of the EMP? The intensity of the electric field vector falls off as a function of distance. What you need to know is not the intensity of the EMP source, but the local intensity where you and the water are.

Anaraxes · 01-20-2021, 10:09 AM

The way I read the OP, the strength of the source is unspecified. The effect at 6 ly is said to be enough to disable electronics. So the question is how much protection do you need at that 6 ly distance to protect your electronics from the EMI field that's already attenuated down to merely just enough to be destructive to electronics.

I don't think water is a particularly effective material. You want something conductive to reflect or absorb EM waves -- usually metal or composite materials like silver or nickel-graphite silicone. I did come across one paper using a multi-layered acrylic and salt water structure in an attempt to build something optically transparent, yet opaque to other wavelengths (in this case, -20 dB in the 7.5 - 8.5 GHz range that was of interest). If you're talking about a lot of water (a few feet or meters), then it might be more helpful. (Several feet of moist soil is useful.)

hal · 01-20-2021, 11:36 AM

From the source dated 1987, the "Storyline" is that the EMP was capable of destroying most electronic equipment as far away as 6 parsecs. If it was capable of destroying equipment that far out, and the rule of electromagnetics is such that something that is 3 AU's away is essentially 1/9th the strength it was at 1 AU.

Doing the math?

If the EMP was able to damage and/or destroy electronics as far away as 1,236,969.045 AU's away, then its strength at 1 AU would be 1.234 Million AU's squared, or 1,530,092,418,288.21 times stronger at 1 AU (About 1.53 Trillion times stronger?)

Said "event" lasted 72 hours and average duration was 3.6 hours between pulses. Said energy was sufficient to raise the world temperature to 250 degrees (not sure if that's Fahrenheit or Celsius). 80% of the world's population was outright destroyed, and the remaining 20% survived only due to undersea cities. Shallow Seas evaporated outright, forests burned, etc.

So - at a guess, such an event should have destroyed much of the algae - which would have damaged the oxygenation of the atmosphere. Destroying the ecosystem should have ruined the rest of the biosphere's abiilty to generate oxygen - and assuming that a plasma wavefront from the Solar flares that take some 21 days to travel 1 AU - probably took a fair chunk of atmosphere with it. That's a repeated hamemring of the world every 3.6 hours (give or take).

So - I was hoping to determine if even the cities with hundreds of feet of water above them, with probably a thickness measured in meters of concrete or concrete like substance - would have been able to protect against such an energy wave front. 1.5 Trillion times the energy necessary to ruin electronics seems to be way too much for the world to have survived even with undersea cities.

So, that's about all the data I have actually. Don't know how much water depth the cities beneath the seas had, nor do I know how much energy is required in an EMP to fry things. That's why I thought I'd check here.

It should be noted, that the writers of this bit of "detail" were writing this in 1987, and likely didn't have access to the data involved. Hell, no one in that time could have predicted cell phone technology, but this book does have what sounds like cell phone technology as a whole, pretty neatly described!

Well, enough on that. Hopefully I've given enough info to be helpful. I just wondered how true to physics this was on a story telling level.

Why does it matter? I'm running a face to face Traveller campaign for two of my players and this tidbit of history is a major supporting pillar in the story.

Thanks everyone. (and yes, I do have a thread in the Traveller section as well, but this is more of a GURPS thing than Traveller so to speak). Might even be useful for "After the End" style campaigns.

whswhs · 01-20-2021, 01:27 PM

I'm not sure I understand the nature of the event. Is the argument that (a) the Sun emitted electromagnetic radiation intense enough to destroy electronics at 6 parsecs, and (b) the Earth experienced much more intense radiation at 1 AU, being closer?

Fred Brackin · 01-20-2021, 01:48 PM

Quote:

Originally Posted by whswhs

I'm not sure I understand the nature of the event. Is the argument that (a) the Sun emitted electromagnetic radiation intense enough to destroy electronics at 6 parsecs, and (b) the Earth experienced much more intense radiation at 1 AU, being closer?

It's an event from Traveller game history and it involved a series of solar flares that had the specified effects on electonics at the specified distances but did not greately damage the base habitability of the Darrian Homeworld in the same system.

I don't think science is going to help a lot with this one.

hal · 01-20-2021, 08:13 PM

Quote:

Originally Posted by whswhs

I'm not sure I understand the nature of the event. Is the argument that (a) the Sun emitted electromagnetic radiation intense enough to destroy electronics at 6 parsecs, and (b) the Earth experienced much more intense radiation at 1 AU, being closer?

100% right on the money.

01-20-2021, 09:16 AM	#1
hal Join Date: Aug 2004 Location: Buffalo, New York	EMP and water Hello Folks, Dumb question time: How effective does water shield against an EMP strong enough to disable computers an other electronics as far away as 6 light years? Anyone got an answer? Thanks.

01-20-2021, 09:26 AM	#2
whswhs Join Date: Jun 2005 Location: Lawrence, KS	Re: EMP and water How far away is the water from the source of the EMP? The intensity of the electric field vector falls off as a function of distance. What you need to know is not the intensity of the EMP source, but the local intensity where you and the water are. __________________ Bill Stoddard I don't think we're in Oz any more.

01-20-2021, 10:09 AM	#3
Anaraxes Join Date: Sep 2007	Re: EMP and water The way I read the OP, the strength of the source is unspecified. The effect at 6 ly is said to be enough to disable electronics. So the question is how much protection do you need at that 6 ly distance to protect your electronics from the EMI field that's already attenuated down to merely just enough to be destructive to electronics. I don't think water is a particularly effective material. You want something conductive to reflect or absorb EM waves -- usually metal or composite materials like silver or nickel-graphite silicone. I did come across one paper using a multi-layered acrylic and salt water structure in an attempt to build something optically transparent, yet opaque to other wavelengths (in this case, -20 dB in the 7.5 - 8.5 GHz range that was of interest). If you're talking about a lot of water (a few feet or meters), then it might be more helpful. (Several feet of moist soil is useful.)

01-20-2021, 11:36 AM	#4
hal Join Date: Aug 2004 Location: Buffalo, New York	Re: EMP and water From the source dated 1987, the "Storyline" is that the EMP was capable of destroying most electronic equipment as far away as 6 parsecs. If it was capable of destroying equipment that far out, and the rule of electromagnetics is such that something that is 3 AU's away is essentially 1/9th the strength it was at 1 AU. Doing the math? If the EMP was able to damage and/or destroy electronics as far away as 1,236,969.045 AU's away, then its strength at 1 AU would be 1.234 Million AU's squared, or 1,530,092,418,288.21 times stronger at 1 AU (About 1.53 Trillion times stronger?) Said "event" lasted 72 hours and average duration was 3.6 hours between pulses. Said energy was sufficient to raise the world temperature to 250 degrees (not sure if that's Fahrenheit or Celsius). 80% of the world's population was outright destroyed, and the remaining 20% survived only due to undersea cities. Shallow Seas evaporated outright, forests burned, etc. So - at a guess, such an event should have destroyed much of the algae - which would have damaged the oxygenation of the atmosphere. Destroying the ecosystem should have ruined the rest of the biosphere's abiilty to generate oxygen - and assuming that a plasma wavefront from the Solar flares that take some 21 days to travel 1 AU - probably took a fair chunk of atmosphere with it. That's a repeated hamemring of the world every 3.6 hours (give or take). So - I was hoping to determine if even the cities with hundreds of feet of water above them, with probably a thickness measured in meters of concrete or concrete like substance - would have been able to protect against such an energy wave front. 1.5 Trillion times the energy necessary to ruin electronics seems to be way too much for the world to have survived even with undersea cities. So, that's about all the data I have actually. Don't know how much water depth the cities beneath the seas had, nor do I know how much energy is required in an EMP to fry things. That's why I thought I'd check here. It should be noted, that the writers of this bit of "detail" were writing this in 1987, and likely didn't have access to the data involved. Hell, no one in that time could have predicted cell phone technology, but this book does have what sounds like cell phone technology as a whole, pretty neatly described! Well, enough on that. Hopefully I've given enough info to be helpful. I just wondered how true to physics this was on a story telling level. Why does it matter? I'm running a face to face Traveller campaign for two of my players and this tidbit of history is a major supporting pillar in the story. Thanks everyone. (and yes, I do have a thread in the Traveller section as well, but this is more of a GURPS thing than Traveller so to speak). Might even be useful for "After the End" style campaigns.

01-20-2021, 01:27 PM	#5
whswhs Join Date: Jun 2005 Location: Lawrence, KS	Re: EMP and water I'm not sure I understand the nature of the event. Is the argument that (a) the Sun emitted electromagnetic radiation intense enough to destroy electronics at 6 parsecs, and (b) the Earth experienced much more intense radiation at 1 AU, being closer? __________________ Bill Stoddard I don't think we're in Oz any more.