In the summer of 1962, the U.S. blew up a hydrogen bomb in outer space(npr.org)
npr.org
In the summer of 1962, the U.S. blew up a hydrogen bomb in outer space
http://www.npr.org/sections/krulwich/2010/07/01/128170775/a-very-scary-light-show-exploding-h-bombs-in-space
74 comments
There's an oblique mention of it near the end:
"When the bomb burst, people told of blackouts and strange electrical malfunctions, like garage doors opening and closing on their own."
The Soviet tests are interesting. They actually managed to burn down an entire electrical power station with the EMP from one of their bombs.
Edit: looking into it more, the destruction of the power station is uncertain. There was definitely a fire at the Karaganda power station, but there's only one vague reference to it being destroyed as a result. Interesting how a question like "did this entire power station burn down in the 1960s?" can remain unanswered today.
"When the bomb burst, people told of blackouts and strange electrical malfunctions, like garage doors opening and closing on their own."
The Soviet tests are interesting. They actually managed to burn down an entire electrical power station with the EMP from one of their bombs.
Edit: looking into it more, the destruction of the power station is uncertain. There was definitely a fire at the Karaganda power station, but there's only one vague reference to it being destroyed as a result. Interesting how a question like "did this entire power station burn down in the 1960s?" can remain unanswered today.
The typical Soviet response to any accident: "What fire? What power station are you talking about? Why were you there instead of in your home? A photograph? Give it here" rip "What photograph?"
Establishing the destruction of that power station today would be extremely difficult, short of American spy photos, I'd wager.
Establishing the destruction of that power station today would be extremely difficult, short of American spy photos, I'd wager.
What's awesome is that this led to the confirmation of the Van Allen Belt. There were some skeptics who felt that blowing up space was a bad idea.
Which, you know, kinda makes me giggle a little. We, the US, attacked space with a hydrogen bomb. The scientific world wasn't actually sure what effects this would have and we're like, "Hold my beer and watch this."
And then, we bombed space. That might actually be one of the most American things we've ever done.
Which, you know, kinda makes me giggle a little. We, the US, attacked space with a hydrogen bomb. The scientific world wasn't actually sure what effects this would have and we're like, "Hold my beer and watch this."
And then, we bombed space. That might actually be one of the most American things we've ever done.
As Professor Fleming puts it: "this is the first occasion I've ever discovered where someone discovered something and immediately decided to blow it up."
It is more American than the 4th of July.
"F*ck you, space! Being all spacey and stuff!" (At least that's what it sounds like in my imagination.)
"F*ck you, space! Being all spacey and stuff!" (At least that's what it sounds like in my imagination.)
I think there are better precedents for that:
"During the Trinity test, Enrico Fermi recalled Teller's idea of igniting the atmosphere. In an attempt to relieve some tension, he started taking bets on whether the test would destroy the world, or merely glass the State of New Mexico."
from: https://www.metabunk.org/debunked-scientists-risked-destroyi...
"During the Trinity test, Enrico Fermi recalled Teller's idea of igniting the atmosphere. In an attempt to relieve some tension, he started taking bets on whether the test would destroy the world, or merely glass the State of New Mexico."
from: https://www.metabunk.org/debunked-scientists-risked-destroyi...
> And then, we bombed space. That might actually be one of the most American things we've ever done.
And it still doesn't really make a difference, on the grand scale of things.
Space would probably just go "That's cute" ..if it even noticed it.
Space is used to vastly more stronger forces – the kinds that create planets and destroy stars. Heck, there's probably more energy being flung around in Jupiter's storms every day if not every hour, than we could ever produce on Earth.
We could literally blow our planet apart (though even that may be nigh impossible) and it still wouldn't make much of a difference to our own solar system, let alone the galaxy around it.
I think we would be a happier species if we accepted our insignificance and tried to make the best of our infinitesimal corner in time and space, rather than having delusions of grandeur, trying to one-up and cower fellow insignificants with insignificant acts..
And it still doesn't really make a difference, on the grand scale of things.
Space would probably just go "That's cute" ..if it even noticed it.
Space is used to vastly more stronger forces – the kinds that create planets and destroy stars. Heck, there's probably more energy being flung around in Jupiter's storms every day if not every hour, than we could ever produce on Earth.
We could literally blow our planet apart (though even that may be nigh impossible) and it still wouldn't make much of a difference to our own solar system, let alone the galaxy around it.
I think we would be a happier species if we accepted our insignificance and tried to make the best of our infinitesimal corner in time and space, rather than having delusions of grandeur, trying to one-up and cower fellow insignificants with insignificant acts..
In my time in the military I was amazed by how the trucks we rode had air-pressure driven brakes and internals - I guess that hardened them to EMPs.
Most big trucks have air powered brakes. These are called "air brakes" and they are usually set up in 2 sets. One, the emergency or parking system, is normally closed rather than normally open. If that system fails, the brakes are immediately applied. The normal operating brakes are Normally open and take pressure from a tank to apply the brake pads.
I believe the reason for using air rather than fluid is heat dissipation. Normal fluid brakes would boil if subject to the heat and the fluid would break down. When air brakes get hot, the pressure just goes up.
I believe the reason for using air rather than fluid is heat dissipation. Normal fluid brakes would boil if subject to the heat and the fluid would break down. When air brakes get hot, the pressure just goes up.
Leaking air also isn't as much of a problem, since a pump just pumps more in, as long as the leak isn't too bad.
My dad watched this detonation and wrote a very detailed letter to his parents about it, which I can't find right now, so I'll summarize from memory: Epic green ball of fire with purple lightning shooting out of it.
There was a great Bad Astronomy post a few years back on the 50th anniversary of Starfish Prime:
http://blogs.discovermagazine.com/badastronomy/2012/07/09/th...
http://blogs.discovermagazine.com/badastronomy/2012/07/09/th...
Fascinatingly, the aftermath of Starfish Prime endangered future space exploration of the era, and created uncertainty surrounding continued human space flight.[0][1]
[0] http://spaceflighthistory.blogspot.com/2016/01/starfish-and-...
[1] http://www.dtic.mil/dtic/tr/fulltext/u2/410338.pdf
[0] http://spaceflighthistory.blogspot.com/2016/01/starfish-and-...
[1] http://www.dtic.mil/dtic/tr/fulltext/u2/410338.pdf
the most pressing argument for a military experiment was, "if we don't do it, the Russians will." And, indeed, the Russians did test atomic bombs and hydrogen bombs in space
Competition has a way of getting out of hand, no?
Competition has a way of getting out of hand, no?
I'm sure the possibility of a bomb there blinding missile detectors was pressing enough to do the tests even if there wasn't any competition spirit.
And Van Allen was quite possibly thrilled about the possibility of measuring his discover, from strength and shape to stability. (Good thing it is stable, otherwise people would keep probing it.)
And Van Allen was quite possibly thrilled about the possibility of measuring his discover, from strength and shape to stability. (Good thing it is stable, otherwise people would keep probing it.)
I was under the impression H-bombs utilized hydrogen in the atmosphere to feed its fusion reaction. If you send it up to "outer space" it wouldn't have any fuel to fuse?
Not at all. The "hydrogen" in hydrogen bombs is in deuterium (proton plus a neutron) and tritium (proton plus two neutrons), both isotopes of hydrogen. Deuterium is stable, but tritium is not. Tritium must either be maintained as it decays (into Helium 3) by topping it off or bred in the nuclear explosion itself from lithium capturing a neutron. In either case, the source material is contained in the bomb itself, so you can initiate the bomb anywhere.
Also, the atmosphere contains almost no hydrogen (except a little bit in the form of water vapor).
Also, the atmosphere contains almost no hydrogen (except a little bit in the form of water vapor).
A H-bomb is a BYOH (Bring Your Own Hydrogen) device - the weapon includes a helping of deuterium (hydrogen with an extra neutron).
The fusion reaction requires an awful lot of energy to get going, so it basically uses a fission bomb as a detonator.
The fusion reaction requires an awful lot of energy to get going, so it basically uses a fission bomb as a detonator.
[deleted]
no, there are hydrogen isotopes in the bomb, deuterium & tritium.
Not to mention there is no appreciable amount of hydrogen in the atmosphere anyway.
https://en.wikipedia.org/wiki/Thermonuclear_weapon
http://climate.ncsu.edu/edu/k12/.AtmComposition
Not to mention there is no appreciable amount of hydrogen in the atmosphere anyway.
https://en.wikipedia.org/wiki/Thermonuclear_weapon
http://climate.ncsu.edu/edu/k12/.AtmComposition
Humidity is considered to be separate from "the atmosphere", as it varies from about 0-4%. Humidity contains Hydrogen since water is H2O.
I'm not sure why you've been downvoted, as your question looks like an honest one, and the answers are very informative. I certainly learned something new from the replies. Thanks for asking!
Well, perhaps because anyone with a 6th grade education knows there is essentially no Hydrogen in the atmosphere? (~0.5ppm)
That's honestly the less important part. Even if the atmosphere were pure hydrogen (whether protium or deuterium or tritium) you would not build a hydrogen bomb without its own encapsulated hydrogen fuel source.
The black magic of a hydrogen bomb is that it focuses the explosive energy of a fission bomb to ignite a fusion explosion. Doing so requires a very specific configuration; any hydrogen on the outside of the bomb, regardless of its concentration, would not reach the appropriate temperature/pressure to fuse.
The black magic of a hydrogen bomb is that it focuses the explosive energy of a fission bomb to ignite a fusion explosion. Doing so requires a very specific configuration; any hydrogen on the outside of the bomb, regardless of its concentration, would not reach the appropriate temperature/pressure to fuse.
Yes but that part needs a 10th grade understanding of science.
H2 is an assumption you've made. When talking about a nuclear explosion. There is hydrogen in a number of compounds (notably water and hydrogen sulfide) present in the atmosphere that could be relevant sources. The ppm being incidental is another issue. You've been unnecessarily condescending to an honest question.
That's an odd thing to "know" considering that the amount of water vapor in the atmosphere is measured in parts per hundred, and a substantial portion of water vapor is hydrogen.
Just as that person was 1 of 10,000 learning something for the first time today, I hope that today you learned that not everyone has exactly your set of knowledge. Also consider that it is quite likely that person is an expert in several things you have never even heard of.
XKCD 10,000: https://xkcd.com/1053/
XKCD 10,000: https://xkcd.com/1053/
Don’t overestimate education systems and peoples ability to learn from them :-)
Edit: now I'm puzzled why this is collecting downvotes. :-)
Edit: now I'm puzzled why this is collecting downvotes. :-)
Others have answered well, but if you want to dig deeper, Richard Rhode's two books 'The Making of the Atomic Bomb' and 'Dark Sun' should more than cover what most non-physicists need to know.
Other comments mentioned deuterium and tritium, but didn't mention why those are used, which is also interesting. Plain old hydrogen is really, really, really difficult to fuse. Plain hydrogen nuclei are just single protons. When you squish two of them together, you get helium-2, which is unstable and immediately decays. It can either decay back into two protons, or it can decay into deuterium, which is a proton and a neutron, by emitting a beta particle which converts one of the protons to a neutron.
The second reaction is really unlikely, so the helium-2 almost always decays back into hydrogens. That means that pure hydrogen fuses extremely slowly. That works out in, for example, the Sun, where tremendous heat and pressure is maintained for billions of years. It doesn't work so well in a bomb which can only maintain fusion-level temperatures and pressures for tiny fraction of a second.
Thus, fusion bombs always use deuterium or tritium. Practical bomb designs typically don't use those directly (hydrogen is a pain to work with), but rather use lithium turns into deuterium or tritium in the neutron-rich environment of a detonating bomb.
The second reaction is really unlikely, so the helium-2 almost always decays back into hydrogens. That means that pure hydrogen fuses extremely slowly. That works out in, for example, the Sun, where tremendous heat and pressure is maintained for billions of years. It doesn't work so well in a bomb which can only maintain fusion-level temperatures and pressures for tiny fraction of a second.
Thus, fusion bombs always use deuterium or tritium. Practical bomb designs typically don't use those directly (hydrogen is a pain to work with), but rather use lithium turns into deuterium or tritium in the neutron-rich environment of a detonating bomb.
Fusion bombs use Deuterium and/or Tritium (in modern bombs the Tritium is bred from neutronic reactions with Lithium) which are isotopes of Hydrogen, that's where the name "Hydrogen bomb" comes from. The fusion fuel capsule is compressed using the power of a fission bomb, which is enough to initiate fusion reactions. Ordinary Hydrogen in the atmosphere would not be of sufficient density to allow for significant fusion reactions. Also, Hydrogen-1 is very much more difficult to fuse than Deuterium/Tritium so even contained in a capsule it would make a quite ineffective bomb.
As far as I recall, the secondary in an H-bomb is indeed compressed by the fusion boosted fission of the primary but this then initiates a fission reaction at the core of the secondary where there is a fission "spark plug". So the lithium deuteride fuel is caught between the incoming compression driven by the primary and outgoing explosion of the secondary spark-plug.
When the fusion fuel burns the resulting neutrons are used to fission the tamper of the secondary and it's this fission is the main energy source for most H-bomb designs.
When the fusion fuel burns the resulting neutrons are used to fission the tamper of the secondary and it's this fission is the main energy source for most H-bomb designs.
Yes, inside the fusion fuel capsule there is typically a small amount of fissile material. The fusion capsule is compressed through the very strong forces from the ablation of the capsule's outer material. This compresses the fusion fuel as well as the "sparkplug" inside. The sparkplug doesn't need to contain much fissile material compared to an ordinary fission bomb core because the high degree of compression makes it easier to achieve critical conditions. The sparkplug explodes as a fission bomb, injecting heat energy into the fusion fuel capsule and driving up the conditions (temperature and pressure) which cause fusion reactions. It also injects neutrons which kickstarts the breeding of Tritium from Li-6 and Li-7.
Sometimes the "pusher" around the fusion fuel capsule is also made of fissile material which gets compressed, or imploded, just like a normal fission bomb core, but with much higher forces and so much greater efficiency and effectiveness.
Additionally, while Uranium-238 is not normally fissile it can be fissioned with high energy neutrons. The "problem" with U-238 is that the energy range of neutrons that induce fissions only partly overlaps with the natural energy range of neutrons produced by fission reactions. Meaning that on average a given neutron emitted by a U-238 fission will cause fewer than 1 additional fissions, so it can't self-sustain a neutron induced fission chain reaction (which, I guess, is a good thing, otherwise nuclear bombs would be nearly trivial to make). However, fusion reactions generate very high energy neutrons, essentially all of which can cause fission in U-238. For this reason many thermonuclear weapons have a natural or depleted Uranium casing. Fission in the casing typically doubles the yield of the weapon compared to the yield from the primary/secondary fission/fusion reactions.
All of this can be dialed to suit different desires for bomb production or yield. For example, the "Tsar Bomba" was a 100 megaton 3 stage thermonuclear warhead design, it was tested without a fissionable Uranium outer casing to avoid production of nearly 50 megatons worth of fission product fallout over the test site (which was in Russia), as a result it exploded at around 50 MT yield, almost all of which (97%) was from fusion reactions. On the other hand, you have a device like the W-88 which is an incredibly compact warhead carried on US SLBM submarines. It is a thermonuclear warhead but you could also look at it as a two stage fission-fission device with a heavily fusion boosted secondary, as most of the yield comes from fission in the secondary and the casing.
Sometimes the "pusher" around the fusion fuel capsule is also made of fissile material which gets compressed, or imploded, just like a normal fission bomb core, but with much higher forces and so much greater efficiency and effectiveness.
Additionally, while Uranium-238 is not normally fissile it can be fissioned with high energy neutrons. The "problem" with U-238 is that the energy range of neutrons that induce fissions only partly overlaps with the natural energy range of neutrons produced by fission reactions. Meaning that on average a given neutron emitted by a U-238 fission will cause fewer than 1 additional fissions, so it can't self-sustain a neutron induced fission chain reaction (which, I guess, is a good thing, otherwise nuclear bombs would be nearly trivial to make). However, fusion reactions generate very high energy neutrons, essentially all of which can cause fission in U-238. For this reason many thermonuclear weapons have a natural or depleted Uranium casing. Fission in the casing typically doubles the yield of the weapon compared to the yield from the primary/secondary fission/fusion reactions.
All of this can be dialed to suit different desires for bomb production or yield. For example, the "Tsar Bomba" was a 100 megaton 3 stage thermonuclear warhead design, it was tested without a fissionable Uranium outer casing to avoid production of nearly 50 megatons worth of fission product fallout over the test site (which was in Russia), as a result it exploded at around 50 MT yield, almost all of which (97%) was from fusion reactions. On the other hand, you have a device like the W-88 which is an incredibly compact warhead carried on US SLBM submarines. It is a thermonuclear warhead but you could also look at it as a two stage fission-fission device with a heavily fusion boosted secondary, as most of the yield comes from fission in the secondary and the casing.
To give a feel for the forces involved, I have read [2] that the pressure generated by ablation that compresses the W88 fusion secondary is around 6 petaPascals.
For comparison, the estimated pressure at the Earth's center [1] is around 360 gigaPascals, about 1/16,000 that of the W88 secondary compression.
[1] https://en.wikipedia.org/wiki/Inner_core
[2] https://en.wikipedia.org/wiki/Thermonuclear_weapon#Comparing...
edited to add W88 implosion pressure link
For comparison, the estimated pressure at the Earth's center [1] is around 360 gigaPascals, about 1/16,000 that of the W88 secondary compression.
[1] https://en.wikipedia.org/wiki/Inner_core
[2] https://en.wikipedia.org/wiki/Thermonuclear_weapon#Comparing...
edited to add W88 implosion pressure link
As others have already explained well, hydrogen in the air doesn't contribute to the explosion.
But what does make a big difference is the air around the bomb---a nuclear explosion in space is way different from one in atmosphere. X-rays from the nuclear reaction heat surrounding air to many millions of degrees [1] and that's what causes (most of) the fireball you see. In space, the only matter available to make a fireball is the weapon's structure, probably only a few hundred kg, and that dissipates and cools rapidly. Nuclear-armed air intercept missiles were built in the nineteen-fifties and sixties that depended for effectiveness on being in air to generate the necessary blast effects to kill a bomber with relatively inaccurate aiming, but in space, a nuclear explosion almost needs be a contact hit to do much mechanical damage...discounting nuclear radiation effects, of course.
[1] Fahrenheit, Celsius, Kelvin...it makes no difference.
But what does make a big difference is the air around the bomb---a nuclear explosion in space is way different from one in atmosphere. X-rays from the nuclear reaction heat surrounding air to many millions of degrees [1] and that's what causes (most of) the fireball you see. In space, the only matter available to make a fireball is the weapon's structure, probably only a few hundred kg, and that dissipates and cools rapidly. Nuclear-armed air intercept missiles were built in the nineteen-fifties and sixties that depended for effectiveness on being in air to generate the necessary blast effects to kill a bomber with relatively inaccurate aiming, but in space, a nuclear explosion almost needs be a contact hit to do much mechanical damage...discounting nuclear radiation effects, of course.
[1] Fahrenheit, Celsius, Kelvin...it makes no difference.
> ...discounting nuclear radiation effects, of course
https://history.nasa.gov/conghand/nuclear.htm
> Third, in the absence of the atmosphere, nuclear radiation will suffer no physical attenuation and the only degradation in intensity will arise from reduction with distance. As a result the range of significant dosages will be many times greater than is the case at sea level. With such weapons the lethal radii (from nuclear radiation) in space may be of the order of hundreds of miles.
https://history.nasa.gov/conghand/nuclear.htm
> Third, in the absence of the atmosphere, nuclear radiation will suffer no physical attenuation and the only degradation in intensity will arise from reduction with distance. As a result the range of significant dosages will be many times greater than is the case at sea level. With such weapons the lethal radii (from nuclear radiation) in space may be of the order of hundreds of miles.
I didn't know that. Thanks!
Also:
Also:
Second, thermal radiation, as usually defined, also disappears.
There is no longer any air for the blast wave to heat and much
higher frequency radiation is emitted from the weapon itself.
If that were the case the first one would've killed us all.
We were sure nuts back then with our atomic toys.
Not just the military toys, either.
"I know! We'll make Polonium-filled spark plugs for people's cars!"
https://www.orau.org/ptp/collection/consumer%20products/spar...
"I know! We'll make Polonium-filled spark plugs for people's cars!"
https://www.orau.org/ptp/collection/consumer%20products/spar...
We did stranger tests. We dropped three nukes down two natural gas wells to test nuclear fracking. (It doesn't work.)
I rather hope they'll try setting off a nuke near an asteroid as research for preventing meteor strikes on Earth. I guess it would vapourize part of the surface facing the bomb, diverting the thing away from there.
I'm not an expert on any of the topics surrounding that, but i heard it wouldnt make much difference (unless it was very far away) because there is no air
Radiation from the bomb will immediately vaporize a thin layer of material on the portion of the asteroid exposed to the detonation. This happens very fast and imparts an impulse to the asteroid. It's an ablation blow-off event.
This will divert the asteroid. How much depends on the mass of the asteroid and the magnitude of the ablation push. The latter is complicated: bomb yield, distance, yield spectrum, asteroid material, etc. If the asteroid is quite fragile (think comet nucleus instead of metal or rocky asteroid), it might break into smaller pieces.
In any event, there's no need for intervening air to couple energy from a nuke detonation to an object in space.
This will divert the asteroid. How much depends on the mass of the asteroid and the magnitude of the ablation push. The latter is complicated: bomb yield, distance, yield spectrum, asteroid material, etc. If the asteroid is quite fragile (think comet nucleus instead of metal or rocky asteroid), it might break into smaller pieces.
In any event, there's no need for intervening air to couple energy from a nuke detonation to an object in space.
[deleted]
Forgive me, but more and more I see the phrase 'outer space' referring to stuff that happens at distances between the Earth and the moon. Is this a thing now?
It's always been a thing. It's, for instance, the sense used in the 1967 Outer Space Treaty.
“Outer space” is basically everything outside of some fuzzy demarcation line (often, specifically, the Kármán line) marking the “edge” of Earth's atmosphere.
“Outer space” is basically everything outside of some fuzzy demarcation line (often, specifically, the Kármán line) marking the “edge” of Earth's atmosphere.
The term you're looking for is deep space.
It's a slightly older form of the term. "Space" is just space, it's everywhere. Your car has space inside it, so does your backpack, so does your living room, it's all just ordinary space. "Outer" space has specifically referred to the space above Earth's atmosphere, to differentiate it from more Earthly kinds of spaces. Over time outer space has become less exotic and so it tends to just be called "space" colloquially these days, with the meaning understood based on context.
You would prefer simply to say "in space" perhaps? Drop the "outer" part?
What else to say instead?
What else to say instead?
"Space" is just a shortening of "outer space" in this case. This is opposed to the "inner space", namely the space within Earth's atmosphere. Everything outside of that is "outer space".
It's just a colloquial way of referring to it in a non-science context.
Outer space is synonym for space.
Deep space refers to space far beyond the earth-moon system and generally earths gravity.
Interplanetary space is the space withing solar system. interstellar space is space between stars.
Deep space refers to space far beyond the earth-moon system and generally earths gravity.
Interplanetary space is the space withing solar system. interstellar space is space between stars.
Hmm. One of the main plot devices for many "asteroid is about to hit Earth" movies. I had no idea a nuke had been exploded in space before.
a nuke would do nothIng to stop any large asteroid at good speed. Like a fly hitting a tank.
You might want to inform NASA.
https://www.nasa.gov/content/asteroid-grand-challenge/mitiga...
https://www.nasa.gov/content/asteroid-grand-challenge/mitiga...
do you have the source of the actual study ?
You wouldn't need to stop an asteroid, just divert it a bit so it misses.
[deleted]
[deleted]
yeah. i remember this. my garage door opened and closed all by itself. and the weird thing is this: i hadn't even been born yet.
What's even stranger is that your garage door was a manual.
But seriously, I wonder what specifically about the side effects here would cause a garage door opener to not only open the door, but also consequently close it again. Perhaps it completed one full cycle as a result of the blast? Guess we'll never truly know.
But seriously, I wonder what specifically about the side effects here would cause a garage door opener to not only open the door, but also consequently close it again. Perhaps it completed one full cycle as a result of the blast? Guess we'll never truly know.
So in the summer of 1962 we've sent clear message to all aliens that we are here, nice.
So when they will arrive with who knows what intentions we know whom to blame.
So when they will arrive with who knows what intentions we know whom to blame.
If there's an intelligent lifeform watching us is probably smart enough to stay away from a species that destroys its own planet in many creative ways.
I wouldn't call our methods very creative, at least on the creativity scale that any species capable of observing us would operate. We pretty much burn or blow up everything we can to generate energy.
You can EMP blast whole continents with it. It is thought that in case of an all our nuclear attack at high up detonation like that would happen early one to disable as many electronics and communication facilities of the enemy.
Then of course countries have been working on EMP hardening military tech.
For example https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse says that:
---
if the Starfish Prime warhead had been detonated over the northern continental United States, the magnitude of the EMP would have been much larger (22 to 30 kV/m) because of the greater strength of the Earth's magnetic field over the United States,
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Then the Soviets also "played" around with that too:
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The monitored telephone line was divided into sub-lines of 40 to 80 kilometres (25 to 50 mi) in length, separated by repeaters. Each sub-line was protected by fuses and by gas-filled overvoltage protectors. The EMP from the 22 October (K-3) nuclear test (also known as Test 184) blew all of the fuses and fired all of the overvoltage protectors in all of the sub-lines.[15]
---