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50th Anniversary of the Starfish Prime Nuclear Weapon Test Today
The Bad Astronomer writes "50 years ago today, the U.S. detonated a nuclear weapon 240 miles above the Pacific Ocean. Called Starfish Prime, it was supposed to help U.S. scientists and the military understand how the Soviets might try to stop incoming nuclear missiles. What it actually did was blow out hundreds of streetlights in Hawaii 900 miles away, damage a half dozen satellites, and create artificial aurorae and intense radiation zones above the Earth. It taught the world what an electromagnetic pulse (EMP) was, and what the effects might be from a powerful solar flare, a nearby supernova, or a gamma-ray burst."
I know!
What it actually did was blow out hundreds of streetlights in Hawaii 900 miles away, damage a half dozen satellites, and create artificial aurorae and intense radiation zones above the Earth.
Sounds like a successful test to me. :-) Assuming they were testing for AWESOMENESS!
"Sir...We're hundreds miles from anything...what could possibly go wrong?"
Comparing a man-made nuclear bomb to a gamma-ray burst seems kind of like comparing one pixel on your monitor to the Sun.
[Sir Garlon] is the marvellest knight that is now living, for he destroyeth many good knights, for he goeth invisible.
You are thinking of "Operation Plowshare"... A not-wildly-successful-but-truly-a-classic-of-the-nuclear-optimism-period project. Essentially, team nuclear realized that mankind now had the power to dig very large holes very quickly and proceeded to see what sorts of civil engineering could be shoehorned into being based on very large holes.
The godless communists, (as is often the case with these cold-war-era things) had an even larger, also not terribly well conceived; but much less euphemistically named project: "Nuclear Explosions for the National Economy".
it was supposed to help US scientists and the military understand how the Soviets might try to stop incoming nuclear missiles. What it actually did was
Thanks for the loaded language; actually, it probably did both. It's nice that now when we know about all the negative effects so we can peer down our nose at the evil scientist puppets of the military but they really didn't know back then. That's why it's called an "experiment".
Bad Astronomer makes it sound like they didn't achieve their objective. They learned a hell of a lot. Modern warheads are heavily shielded against EMP, so it's not a great point defense. What's more, setting off EMP over your own territory is a bit like breaking your car so you won't get into a car accident.
A somewhat similar idea (but not too similar) is the idea of X-ray pindown. To facilitate an attack, the aggressor would detonate a neutron bomb high over the target country, bathing it in x-rays so harsh that the target country's ICBM's would be damaged if they tried to launch in retaliation.
Another interesting aside (at least I think it is): the early anti-ballistic missile programs, Sentinel and Safeguard, were designed to destroy incoming nuclear warheads by... blowing them up with other nuclear warheads. This had the positive effect of taking out one or two incoming warheads, and the very negative effect of blinding the system's radar to any other incoming warheads.
Mind your emissions, gentlemen.
Was this a factor leading up to the above ground test ban treaty? I mean it wouldn't be good to accidentally wipe out the world's electronics industry. (Now doing it on purpose, that's something else entirely). The test ban treaty probably stopped the development of "shaped" nuclear charges (blasting a city from an explosion in orbit) and other exotic weapons like fission bomb pumped x-ray lasers. Oh well, let's hope the Aliens are friendly!
Note: I'm going completely off memory here, quite likely to get some details wrong.
This test (and Soviet counterparts) drove a high-altitude test ban treaty (that might actually be the name). They both rather quickly saw that continuing this would bring only ruin to them both.
That probably was a major factor in the later above-ground and then comprehensive test bans, proving that the two countries could write and abide by a treaty limiting nuclear weapons in any way. But those were years later.
Dinosaurs aren't real, they were just made up to discourage time travelers.
While the effects you describe are definitely real and a huge issue, significant-footprint EMP really requires a thermonuclear device, not a "small" fission one.
For maximum EMP damage, 10,000 feet is far too low an altitude. You want a minimum of 50km altitude. So, to do a EMP, you must have orbital launch capability (i.e. Intermediate Range Ballistic Missile or better capability). Loading a nuke onboard a plane and detonating it at 40,000 feet won't work for producing an EMP of any effect.
Maximum area of the EMP is limited to "line of sight" to the detonation point. So, detonating higher in the atmosphere gives a larger potential EMP radius. However, the higher the altitude, the lower the total amount of radiated energy from the blast converted into EMP. This is primarily due to the atmosphere absorbing a significant amount of the energy before it reaches ground level. And, of course, EMP is not some binary works-or-not; it's a power level, and each device has a different level of interference that it can withstand before frying. So, you're faced with a tradeoff: the higher you detonate the warhead, the larger the potential area of the EMP, but the weaker the EMP is throughout the entire area.
Realistically speaking, warheads under 100kt don't produce usable EMP. At the minimum effective EMP altitude of about 30km, 100kt produces a useful EMP (one which will fry unshielded simple commercial electronics) directly underneath the weapon detonation, perhaps in a hectare or so. A 200kt weapon (the maximum effective yield of a non-boosted, pure fission weapon) could produce a EMP with maybe a few km or so radius.
Effective EMP areas require 300-400kt or more, which requires, at minimum, a boosted fission/fusion weapon, which is much more difficult to build than a pure fission weapon. With these, you might be able to get an EMP radius of 50-100km or so. To get the really big EMP, you need a thermonuclear weapon, ideally in the low MT range (2-5MT). These are the weapons that were used in the USA and USSR's Fractional Orbital Bombardment systems you read about in fiction books. They can produce the 1000km+ radius effects.
Given all the above, to do any real EMP, you need BOTH orbital launch capability, AND boosted fission nuclear weapon ability. At this point, a total of 6 countries (USA, Russia, UK, France, China, India) have this ability, with two possibly working on it (Pakistan, North Korea), and nobody else getting there anytime soon (even Israel is unlikely to have the requisite missile capability). In the big scheme of things, not something that we really have to worry about more than general nuclear weapon use, as EMP use is far beyond the capabilities of any non-state actor, and fairly obvious if any state-level attempt is being made to produce one.
-Erik
There are always four sides to every story: your side, their side, the truth, and what really happened.
As 'luck' would have it, currently it is believed that an EMP pulse over North America would be worse than in Hawaii due to the difference in the geomagnetic field in the two locations. For example, it is believed that a blast over the Dakotas would mostly cause problems south of the blast vs a circle all the way around.
Now, I think from my reading that his numbers are wrong (it would need to be higher), but the total kt isn't as important (and a smaller bomb could be constructed to emphasize EMP over blast).
Check out the US Army's document "Nuclear Environment Survivability." (Report ADA278230)
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