Serious Scientific Answers to Absurd Hypothetical questions

[Diche Bach]

I guess you don't want to "fall off of" some of the smaller asteroids out there. Long way "down" . . .

[ARS]

Read the highlighted sentence

Is that... really possible with our current technology to build that? 

[Green Baron]

idk, but where is that nonsense from ?

[mikegarrison]

32 minutes ago, Green Baron said:

idk, but where is that nonsense from ?

Google knows: https://en.wikipedia.org/wiki/Genocidal_Organ

[Zeiss Ikon]

27 minutes ago, ARS said:

Read the highlighted sentence

Is that... really possible with our current technology to build that? 

Absolutely.  Any idiot with access to explosives, medical radioactives, and a detonator can built a dirty bomb that will render a small portion of a city uninhabitable until either a very expensive cleanup is completed, enough time elapses (⁶⁰Co has a long half life and emits neutrons, making everything around it radioactive as well), or people just forget living there is a death sentence.

Making an actual nuclear fission bomb -- the kind that could "destroy" Sarajevo -- is a good bit harder, as noted in the "medieval nuke" question up thread a bit.  IFF one had access to enriched uranium, a gun type bomb is relatively easy -- easy enough that the United States military didn't bother to make and detonate a test article before dropping Little Boy on Hiroshima.  They were that sure it would work.  All that's needed is suitably shaped uranium slugs, explosive propellant (reloading powder would work, they used cordite in Little Boy), and tampers to keep the uranium together long enough to get an acceptable level of reaction.

Making a plutonium bomb is harder still -- you can't assemble the critical mass fast enough to get a reasonable reaction level with a gun type device (likely because plutonium is all fissionable, where only the ²³⁵U part of uranium is -- around 3% in bomb metal), so you need some kind of implosion trigger, and those are far more difficult to build.  Implosion was tricky enough that the the original builders -- including some pretty danged smart people, Fermi, Oppenheimer, and so forth -- felt it necessary to explode a test unit to be sure they had it right.  If you had a modern nuclear physicist on your team, and access to something that will pass for a supercomputer (Bitcoin mining rig, maybe?), it might be possible to be reasonably confident in building an implosion device without a test article.

Further, either way, you need suitable bomb metal.  3% enriched uranium required a national effort (in 1944) to get enough to make one bomb.  It's not something you'll do in hiding from the world, not in today's world.  Reactor fuel, of either type, would require extensive reprocessing to turn into bomb metal.  In fact, the most likely source of bomb metal for a terrorist bomb is, well, a bomb.  There are (after 70+ years of the nuclear age) a number of "missing" nuclear devices that could potentially come into the possession of folks who, even if they couldn't resurrect the electronics to be able to fire the bomb as it stands (or couldn't depend on the fusion core due to age), could use the bomb metal to make another bomb.

Or were you referring to the "total surveillance state?"

[ARS]

10 minutes ago, Zeiss Ikon said:

Or were you referring to the "total surveillance state?"

No, the total surveillance state is created AFTER the nuke was exploded. But then, back to the main question, assuming an access to enriched uranium is available, would it be possible to build a homemade nuclear bomb with current technology? The one which you usually see on most urban residence such as the tools and materials from garage or metal workshop?

The nuke would be obviously an improvised type since being homemade usually means the materials and parts (excluding the enriched uranium, which we assume we have access) is being inferior from military grade nuclear bomb, but even with such limitation, could it be built on strategic scale (like the one written above which blasted Sarajevo), or would it be limited to tac nuke scale?

[radonek]

3 hours ago, ARS said:

No, the total surveillance state is created AFTER the nuke was exploded. But then, back to the main question, assuming an access to enriched uranium is available, would it be possible to build a homemade nuclear bomb with current technology? The one which you usually see on most urban residence such as the tools and materials from garage or metal workshop?

The nuke would be obviously an improvised type since being homemade usually means the materials and parts (excluding the enriched uranium, which we assume we have access) is being inferior from military grade nuclear bomb, but even with such limitation, could it be built on strategic scale (like the one written above which blasted Sarajevo), or would it be limited to tac nuke scale?

Small tac nukes are harder to build then simple gun type fission device. Latter could be built with big chunk of fissionable, artillery piece and some cutting&welding. It is not particlary effective, but can squeeze out enought  kilotons to level a small city.

It is not very plausible scenario though. "Access" to fissionable materiel is questionable - not only is weapons grade stuff hard to come by,  fissionables are also not exactly easy to move around undetected. (Last time somebody tried to smuggle some dirty stuff from Ukraine, they didn't get past Slovakia).  But most damning is that you need smart people to handle stuff without blowing themselves up, pretty much opposite to idiots gravitating  to extremist groups. So your scenario is in some way technically possible, but in reality would end up in a fizzle. And people with smarts to pull this off will realize they can get farther with chemical agents.

OTOH if you are after pretext to reign of fear, fizzle is more then enough. Having likes of a Goiânia inccident anywhere in europe, connected with proliferation and terrorism is pretty big deal.

[TheSaint]

5 hours ago, Zeiss Ikon said:

Absolutely.  Any idiot with access to explosives, medical radioactives, and a detonator can built a dirty bomb that will render a small portion of a city uninhabitable until either a very expensive cleanup is completed, enough time elapses (⁶⁰Co has a long half life and emits neutrons, making everything around it radioactive as well), or people just forget living there is a death sentence.

Making an actual nuclear fission bomb -- the kind that could "destroy" Sarajevo -- is a good bit harder, as noted in the "medieval nuke" question up thread a bit.  IFF one had access to enriched uranium, a gun type bomb is relatively easy -- easy enough that the United States military didn't bother to make and detonate a test article before dropping Little Boy on Hiroshima.  They were that sure it would work.  All that's needed is suitably shaped uranium slugs, explosive propellant (reloading powder would work, they used cordite in Little Boy), and tampers to keep the uranium together long enough to get an acceptable level of reaction.

Making a plutonium bomb is harder still -- you can't assemble the critical mass fast enough to get a reasonable reaction level with a gun type device (likely because plutonium is all fissionable, where only the ²³⁵U part of uranium is -- around 3% in bomb metal), so you need some kind of implosion trigger, and those are far more difficult to build.  Implosion was tricky enough that the the original builders -- including some pretty danged smart people, Fermi, Oppenheimer, and so forth -- felt it necessary to explode a test unit to be sure they had it right.  If you had a modern nuclear physicist on your team, and access to something that will pass for a supercomputer (Bitcoin mining rig, maybe?), it might be possible to be reasonably confident in building an implosion device without a test article.

Further, either way, you need suitable bomb metal.  3% enriched uranium required a national effort (in 1944) to get enough to make one bomb.  It's not something you'll do in hiding from the world, not in today's world.  Reactor fuel, of either type, would require extensive reprocessing to turn into bomb metal.  In fact, the most likely source of bomb metal for a terrorist bomb is, well, a bomb.  There are (after 70+ years of the nuclear age) a number of "missing" nuclear devices that could potentially come into the possession of folks who, even if they couldn't resurrect the electronics to be able to fire the bomb as it stands (or couldn't depend on the fusion core due to age), could use the bomb metal to make another bomb.

Or were you referring to the "total surveillance state?"

Mostly right. Weapons-grade uranium is not 3% enriched, it's 85% enriched, or more. 3% enriched would be suitable for commercial-grade reactor fuel. If you could build a bomb with that, we'd be in big trouble.

And, yeah, a much more likely source for a terrorist nuclear weapon today would be a stolen Russian weapon. Or an Iranian or North Korean weapon made to resemble a stolen Russian weapon. But I'm probably flirting with 2.2b there.

[peadar1987]

It's worth noting that screening for radioisotopes is so strict in western Europe and the US that containers of bananas regularly set off detectors, because of their high content of naturally-occurring radioactive isotopes of Potassium.

[Diche Bach]

38 minutes ago, peadar1987 said:

It's worth noting that screening for radioisotopes is so strict in western Europe and the US that containers of bananas regularly set off detectors, because of their high content of naturally-occurring radioactive isotopes of Potassium.

That might be reassuring, but it depends on how many containers contain bananas!

My understanding was, up through 10 years or so ago, it was ridiculously easy to slip contraband through customs on massive supersized cargo ships. That may be urban legend wisdom but, anyway . . .

[DDE]

8 hours ago, ARS said:

Read the highlighted sentence

Is that... really possible with our current technology to build that? 

I'm pretty sure it's a GDI cover-up for what actually happened.

[MatterBeam]

5 hours ago, Diche Bach said:

Interesting stuff! Thanks for answering

So, to see if I get this by putting it my laymans terms:

The 1 MW LIGO laser does not incinerate its mirror (even though it would incinerate a human head) because . . .

(a) it is only 1 MW not 10MW

(b) its wavelength (or other characteristics) is tuned for the properties of the mirror

(c) the mirror (and or other aspects of the mechanism) is made of exactly the right materials that it can always disssipate more heat than it absorbs and thus stay cool despite being bombarded by photons for months and years at a time

(e) some combination of some or all the above

 

ADDIT: to put it another way: It is quite obvious one can build a functioning laser + mirror pair in which the mirror will REFLECT the laser, and not be damage, for a very long time (if ever)--at least up to 1MW.

Why would it NOT be possible to device general purpose mirrors that could reflect combat lasers, and not be damaged--at least up to a certain laser power?

Intensity, not absolute power output is what counts. Even a laser pointer can burn through a mirror if focused enough. 

Mirrors have a threshold intensity, yes.

A general rule is that the better you design a mirror to be reflective, the narrower the range of wavelengths it can handle. In a war, lasers of many different wavelengths will be used, so you cannot rely on your own mirror to handle your enemy's wavelengths. With free electron lasers, your enemy can tune their laser output to wavelengths as long as 1mm or as short as 100nm, or less!. No material is able to reflect all these wavelengths well. 

[magnemoe]

3 hours ago, Diche Bach said:

That might be reassuring, but it depends on how many containers contain bananas!

My understanding was, up through 10 years or so ago, it was ridiculously easy to slip contraband through customs on massive supersized cargo ships. That may be urban legend wisdom but, anyway . . .

It depends that you want to skip trough customs. And note this is not part of customs either. This is simply an radioactivity detector who detect radioactivity from containers. 
Not heard the banana case but know that various low level radioactive waste tend to trigger them. Has been cases there people try to export expensive to dispose waste as used equipment to 3rd world countries. it work as low priority container freight is very cheap. 
Smuggling simply gamble on that your cargo is not checked. This works well as you can not check all at least in details. 

[magnemoe]

23 hours ago, mikegarrison said:

That's known as a "combi". Some combi airplanes have the freight in front and the passengers in back. Others have the reverse.

A "convertible" airplane is another way to share passengers and freight on the same airframe (but not at the same time). In the case of a convertible the passenger cabin is palletized. So you can slide the passenger cabin out the cargo door and you have a freighter. If you want to carry passengers again, you just slide the passenger cabin back in.

Saw an design of this, it has the benefit that you can also swap classes easy depending on role, and as you say add more cargo. It also let you convert the plane to various special use and back later. Don't think this exist? 

[Zeiss Ikon]

11 hours ago, ARS said:

No, the total surveillance state is created AFTER the nuke was exploded. But then, back to the main question, assuming an access to enriched uranium is available, would it be possible to build a homemade nuclear bomb with current technology? The one which you usually see on most urban residence such as the tools and materials from garage or metal workshop?

The nuke would be obviously an improvised type since being homemade usually means the materials and parts (excluding the enriched uranium, which we assume we have access) is being inferior from military grade nuclear bomb, but even with such limitation, could it be built on strategic scale (like the one written above which blasted Sarajevo), or would it be limited to tac nuke scale?

A gun type nuke (works at nuclear yields only with uranium, not plutonium) is well within the capability of a knowledgeable munitions tinkerer (who doesn't mind the high probability of dying soon after the job is done from radiation/chemical poisoning due to exposure to the bomb metal).  It isn't super-science.  Fortunately, highly enriched uranium hasn't been made in decades (in most of the world, anyway) and there likely aren't any old weapons around that were built from it (plutonium has been preferred since Fat Man went off; it's likely that if there's still a uranium bomb around it's 60+ year old, which further complicates efforts to either detonate it as is or extract the pit -- radiation from the pit has had a lot of time to damage stuff inside the bomb case).

Nuclear power (in general) runs on plutonium produced in breeder reactors, which can use natural-ratio uranium as breeding stock (it's the ²³⁸U you actually want in that case, because it absorbs a neutron and emits a beta to become ²³⁹Pu) -- and as noted multiple times, reactor fuel won't work for making bombs.  Even partially spent breeder rods would require reprocessing to recover the plutonium -- and there are only a half dozen places on Earth that can make bomb metal from that stuff (most of them in shutdown for the past 20-40 years).  Over the past 30 years, many new nuclear fuel assemblies have been reprocessed from decommissioned bomb cores as arms limitation has taken hold.

Making a bomb out of the pit of an existing bomb is the much taller order, requiring an implosion (very hard to do successfully) to assemble the critical mass fast enough to get anything you'd think of as a nuclear blast -- try to make a gun type bomb with plutonium and you'll get a fizzle -- lots of soft X-rays and neutrons, and "explosive" disassembly of the core as bomb metal fragments and vapor; in essence, a really, really ugly "dirty bomb".  You'd quickly kill a relatively small number of people close to the detonation, and the scattered bomb material would very heavily contaminate a small area, with reduced contamination potentially running to many miles downwind.

To get a high-yield detonation with materials terrorists might be able to obtain, you'd need someone who has extensive knowledge of nuclear physics, explosives, and rather specific knowledge and experience from a nuclear weapons program.  Folks like that tend to have little use for the "blow up the world" mentality -- but presuming you found one who was an ideologue of the right flavor, it's a possibility.  Ever read The Sum of All Fears?

[mikegarrison]

2 hours ago, magnemoe said:

Saw an design of this, it has the benefit that you can also swap classes easy depending on role, and as you say add more cargo. It also let you convert the plane to various special use and back later. Don't think this exist? 

Yes, it exists.

[YNM]

17 hours ago, ARS said:

Read the highlighted sentence

Is that... really possible with our current technology to build that? 

There's two :

- A thermonuclear (ie. nuclear-reaction) device

- A nuclear/radiation-littered device ("dirty bombs")

To which answers is yes and yes. (alright, one is a long, long stretch...)

[DDE]

4 hours ago, YNM said:

A thermonuclear (ie. nuclear-reaction) device

North Korea has a few more fancy pieces of kit than a garage tinkerer. They’re not in this alone, after all.

https://i.imgur.com/2PKicFU.png

Edited November 10, 2017 by DDE

[wumpus]

19 hours ago, magnemoe said:

It depends that you want to skip trough customs. And note this is not part of customs either. This is simply an radioactivity detector who detect radioactivity from containers. 
Not heard the banana case but know that various low level radioactive waste tend to trigger them. Has been cases there people try to export expensive to dispose waste as used equipment to 3rd world countries. it work as low priority container freight is very cheap. 
Smuggling simply gamble on that your cargo is not checked. This works well as you can not check all at least in details. 

Any country that consumes foreign illegal drugs will have plenty of professionals  fully capable of bypassing customs (I suspect even places with legal drugs will still have smugglers, just a lot less).  Of course, they are used to having a certain amount going missing, and customs expect to find a certain amount of missing drugs.  Finding smuggled plutonium should set off extreme alarms.

The other catch is you really don't need significant amounts of plutonium (presumably well under 100kg), so all you have to do is break it up into sufficiently small pieces and reassemble it on site.  Thankfully, *any* plutonium is significantly difficult to manufacture and hopefully almost as hard to buy/steal.

On 11/9/2017 at 4:27 AM, ARS said:

"democracies transformed to total  surveillance states"

For values of "democracy" including the US and UK, I'm completely uncertain that the state apparatus could possibly process any more surveillance data.  Presumably you could disperse more of that data down to the local level (expect more resistance from the surveillance agencies losing their fiefdoms than from the citizenry), but otherwise it would be hard to tell the difference.  While there is certainly data that they are missing, the real problems the surveillance agencies appear to have is that they are drowning in data (not that the FBI isn't demanding that the rare corners that they might miss be removed.  See recent complaints about encryption as an example).

This isn't just a political rant, it is also a great example of false positives and error bars.  The issue is that if you need to do a global search for nuclear terrorists, the number is so vanishingly small and the correlation between total surveillance data is pretty weak that you will be hauling huge parts of the population of for interrogation thanks to false positives (and of course it doesn't take that many false negatives to set off the bomb).  It is one of the reasons that biometric detectors routinely fail for anything other than personal locks.  Of course, if neither the electorate nor the politicians have any interest in the math, expect them to fall for the 'easy way" of technological magic from sellers of snake oil.  Yet another danger of innumerate populations.

Edited November 10, 2017 by wumpus

[sevenperforce]

Strictly speaking, a "thermonuclear device" refers to a fission-triggered fusion bomb, in which the heat ("thermo-") from a fission device is used to initiate a separate nuclear fusion reaction. The other options are fusion-boosted fission devices (fission weapons with a small amount of fusion fuel to increase yield), fission devices (fission-only bombs), and chemical-munitions radiological weapons (radiological dispersal devices using conventional explosive to disperse radioactive isotopes). 

There are a few other common terms, too. A "dirty bomb" typically refers to a thermonuclear device with a high amount of fissionable material in the tamper, resulting in large amounts of fallout. A "clean bomb" typically refers to a thermonuclear device with little or no fissionable material in the tamper, such that the majority of the energy comes from fusion. A "neutron bomb" is typically a small thermonuclear device designed to maximize neutron flux and thus improve kill rates against blast-hardened targets.

[YNM]

@sevenperforce I'm well aware of the "established nicknames". I'm just wondering, how would you call, for instance, a conventional bomb littered with Iodine-131 ? Or something along such lines ? The reason I call'em "dirty bomb" is because they're normal explosive bombs dirti-ed with radionuclides.

[Diche Bach]

Sheeze, this thread got gruesome quickly. Sign of the times I guess.

Things used to be so much simpler . . .

 

Edited November 10, 2017 by Diche Bach

[sevenperforce]

1 hour ago, YNM said:

@sevenperforce I'm well aware of the "established nicknames". I'm just wondering, how would you call, for instance, a conventional bomb littered with Iodine-131 ? Or something along such lines ? The reason I call'em "dirty bomb" is because they're normal explosive bombs dirti-ed with radionuclides.

The technical name for that is a "radiological dispersal device". However, upon review, it looks like "dirty bomb" is used interchangeably between RDDs and high-fallout thermonuclear devices.

[magnemoe]

3 hours ago, wumpus said:

Any country that consumes foreign illegal drugs will have plenty of professionals  fully capable of bypassing customs (I suspect even places with legal drugs will still have smugglers, just a lot less).  Of course, they are used to having a certain amount going missing, and customs expect to find a certain amount of missing drugs.  Finding smuggled plutonium should set off extreme alarms.

The other catch is you really don't need significant amounts of plutonium (presumably well under 100kg), so all you have to do is break it up into sufficiently small pieces and reassemble it on site.  Thankfully, *any* plutonium is significantly difficult to manufacture and hopefully almost as hard to buy/steal.

For values of "democracy" including the US and UK, I'm completely uncertain that the state apparatus could possibly process any more surveillance data.  Presumably you could disperse more of that data down to the local level (expect more resistance from the surveillance agencies losing their fiefdoms than from the citizenry), but otherwise it would be hard to tell the difference.  While there is certainly data that they are missing, the real problems the surveillance agencies appear to have is that they are drowning in data (not that the FBI isn't demanding that the rare corners that they might miss be removed.  See recent complaints about encryption as an example).

This isn't just a political rant, it is also a great example of false positives and error bars.  The issue is that if you need to do a global search for nuclear terrorists, the number is so vanishingly small and the correlation between total surveillance data is pretty weak that you will be hauling huge parts of the population of for interrogation thanks to false positives (and of course it doesn't take that many false negatives to set off the bomb).  It is one of the reasons that biometric detectors routinely fail for anything other than personal locks.  Of course, if neither the electorate nor the politicians have any interest in the math, expect them to fall for the 'easy way" of technological magic from sellers of snake oil.  Yet another danger of innumerate populations.

Yes its weird the drug and other smugglers don't use containers more, you must use an dummy company or have people on the inside on both ends, this probably complicates things 

Breaking up the plutonium would be very stupid, first you have to be lucky in custom multiple times. If its found its an good chance it will continue but being replaced with an tracking device. This happens with drugs in containers, the detectors are sensitive and one major source of extra radioactivity is escaped dust. 
You would also need the bomb factory in the target country. Have fun with that. 

And getting the bomb in the first place would be impossible, its 25 years since Soviet Union fell, that was an window for an theoretical chance of getting nukes it passed an long time ago.  
It was an fun story over 10 years ago, An Egyptian arms dealer was contacted by Russian mafia trying to sell plutonium I guess, some islamists was trying to buy it. 
It turned out the islamists was CIA and Russians was SVR (Russian CIA), it was pretty confusing as the US and Russians thought the other part was real.
 
The arms dealer was an fool anyway, yes he might be told from the Russians that the plutonium would not work in an bomb, too unclean and wrong isotope, so he would just get an aircraft carrier after him not an nuclear strike, some stuff is just to dangerous to touch. 
If you find an gun in an trash can close to an murder site, cool an free gun is not smart thinking. And yes this has happened many times. 

21 minutes ago, sevenperforce said:

The technical name for that is a "radiological dispersal device". However, upon review, it looks like "dirty bomb" is used interchangeably between RDDs and high-fallout thermonuclear devices.

Think its an low interest of high fallout nuclear bombs. It was relevant back in 1950, in 1980 the game changed to trying to take out the other sides missiles. 
RDD is some danger and more relevant. 

[sevenperforce]

7 minutes ago, magnemoe said:

Think its an low interest of high fallout nuclear bombs. It was relevant back in 1950, in 1980 the game changed to trying to take out the other sides missiles. 
RDD is some danger and more relevant. 

Yeah, I was thinking in terms of the old usage.

RDD is actually not that deadly, all things considered. Has more value as a weapon of mass chaos than actual mass destruction. Most more-available dangerous radionuclides are very short-lived. You need a reactor or a nuke to get the stuff that's both deadly and long-lived.