Oppenheimer Movie Review

[coppice]

Regular tests are taking place these days too, but without the active material. So you can just do it in a bunker.

They must be using MOSFETs or similar nowadays. It is very easy. About 30 years ago I designed a handheld exploder device (these are widely used to trigger demolition/mining charges) and the spec is typically a few hunded volts and a few amps, discharged from a specific capacitor. There is a spec on the V/I profile to be achieved. The krytron or similar device does the job nicely (even at ~10000G for a 155mm shell - https://en.wikipedia.org/wiki/W48) and at the time there was nothing else because valve technology won't deliver high currents. The krytron works by flashing over. There is totally no reason to use them today.

They have concerns, like radiation hardness, that you might not.

[themadhippy]

like radiation hardness

recall a story from years back were the west was laughing about russia still using valves and wasn't clever enough to use something a bit more modern.

[KE5FX]

(Shrug) Ours still work.  Do theirs? 

[msuffidy]

(Shrug) Ours still work.  Do theirs?

That is a good question. It seems Russia is so dysfunctional they may not really have anything left to send back. That is coincidentally maybe the problem with what is happening right now with hitting Moscow. That is to say all the expensive property in Russia may be keeping nuclear exchange from happening, and is now being attacked anyway. You can't blame Ukraine for wanting some retribution, but it probably is the best way of getting WW3 happening. It may also be an active plan to try to get a war going to save Ukraine.

[peter-h]

The problem is that out of the few k they have, even if only a few work, it will be bad news.

[David Hess]

One reason Russian conventional forces are in such poor shape is that after the fall of the Soviet Union, Russia could only afford to maintain their nuclear weapons and launchers first, and their conventional forces second.  They were more confident in their nuclear deterrent defending themselves from the West.

[Wolfram]

Regular tests are taking place these days too, but without the active material. So you can just do it in a bunker.

They must be using MOSFETs or similar nowadays. It is very easy. About 30 years ago I designed a handheld exploder device (these are widely used to trigger demolition/mining charges) and the spec is typically a few hunded volts and a few amps, discharged from a specific capacitor. There is a spec on the V/I profile to be achieved. The krytron or similar device does the job nicely (even at ~10000G for a 155mm shell - https://en.wikipedia.org/wiki/W48) and at the time there was nothing else because valve technology won't deliver high currents. The krytron works by flashing over. There is totally no reason to use them today.

What was the exploder for? Bridgewire detonators as used in nuclear weapons require currents and voltages many orders of magnitude higher than used for regular pyrotechnic ones. From the NWFAQ:

The detonators that fire high explosive implosion systems (exploding wire or
exploding foil detonators) require voltages in the range of (roughly) 2-20
kilovolts, a complete detonating system may draw currents ranging from 10
to 100 kiloamps. Pulse neutron tubes, used to precisely control the
initiation of fission chain reactions, require voltages of 100 to 200
kilovolts, and currents in the ampere range. These currents must be turned
on rapidly and precisely, timing accuracies of tens to hundreds of
nanoseconds are required.

https://nuclearweaponarchive.org/Library/Pasley1.html

This is well out of the practical range of solid state switching even today, especially considering the radiation environment.

[KE5FX]

One reason Russian conventional forces are in such poor shape is that after the fall of the Soviet Union, Russia could only afford to maintain their nuclear weapons and launchers first, and their conventional forces second.  They were more confident in their nuclear deterrent defending themselves from the West.

Yes, they spent a lot of money on nuclear weapons procurement and maintenance, but how much of that money ended up being used for yacht procurement and maintenance? 

I mean, consider the incentives.   You're an apparatchik in the Russian equivalent of the US Department of Energy.  A large amount of funding for stockpile maintenance crosses your desk.  If you "divert" it, nobody will ever find out... and if they do, it will be the least of your problems (and theirs).  An easy decision to make, it would seem.

[peter-h]

Wolfram - for various reasons I don't believe that is true. There is no reason it should be. Bridgewire detonators are commonly used today.

Also the neutron initiator in implosion devices does not necessarily need any power or any external connection. It can be just squeezed by the implosion, and off it goes all by itself.

More complex designs do involve more complex timed events but those numbers seem totally wrong. Maybe deliberately - as with so much stuff in this business.

There are good reasons terrorists have not managed to get hold of these weapons. It is mostly the material but there is also a lot of detail. Fuchs for example gave the Russians a good start by supplying them with dimensioned drawings, and sure enough their first tested design was a copy.

The guy who wrote that Pasley page admits to not knowing much about anything there. I've read extensively on this topic, and used to work in high voltage, and the idea of those astronomical numbers just to get a detonator to work is bizzare. IMHO somebody made that up on the spot. No argument with the timing precision - tens of ns or better is needed.

[vad]

Radioisotope-based neutron sources, such as PoBe, were superseded by neutron generators capable of delivering many orders of magnitude greater neutron flux with higher timing precision. Neutron generators have a longer lifetime than the decaying isotopes. They also improve the safety of the device. Unlike PoBe beads that can get activated from physical damage (caused by high Gs from an accident, for example), a neutron generator will not work without being energized.

I doubt that krytrons/sprytrons, which are more immune to EMP, have been replaced by IGBTs or FETs.

[dietert1]

..
There are good reasons terrorists have not managed to get hold of these weapons. It is mostly the material but there is also a lot of detail. Fuchs for example gave the Russians a good start by supplying them with dimensioned drawings, and sure enough their first tested design was a copy.
..

You may feel uncomfortable with this, but shouldn't we consider people who used nuclear weapons on towns with hundreds of thousands of people terrorists? Think about it.

Regards, Dieter

[peter-h]

As was correctly pointed out in the film, the same number was killed daily with conventional bombing, and brought Japan no nearer to surrender.

The physical effects were also not much different.

[DonKu]

Yes, that's it.

[coppice]

There are good reasons terrorists have not managed to get hold of these weapons. It is mostly the material but there is also a lot of detail. Fuchs for example gave the Russians a good start by supplying them with dimensioned drawings, and sure enough their first tested design was a copy.

There is one single reason - limited funds. There are a lot of people who could put together a fairly modern weapon, without massive effort. Much simpler techniques now exist than the approaches used in WW2. They were actually developed quite rapidly after the first explosions. Producing suitable material is the stumbling block. You need a large scale industrial activity to produce that. This is why people were so concerned when the USSR crumbled. So much fissile material was poorly managed, there was a real concern that some might get into bad hands, bypassing that industrial scale requirement, and there would have been no stopping them.

[David Hess]

You may feel uncomfortable with this, but shouldn't we consider people who used nuclear weapons on towns with hundreds of thousands of people terrorists? Think about it.

Luckily for those people, they were on the side which won the war.

[Stray Electron]

..
There are good reasons terrorists have not managed to get hold of these weapons. It is mostly the material but there is also a lot of detail. Fuchs for example gave the Russians a good start by supplying them with dimensioned drawings, and sure enough their first tested design was a copy.
..

You may feel uncomfortable with this, but shouldn't we consider people who used nuclear weapons on towns with hundreds of thousands of people terrorists? Think about it.

Regards, Dieter

  I have thought about it and no, I don't consider them terrorists and I consider that view to be asinine.  Why would they be considered any more of a terrorist then anyone that ever bombed a town from the air, or shelled one with a piece of artillery or any of the other million and one ways of attacking a city? Or any target for that matter?

  You clearly have no idea of the definition of a terrorist.

[helius]

A simple dictionary definition would hold a terrorist to be anyone who uses terror (a justified fear of mass torture, death, or worse) as a means to an end. That would include the French Jacobins of the 1790s, Napoleon's armies, the United States Army during the Indian Wars from the 1830s to the 1880s, the Bolsheviks in 1917, both sides of the Spanish Civil War, and many political movements, both hegemonic and subaltern, and various military forces since WW2.

Wikipedia refers to

The term terror bombing is used to describe the strategic bombing of civilian targets without military value, in the hope of damaging an enemy's morale.

There have been attempts to defend the bombing of cities during WW2 as having "military value", but they don't stand up to much scrutiny. In some cases planners justified the presence of rail facilities, mainly used for civilian purposes, as "military targets".

[David Hess]

I have thought about it and no, I don't consider them terrorists and I consider that view to be asinine.  Why would they be considered any more of a terrorist then anyone that ever bombed a town from the air, or shelled one with a piece of artillery or any of the other million and one ways of attacking a city? Or any target for that matter?

Before the war, there was a general consensus that bombing civilian targets was a war crime.  This broke down when all sides discovered that strategic bombers could not reliability hit targets smaller than entire cities, and sometimes even missed those.

The allies committed many war crimes which were never prosecuted.  Often they were deliberately ignored or even covered up by higher authority.

[TimFox]

Before WW II, the Italian general and military theorist Giulio Douhet was a driving force behind the massive use of aircraft in the bombardment of cities.
Douhet believed that bombing cities would totally paralyze industry and the power centers of society, and would decisively undermine the morale of civilians, who would stop supporting their leaders and force them to accept their enemy’s conditions.
During WW II, this didn't seem to work. 
Coventry, London, Dresden, Tokyo, and other strategic bombing campaigns did not appear to force surrenders.
Later, the bombing of North Vietnam had similar results.
Perhaps the only case where a bombing of a civilian target had the desired effect was the nuclear bombing of Japan, but revisionist historians dispute that.

[Bud]

You may feel uncomfortable with this, but shouldn't we consider people who used nuclear weapons on towns with hundreds of thousands of people terrorists? Think about it.

Luckily for those people, they were on the side which won the war.

Next time they may not be that lucky.

[KE5FX]

"Terrorist" traditionally implies a non-state actor.  Of course the distinction is largely lost at the receiving end.

[dietert1]

Nowadays the term "terrorist" is used for state actors (e.g. Russia). It's in the news everyday. So the modern western world considers massive bombing of civilians a cruelty of past ages. Of course, we can never be shure. More than enough nuclear weapons on this planet.
Everybody who has weapons of mass destruction needs to demonstrate they are willing to use them in the most horrible way possible? Obviously those people thought they are exempt from all rules and standards.

Regards, Dieter

[Stray Electron]

"Terrorist" traditionally implies a non-state actor.  Of course the distinction is largely lost at the receiving end.

   A terrorist is also someone that is willing to strike at PURELY civilian targets and in countries that his country is NOT at war with. And usually their objective to achieve a political or religious object and not any kind of military objective.  Consider all the bombings in civilian mosques in Iraq between the two different Islamic religious factions.  And just a week ago the bombing of a civilian market place in Pakistan. And going back some years, the bombing of the World Trade Center in New York and then later the aircraft attack on the Twin Towers in New York.

   Some of you can bury your heads in the sand and claim that the atomic bomb attacks on Nagasaki and Hiroshima are in the same category but they're not.

   In the first place those attacks were carried out by countries at war with each other. Second, the attacks were carried out by recognized and uniformed members of their country's military forces, just as the attack on Pearl Harbor by the Japanese was. An attack BTW that did kill a large number of civilians and by a county that was not yet at war with the U.S.  Third, all of the cities in Japan were involved in war production and in supporting the war, even if the city had nothing more than a road junction in it. That made every city in Japan a legitimate military target, just as it did in Germany and Austria and until they surrendered, Italy.  I defy anyone of you to go find any kind of supporting documents that shows that Hiroshima and Nagasaki produced nothing of benefit to Japan during the war or aided, in anyway directly or indirectly, to the continuation of the war. Just from what I know of the two cities, Hiroshima was the headquarters of a large reserve army that would have been committed if the U.S. had invaded Japan, and Nagasaki had the large steel production center. Both were military targets that had already been considered for fire bombing but the U.S. high command spared them (temporarily) so that the effects of the atomic bombs could be accessed without the effects of other bombing.

[TimFox]

The reason it's called "terrorism" is that the aim is not so much to damage or destroy infrastructure, military units, etc., but to instill fear in the population.

[themadhippy]

but to instill fear in the population.

bit like what the mainstream media and government do in the uk