General > General Technical Chat
Oppenheimer Movie Review
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:
--- Quote from: peter-h on July 31, 2023, 08:17:57 am ---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.
--- End quote ---
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:
--- Quote ---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.
--- End quote ---
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:
--- Quote from: David Hess on August 01, 2023, 11:20:05 am ---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.
--- End quote ---
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.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version