4 ms·

I imagine that between the '40s and '70s many of the really hard problems became a lot easier. E.g. using solid-state electronics for the timing, modelling shap

I imagine that between the '40s and '70s many of the really hard problems became a lot easier. E.g. using solid-state electronics for the timing, modelling shaped charges as a textbook exercise rather than a research problem, etc. What surprises me is that he managed to get a dirt-cheap initiator.

manholio 4y ago
Maybe he designed a geometry that can achieve the required implosion speeds with slow, easily available explosives ex. AN, KN, AP etc. The size of the device (a container) seems to suggest this. The actual initiation is the easy part and would have been easy in the 70s, exploding wires that are subjected to a number of kilo Ameperes by some kind of avalanche, solid state switch.
- topynate 4y ago
  I meant a modulated neutron initiator, not the explosive detonator. India was still using vapour deposition of polonium to make theirs, around the same time. I'm no engineer but that sounds like it costs a lot more than $2000.
  - deleted 4y ago
    [deleted]
  - baybal2 4y ago
  - Xx25 4y ago
    HN never ceases to surprise! I am really curious how you happen to know such details about India's nuclear bomb.
    - danbruc 4y ago
      The internet probably. [1] [1] https://nuclearweaponarchive.org/India/IndiaSmiling.html https://nuclearweaponarchive.org/India/IndiaSmiling.html
atemerev 4y ago
The cheap initiator is a solved problem since 1989.
- topynate 4y ago
  Yeah, we've got better at making neutrons since 1970. Mostly this is a good thing!
- thombat 4y ago
  Since his design dates from 1976, you reckon it would be cheaper now?
alfiedotwtf 4y ago
> using solid-state electronics for the timing Curious... is timing actually that big of a deal when you've already got critical mass? What would happen if you just dropped one half critical mass from 1m above to the other half?
- smilespray 4y ago
  It would preignite and fizzle. No nuclear yield, but a pile of radioactive stuff.
  - alfiedotwtf 4y ago
    ah, ok thanks for that. Even though OP had their research taken away, I wonder how long it will be before you could simply ask GPT-3 how to make a nuke for under $2k
- MertsA 4y ago
  With an implosion type bomb you need to make sure that the shockwave from the explosives hits the plutonium pit all around it almost simultaneously. If there was a portion where the explosive shockwave was delayed then the forces on the rest of the pit are going to tend to "squish" it out towards the portion where the explosion hasn't hit it yet. This asymmetrical compression means now you don't get the ideal compressed sphere so now while it's still going to reach criticality, it's going to be blasted apart with much less of the fissile material being fissioned. A great real world example of why timing is so critical is the first North Korean nuclear bomb test. https://en.wikipedia.org/wiki/2006_North_Korean_nuclear_test#Yield_estimates_and_authenticity https://en.wikipedia.org/wiki/2006_North_Korean_nuclear_test... They had a yield of less than a kiloton. Obviously way greater than conventional explosives but it should have been an order of magnitude more powerful. In order for the explosives to form that crucial explosive lense you need detonation across numerous points on the outside simultaneously so you need a detonator that's extremely consistent on timing so a simple resistive detonator with some primary explosives packed around a filament is not going to be effective. The method of choice is an exploding bridgewire design. Basically you have a thin wire and you pass enough current through it to vaporize the wire so quickly that the wire itself generates the initial shockwave as it gets turned into plasma. The rest of the explosive lense is just two different types of explosive with different propagation velocities. The two are combined with a parabolic (or hyperbolic, I forget off the top of my head) face between the two layers so that the explosion that started from a single point goes from convex to concave so it hits the outside of the pit all at the same time. If you simply dropped a half-critical mass onto another and it was prompt critical then yes, it would explode, but with not nearly as much energy being released as a proper nuclear weapon.

manholio 4y ago

Maybe he designed a geometry that can achieve the required implosion speeds with slow, easily available explosives ex. AN, KN, AP etc. The size of the device (a container) seems to suggest this. The actual initiation is the easy part and would have been easy in the 70s, exploding wires that are subjected to a number of kilo Ameperes by some kind of avalanche, solid state switch.

topynate 4y ago
I meant a modulated neutron initiator, not the explosive detonator. India was still using vapour deposition of polonium to make theirs, around the same time. I'm no engineer but that sounds like it costs a lot more than $2000.
- deleted 4y ago
  [deleted]
- baybal2 4y ago
- Xx25 4y ago
  HN never ceases to surprise! I am really curious how you happen to know such details about India's nuclear bomb.
  - danbruc 4y ago
    The internet probably. [1] [1] https://nuclearweaponarchive.org/India/IndiaSmiling.html https://nuclearweaponarchive.org/India/IndiaSmiling.html

atemerev 4y ago

The cheap initiator is a solved problem since 1989.

topynate 4y ago
Yeah, we've got better at making neutrons since 1970. Mostly this is a good thing!
thombat 4y ago
Since his design dates from 1976, you reckon it would be cheaper now?

alfiedotwtf 4y ago

> using solid-state electronics for the timing Curious... is timing actually that big of a deal when you've already got critical mass? What would happen if you just dropped one half critical mass from 1m above to the other half?

smilespray 4y ago
It would preignite and fizzle. No nuclear yield, but a pile of radioactive stuff.
- alfiedotwtf 4y ago
  ah, ok thanks for that. Even though OP had their research taken away, I wonder how long it will be before you could simply ask GPT-3 how to make a nuke for under $2k
MertsA 4y ago
With an implosion type bomb you need to make sure that the shockwave from the explosives hits the plutonium pit all around it almost simultaneously. If there was a portion where the explosive shockwave was delayed then the forces on the rest of the pit are going to tend to "squish" it out towards the portion where the explosion hasn't hit it yet. This asymmetrical compression means now you don't get the ideal compressed sphere so now while it's still going to reach criticality, it's going to be blasted apart with much less of the fissile material being fissioned. A great real world example of why timing is so critical is the first North Korean nuclear bomb test. https://en.wikipedia.org/wiki/2006_North_Korean_nuclear_test#Yield_estimates_and_authenticity https://en.wikipedia.org/wiki/2006_North_Korean_nuclear_test... They had a yield of less than a kiloton. Obviously way greater than conventional explosives but it should have been an order of magnitude more powerful. In order for the explosives to form that crucial explosive lense you need detonation across numerous points on the outside simultaneously so you need a detonator that's extremely consistent on timing so a simple resistive detonator with some primary explosives packed around a filament is not going to be effective. The method of choice is an exploding bridgewire design. Basically you have a thin wire and you pass enough current through it to vaporize the wire so quickly that the wire itself generates the initial shockwave as it gets turned into plasma. The rest of the explosive lense is just two different types of explosive with different propagation velocities. The two are combined with a parabolic (or hyperbolic, I forget off the top of my head) face between the two layers so that the explosion that started from a single point goes from convex to concave so it hits the outside of the pit all at the same time. If you simply dropped a half-critical mass onto another and it was prompt critical then yes, it would explode, but with not nearly as much energy being released as a proper nuclear weapon.