<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>alkonaut</author><text>If you just want a bad atomic bomb, isn&amp;#x27;t it enough to put 2 chunks of fissile (enough) material at either end of a very thick steel tube and shoot them together using explosives? The question is how you use $2k to buy or produce the fissile material, because if the BOM was really $2k including &amp;quot;weapons grade&amp;quot; fissile material then the interesting question is how to get the fissile material that cheaply.&lt;p&gt;If the BOM is $2k &lt;i&gt;excluding&lt;/i&gt; the fissile material then... is that really surprising? I thought crude bomb designs were pretty easy to create if you have no interest in maximizing yield or minimizing how dirty the bomb gets?</text><parent_chain></parent_chain></comment><story><title>John A Phillips</title><url>https://nuclearprinceton.princeton.edu/people/john-phillips-1955-present</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>atemerev</author><text>Nuclear simulations are my hobby, and I have a few pet projects in the area. It is impossible to build a bona fide nuclear device for $2k (it is possible to build a dirty bomb with this budget, but it is not interesting in any way).&lt;p&gt;To achieve sustainable prompt criticality, you need high-quality starting material with low spontaneous fission, and a fast assembly (microseconds). &amp;quot;Gun-type&amp;quot; assembly is not used anymore even by new nuclear programs, as it is very inefficient (and still requires quite a lot of precision engineering). With implosion assembly, you need to learn quite a lot about shock compression, numerical simulations of detonations, and again it requires some precise engineering. &amp;quot;A nuclear bomb is like a half-ton Swiss watch&amp;quot;, as somebody have said.&lt;p&gt;I believe it is possible to build a nuclear device from scratch, but you need a few years, explosion testing rigs and radiography equipment, a team of engineers and physicists, and a few millions budget. If you don&amp;#x27;t have starting material, it will be much more expensive.</text><parent_chain></parent_chain></comment><story><title>John A Phillips</title><url>https://nuclearprinceton.princeton.edu/people/john-phillips-1955-present</url></story>