<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>twic</author><text>Take spullara&amp;#x27;s numbers:&lt;p&gt;2.01410177811 u = 3.34449439340696e-24 g deuterium&lt;p&gt;3.01604928 u = 5.008267217094e-24 g tritium&lt;p&gt;17.6 MeV = 7.832863e-19 kWh energy&lt;p&gt;Divide through, and you will see that you need 4.27 ug&amp;#x2F;kWh of deuterium, and 6.39 ug&amp;#x2F;kWh of tritium.&lt;p&gt;A random source [1] says that New York will use 50.6 TWh per year by 2027. That would require ~216 kg&amp;#x2F;yr of deuterium and ~323&amp;#x2F;yr kg of tritium.&lt;p&gt;This is all assuming 100% efficiency. A quick read suggests 50% efficiency might be practical, so double those quantities.&lt;p&gt;Also, i could easily have messed up that calculation somewhere, so please do check it!&lt;p&gt;[1] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.buildingcongress.com&amp;#x2F;advocacy-and-reports&amp;#x2F;reports-and-analysis&amp;#x2F;Electricity-Outlook-2017-Powering-New-York-Citys-Future&amp;#x2F;The-Electricity-Outlook-to-2027.html&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.buildingcongress.com&amp;#x2F;advocacy-and-reports&amp;#x2F;report...&lt;/a&gt;</text><parent_chain><item><author>subsubzero</author><text>Do we know how much tritium is needed for a city&amp;#x27;s energy generation? What about a state etc? Reason I ask is the only uses I have seen for tritium is on old watch dials made in the pre-90&amp;#x27;s. Curious how much of this resource is out there.</text></item><item><author>spullara</author><text>If you look at the mass before of their fuel, 1 deuterium atom + 1 tritium atom:&lt;p&gt;&lt;pre&gt;&lt;code&gt;    2.01410177811 u + 3.01604928 u = 5.03015105811 u
&lt;/code&gt;&lt;/pre&gt;
vs the mass of the fusion products of 1 helium atom and 1 neutron:&lt;p&gt;&lt;pre&gt;&lt;code&gt;    4.002602 u + 1.008 u = 5.010602 u
&lt;/code&gt;&lt;/pre&gt;
You&amp;#x27;ll notice that even though we started with 5 neutrons and 2 protons and ended up with the same number there was some additional binding energy that is unaccounted for in the new configuration. This is the energy released by the fusion reaction via E = mc^2. Here we see the mass difference is:&lt;p&gt;&lt;pre&gt;&lt;code&gt;    5.03015105811 u - 5.010602 u = 0.01954905811 u
&lt;/code&gt;&lt;/pre&gt;
Converting that to energy you find that is 17.6 MeV. As you go up the periodic table fusing nuclei you will get less and less marginal energy until you get to iron where at that point fusion become net negative and fission is then takes over where breaking nuclei apart gains energy, marginally more as you go up the periodic table. That&amp;#x27;s why you want to fuse light particles and fission very heavy particles. It is also why there is so much iron as it is kind of the base state of both of these reactions.</text></item><item><author>bmmayer1</author><text>This is a stupid question but I don&amp;#x27;t know anything about fusion:&lt;p&gt;How is it possible for X energy to create X+Y energy in output? Doesn&amp;#x27;t that violate some fundamental law of physics?</text></item><item><author>jkelleyrtp</author><text>&amp;gt; LLNL’s experiment surpassed the fusion threshold by delivering 2.05 megajoules (MJ) of energy to the target, resulting in 3.15 MJ of fusion energy output, demonstrating for the first time a most fundamental science basis for inertial fusion energy (IFE)&lt;p&gt;Yesterday, everyone was complaining about the 2.2:2.0 ratio, but now we&amp;#x27;re working with 3.15:2.05.&lt;p&gt;With modern lasers, that&amp;#x27;d be a total Q of 0.375 assuming 100% efficiency through direct-energy-capture.&lt;p&gt;The jumps to get here included&lt;p&gt;- 40% with the new targets&lt;p&gt;- 60% with magnetic confinement&lt;p&gt;- 35% with crycooling of the target&lt;p&gt;The recent NIF experiments have jumped up in power. The first shot that started this new chain of research was about 1.7 MJ of energy delivered. Now, 2.15 MJ. However, the output has jumped non-linearly, demonstrating the scaling laws at work.&lt;p&gt;&amp;gt;  I’ve helped to secure the highest ever authorization of over $624 million this year in the National Defense Authorization Act for the ICF program to build on this amazing breakthrough.”&lt;p&gt;It&amp;#x27;s nice to see this milestone recognized, even if the funding it still rather small.</text></item></parent_chain></comment><story><title>US Department of Energy: Fusion Ignition Achieved</title><url>https://www.energy.gov/articles/doe-national-laboratory-makes-history-achieving-fusion-ignition</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>S04dKHzrKT</author><text>Real Engineering recently made a video that covers fuel needs.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=BzK0ydOF0oU&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=BzK0ydOF0oU&lt;/a&gt;</text><parent_chain><item><author>subsubzero</author><text>Do we know how much tritium is needed for a city&amp;#x27;s energy generation? What about a state etc? Reason I ask is the only uses I have seen for tritium is on old watch dials made in the pre-90&amp;#x27;s. Curious how much of this resource is out there.</text></item><item><author>spullara</author><text>If you look at the mass before of their fuel, 1 deuterium atom + 1 tritium atom:&lt;p&gt;&lt;pre&gt;&lt;code&gt;    2.01410177811 u + 3.01604928 u = 5.03015105811 u
&lt;/code&gt;&lt;/pre&gt;
vs the mass of the fusion products of 1 helium atom and 1 neutron:&lt;p&gt;&lt;pre&gt;&lt;code&gt;    4.002602 u + 1.008 u = 5.010602 u
&lt;/code&gt;&lt;/pre&gt;
You&amp;#x27;ll notice that even though we started with 5 neutrons and 2 protons and ended up with the same number there was some additional binding energy that is unaccounted for in the new configuration. This is the energy released by the fusion reaction via E = mc^2. Here we see the mass difference is:&lt;p&gt;&lt;pre&gt;&lt;code&gt;    5.03015105811 u - 5.010602 u = 0.01954905811 u
&lt;/code&gt;&lt;/pre&gt;
Converting that to energy you find that is 17.6 MeV. As you go up the periodic table fusing nuclei you will get less and less marginal energy until you get to iron where at that point fusion become net negative and fission is then takes over where breaking nuclei apart gains energy, marginally more as you go up the periodic table. That&amp;#x27;s why you want to fuse light particles and fission very heavy particles. It is also why there is so much iron as it is kind of the base state of both of these reactions.</text></item><item><author>bmmayer1</author><text>This is a stupid question but I don&amp;#x27;t know anything about fusion:&lt;p&gt;How is it possible for X energy to create X+Y energy in output? Doesn&amp;#x27;t that violate some fundamental law of physics?</text></item><item><author>jkelleyrtp</author><text>&amp;gt; LLNL’s experiment surpassed the fusion threshold by delivering 2.05 megajoules (MJ) of energy to the target, resulting in 3.15 MJ of fusion energy output, demonstrating for the first time a most fundamental science basis for inertial fusion energy (IFE)&lt;p&gt;Yesterday, everyone was complaining about the 2.2:2.0 ratio, but now we&amp;#x27;re working with 3.15:2.05.&lt;p&gt;With modern lasers, that&amp;#x27;d be a total Q of 0.375 assuming 100% efficiency through direct-energy-capture.&lt;p&gt;The jumps to get here included&lt;p&gt;- 40% with the new targets&lt;p&gt;- 60% with magnetic confinement&lt;p&gt;- 35% with crycooling of the target&lt;p&gt;The recent NIF experiments have jumped up in power. The first shot that started this new chain of research was about 1.7 MJ of energy delivered. Now, 2.15 MJ. However, the output has jumped non-linearly, demonstrating the scaling laws at work.&lt;p&gt;&amp;gt;  I’ve helped to secure the highest ever authorization of over $624 million this year in the National Defense Authorization Act for the ICF program to build on this amazing breakthrough.”&lt;p&gt;It&amp;#x27;s nice to see this milestone recognized, even if the funding it still rather small.</text></item></parent_chain></comment><story><title>US Department of Energy: Fusion Ignition Achieved</title><url>https://www.energy.gov/articles/doe-national-laboratory-makes-history-achieving-fusion-ignition</url></story>