<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>dfdx</author><text>Anecdotally, ITER was the largest of few options for a fusion researcher to run their experiment in a new tokamak. Everybody wanted to put their work into it, and as more features were added, the more funding it sucked up, leaving less money for other experiments, leading to more people wanting to put their experiment into ITER. Here&amp;#x27;s a presentation [0] that goes over why SPARC, being so much smaller and simpler than ITER could be more likely to succeed.&lt;p&gt;[0] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;library.psfc.mit.edu&amp;#x2F;catalog&amp;#x2F;online_pubs&amp;#x2F;iap&amp;#x2F;iap2016&amp;#x2F;mumgaard.pdf&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;library.psfc.mit.edu&amp;#x2F;catalog&amp;#x2F;online_pubs&amp;#x2F;iap&amp;#x2F;iap2016...&lt;/a&gt;&lt;p&gt;This quote from the presentation summarizes it well:&lt;p&gt;“The more money that&amp;#x27;s involved, the less risk people want to take. The less risk people want to take, the more they put into their designs, to make sure their subsystem is super-reliable. The more
things they put in, the more expensive the project gets. The more expensive it gets, the more instruments the scientists want to add, because the cost is getting so high that they&amp;#x27;re afraid there won&amp;#x27;t be
another opportunity later on- they figure this is the last train out of town. So little by little, the spacecraft becomes gilded. And you have these bad dreams about a spacecraft so bulky and so heavy it
won&amp;#x27;t get off the ground- never mind the overblown cost.”&lt;p&gt;“That boils down to the higher the cost, the more you want to protect your investment, so the more money you put into lowering your risk. It becomes a vicious cycle.”
- Rob Manning, Chief spacecraft engineer, JPL</text><parent_chain><item><author>zetalyrae</author><text>I&amp;#x27;ve always wondered: why exactly is ITER so expensive, and slow? Is the engineering required at such a standard that it should takes decades of planning and construction and tens of billions of dollars? The timeline is so dilated (started in 1988, first plasma planned for 2025!) it feels like the kind of project that&amp;#x27;s expected to be cancelled from the start.&lt;p&gt;It just doesn&amp;#x27;t strike me as obvious that reducing the major radius by a few meters would have such a huge impact on cost&amp;#x2F;timelines.</text></item><item><author>dfdx</author><text>Plenty of skepticism in these comments. I&amp;#x27;ve been following CFS for a while and can present a point of view for why this time might be different.&lt;p&gt;Fusion energy was actually making rapid progress in the latter half of the twentieth century, going from almost no power output in the fifties and sixties to a power output equal to 67% of input power with the JET reactor in 1997. By the eighties there was plenty of experimental evidence to describe the relationships between tokamak parameters and power output. Particularly that the gain is proportional to the radius to the power of 1.3 and the magnetic field cubed. The main caveat to this relationship was that we only had magnets that would go up to 5.5 Tesla, which implied we needed a tokamak radius of 6 meters or so in order to produce net energy.&lt;p&gt;Well that 6 meter tokamak was designed in the eighties and is currently under construction. ITER, being so large, costs tens of billions of dollars and requires international collaboration; the size of the project has led to huge budget overruns and long delays. Recently however, there have been significant advances in high-temperature super conductors that can produce magnetic fields large enough that we (theoretically) only need a tokamak with a major radius of about 1.5 meters to produce net gain. This is where SPARC (the tokamak being built by the company in the article) comes in. The general idea is that since we have stronger magnets now, we can make a smaller, and therefore cheaper tokamak quickly.&lt;p&gt;Small tokamaks do have downsides, namely that the heat flux through the walls of the device is so large that it will damage the tokamak. There have been breakthroughs with various divertor designs that can mitigate this, but to the best of my knowledge I&amp;#x27;m not sure that CFS has specified their divertor configuration.&lt;p&gt;This was just a short summary of the presentation by Dennis Whyte given here [0]. I do not work in the fusion community.&lt;p&gt;[0] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=KkpqA8yG9T4&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=KkpqA8yG9T4&lt;/a&gt;</text></item></parent_chain></comment><story><title>MIT-designed project achieves major advance toward fusion energy</title><url>https://news.mit.edu/2021/MIT-CFS-major-advance-toward-fusion-energy-0908</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>sbierwagen</author><text>Here&amp;#x27;s a render of the completed reactor: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.iter.org&amp;#x2F;doc&amp;#x2F;all&amp;#x2F;content&amp;#x2F;com&amp;#x2F;gallery&amp;#x2F;media&amp;#x2F;7%20-%20technical&amp;#x2F;tkmandplant_2016_72dpi.jpg&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.iter.org&amp;#x2F;doc&amp;#x2F;all&amp;#x2F;content&amp;#x2F;com&amp;#x2F;gallery&amp;#x2F;media&amp;#x2F;7%20-...&lt;/a&gt; Note human for size.&lt;p&gt;It&amp;#x27;s all completely bespoke scientific equipment hand made for this project only. The cryostat will be the largest stainless steel vacuum vessel ever made-- all welded by hand.&lt;p&gt;After welding, a substantial number of in-vessel components have to be installed by threading them through access ports, which is also quite a task: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=pt70mO2nQac&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=pt70mO2nQac&lt;/a&gt;</text><parent_chain><item><author>zetalyrae</author><text>I&amp;#x27;ve always wondered: why exactly is ITER so expensive, and slow? Is the engineering required at such a standard that it should takes decades of planning and construction and tens of billions of dollars? The timeline is so dilated (started in 1988, first plasma planned for 2025!) it feels like the kind of project that&amp;#x27;s expected to be cancelled from the start.&lt;p&gt;It just doesn&amp;#x27;t strike me as obvious that reducing the major radius by a few meters would have such a huge impact on cost&amp;#x2F;timelines.</text></item><item><author>dfdx</author><text>Plenty of skepticism in these comments. I&amp;#x27;ve been following CFS for a while and can present a point of view for why this time might be different.&lt;p&gt;Fusion energy was actually making rapid progress in the latter half of the twentieth century, going from almost no power output in the fifties and sixties to a power output equal to 67% of input power with the JET reactor in 1997. By the eighties there was plenty of experimental evidence to describe the relationships between tokamak parameters and power output. Particularly that the gain is proportional to the radius to the power of 1.3 and the magnetic field cubed. The main caveat to this relationship was that we only had magnets that would go up to 5.5 Tesla, which implied we needed a tokamak radius of 6 meters or so in order to produce net energy.&lt;p&gt;Well that 6 meter tokamak was designed in the eighties and is currently under construction. ITER, being so large, costs tens of billions of dollars and requires international collaboration; the size of the project has led to huge budget overruns and long delays. Recently however, there have been significant advances in high-temperature super conductors that can produce magnetic fields large enough that we (theoretically) only need a tokamak with a major radius of about 1.5 meters to produce net gain. This is where SPARC (the tokamak being built by the company in the article) comes in. The general idea is that since we have stronger magnets now, we can make a smaller, and therefore cheaper tokamak quickly.&lt;p&gt;Small tokamaks do have downsides, namely that the heat flux through the walls of the device is so large that it will damage the tokamak. There have been breakthroughs with various divertor designs that can mitigate this, but to the best of my knowledge I&amp;#x27;m not sure that CFS has specified their divertor configuration.&lt;p&gt;This was just a short summary of the presentation by Dennis Whyte given here [0]. I do not work in the fusion community.&lt;p&gt;[0] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=KkpqA8yG9T4&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=KkpqA8yG9T4&lt;/a&gt;</text></item></parent_chain></comment><story><title>MIT-designed project achieves major advance toward fusion energy</title><url>https://news.mit.edu/2021/MIT-CFS-major-advance-toward-fusion-energy-0908</url></story>