<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>beerandt</author><text>And then on top of it all, throttling ability.&lt;p&gt;People don&amp;#x27;t grasp what an unbelievably complex engineering problem that is. It&amp;#x27;s at least an addition of difficulty at the same magnitude as building a steady-state 63000 hp turbine pump in the first place.&lt;p&gt;Mechanically implementing it in the inherently steady-state design rocket of most rocket cycles. Having variable controls able to work at those pressures. Testing structural dynamics for a range of harmonic conditions instead of one. And do all of that with materials that need to tolerate temperatures going from cryogenic to white hot, without allowing thermal expansion to affect the mechanical tolerances of parts running at thousands of RPMs. And now you have varying flow rates and negative pressures in the lines coming from the external tanks, so have to design such that cryogenic liquids (that normally would require immense positive pressure to keep liquid) don&amp;#x27;t spontaneously boil or cavitate or cause a shock-like wave (think water hammer turning off your bath faucet) under changing negative pressures.&lt;p&gt;It&amp;#x27;s really difficult even for seasoned engineers to grasp the scale of difficulty involved.</text><parent_chain><item><author>HPsquared</author><text>I the power level of these engines is difficult to comprehend. The &lt;i&gt;fuel pump&lt;/i&gt; has thousands of horsepower. Compare this to the fuel pump on a car engine, which is a tiny little electric thing. The combustion power must be in the gigawatt range.&lt;p&gt;Edit: the SSME high pressure fuel pump turbine produces 63000 hp (46 MW). There&amp;#x27;s also one for the oxygen, and a pair of low pressure pumps as well. Crazy...&lt;p&gt;Edit edit: the fuel pump transfers 155 lb&amp;#x2F;sec of liquid hydrogen. If fully combusted (142 MJ&amp;#x2F;kg), that would release 10.0 GW of heat per engine.</text></item><item><author>opwieurposiu</author><text>This thing I can not comprehend about rocket engines is how the turbopump manages to hold together.&lt;p&gt;A turbine blade in the SSME about the size of your thumb makes 600 horsepower.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.enginehistory.org&amp;#x2F;Rockets&amp;#x2F;SSME&amp;#x2F;SSME6.pdf&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.enginehistory.org&amp;#x2F;Rockets&amp;#x2F;SSME&amp;#x2F;SSME6.pdf&lt;/a&gt;</text></item></parent_chain></comment><story><title>Engine cooling – why rocket engines don’t melt</title><url>https://everydayastronaut.com/engine-cooling-methodes/</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>7952</author><text>Saturn V at take off had an equivalent power of 166GW.  If that was electricity it would be around 2x the total capacity of all the power stations in the UK.</text><parent_chain><item><author>HPsquared</author><text>I the power level of these engines is difficult to comprehend. The &lt;i&gt;fuel pump&lt;/i&gt; has thousands of horsepower. Compare this to the fuel pump on a car engine, which is a tiny little electric thing. The combustion power must be in the gigawatt range.&lt;p&gt;Edit: the SSME high pressure fuel pump turbine produces 63000 hp (46 MW). There&amp;#x27;s also one for the oxygen, and a pair of low pressure pumps as well. Crazy...&lt;p&gt;Edit edit: the fuel pump transfers 155 lb&amp;#x2F;sec of liquid hydrogen. If fully combusted (142 MJ&amp;#x2F;kg), that would release 10.0 GW of heat per engine.</text></item><item><author>opwieurposiu</author><text>This thing I can not comprehend about rocket engines is how the turbopump manages to hold together.&lt;p&gt;A turbine blade in the SSME about the size of your thumb makes 600 horsepower.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.enginehistory.org&amp;#x2F;Rockets&amp;#x2F;SSME&amp;#x2F;SSME6.pdf&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.enginehistory.org&amp;#x2F;Rockets&amp;#x2F;SSME&amp;#x2F;SSME6.pdf&lt;/a&gt;</text></item></parent_chain></comment><story><title>Engine cooling – why rocket engines don’t melt</title><url>https://everydayastronaut.com/engine-cooling-methodes/</url></story>