Here in Falcon 1 user guide, in table 2-1 in page 8, heated Helium is mentioned as used for tank pressurisation. What will be the temperature of such He and why is heated He used?
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1$\begingroup$ Sorry Karthik, didn't notice you were asking about the first reference to it, added an image to avoid confusion. $\endgroup$ – Magic Octopus Urn Sep 17 '18 at 17:34
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1$\begingroup$ If you haven't already read all of the answers to questions like Why does the Falcon 9 require a helium pressurization system? and How does tank pressurization work? and Why Use Helium? and Why do pressure-fed systems have to be pressurized with helium or nitrogen? this might be a good time. To "why is heated He used?" isn't the answer just that that's what generates the pressure? $\endgroup$ – uhoh Sep 17 '18 at 18:10
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1$\begingroup$ @uhoh I take the question to mean "why heated helium." $\endgroup$ – Wayne Conrad Sep 17 '18 at 18:53
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2$\begingroup$ @WayneConrad as do I. Isn't the heating the helium what causes the helium to become pressurized, "the heating" being the thing that actually "generates the pressure?" A tank of liquid helium at its 1 bar boiling point will have a slow boil-off rate, nothing close to enough to help the tons per second of propellants out of the tank. Isn't the heating of the helium the thing that does the propellant-helping? $\endgroup$ – uhoh Sep 17 '18 at 19:05
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3$\begingroup$ If gaseous helium is stored in a high pressure tank, its temperature will drop a lot during expansion. To compensate the temperature drop and to get more volume per mass, the helium is heated after expansion. $\endgroup$ – Uwe Sep 17 '18 at 22:21
