Cryogenic engine prop tanks vent in order to control tank pressure. Thermal energy that (inevitably) gets conducted into a cryo tank raises the propellant enthalpy and so the pressure of the critical fluid in the tank. Thus the tank must occasionally vent in order to maintain proper (P,T) condition. Is this correct?

So then, is it the same with an N2O tank at high (but maybe not critical?) pressure (about 500 psi)and ambient temperature?

After propellant loading, how does a hybrid system control N2O tank pressure?

Hybrid motors are simple in many ways but isn't it a little bit tricky to maintain N2O at required (P,T)? And if so, how is it done on a launch vehicle or spacecraft?

  • $\begingroup$ "...but isn't it a little bit tricky to maintain N2O at required (P,T)?" what is it exactly that make you think it's more tricky for N2O in particular? $\endgroup$ – uhoh Oct 15 '19 at 2:45
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    $\begingroup$ I was thinking (numbers approximate) that N2O requires 500 psi to stay liquid at room temperature. So then if you are carrying half a dozen tons of liquid N2O for a few hours in a prop tank, then the (P,T) in the tank will need active control? But maybe you just make a strong heavy tank and don't worry about it? Also I reminded of link , N2O (P,T) is difficult. Just wondering if N2O venting is the right method of controlling P for N2O as it is for cryogens. $\endgroup$ – Superfort Oct 16 '19 at 14:10
  • $\begingroup$ Okay I see your thinking now. That's the kind of explanation that would be great to add back in to your original question; sometimes people don't read through comments. Thanks! $\endgroup$ – uhoh Oct 17 '19 at 0:30
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    $\begingroup$ thanks for the tip! $\endgroup$ – Superfort Oct 18 '19 at 13:43

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