I assume that in a LOX/RP-1 engine where RP-1 is used as a coolant, we need not consider the freezing issues. The reason for my assumption is that we need not bring the chamber and injectors to the LOX temperature during the start of the engine. After ignition, the temperature of combustion and subsequent heat transfer should avoid the RP-1 freezing

Whereas in a LOX cooled engine, the thrust chamber has to be chilled down and brought down to LOX temperature (i.e., <90 K). The freezing point of RP-1 is ~ 196 to 233 K.

Would the incoming RP-1 freeze before the start of combustion? If so, how would've this been avoided in a LOX cooled semi-cryo engines?

  • $\begingroup$ Cold chamber isn't a problem because the fuel never touch the chamber anyway. $\endgroup$ Jun 29, 2020 at 6:57
  • $\begingroup$ Chilling down the chamber essentially means the injector plate will also be chilled down, right? The LOX will be passed through regen lines and out of the injector plate $\endgroup$
    – Vasanth C
    Jun 29, 2020 at 7:09
  • $\begingroup$ Is there any example of a LOX cooled semi-cryo engine? A reliable engine used many times? $\endgroup$
    – Uwe
    Jun 29, 2020 at 7:55
  • $\begingroup$ @Uwe - Not a flight tested one. A company named Launcher are testing LOX cooled engines to increase their C* efficiency. - twitter.com/launcher/status/1149779527004016642. $\endgroup$
    – Vasanth C
    Jun 29, 2020 at 8:02


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