As far as I know, propane with oxygen will burn at 2800 °C and steel will melt at ~1500 °C. Brass is even less.

What I am trying to do is a rocket nozzle.

Is there a way I can built this with steel or is it simply too hot? And for the burning temperature of propane, 2800 °C, is it the temperature IN the nozzle, OUT of it, or IN the combustion chamber?

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  • $\begingroup$ Without efficient cooling this nozzle would work only a very short time. But the combustion chamber needs powerful cooling too. The WW2 rocket V2 used alcohol mixed with some water and liquid oxygen burning less hot. But without liquid cooling, the rocket engine and the nozzle would be destroyed in a very short time. $\endgroup$
    – Uwe
    Feb 19, 2017 at 19:53

2 Answers 2


The answer is that in order to survive and function, the rocket nozzles need to be cooled. How that's done varies with the application, but includes:

  • Liquid Cooling Jacket: The liquid propergols and/or fuels ar circulated through a jacket around the nozzle before being directed to the combustion chamber. This is how the Saturn V F-1 engines and the Space Shuttle Main Engine operated. In other applications, th fuel is circulated through a jacket but is dumped rather than sent to the combustion chamber
  • Ablative cooling: The combustion chamber and/or nozzles are designed to wear away and be ejected along the exhaust stream. This is typically how solid fuel rockets operate, but some liquid fueled engines work this way as well. One problem is that as the material is worn away, the geometry of the nozzle and combustion chamber change, possibly affecting engine performance
  • Radiative/convective cooling: The heat is radiated through the material at a fast enough rate that the material never gets too hot. This only works on relatively small engines.
  • $\begingroup$ Would spraying water on it work? $\endgroup$
    – Dat Ha
    Feb 14, 2017 at 17:55
  • $\begingroup$ @DatHa That would be convective cooling. So according to the answer it may work for small engines. $\endgroup$
    – JMac
    Feb 14, 2017 at 18:33

To answer the other part of your question, the temperature is that in the chamber, but note that that figure assumes perfect combustion, which may not be the optimum point for specific impulse in your geometry. Many rockets run fuel rich as a reducing atmosphere in the hot bits is easier to cope with then an oxidising one.

The largest thermal flux is usually at the nozzle throat, as that is where the combination of high pressure, high temperature and high mass flow come together.

The nozzle is a complex thermodynamic machine, which trades hot and high pressure, for cooler, a pressure ideally just above external atmospheric, and high velocity.

For ablative nozzles, graphite is a magic material.


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