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HTP or high test peroxide has a long history as a low cost and high reliability oxidiser, and has had a lot of recent attention for its pseudo hypergolic nature when passed over a catalyst bed. Unfortunately, catalyst beds often incur a high weight and use expensive metals (such as platinum), and although HTP can be burnt without a catalyst bed, it either needs a very high concentration of catalyst in the fuel(5-20% depending on catalyst type and other circumstances) which is both a drain on ISP and makes the cost of fuel extremely steep, or otherwise, without any catalyst, combustion is intolerably unstable and temperamental. Another way exists to decompose HTP however, which is applying a lot of heat. So, hence my question: is there enough heat transfer in a regenerative cooling loop to decompose HTP such that it is suitable for combustion, and would the superheated steam/oxygen produced have enough pressure to drive a turbine/propellant pump, making it suitable for a (closed) expanded cycle?

Another consideration is that because the decomposition of HTP produces mostly water as apposed to oxygen, a very high O/F ratio is required, meaning that there would be a lot of HTP travelling through the cooling loop compared to the size of the nozzle, possible reducing the change in temperature the HTP receives. As well as this, could the hot oxygen generated in the cooling loop oxidise the metal surface of the cooling channels/introduce the need for some super alloy like those seen in the raptor engine?

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  • $\begingroup$ I suspect the cost and weight penalty from making the heat exchanger hot-oxygen-proof will outweigh the gain from losing the catalyst bed. $\endgroup$ Aug 27, 2021 at 6:43

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I think the main concern is the explosive characteristics of H2O2 vapor. If you go through some literature, You would find that the vapor of more than 26-mole percent of H2O2 is likely to face an explosion(detonation). Regenerative cooling using H2O2 seems promising (actually there is research conducted using 98 % H2O2 and the results were pretty good), but the boiling part and resulting vapor explosion is pretty tricky to handle.

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  • $\begingroup$ That sounds awesome could you link any of those papers? $\endgroup$ Apr 28 at 6:49

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