>>12139193Yes I know how hydrocarbon chemistry works and what the mechanisms that lead to coking are. The reason I say "if" is because propane exists in this kind of border region of carbon to hydrogen ratio where it MAY be favorable in terms of a fuel rich combustion cycle, which is a prerequisite to allowing FFSC, which is the best closed cycle for a reusable engine because you have two entirely separate preburner-pump assemblies which are either fuel rich on both sides or oxygen rich on both sides, which completely eliminates any need for zero leak high pressure seals on rotating shafts.
Methane, for example, does not form ANY coking deposits when burned, or even when pure methane is thermally decomposed via an arc torch, because the hydrogen to carbon ratio is very high, and even if a carbon atom only has a single hydrogen attached and three unpaired valence electrons just hanging in the wind, that radical is still a volatile and doesn't deposit as carbon soot.
Kerosene DOES for coking deposits because it has a hydrogen to carbon ratio of just a bit over 2:1. This is not enough to ensure that every single carbon atom in the decomposition soup manages to hold onto at least one hydrogen atom, and even worse is the fact that with a longer chain hydrocarbon the chance that any two carbon atoms will form double bonds goes up. While C-H is a volatile radical, C2-H radicals are not, and will deposit out as well as polymerize into even longer tangled messes of carbon double and single bonds.
Propane is somewhere between, because it has a hydrogen to carbon ratio of 8/3, or 2.66. It's also relatively short, only having three carbons per molecule, so it may be less likely to form nonvolatile radicals and carbon-carbon polymers.
