What is RP-1 rocket fuel?
Also called: rocket propellant 1, rocket kerosene
RP-1 is a highly refined kerosene used as rocket fuel, burned with liquid oxygen. It is close to jet fuel but cleaner, with strict limits on sulphur so it does not clog the engine.
It is dense, safe to handle at room temperature and cheap compared with the alternatives, which is why it has been used since the 1950s.
Falcon 9 burns it with sub-cooled liquid oxygen. The mixture runs deliberately fuel-rich, which is why the exhaust is bright orange rather than clear.
Its drawback is soot. Methane, which Starship uses, burns cleaner and leaves engines easier to reuse.
See it happen
Push & GoWhy rockets flySource: Falcon 9 Block 5 — specifications