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Raptor won't fly on the Falcon, so it depends on the arrival of the BFR. Elon wants that to be doing Mars missions in the 2022 window, so test flights would have to precede that by some time. Construction of the first BFR is due to start around Q2 next year; when it gets in the air is anybody's guess.

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There is still a good chance they might do a FH Raptor-powered second stage :)

A higher-impulse second stage on the Heavy would make sense in payload terms, but have you seen anything from SpaceX indicating that they actually are thinking about doing this? My understanding of their design philosophy is that they prioritise the operational efficiencies of only having one type of engine and one type of propellant to worry about on the pad.

SpaceX's initial money from the Air Force for Raptor involved the possibility of a new Raptor-powered FH upper stage. There's no sign that such a stage is still planned (or was ever seriously considered, really.)

Huh, I'd forgotten about that -- thanks.

Yeah, I doubt it was seriously considered. Probably just didn't want to tell the Air Force what they were really planning to use the Raptor for. Can't say I blame them!

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