Yes! Amazingly, although the nozzle looks just like a bell-shaped piece of sheet metal, it in fact uses "regenerative cooling" which means the nozzle is full of small pipes which wind back and forth like a radiator. The rocket fuel is passed through these pipes before combustion, resulting in a heat exchange which is doubly beneficial, keeping the nozzle (relatively) cool and also heating up the rocket fuel so it combusts more efficiently.
> the exhaust into the vacuum looks like a messy grey cloud, not the bright cone I might have expected
Yep, since there is no atmospheric pressure squeezing it into a cone shape, the exhaust just kind of flies everywhere!
Merlin 1C Vacuum had a regeneratively cooled combustion chamber but radiatively cooled expansion nozzle. I'm not sure if Merlin 1D Vacuum differs from this though.
You're correct for the last generation of engines - Merlin 1C Vacuum was radiatively cooled. However I haven't found any confirmation one way or the other for the 1D Vacuum engine, which they're using currently. It's possible they haven't made this info public yet due to ITAR.
Yes! Amazingly, although the nozzle looks just like a bell-shaped piece of sheet metal, it in fact uses "regenerative cooling" which means the nozzle is full of small pipes which wind back and forth like a radiator. The rocket fuel is passed through these pipes before combustion, resulting in a heat exchange which is doubly beneficial, keeping the nozzle (relatively) cool and also heating up the rocket fuel so it combusts more efficiently.
> the exhaust into the vacuum looks like a messy grey cloud, not the bright cone I might have expected
Yep, since there is no atmospheric pressure squeezing it into a cone shape, the exhaust just kind of flies everywhere!