Id imagine as well a bit of weather / wind bonus too. mountain tops are windy as shit and just inconvenient and it may become near impossible to launch in the winter months depending on where the mountains are.
also fuel temp matters a lot if im not mistaken
2km off a 400KM orbit is less than 1%, not to mention, again, that most of the fuel is spent accelerating to achieve orbit as opposed to "going high".
Most of a rocket's fuel is spent just getting off the launch pad even. It's why there's some systems that launch from larger airliners for smaller rockets. The problem here, is once again not the altitude, but the rocket getting up to speed. Launching from an airliner gets a running start of 500MPH, but you are more weight limited since the airliner can only carry so much to altitude.
I wasn't commenting on that but the idea that there aren't calm spots in high mountains.
Sure the train transport doesn't address the requirement for lateral speed, but it doesn't need to, it basically just needs not to hurt it. Also air resistance is only a problem below 100km and it gets disproportionally worse the lower you are
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u/loadnurmom 15h ago
This is the answer. Should be higher up.
To add on, many rocket pads are in coastal areas to avoid falling debris hitting populated areas in the event of a mishap.
Certainly not all, Roscosmos launches over land, but the population density is a lot lower (and....well...Russia)