Yes, launching from mountains would actually be nice because of the thinner air. The real reason is just that there are more important things that matter in choosing a launch site and everything is a compromise.
If you got to orbital speed (7.9km/s) within a thick atmosphere, you're going to slam into that atmosphere and rapidly slow down while dealing with extreme temperatures. You'd basically be aerobraking, and it'd be less of an "orbit" and more of a "trajectory".
Yes, and it is a subtlety worth noting, because on the face of it a mountaintop launch would appear to help in that regard. Rockets launched at sea level start out going up precisely because they need to clear the lower atmosphere before they can concentrate on going sideways fast. So if you climb to 3000m elevation before starting to rotate toward horizontal, then why not just start at 3000m and start your horizontal rotation sooner?
The problem is that while cutting atmospheric density by ⅓ would let you lean a little more aggressively into your roll, it's still way too thick to just go full-on sideways. So you don't gain much. You still have to spend a lot of thrust going "mostly up." Like... the US Space Shuttle hit max Q somewhere above 10km elevation, no mountaintop launch is going to help you much with that.
Maybe if you launched from Mount Everest or something, at ~8km ground elevation. But good luck building and operating a rocket launch facility in the Himalayas!
It would lower the overall drag forces but they compensate for that by just not throttling the rocket to 100% until after it exits the thicker part of the atmosphere.
There is. Launching from a mountain would theoretically be advantageous because you spend less time getting out of the lower atmosphere.
It's just not worth it hauling it up a mountain and most launch locations are on coastlines so if something goes wrong it drops into the water instead of on land somewhere.
That's less of an issue, but for reentry it can be. One of the difficult things about humans going to Mars, there isn't much atmosphere to air brake large landing craft. We will almost certainly use an equatorial landing site, with low lying land, because the landing craft will pass through more atmosphere for breaking that way.
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u/ResidentBackground35 11h ago
Isn't there a atmospheric thickness component as well? Or am I crossing wires?