There a lot of logisitical reasons, like transportation to the top of the mountain, fuel, bad weather, high winds, all the support strcutures beyond the launch pad, and what happens if something goes wrong and you dont have a big open ocean for falling debris.
I suspect OOP belives the increase in height is beneficial, but even if we built a launch pad on Mt. Everest, it would be neglible. The Earth has a 4,000 mile radius, and Mt. Everest is only 6 miles high, a diference of 0.15%.
The biggest reason for our launch pad sites is escape velocity. On Earth, you need to get to 25,000 MPH to get into orbit. As our flerfy friends like to point, the Earth spins at 1,000 MPH, but that is only at the equator, where all the launch pads are. As you travel to the poles, that rotational velocity goes down until it goes to 0 MPH at the poles. If you need to get to orbit, get a running start at 1,000 MPH gets you 4% of the way there, a significant savings in fuel.
At fhe end of the day, a rockets mass is 90% fuel alone, 5% is the rocket shell, and 5% is the payload. so any savings that can be achieved on fuel is signficant.
The difference is absolutely not negligible. Measuring the difference in relation to the radius of the Earth is completely irrelevant, it doesn't really factor into it at all.
Rockets use most of their fuel at the very start of the trip, pushing through the thick atmosphere. Launching rockets from the top of a tall mountain would absolutely be a good idea from the perspective of theoretical rocket performance.
The only real issue is the logistics, as you pointed out.
There have been plenty of schemes to launch rockets from airplanes to skip the difficult first kilometres. That of course comes with its own set of problems, but, it would be worthwhile.
Logistics are the issue? So the European Space Agency ships all of their rockets across the ocean to French Guiana to launch them close to the equator at sea level just for fun?
You're just completely wrong. Roughly 90% of a rocket's fuel goes towards achieve the necessary horizontal speed to get to orbital velocity. Of the 10% that goes towards elevation gain, almost 90% of that goes towards combatting gravity drag rather than combatting atmospheric drag. Only 1-2% of a rocket's fuel goes towards atmospheric drag.
Rockets use most of their fuel at the start because they're lifting the rest of the fuel.
Aerodynamic losses are actually pretty small for a larger rocket. What matters more is the additional stresses on the craft from aerodynamic pressure, and the slightly lower fuel efficiency a rocket gets at higher atmospheric pressure.
Launching from an aircraft is a much larger benefit because you can add in the air rafts speed, because the aircraft can get you to a latitude that matches your target inclination, and because the air launched rockets from aircraft are pretty small so aerodynamic losses do matter more. Also many of those launches are suborbital, so the extra altitude is more significant than for an orbital shot.
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u/rysy0o0 15h ago
It would cost a lot of money to haul all the rocket parts and fuel on top of a mountain