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 radius of Earth is completely irrelevant. The problem is the dense portion of the atmosphere near sea level, which prevents a rocket from rolling over and dumping its energy into horizontal motion. The atmosphere at the top of Everest is about 35% as dense as the atmosphere at sea level. Everest is also closer to the equator than Cape Canaveral.
If it was logistically possible to launch from Mt Everest, it would definitely be worthwhile. Between reduced drag, earlier gravity roll, and improved specific impulse, I think it would save about 300 m/s to LEO, plus whatever advantage the ISP provides. The rocket equation being certifiably nuts in its exponentiality, that's about a 12% reduction in fuel required at launch.
This is completely wrong. The earth's spin in incredibly important. The European Space Agency literally launches from French Guiana in South America because of the rotational slingshot effect.
The spin is extremely important; I never said it wasn't. However, the percentage increase in distance from the center of the planet (and therefore the radius) isn't part of the reason that launching from high altitude is beneficial. The increased velocity from that is negligible. Hence, it is completely irrelevant to this discussion.
You're wrong. Launching from the Equator vs launching from Canaveral is only 80m/s difference in dV. (Earth is spinning at about 400m/s at canvaeral vs 480 at the Equator) If you launch due east. That's very small, even considering the rocket equation. A rocket needs 9 - 9.5km/s to get to LEO, depending on gravity, cosin and aerodynamic losses.
The reason they launch from there is that you can target a very wide range of orbital inclinations AND you can launch east over the water so spent stages fall someplace safe. You can't get that launching from anywhere in Europe.
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u/rysy0o0 4d ago
It would cost a lot of money to haul all the rocket parts and fuel on top of a mountain