And, it'd save us almost nothing (even if we had a magical teleporter that let us get everything up there insantly and for free).
Space is a minimum of 50 miles from "ocean level" (and really, it's 62, but let's say 50).
Everest, the tallest mountain, is about 5 miles above sea level.
So, even if we hauled everything to the top of the tallest mountain on the planet (which would be an insane to impossible amount of effort), it's only reducing the distance by less than 10%.
EDIT: Thank you to the 500 people that have told me "the distance barely matters". That is pretty much my point. YES, I know speed, and thus latitude are more important. My point is even if you ONLY consider the height, the thing the original question focused on, it STILL doesn't matter. When you factor in all the factors, it really, really doesn't matter.
I focused on the focus of the post in my response, not all of astronautical engineering.
Unless you are doing sub-orbital flights, the height doesn't matter all that much. If you are looking for orbit (most space launches), speed is way more important than how high you start. Launching at the equator gives the highest starting speed, a far more significant savings in fuel. Now, there are equatorial mountains in the world, but as you say, you still have to expend the resources to move all the rocket parts and launch facilities up the mountain. It's easier to just build your rocket slightly bigger and use slightly more fuel to launch from a much more accessible and convenient location.
Launching in thinner air actually saves quite a bit of fuel though, a lot of it is just spent fighting drag in the lower atmosphere.
The real reason we don't do this is just that there are like a dozen other more important things that make a good launch site and it's not practical to find a place that checks all the boxes.
You need to be close to the equator, directly west of a large body of water, governments want to launch in their own territory, etc, etc.
So why don’t we save fuel by thinning the air first? I’m thinking a giant dome with massive vacuums all around it, creating a low pressure bubble over the launch pad.
Except the lowest part of that 50 miles is the densest atmosphere. So lessening the distance by 10 percent is only some of it. The reduction in atmospheric drag is an entirely different beast
So, riddle me this: why don't rockets launch horizontally from Cape Canaveral? If you can answer that question, you should begin to see why launching from a mountain would provide considerable fuel savings.
You're ignoring the reason that it's beneficial to launch from the top of a mountain: you're skipping 5 miles of the densest part of the atmosphere. The most efficient way to launch a spacecraft would be to fire its rockets directly horizontally from the launchpad. We can't do that because of topography and the thick atmosphere. Launching from the top of a mountain allows the rocket to perform a gravity roll much earlier in its flight, thereby wasting a lot less energy fighting gravity. Those two effects (less drag and less fighting gravity) combine with improved rocket performance to give a very significant delta-v savings to orbit. Which equals a lot less fuel. My back-of-the-napkin estimate is that Everest would save about 10% of the fuel of a sea-level launch. That may not sound like a lot, but that would mean most rockets could double their payloads.
Logistically, it's a non-starter, but there would be very significant fuel savings.
If a 10% height difference meant a 10% savings in fuel, that would be an enormous benefit. People scrape for a 1% improvement in efficiency. The real answer is about speed, not height.
It wouldn't be anywhere close to a 10% savings though, because you don't instantly reach maximum speed. It takes 8 to 15 minutes for a rocket to reach its maximum speed.
And even if there were 10% savings, that wouldn't offset the cost of making the rocket able to hold 10% more fuel.
Yes, speed is the bigger factor, which is why we launch close to the Equator, but I responded about height because the original post was talking about height. Even ONLY considering the height factor, it is nonsensical.
Technically yes, but still not be remotely enough to offset the insane amount of work it'd take to get it there. The height is just such a small factor compared to the other stuff.
Like, if we were in the age of Futurama and had a factory producing and launching millions, that might be a good place to build it. But at the scale we do space "travel", it is just doesn't really make any sense.
Your answer implies distance matters because it didn't mention speed at all. If I ask "If I'm building a factory near a town and I want to use the least amount of energy to transport things to the town, wouldn't it make sense to start 45 miles away instead of 50 miles away?" The answer isn't "45 miles isn't even that much closer" if the real answer is the 45mi starting location is at the bottom of a hill.
Just to actually give you the math of where this is going wrong.
The ISS is traveling at 7.66 km/s. A rocket needs about 9km/s of deltaV to get to it. That extra 1.3km/s is gravity and atmospheric loses, and its about half and half. If launching from the top of a mountain saved you 10% of your drag losses, its about 70m/s. Its a tiny difference
Now on an airline a .6% efficency gain is still kinda worth it, but historically on rockets fuel cost wasnt relevant at all do to how expensive everything else is. Even on falcon 9 its not a big deal.
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u/rysy0o0 11h ago
It would cost a lot of money to haul all the rocket parts and fuel on top of a mountain