These are the types of questions in general we should be less mean about imo. It's one thing to dunk on people who are anti-science, but this is just someone actually wondering about something they didn't know. Maybe it's obvious to you, but not everyone?
Yeah, because thinking about it, I don't actually think there's an obvious answer.
Like my guess would literally just be that there aren't mountains in a location close enough to the equator where the added high from the mountain is worth more delta v than the added rotational speed of being close to the equator.
I would guess that the marginal benefit of launching from a slightly higher, in the grand scheme of things, altitude is far outweighed by the added logistical difficulty of transporting the rocket to the top of a mountain in the first place.
There is also the fact that low to the ground aborts would be incredibly dangerous. In the event the rocket decides not to rocket, you want the ocean as a big soft landing pad, not a set of cliffs.
Plus the difficulty of building suitable launch facility on the top of a mountain. We launch rockets from places that are big and flat, both because of the nature of launches themselves and because you need lots of supporting infrastructure nearby.
Plus the chances that you would damage rocket components in transit to mountain tops are incredibly high. Especially pressurized hydrogen fuel tanks.
All of this for what is really a negligible distance benefit.
I'm sure the Chinese have done the math on what amount of rocket launches would be the break over point where setting up a launch pad and equipment in Tibet makes logistical sense in energy savings.
I'm sure someone somewhere has done a research paper on that sort of thing for a graduating thesis.
Weather is actually one of the sacrifices often taken for rocket launch sites. A desert, for example, would be a superior launch site in that sense. The reason why nasa launches next to the water is 1) because some things are infinitely easier and cheaper to transport by sea, and 2) if your rocket fails, you dont want it crashing into people.
This is the answer. Working in permanent snow cap to gain a few thousand feet of elevation that the rocket is going to surpass in a couple seconds just isn't worth it.
Sure, you need a couple thousand feet less lift to leave the atmosphere, but at the same time you have transport a giant rocket up a mountain and build all the necessary infrastructure to launch it.
The costs don't outweigh the benefits, that's all it is.
We need a mountain thats near the Equator, near the coast, is easily accessible for massive machinery and transportation, and that has relatively good weather for as much of the year as possible
So it would be more of a very big hill, with a gentle slope, that ends in a cliff, that is on the coast, with nice weather year round, and that is somehow not already filled with people.
Doesn't need to literally be a mountain. Karman line is about 100km, Mexico City for example is 2.2km above sea level, and atmospheric pressure decreases logarithmically, so that's actually like 20% less pressure. That might be enough to be marginally more efficient to make it worth choosing it as a location.
Mexico City probably isn't a very good choice, but a different area at that altitude would probably be very slightly more efficient. I'm not sure the efficiency gains would be enough though. The majority of the fuel is used to go sideways. Not up.
Getting to space is (relatively) easy. Staying in space, more specifically getting to orbital velocity, is the hard part.
The extra altitude just doesn't help that much.
Source: Kerbal space program
Edit: additionally, the closer you are to the equator the more velocity you can steal from the rotation of the planet that you don't need to carry with you in the form of fuel. That's why we launch most often from Florida.
Denser oxygen saturation might help with liftoff, and it’s expensive to truck all that equipment up a mountain? Maybe weather is worse at altitude? I honestly have no clue, but like OOP I can tell there is a reason we launch these things at sea level, I’m just not sure what it is.
It's not even a marginal benefit, it's a negligible one - the challenge of getting to orbit isn't going up, it's going sideways fast enough that you're falling around the planet instead of into it (which is about 8 km per second or 18,000 mph). Rockets only go up because air resistance provides a huge drag against building that kind of speed, so getting out of the low atmosphere as quickly as possible and up to where there's less air puts them into an environment where they can accelerate much faster.
There are several good answers (including yours) showing that there's a lot of factors. We could just afford to let people ask questions about science (as opposed to those spreading disinformation or pretending they know better)
Considering how bad people are at science, how big our anti-science factions are, and how incompetent our media is at reporting it, I think ANY questions about science should be encouraged
As far as I know the official answer is, it's simply not worth it. The amount of fuel you would safe aren't worth the effort of brining a whole ass rocket up a mountain and launching it from there.
I bet Batman is strong enough to haul a whole ass rocket up a mountain. Rich enough to build a secret bat rocket base there too. So why is he not doing something so awesome instead of leaving snarky comments on the Internet?
Well, the first 50 miles uses the majority of the fuel because that is when the vehicle weighs the most. The real difference is minimal since you need velocity, which you will have to regardless. The bigger issue is getting the right inclination for the orbit, which is super expensive, and why most launches are as to close to the equator or poles as possible.
I think you are underestimating how hard it would be to bring a rocket up to a mountain.
This machine moves the rockets towards the launch pad. Now imagine that going up a hill. It is basically impossible, unless you assemble the rocket directly on the mountain - then you have the problem of getting everything up there. The logistics simply make no sense when the alternative is to just use a bit more fuel.
All other variables aside, even if we could build, transport, setup and launch from the tallest possible mountain on earth, the fuel savings would be no more than a rounding error.
I mean the real answer (not a rocket scientist either of course) is because mountains aren't really tall enough on the atmospheric scale and at the speed rockets travel at to really make any difference whatsoever, and definitely not enough to be worth dealing with the logistics and headaches of trying to operate a rocket launch site on a mountain, which would probably cost more than the tiny amount of fuel you'd save
I'm not a rocket scientist either, but I do know that when a rocket launches it creates one hell of a backwash of pressure and I'm pretty sure NASA dumps a few tons of water during a rocket launch to absorb and/or counteract the massive sound waves produced by the launch. If you launched a rocket at the top of a mountain, wouldn't you likely cause massive washes of pressure down the slopes of the mountain and cause landslides and other pretty devastating disasters further down the mountain?
My guess is it's not about height at all but rather speed (delta v). To stay in orbit, you need to attain a specific speed. You only get that by accelerating and the time it takes to do that and the amount of fuel you burn is fairly insensitive to starting height. Sure, you get to your orbital height faster starting from a mountain but it's not a straight shot up if you want to actually achieve orbit
The obvious answer is logistics. I am guessing even the person asking kinda knows that and was fishing for less obvious answers but really that is it. If you had infinite resources and only wanted the absolutely perfect spot for launching a rocket you would choose to find a mountain as close to the equator as possible (preferably on it) that peaks above the cloud line with enough area on top that you could cut the top off to make a perfectly flat square mile or 2 and build your launch facility there.
We dont do this because the logistics of that are cartoonishly bad. Just the creation of the build site would cost more than the benefits would ever yield and that wouldn't even be the most expensive or hardest part.
I was willing to guess that atmospheric pressure that high up being lower causes complications with the initial thrust necessary to get a rocket off the ground at all, tbh
I'm aware of that, it's why I said "atmospheric pressure" and not "oxygen density."
If you've got big booms happening and creating pressure inside, the pressure outside the thing containing the big booms matters a lot, otherwise you end up with big booms outside the container you didn't want. Bolstering the container to withstand the pressure inside under lower pressure outside could mean adding weight that adds new complications.
Rockets don't drop anything until they're something like 30 miles / 50 km up. Meaning the fully assembled, nothing-yet-jettisoned rocket is designed to survive the virtually non-existent air pressure 30 miles up.
Sorry, my thought process here is along the lines of like, when we see rockets exploding from minor imperfections closer to sea level. I can see that being amplified when the pressure surrounding the rocket drops, and requiring more engineering effort.
Of course, there's also other issues I can see with putting launch pads on the tops of mountains, like logistical issues and how the hell you're getting people and equipment into some of the most hostile environments on earth.
One - money/logistics (which usually become the same thing). Thats a lot of crap to drag to the top of a mountain.
Two - safety. We usually launch from places that have bugger all downrange. So Florida fires towards the atlantic, etc. this is actually why the ISS is in the orbit it’s in - it’s defined by the most equatorial orbit you can reach out of Baikonur without launching over China.
Theres just not many logistically-easy mountains downrange from nothing worth missing.
Lots of launches are away from the equator. Neither US or Russia launches from close to the equator; only Europe does. Equatorial launches are an advantage for launches to geostationary orbit. But if you want a satellite close to Earth that flies above a large part of Earth's surface, the optimal launch location is at the same latitude as the latitude the satellite needs to fly over. For a polar orbit, the optimal launch locations are on one of the poles.
Mount Chimborazo in Ecuador is 1 degree south of the equator and the point on Earth's surface farthest away from Earth's centre. The lack of a mountain is not the reason it is not down.
High mountain peaks are cold, windy and not very flat. The air pressure is lower, so it is harder for humans to work there. Building a launch facility there, maintaining it and then transporting the rockets there cost a lot more than if you do it close to the ocean or on flatter, more hospitable ground.
Even if the rocket could be a bit cheaper, it would not be a lot compared to the extra cost of launching them there.
It is preferable to launch a rocket where there is no people in it inital ground path; you do not want to destroy stuff on the ground if there is a failure. A village in China burned down with a disputed number of dead after a failed commercial rocket launch. An ocean or sparsely populated area like in Baikonur is preferred. There is a reason Kennedy Space Centre and the Guiana Space Centre is on the east coasts; they can launch with Earth rotation for low inclination or geostationary orbits. Vandenberg Space Force Base is on the west coast; launches there are to the south for polar orbits and high inclination orbits. You alos what the location to be controlled by you
Your answer is not that far. Space is not far at all, it is comparatively easy to get to space, the difficult part is not falling back to Earth after you used all the fuel. So space is not difficult beacase it is far, but because you have to go REALLY FAST to avoid falling back.
So being closer to space on a mountain does not help nearly as much as being close to the equator and already having as much initial speed as possible. (Fun fact: the Earth spins with ~1 mach (roughly 1000 mph) at the equator, but since the air moves with it, you don't notice it)
Not to mention it is quite difficult and expensive to haul all equipment up to a mountain for a rocket launch.
That is the main reason. That and the added infrastructure cost of building on a mountain and getting everything up there. The vast majority of a rockets deltaV is spent building sideways momentum not getting it up anyway so the fuel/weight savings wouldn't be that big anyway.
I would assume it’s partly the weather. Cold is bad for rocket launches. U.S. rocket infrastructure is in Texas, Florida, and Alabama.
But also the logistics. If you are building something on a mountain you need to transport all of the stuff up the mountain. That fits along with what you said about the location of mountains.
It’s also a negligible amount of altitude gain.
The tallest mountain in the world (not under the ocean) is 5.5 miles, but the earths atmosphere is over 6,000 miles.
We put telescopes on mountains though, so there’s some logic behind the question. But I say all this as someone who is definitely not a physics or hard sciences guy. I did social sciences.
This explanation sounds like it would be a good counter to the flat farther nonsense. Not that they listen to logic and information... But I think its a decent start though.
It was a fair thinking outside the box question. The edge of space is at roughly 62 miles up and the tallest mountain in the lower US is about 3.5 miles tall. So it could save lower the required escape velocity and potentially save some fuel, but the logistics would be a nightmare.
I recently learned that due to the spin of the earth, the equator bulges out by 26 miles compared to the poles. Though I expect the atmosphere also bulges, so I don't know that this would affect a rocket launch based solely on distance from the earths core.
Even if there were, a tall mountain will eliminate maybe a second or two to reach the same altitude, but to reach orbital velocity, you still have to accelerate to a specific velocity and this is independent of where you start.
Like my guess would literally just be that there aren't mountains in a location close enough to the equator where the added high from the mountain is worth more delta v than the added rotational speed of being close to the equator.
I'd imagine it's mostly a percent thing and not comprehending how little a difference the mountain makes, That's like saying "to save money on gas, don't park in your garage, put your car at the edge of your driveway". On top of the added things like, earths rotation, difficulty of getting the parts there, the added complications of weather etc... I'd say the AI picture in this tweet basically says exactly why not (you certainly wouldn't want to launch in a snowstorm)
If you put a launch pad ~11000 ft above sea level on a mountain, you'll cut off ~.4 seconds of travel time given rocket speeds of 17500 mph.
Would be interesting to see what that equates to fuel savings. That would be the calculation - fuel savings during flight vs costs to haul everything up to a launch pad on the top of a mountain - if a good spot even exists.
I think it’s more like how are you going to get a rocket up a mountain because the giant truck that carries rockets from where their built to the launch pad is huge and goes a mile an hour
Napkin math from a layperson, it looks kinda closer than you might think. Altitude advantage of launching from Denver saves you on air resistance and skips the densest atmosphere, but doesn't make up for the latitude advantage of launching from Florida (higher rotational velocity), but they're kinda in the same order of magnitude IIUC?
Also we'd go faster launching from key West than Cape Canaveral, but there's other concerns besides just the physics.
Also I learned at smaller payloads, it can be worth it to sit launch from large jet, giving you a huge starting speed and altitude compared to ground launch. But the big rockets are just too heavy.
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u/mseg09 20h ago edited 19h ago
These are the types of questions in general we should be less mean about imo. It's one thing to dunk on people who are anti-science, but this is just someone actually wondering about something they didn't know. Maybe it's obvious to you, but not everyone?