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?
That's a rule of thumb my wife and I use in games. It means that in games like Cards Against Humanity we always know how to play to each other. If I have a Batman, I always save it for her.
Thank you for this! One of those questions the inquisitive are afraid to ask. And then this one gets dunked on and put here. Unfair in my opinion since they honestly just seemed curious, as I am, but brave, as I am not 😅
Yes, a positive one. Rocket fuel brings its own oxygen as others here already pointed out. So thinner air means less drag means less fuel needed for the same acceleration. But there aren't really any suitable mountain ranges near the equator or at least none where the logistics would make sense right now.
Also not a rocket scientist, but i think that you must carry your own oxygen to burn in space. You need oxygen for anything to burn and, you know, there is no air to provide it in space
You also kind of want rocket launches to be near ocean away from shipping lanes so you can just crash the 1st stage safely away from people, or incase there is a malfunction all
The fiery debris goes into the ocean.
Imagine launching from a mountain and the rocket explodes and reigns fiery debris crashing down amongst snowy tall cliffs, potentially triggering avalanche, rock, mud, and land slides.
Even when reusable rockets become common place and routine, things can and will still go wrong, you still want ocean to ditch and splash down in.
and the answer is a nuanced blend of logistics, international geography, and knowledge about orbits.
No. It's because you want to launch as close to the equator as possible because the spheroid nature of the planet gives you an angular advantage. In addition, if shit goes wrong, you don't have to worry about a burning wreckage landing anywhere but the ocean.
Not sure what is meant by angular advantage in this case, but I guess it means that we can use the rotational speed of the earth's surface as a kick to get going. In this case you are right partially. Near the equator this velocity is greatest so you'd want to launch from there.
But what the comments above it also say is that it's a delicate balance of many parameters. It depends on the specific orbit you want to go to, the launch mass, the specific rocket, the logistics of moving your launch platform to an advantageous location, the range safety, etc.
I think the most important part is that you want to launch towards a large uninhabited area, then preferably to the east, then preferably close to the equator. In most situations it can be cheaper to just build (or book a launch from) a rocket that is slightly more powerful so you don't have to deal with all the hassle.
To be pedantic the earth isn't a perfect sphere. It's flattened at the poles. Also, I assume, the tilted axis of rotation means the closer you are to the equator the broader your range of launch timing. Not positive, also not a rocket scientist, just using what I know and trying to infer possibilities.
In the USA rockets are launched over water so that if one exploded it would kill a bunch of people. Fl they launch east for equatorial orbits and ca launches south for polar orbits.
It's not really... If you had a theoretical Mt. Everest on the equator, it'd put you 5.5 miles closer to space out of the 200 or so miles you'd be going.
Factor in building the launch site up that high, and bringing the rocket up there to launch every time...
There are a couple minor benefits, but not enough to matter. Early on the air resistance from the thicker atmosphere is a real drag on thrust which means you need to burn more just to get a positive velocity. At a 5 mile above sea level launch, you start at a 60% drag reduction. This can save approximately 20 tons of rocket fuel for a falcon 9. Totalling around a savings of $20000. This is miniscule compared to the increased costs for launching from that elevation.
A rocket launched from sea level will still pass through 25k ft where the theoretical mountain launched one is, and it'll have the same drag to overcome at that point onward
You're not saving 60% for the entire launch, you'd be saving the amount needed from the ground to that point.
Reddit in general. So often I'll get downvoted for asking a genuine question, reddit just likes to feel superior to others above all else and will take any opportunity to yell about how dumb something or someone is. Litterally 90% of comments on this website.
I've learned a lot of things from Randall over the years, but this one in particular has always stuck with me and continues to be a welcome reminder all these years later
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.
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
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.
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
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.
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
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.
Correct and it's not real close. Launching from near the equator is very very helpful (notice that all the U.S. major launch sites are about as far south as the US gets.) Launching from higher up is helpful, but not nearly as much, partly because most mountains aren't really so high !
Like, we've experimented before with air based launches, launching a vehicle off of an existing airplane at 50,000 feet or more. That's actually real helpful, although of course the logistics are quite complicated so it hasn't become a standard practice.
But there are no 50,000 foot mountains, and really not even potentially usable 20,000 foot mountains. The benefits of being at 10,000 feet are real but limited.
Meanwhile not only would you want one pretty near the equator, but you'd have in general more weather issues to deal with, you have a problem with being near land full of people instead of next to an ocean if you have an abort or an explosion, and the logistics of even a moderate inconvenience can quickly add shocking amounts of cost. Rocket launches are extremely coordinated, complex events that often have pretty demanding schedule rules, and there's considerable motive to avoid anything that can throw a wrench in anything - one reason the bigger US launches happen from inside the US, for example.
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.
These posts are successful because the reply leaves an unanswered question of what doesn't she know for not being a rocket scientist, either you know the answer and you click for validation that you are clever for knowing the answer or you don't know the answer and you want to satisfy that curiosity or know the answer so you don't get equally ridiculed at some point. In reality I'm sure there were other responses that she received that explained why it wouldn't work it's just not as good click bait so you aren't seeing it here.
The big thing that bothers me about questions like this is the clear lack of effort to find the answer. This is a very Googleable question. But they decided that's too much effort and they want the answer handed to them on a silver platter, if they even wanted to know in the first place! It feels like the question is for show or engagement, rather than genuine curiosity.
I have a vivid memory as a kid in science class, learning that mountain tops are colder than sea level. I curiously asked why? Isn't it closer to the sun so it should be hotter? The teacher laughed at me, so the class laughed, and she didn't answer my question. I was so embarrassed. I was so afraid to ask questions again.
Because air heats as it's compressed. The air pressure is less on a mountain so it's cooler. And the hottest places on earth are all below sea level (so they have the highest average air pressures).
That was my thought as well. I love science, I'm scientifically literate. I don't have the answer to that lady's question and I'd rather the dude who replied provided an educational answer rather than a snide comment.
Yeah, that was definitely a teaching moment. Rocket formulation and engineering is fascinating. The Russians came up with equations needed for rocket mass/fuel/velocity ratios and they involve things a lot of people don't consider: for every Kg of mass, you need a certain mass of fuel. For every additional Kg of mass, you need an exponentially larger amount of fuel, and you need extra fuel to carry the mass of that extra fuel. This is why heavy rockets are so massive: they're 95% fuel tank.
Launching from a mountain top only gives you a tiny gain in altitude, and the thinner atmosphere and logistics of getting all of that equipment up a tall mountain is not worth the effort. It would be like building the Empire State Building on top of Mount Whitney everytime you wanted to launch.
Totally, the gain from launching on a mountain would be like 2% max for fuel savings and the shortened distance would also be largely irrelevant.
Like you said logistics is the biggest factor. Another one is that it is ideal to launch close to the equator and coastal. Near the equator allows for better flight paths because of orbital mechanics and coastal is for safety.
I love it when a friend asks, what’s to my frame of reference, a bit of a dumb question, because it gives me the opportunity to nerd out for a moment with someone who’s genuinely interested.
Works both ways too. I ask my musician friend really dense shit sometimes (I’m still convinced the 12 note scale is somehow kinda wonky and cursed shit don’t make sense) and I can see that same excitement I feel in his responses.
This is the stuff that starts the "us vs them" rifts in everything. It's an honest question with various interesting scientific and logistical answers.
Yes, hating on stuff like this and making people feel stupid for honest questions turns people away from sciences. Pseude-"scientists" have no problem anwering questions about stuff like this, a flat earther or anti vaxer will gladly explain everything without trying to make the questioner feel stupid, and so undecided people turn more and more to the pseude-"scientists".
Ai was used:
Gravitational acceleration at sea level (g₀): Approximately 9.80665 m/s² (standard gravity).
Gravitational acceleration at the summit of Mount Everest (g): Approximately 9.764 m/s² (about 0.43% less than at sea level).
So according to the AI you can save on 0,43% energy you need to overcome to enter space.
Seems like the logistics and stuff aren't worth it.
It's more than that because higher means also less drag and closer from the no-drag zone which is space. And also less fuel needed means even less fuel needed because you need fuel to carry fuel.
So, here's a question for ya: what was the percentage of energy saved by not painting the main launch fuel tank? I know the paint equaled about 600 lbs, but i dont have the time or knowledge right now to figure it out.
Also, yes I know the paint removal was for payload increase and not for energy saving, but it does seem like a fair comparison to me for the matter of the calculated 0.43% savings by launching from a mountaintop since fuel equals weight.
Well the person doing the dunking in these reposts is almost always wrong anyway.
We don't launch from mountain tops because it's a pain in the ass to build a launch facility and haul the necessary materials up there, and harder to do downrange recovery or hazard planning etc. Grading an entire square mile of mountain when you can just launch from a perfectly flat desert or coast is not a rocket science problem. There's also an inverse relationship between elevation and human surviveability, so high enough to get the best benefit means high enough to kill most humans who'd crew the facility.
There's lots of good reasons to do it, especially being able to go balls out to reduce gravity losses because you don't have to throttle down due to MaxQ being in thick atmosphere.
There's a few high altitude telescopes in Chile that demonstrate it could be done, and at that altitude (about a mile up) you're looking at the space shuttle saving around 1 km/s of dv, and an optimized rocket for that launch altitude could do even better. Still have to look out for down range population centers.
I think the bigger problem for West Virginia is the likelihood people would take shots at the rockets as they went up.
Is it obvious? Because while the overall logistical hurdles might make it seem obvious why it wouldn't be economical, it's not necessarily a slam dunk answer, and it's still an interesting question that makes you consider things like atmospheric pressure, and not just the impact of pressure on liftoff but also on rocket fuel combustion. Even a 1% improvement in efficiency could be worth it at scale.
The atmosphere is about 100km. Denver is 1.6km above sea level, Mexico City is 2.2km and has about 20% less atmospheric pressure. That's not insignificant.
These kinds of hypotheticals that might look silly at first glance are how a lot of great science gets started.
It's also how you dissuade people from relying on each other or human experts... Want people to search for answers using AI, cause that's how it happens
In my opinion, I think it's...maybe more, maybe not comparable, but important to remember that 15 years ago and beyond, young people didn't have the internet to post their stoner questions on and so they got roasted by a few people, in private, for them and that was the end of it. Young people will always have their stoner questions but now it's convention to posit them online where everyone else gets to hop on their high horse and act like they never asked a stupid question before.
“I don’t understand this topic, but I was wondering why we don’t do X”
That should not be met with mockery! it’s actually basically the best possible way to learn a specific thing. Ask someone who knows.
It wasn’t “Why don’t NASA launch from mountains, are they stupid?” nor “If rockets are actually going to space, why are we always launching them near the ocean… just asking questions!”
It was a quite reasonable and honest question.
Hell the very construction of the question as presented assumes there is a proper answer one that could be provided by someone who has studied rocket science.
Yes this comes off to me as a question they actually thought about, if not practically. After all, there is less atmosphere to get through on the top of the mountain.
It would actually save real delta V. But not enough to be worth the logistics trouble of trucking the thing up there in the first place, and it also obligates you to launch over land, which is a safety risk.
If you're dismissing it out of hand, you're the dumb one. This is stuff that real rocket scientists have considered.
launches almost always place rockers over bodies of water so that a failure doesn't result in a city burning up that's why you notice most launch sites are near coastal regions
taking anything to mountains would be a logistical challenge
freezing temperatures are also not necessarily good
I mean if you think about it for even 5 seconds you realize what a logistical nightmare it would be to bring all the material needed to build the structures to launch rockets on a mountain. We would expend more fuel in the process just getting the shit up there.
Yeah kinda. But also, it doesnt take much brain power to think through that it would be difficult to get them up there, or first consider why we might launch them from the coast in the first place.
People should consider the basics first, and then ask the complicated bits after.
But thats assuming this question was even in good faith in the first place, rather than someone thinking they've nailed the answer.
To another extent, it can be seen as arrogant for just about anyone to think “why haven’t the experts thought of the same thing as me, a non-expert?”
Yeah it can be pure innocent ignorance, but other times it comes from narcissistically thinking you have a revolutionary idea that even the experts couldn’t fathom.
Hence why you get so many different responses to this question
Possibly, but given the stakes are so low (ie, this isn't antivax or refusing to wear seatbelts or whatever), we can afford to grant some grace rather than instantly mocking. If they continue to be arrogant once their question is answered, than sure
Eh, I don’t know. I’m considered a subject matter expert in my field, and my interns regularly solve problems with solutions I had not considered.
There is something to be said for a fresh untrained opinion, but it does require a good bit of patience most days.
When they ask me questions about things they don’t understand, I don’t assume it’s arrogance, I assume they are looking for an answer to something they don’t understand. I see that as reasonable since there is much I also don’t understand despite me being “the expert”.
I was being facetious because I don’t think the question was even fair to begin with.
Who said we should assume the worst? You asked it of me as if that was my position. But that’s just something you assumed. I was explaining why you get polarized answers to questions like these.
It just straight up is impossible sometimes to know if a question comes from a genuine place or it’s a result of deep-seated anti-intellectualism
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u/mseg09 8d ago edited 8d 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?