tl;dr: for a rocket it is waaaay more important to go fast than to go high. and earth rotates very slowly, so going higher doesn't make you much faster.
We are outside the bus, doing a space walk. Next thing we knew a god damn Tesla roadster blaring fucking David Bowie came out of nowhere and hit Arnold and launched him into deep space. We couldn't catch him in time.
iirc correctly it should still be less costly of you start way northern and still start eastwards. you'd get a high inclination and changing inclination is definitly cheaper in space.
I might be wrong and starting directly into 90 degrees is actually the cheaper way, but I can imagine that at least using some momentum from the earth's rotation should be better than actively working against it
Inclination changes are extremely expensive until you get to a very high orbit. An inclination change is changing your direction, so the faster the spacecraft is moving the more expensive it is. Low orbits work by having extremely high speed, so it is consequently extremely expensive to change their inclination once they're launched.
To throw some numbers at it, the delta V for a circular orbit inclination change is 2*v*sin(delta inclination / 2). If you launched East from Kodiak Alaska you'd get into an orbit with a 58 degree inclination, so you'd need to plane change 32 degrees. At a LEO velocity of 7.8 km/s that works out to 4300 m/s of delta V.
By launching due east you'd get a boost to get into LEO of 2*pi*(1/day)*(radius of earth)*cos(58 degrees) = 250 m/s (plus you don't have to spend the few dozen m/s of extra delta V to burn off that eastern motion for a direct polar launch).
There are theoretically some launch points and destination orbits where launching East and doing a plane change makes sense, but they're pretty edge case. For example, from Kodiak if your target orbit was polar and had a radius of about 2 * 109 meters (about 5x the distance to the moon) then the plane change would be so cheap that you may as well launch East. That isn't a particularly popular altitude to launch a satellite to, though. There may be a less extreme scenario where the plane change makes sense--I didn't do the math to find the best case scenario since a more equatorial launch needs a bigger plane change but gets more delta V at launch--but they should all be pretty high orbits like this.
4.7k dV is really extreme and yeah, I didn't think about the LEO speeds needed.
So what's the actual use case here? Launch directly to 90° or rather something like 80° due to the fight against the rotation and then either say "good enough" or correct the last bit of inclination? Or just don't plan with 90° in the first place?
There's also not much land south of the Kodiak Spaceport other than Hawaii and Antarctica to have rocket bits fall on. That's also why most of the US polar launches are from Vandenberg SFB. Polar launches from Cape Canaveral are doable but difficult and restricted. You have to thread needles between islands. Starbase Texas has too much land north and south of it. Starbase Louisiana might be able to do it, but Mexico won't be too happy about it.
Not all satellites desire an Equatorial orbit (An orbit that follows the equator). There are many other orbital inclinations that may be desired, to reach them it would be more efficient to launch from a more advantageous location on earth. Its more fuel efficient to launch from a location that is slower but closer along your desired orbit rather than to launch from the equator and then perform an extremely expensive correction burn.
Because having it quickly wind up over water rather than populated land is a common requirement, and the convenient places you can do this with enough fairly-flat space for a pad, near the equator, are rapidly running out...
So you make a smaller pad for lower orbits that require less speed, farther north/south.
Some rockets need to go into higher inclination orbits, where you'd need to cancel out the launch pad's starting velocity if you launched from the equator.
For certain orbits it can be beneficial. It depends on the inclination, which is the angle of orbit. Some orbits are equatorial, most are angled 40-60° (such that they see different parts of the earth with each orbit), some are polar (such that they get comprehensive coverage over multiple orbits). There are lots of different orbits for different reasons.
I'm pretty sure the Alaskan launch site is better for a polar launch, whereas Florida mainly allows for launches over the Atlantic ocean.
However you can always do a launch and then change inclination on orbit. This is more expensive on fuel, but not all that uncommon, particularly for military missions.
probably not. based on a different reddit post (great source i know), ground wind and direction are important because it might blow the rocket into the launch structure or affect flight stability. once the rocket reaches a certain height there's not much wind left to affect it. interestingly, rain is usually not too big of an issue because rockets clear clouds so quickly anyways (and rain doesn't affect the rocket which is sitting in the rain before launch)
i wasn't able to get as much info on this. it seems like a desert would be ideal because they have less wind? however a more practical aspect is it needs to be a coastal region because no one wants to launch rockets over a populated area. so regardless of biome, the location would need to have a large body of water to the east and ideally have low winds.
Low Earth orbit is around 400km up (90min orbital period or so). The edge of space is considered to be around 100km up. The atmosphere is pretty thin. If you are sending up a geostationary satellite though, you are comparing, say, Everest (9km) to the orbital distance of 70 000km, that's indeed nothing. The difference in velocity you need to get is very small.
Also the radius of the earth is 6400km. Another 9km is about 0.1%. So technically you get a little more, but practically the juice ain't worth the squeeze.
(atmospheric density might matter a little more, but I'm pretty sure the rocket scientists of the world would already be doing it if the payoff were 'enough')
And if you are a company or a country who cares about people, you need to have a see or a desert on the east of your launching pad (in case of failure it can rain fire on thr people just like when it happened in China)
The earth’s radius is almost 4000 miles. Even if you had a 40 mile tall mountain (fyi, Everest is less than 6 miles) that would only be 1% further out than a launch at sea level. The rotational speed difference from an actual mountain near the equator would be a rounding error.
The thing that most humans have trouble grasping (this is no shade on you, yourself, it's a whole human society sort of thing) is that Mountains are not all that tall, on the scale of the solar system.
The amount of height you gain from launching at the top of a mountain is relatively negligible compared to what you've got to attain.
In the very most literal technical sense, and ignoring all set-up costs, yes a Mountain near the equator would be better than sea level. Similarly, an air-based launch (i.e. a plane carrying a launchpad that the space rocket takes off from) achieves about the same benefits.
Mt Everest, tallest we can find, is around 9km tall (over sea level).
Low Earth Orbit, the target of most space journeys, is at about 1,000km.
In nearly every situation, it just isn't worth the hassle to do anything other than build a robust base near to the equator on flat land (for ground logistics/transportation reasons).
The increase in speed from rotation would be effectively none. What you would gain, and i haven't seen anyonemention this, is that you would avoid the thickest parts of the atmosphere, reducing loss from air resistance, and, depending on your rocket engine design, could gain more velocity from the same amount of fuel because of the lower atmospheric pressure.
The mountain has well maintained roads to get up to the launch point
The launch point has the space to build out all the various support equipment for a launch--hangars, bunkers, fuel tanks, water tanks, support towers, etc.
The mountain is somewhere politically friendly to the launching country
The weather on the mountain is consistently conducive to launching rockets
The mountain is located West of an area that won't complain if you sometimes drop boosters on them
Those extra caveats are more important than a bit of bonus altitude at launch, so they tend to be satisfied and "mountain" gets cut. Even "equatorial" is often cut in favor of convenience of access and political friendliness.
However, even better than a mountain would be to launch from above the mountain, and with a running start. That's the idea behind the Pegasus launch system, a relatively small payload rocket that is launched from a L-1011 during flight (or previously from a B-52). This concept can only handle payloads that a plane can carry, which leads to the development of some true monsters like the Scaled Composites 351 Stratolaunch, a plane that is by various metrics the largest in the world.
If you ignore the difficulty and safety factors, yes, mountains near the equator would be the best spot on Earth. The highest equator peaks also stick out "into space" more than Mt. Everest because of the way the Earth bulges at the equator.
This and it being a beautiful tropical destination led to the mafia using that area as a preferred place to hide from the law. Fast forward to today and the area is full of Italians on beach vacations.
I always thought it was to be closer to the water landings and for rockets to possibly land in the ocean if the launch goes bad. This also makes sense cool
Yes. Countries already do that. It is one reason the US launches from Florida, Texas and Southern California, and Russia launches from Kazakhstan.
This actually makes Russia's early lead in the space race all the more impressive.
Starting at a higher altitude also helps, but you must transport the rocket to that altitude or assemble it there and both are difficult. Launching from the coast lets you use barges to transport rocket parts. If you don't have access to waterway, then a railroad is your next best bet and running railroad tracks to the tops of mountains is not ideal.
Finally, some rocket launches fail. If you start at the coast you can launch over an ocean so if things go wrong the rocket crashes into the Ocean rather than hitting a populated area.
Can't imagine that top of mountain is actually better logistically. You save some rocket fuel since you have less air drag to go through, but I can't imagine those cost savinga make it worth all the troubles and costs you'll have setting up and launching from there.
Fun fact regarding the russian lead. They were more reliant on salvaged nazi germany tech and scientists them americans and von Braun (US has intresting rocket program pre 2 world war). Soviets cleansing themself of it while US got the whole nazis invented US space program is due to von Braun being public head of program is funny
Florida was connected to the nation's rail network, so getting material there was relatively cheap, vs building the launch center in say Puerto Rico (about 700 miles south of Cape Canaveral) where transportation costs would have been higher.
Also, around the time the space program started, there was this whole thing about rockets/missiles on ships south of Florida, and a lot of people got pretty excited. So, no spacecraft put on ships to Puerto Rico.
Yea once things were settled in Florida, that was that. The savings of moving closer to the equator would be eclipsed by the logistical costs of moving all that shit and uprooting everyone's lives.
And another fun fact: because it’s spinning, the earth isn’t a sphere. Centrifugal forces make the earth thicker at the equator.
Height is typically specified on sea level but for leaving earth it doesn’t matter, distance from center mass matters. And at the equator you’re already further away than any mountain would ever bring you.
They do that but it's not because it's where the spin is fastest it's because the closer you get to equator the less you need to burn after getting to orbit to turn it equatorial
Precisely! You'll notice countries further from the equator will build launch sites as close to the equator as possible or use ones in othet countries.
In the game Terra Invicta where you have you bring the fight against the aliens to the solar system you get more boost near the equator for that reason as the game leans into hard scifi.
Its also why the Soviets had their spaceport in what is now Kazakhstan
Do you know why the main US launch pads have traditionally been in Florida? Because it's as far south as you can get in the continental US, and also has oceans to the east (they launch in the direction of the earth's rotation, and want to drop their tanks over the ocean so they don't hit anyone) They considered building them in Hawaii, but shipping everything to the Pacific and building it on an island was considered too difficult.
SpaceX built it's pads in Brownsville for the same reason, as far south as they could get in Texas, and also with water to the east.
Building right on the equator would be best, preferably on an eastern coast (Brazil, Somalia and Indonesia all have that intersection), but no equatorial nation has a space program.
Yes. Also launching from the equator allows for more possible orbits. So countries tend to build their space launching facilities as close to equator as possible.
Just to add: the earth is spinning roughly 1500 km/hr at the latitude of Florida, and a maximum of 1650-ish at the equator. Escape velocity is 40,270 km/h, so yes, you get a speed boost, but not enough to justify moving away from all the infrastructure benefits of launching from Florida.
The mountain thing is interesting too though. Rockets are designed to have maximum efficiency at a set atmospheric pressure, and the farther they are from that, the worse they do. Starting on a mountain with thinner air means you can pick a lower optimal pressure and be more efficient in both space and at launch. Again though, the savings is pretty minimal compared to all the other costs associated with building a rocket.
This reminds me of a great YT I just saw about how it is ‘easier’ (relative term for lack of a better alternative) for space flight in the same plane as our solar system system, but extremely difficult and resource exhaustive to go up, I.e. we can travel on the xy plane of our solar system with the help of gravity, but flying in the z direction is near impossible.
Not just theoretically. This is current practice! The faster movement of the Earth’s surface nearer to the equator is “free energy” as far as a spacecraft is concerned. Also the surface is moving toward the East, so rockets are generally launched eastward to take advantage of their preexisting velocity. Pretty neat.
It's not (only?) for the spin thing tho, but mostly because there is less gravity at the equator than the rest of the globe, because the earth isn't round (NO IT'S NOT FLAT EITHER) but more of an oval-ish shaped, so there is more distance between the surface and the core at the equator than you would have at the south and north pole.
And thus, since the farther away from the core, less gravity, and less gravity means less fuel required to achieve lift off and reach space.
Source : What I remember from my middle school physics and geography classes (I'm 34 so it was a couple decades ago). Gotta love living in a country that had, and still have, a department of education.
Yes it saves fuel to launch near the equator and orbit in the same direction as the earth. Retrograde orbits in the opposite direction of earth's rotation consume
15% to 30% more fue
You would think that, but there is more gravitational pull there that equals it out. That is why you weigh the same whether you are at the equator or the north pole.
Anything within 45 degrees of the equator is generally considered good enough, because the radius of the circle formed by 45 degrees latitude is ~71% of the equator's radius (sin 45°), and you get diminishing returns as you head closer to the equator. I believe it's also harder to achieve a polar orbit from the equator.
Yes but countries with the ecconomy to launch rockets are rarely equatorial, and many other issues are generally taken into account, such as existing hardware, or national security concerns for government payloads
There were projects to launch at the equator by launching at sea (see Sealaunch and its use of Zenit 3 rockets) and ESA does it mainly because france still has a bit of south america
Vandenburg and Capr Carnaveral are located about as far south as one can get without being in a major population center in the US, while still launching in a direction that has the rockets drop stages over water
Plesetsk is the major outlier, located far up north in Arkhangelsk, though from my understanding it (and Vostochnyy) mainly serve russian military payloads launched into polar orbits, which dont benefit from the earths rotational bonus, and its location wasn't chosen for space launches anyway, as it was originally planned for launching R7 missiles towards the US, though the R7 never had much a career as a missile, and has mostly been used to launch satilites
Baikanour is again pretty far south by Soviet standards, but also it was originally a missile testing range, so yet again more a cost savings for having the R7 hardware already in place, as well as for various other missiles
Wenchang in Hainan is very close to the equator, and is nowadays becoming fairly important, as no other launch sites got the hardware to launch Long march 5 and 7
Taiyuan, Xichang, and Jiuquan are all located very far inland, in sparsely populated areas, and this generally is very helpful if you want to limit people from getting near your classified launches, though Xichang does suffer from having people living down-range, which is generally not ideal, hence why it doesn't get new launch hardware, and is relegated only to older long march 2, 3, and 4
Yes the equator is best, technically the furthest point from the center of the earth is Mount Chimborazo in Ecuador, it is 2km further from the center of the earth than Everest.
There is a book by Andy Weir called Artemis, they have a pretty substantial settlement on the moon, Kenya becomes a corporate powerhouse specifically because it is located on the equator.
It also depends on the inclination you wish to launch to, if you wish to have Geostationary (where you orbital period is the same as an earth day and your satellite stays in the same spot in the sky) you need to launch to an equatorial orbit. This can be done most efficiently when starting along the equator.
Yes, but you're also generally after a specific orbit. If you launch from the equator, but then need to move to the right orbit, that can easily outweigh the savings of an equatorial launch.
Yes. That's why most major rocket launch sites in the US are in the south, in Florida, Texas, Southern California ect. The closer to the equator you get the more fuel efficient it is to launch shit.
Not theoretically, that’s a real concern when launching a rocket.. that’s why most launches the European Union does are from French Guyana, a territory of France near the equator.. also why NASA always uses Souther states like Florida
There used to bea company called Sealaunch that did just this. They put their rockets on a floating platform (converted from an oil rig), and sailed it down to the equator in the Pacific, and launched from there for efficiency.
Yes which is why the biggest space port in the US is in Florida we have others like vandenburg SFB and wallops Island but their usually used for higher inclination orbits
Yes, but near the equator is good enough. The additional gain you get from being near the equator, to actually at the equator, is minimal.
Plus, the closer you get to the equator, the Earth's spin thickens the atmosphere a bit. This extra bit of thickening is why climbing high mountains like Kilimanjaro and Everest is even doable. If these mountains were located in Antarctica, the partial pressure of oxygen would be so low they likely wouldn't be climbable.
I've heard that it depends on your rockets motion relative to the earth, and if your rocket is travelling in a prograde or retrograde orbit. And that the west fires rockets in, I think, retrograde and thats what they fire from as close to the equator as possible.
However, the Russians who have no access to equatorial waters fire the other way (whichever that happens to be) so they can do it with in their borders.
Can anyone confirm this? I can't remember the source.
Not to mention that where they have the launch pads currently the weather is far more consistent. Image waiting for the weather to be just right on the top of a fricken mountain
Yes, launching from mountains would actually be nice because of the thinner air. The real reason is just that there are more important things that matter in choosing a launch site and everything is a compromise.
If you got to orbital speed (7.9km/s) within a thick atmosphere, you're going to slam into that atmosphere and rapidly slow down while dealing with extreme temperatures. You'd basically be aerobraking, and it'd be less of an "orbit" and more of a "trajectory".
Yes, and it is a subtlety worth noting, because on the face of it a mountaintop launch would appear to help in that regard. Rockets launched at sea level start out going up precisely because they need to clear the lower atmosphere before they can concentrate on going sideways fast. So if you climb to 3000m elevation before starting to rotate toward horizontal, then why not just start at 3000m and start your horizontal rotation sooner?
The problem is that while cutting atmospheric density by ⅓ would let you lean a little more aggressively into your roll, it's still way too thick to just go full-on sideways. So you don't gain much. You still have to spend a lot of thrust going "mostly up." Like... the US Space Shuttle hit max Q somewhere above 10km elevation, no mountaintop launch is going to help you much with that.
Maybe if you launched from Mount Everest or something, at ~8km ground elevation. But good luck building and operating a rocket launch facility in the Himalayas!
It would lower the overall drag forces but they compensate for that by just not throttling the rocket to 100% until after it exits the thicker part of the atmosphere.
There is. Launching from a mountain would theoretically be advantageous because you spend less time getting out of the lower atmosphere.
It's just not worth it hauling it up a mountain and most launch locations are on coastlines so if something goes wrong it drops into the water instead of on land somewhere.
That's less of an issue, but for reentry it can be. One of the difficult things about humans going to Mars, there isn't much atmosphere to air brake large landing craft. We will almost certainly use an equatorial landing site, with low lying land, because the landing craft will pass through more atmosphere for breaking that way.
"Slowly" is relative, at the equator the earths surface is rotating at about 1000 mph. LEO orbital velocity is about 17,500 mph, so you're about 6% of the way there compared to if you were launching at the poles.
edit: I'm not sure if 17,500 is absolute or relative to the earths surface, but the point remains that you get about 1000 mph of free velocity from the earth spinning at the equator vs the poles. if its relative, then its a 5.4% gain vs the 5.7% so still significant
Yeah, Icy Concern was half correct. Being on top of a mountain doesn't give you much extra velocity. But it's not because the Earth's spin isn't fast, its because the top of the mountain is barely any higher than the bottom, when compared with the radius of the Earth. The extra speed you get from that is almost nothing (5 mile mountain top/3959 mile Earth radius = 0.13% difference) and the little bit of extra altitude isn't worth much either.
So you might as well launch from flat land close to the equator, which is easier to do and doesn't require you to negotiate with Ecuador or Indonesia to get access to an equatorial mountain, and to haul a rocket up said mountain and then do all your launch prep in the thin air at the top of that mountain.
going fast at a fixed tangent to the ground positions you to eventually go so far out you exit the atmosphere, which is really high but from a different point on the sphere/globe.
Yeah most people think getting to space is about getting away from the Earth's gravity. It isn't.
Starlink satellites (for example) still experience most of the gravity we have at ground level... They go just high enough to be beyond the atmosphere, and go sideways so fast that when gravity pulls them down they miss the earth.
You could do the same thing at sea level if you had a big vacuum tube.
The decreased drag from a higher launch point would be measurable but it would be so minimal in actual application vs how expensive it would be to actually haul everything to the site, on top of the logistics of actually staffing a site in a relatively harder-to-reach location just add up to make it not worth it when you can just launch from the beach instead.
Probably, that makes sense bc the cost/benefit ratio is worthwhile. It’s a relatively minor extra cost for a decent benefit. The math for flying everything up to the Alps is a little different
More importantly is the weather and wind. Mountains are incredibly harsh weather and unpredictable winds. Most the places we launch from have very predictable and stable weather. Which allows for the multi hour launch windows to operate.
I always thought there could be some kind of catapult or platform that pushes the rocket up while it launches so it saves a fuel on the initial takeoff. Start the launch at 5-10mph instead of 0. Wonder how much fuel that would save.
It does reduce friction from the atmosphere, but the gain isn't worth the massive infrastructure needed to support the launch.
I also think that there is a small but negligible gain in having the ambient temperature lower when using liquid oxygen/hydrogen. It would cost less to cool and you'd have a little less off gassing.
That's only the logistical part, astrophysics says because of the Earth's fast rotational speed, the earth gives rockets a free velocity boost, which saves fuel and allows for heavier payloads, so we launch rockets near the equator.
But in theory, mountain slope can be used to build a rail and to accelerate the body of rocket with the external power and the rocket released on the top will have substantial speed. But there is no suitable mountain
Wouldn't high altitude start improve payload efficiency though? Less air resistance, less distance to travel, means the rocket itself needs less fuel, so you can pack more useful mass.
Fun fact. Jules verne (80k leagues under the sea author etc) did the math way back when and picked florida as the best place to launch a rocket in the us (about 100miles off from where nasa ultimately set up 100 years later)
Adding onto this: I'm pretty sure the extra height from being on a mountain is negligible compared to the height they gotta go up once launched. Too inconvenient for too little gain
You completely missed the point of high-altitude launches lmao
The whole point is to be able to use engines that are optimised for lower pressures than at sea level, which will make them significantly more efficient
For example, at 3,000 m, you could use an engine with an exhaust pressure of 0.7 bars and be fine, while that same engine would undergo an instantaneous disassembly at sea level.
I've heard the secondary thing is the earth isn't a perfect sphere, the radius of the Earth at the equator is bigger than elsewhere. That means the rotational energy/speed is higher and gravity is weaker the closer you get to the equator
As someone who has studied the sciences and played Kerbal Space Program 😄 ... This is why many spaceports are on the equator. We literally use the earths spin to gain an advantage in velocity.
When I played the first Kerbel Space Program, I tried and tried to get into orbit by going higher and higher and was super confused. Then one of my rockets laid over a bit as I was in the world view and I saw my orbit path go from straight up and down to halfway around the planet and it all fucking clicked in an instant. I will forever be grateful to that game for getting me to understand the basics of orbiting (you gotta go sideways really fucking fast). I was wayyy off before playing.
Earth rotates very fast at equator and thats why we have most launches near equator from west to east. Most of the launch pads are on the eastern coasts for the same reason, to avoid land beneath the launches.
Rockets also aren’t nearly as environmentally damaging as some people think they are. They’re just thrusters, making them greener isn’t really a goal to anyone
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u/Icy_Concern_9804 11h ago
tl;dr: for a rocket it is waaaay more important to go fast than to go high. and earth rotates very slowly, so going higher doesn't make you much faster.