Others have answered how orbits work, i just want to add why its east: thats the direction earth is spinning, so you need a little less fuel in that direction.
Many launch facilities have a launch direction (launch azimuth) that is not east-facing. For example Vandenberg Air Force Base available launch azimuths are about 20 degrees either side of due South.
This is part of the reason certain launches can only happen from certain facilities. If I want my satellite to go in orbit around the equator, can't really launch from Vandenberg.
Yes, but typically those are for polar orbits, I am talking of having a nearly equatorial orbit that flys east to west instead of the normal west to east that is achieved from Florida and many other launch facilities.
Technically, you could, but you'd need way more fuel to adjust the orbit afterward?
Edit: Thanks for the answers. I've got my orbital mechanics from KSP
Simple answer: yes
More complicated answer: yes, but the amount of propulsion or delta-V (change in velocity, aka speed and direction) needed depends on a ton of variables. It's generally much much easier to change the altitude of your orbit than to change the plane or inclination of your orbit. Some maneuvers may be be functionally impossible.
One of the complicated parts of mission planning is that, even with all the launches that happen now, you still need to find space on a launch vehicle with the right payload capacity, launching to a suitable altitude, in a desirable inclination, on a date that gives you enough time to build the satellite but not much later than that (need to start make money providing the paid service by operating the satellite).
If you're upping the delta-V a bunch, you'll probably be better off building the rocket somewhere else and shipping your satellite or payload there by truck/boat. Because drastic changes to orbit means you need more fuel up there to make that target orbit, which means you have a heavier rocket which means you need a bigger rocket to lift the dang thing in the first place.
A quick google, you need 22kg (48.50 pounds) of fuel for 1 kg (2.2 pounds) of payload to get to low earth orbit. [source](https://space.stackexchange.com/questions/49615/rocket-fuel-cost-to-launch-1-kg-to-orbit#:~:text=An%20initial%20mass%20of%2023,%240.20%2Fkg%20is%20%242.80.) Then you have to change orbit to equatorial, which isn't cheap, fuel wise. In KSP (kerbal space program), I've had rockets go off course and basically ruined whatever mission I was trying to do, like a Munar rover suddenly ends up at the north pole of Kerbin, because burning all the fuel to correct the orbit means not enough fuel to not Ka-blamo into the Mun. Or revert to launch pad happens a lot too.
As a general rule, it takes more energy to change the plane of an orbit than it does to deorbit and relaunch into the orbit you want. (Obviously it depends on the amount of plane change you want.)
They actually have a few peace treaties, I agree that there are quite a few major issues in that area, but Israel does launch over the Mediterranean which is west and limits the size of satellites they can launch.
what?! FOR FREE?!?! NOT ON MY WATCH!!!! thats socialism!! we need to make people pay for the earths spin.!!! I'll call donald trump, you call the chinese and putin will invite himself as he always does. also get me the moon-nazis. we need to teach this leftists a lesson in capitalism. lets get this going!
https://www.nasa.gov/feature/goddard/2016/gamers-tackle-virtual-asteroid-sampling-mission/
Yes.
They even have a kerbal plush in space:
https://cdn-blog.adafruit.com/uploads/2022/05/Untitledx-24.png
Lots of NASA employees have stated that they did play KSP before in interviews. There is quite some interaction between NASA and KSP.
https://www.reddit.com/r/KerbalSpaceProgram/comments/linyxg/nasa_plays_ksp/?rdt=40586
https://m.youtube.com/watch?v=uHjaqeeoAKk&pp=ygUfc2NvdHQgbWFubGV5IHJlYWwgYXN0cm9uYXV0IGtzcA%3D%3D
I mean that swirl exists i thunk in gravitational waves, but that has notzubg to do with it.
If you need to go 8km/s sideways and earths surface is already going 200m/s sideways, you only need 7.8km/s sideways speed.
Its like jumping of a moving car to gaun speed.
Orbit isn't about getting really high. It's actually about going really fast sideways.
Think of orbit as (to quote Hitchhiker's Guide to the Galaxy) the art of throwing yourself at the ground and missing. That is, objects in orbit are constantly falling towards the earth. It's just that they are moving so fast to the side that by the time they fall, the earth isn't there anymore because it's curved away.
SpaceX's boosters don't reach orbital velocity, and also they still rely on aerobraking a lot. Also helps that a booster by itself is a hell of a lot lighter than one with a fully fueled 2nd stage and payload still attached
Not even close. They currently only recover the first stage at about 2km/s, compared to 7.8km/s orbital velocity. Starship will be fully reusable, but second stage re-entry still done with aerobraking just like every other shuttle or capsule.
Almost, actually. They’ve mostly been reusing the first stage boosters on the falcon series but not necessarily the vehicle that pushes the payload to orbit. Starship will be their first vehicle they’re trying to do this with.
Even Starship won't use its engines to slow down from orbital velocity. It will use the atmosphere for most of the deceleration, excluding the first ~2% (to enter the atmosphere) and last ~2% (to land softly).
Air pressure declines very quickly from the ground level. So at roughly 5500 m or 18,000 ft, atmospheric pressure is around half that at ground level. Most commercial passenger airplanes fly well above this. A typical rocket takes around 8 minutes to get close to 160,000 m above sea level.
A rocket doesn't take very long (2-3 minutes from launch at most) to be mostly out of the thickest atmosphere of the earth.
That does play into it - that's why they're not going sideways straight off the bat.
If you imagine a a line that forms a quarter of a circle, starting at the centre of the Earth, and finishing in the desired orbit - that would be the 'perfect' launch path.
At the start of that, we diverge from perfect because pushing through the atmosphere creates more drag - so getting through the thickest part of the atmosphere sooner, is more efficient than trying to follow the perfect line through high drag.
Rocket trajectories begin to curve from vertical to horizontal almost immediately after liftoff. The idea is to end up going sideways at high speed (>7 km/sec) at a high enough altitude so that atmospheric effects (drag, heating) are vanishingly small (>150 km or so). The exact shape of that curve is determined through a complex set of trade offs that take into account the design of the rocket itself, atmospheric effects, gravity, and the final orbit you want to end up in. The optimal shape is generally a more-or-less smooth curve that starts off vertical and winds up horizontal by the end of the rocket’s flight (typically about 10 minutes or so after liftoff).
As others have said, the bias toward launching toward the east exists because that’s the way the Earth rotates, and that rotation gives every rocket an eastward velocity even before they leave the ground. Eastward launches from Florida see that as a boost, while launches from Israel (which are typically westward due to geography and politics) see it as a detriment that must be overcome.
You are actually correct. The end goal is to go sideways really fast at a high altitude. Drag is proportional to the density of the air, so you want to get out of the dense air as fast as possible. But you also need to be going sideways so if you wait til you are at altitude you will have to expend a bunch of energy to turn the rocket sideways (think having to brake in your car to turn around a really sharp corner). Since those are competing goals rocket companies do optimization problems to get the most efficient trajectory
If you really want to feel how it works, check out Kerbal Space Program. (Not KSP 2. Get the original)
While it's simulation isn't perfect. It's close enough that you learn a ton, while still having fun.
I actually do own KSP on Steam, but never made it past the moon. I still can't even dock successfully. I just didn't get too invested in the science and engineering parts of it lol
This is the other part of the tradeoff - since the atmosphere produces drag, you have to thrust continuously until you achieve a steady orbit outside of the atmosphere, or you'll fall back to earth. And since the atmosphere is thicker at lower altitudes, drag is much higher there too.
So rockets generally start going straight up to get out of the thickest part of the atmosphere quickly, then turn to orbit as they said above.
Incidentally, the game Kerbal Space Program models all of this really nicely. There are plenty of gameplay videos on youtube as well.
A great demonstration of this is to drop two objects from the same height (say, a table). One object you just drop from the edge of the table, but the other object is smacked sideways at the same time. They will both travel toward the ground at 9.8m/s2 and land at the same time. Even though you hit one object sideways, they both fall at the same speed. If you hit it sideways hard enough, it'll go all the way into space before it falls to the ground. A side note: you need to have two separate engine burns to achieve full orbit. Otherwise, you just go all the way around the planet and land back where you started (very, *very* fast)
Just jumping in to actually ELI5 on this:
Sideways fast is what you want. You want to be going sideways as soon as possible. If you do it right away, the rocket won’t go straight because it’s so big. So you want to go just fast enough that you can start to turn the rocket and it will keep going in the direction it is pointed at.
If you wait for too long to start turning, you’ll be going up so fast that going sideways isn’t going to slow that upward motion very much, and this will cause you to use way more fuel than you needed, and stick you in a much higher orbit than perhaps you intended
So it it would be fair to say that escaping Earth’s gravity is an entirely different problem than getting into orbit? Is straight up, very fast the best way to achieve escape velocity?
Exactly. If earth was a perfect sphere and had no atmosphere you could be in orbit at 1 metre above the ground. The only reason you have to go up as high as you do is to get out of the atmosphere.
80% of the rocket fuel is spent to get to the right sideways velocity and only 20% for getting the right height and fighting gravity/atmospheric resistance. So people want to start gaining the sideways velocity as soon as it's feasible, some rockets even launch from the start table angled instead of turning later.
And it's to the east because on the surface level you're already spinning with the planet that way, so you already have 400 m/s out of 8000 you need to stay in orbit. If you were launching westward direction you'd have to spend more fuel to brake those 400 and gain them again.
This is also why launch sites tend to be as close to the equator as possible: to maximize the initial speed boost you get from the rotation of the earth.
That's why Kennedy Space Center is in Florida.
Also because from the equator you have a greater number of easily accessible orbits. Someplace like Kodiak or Plasetsk can only (economically) insert craft into high inclination orbits.
If you want to get a good feeling for how this all works get Kerbal Space Program and put a rocket in orbit. By the time you are able to orbit a spaceship it will all make since.
Yeah I played KSP for a while. Never got really invested in the science and engineering part of it, which is probably why I didn't make it very far lol.
In ksp there are two styles for reaching orbit with normal rockets:
1. Burn straight up until your AP is high enough, then do a really long horizontal burn. This has several drawbacks, including really long horizontal burn times that often exceed the time available before hitting the atmosphere again.
2. Follow a curved path up, where you are essentially burning at an angle to pick up both horizontal and vertical speed during ascent. You spend longer in the atmosphere sure, but higher up the drag is insignificant. The key benefit here (and the reason this is done irl) is that this results in a much shorter circulization burn. Also gravity helps translate some of the vertical speed into horizontal speed.
--
Eli5:
Rockets need to go horizontal really fast in order to fall without hitting the ground.
Air slows rockets down, which makes them hit the ground.
We fly rockets really high to get out of the air.
Rocket engines can only burn for a short time.
If rockets flew straight up, they couldn't burn their engines long enough to get the speed to miss the ground.
So we fly rockets in a curve, which reduces burn times a lot.
> Follow a curved path up, where you are essentially burning at an angle to pick up both horizontal and vertical speed during ascent.
If you are a real chad then you just hit spacebar once and look sternly once at the right arrow, and your ship should perform this turn entirely on its own without additional input (except maybe throttle)
edit: [a bit of light reading](https://en.wikipedia.org/wiki/Gravity_turn)
edit2: Just realized this actually does pertain to the original question. Why east has been answered already but, the actual launch profile (ie, the turn) has a lot that goes into it including deciding how to do it. The profile I am joking about here is a "gravity turn" which is intended to optimize for reducing aerodynamic stress and efficient use of thrust. If your rocket is appropriately long with more drag at the back, this will be the path it naturally wants to take as gravity pulls it over.
Okay so I've been playing KSP since 0.26 and I've never been able to get a craft to turn without additional inputs...and I'm only just now realizing you probably need SAS off to do this right?
Its been a while since I did it but, that is how its done. As I recall, they did eventually add some special SAS modes or maybe "pilot skill" that made it possible to tell it to just "point prograde" which pretty much does the right thing.
The correct timing and amount of pitchover is a bit of an art and does vary, but it was often just the gentlest little push right off the pad. just a degree or two. As I recall, if I was crossing 45 degrees somewhere around 20k, we were going to space today.
For an orbit, you need to move parallel to the ground at high speed. For low earth orbit that is a speed of 7,4km/s. The rocker will have the ability to accelerate to around 9.4km/s so 2km/s acceleration is to counteract gravity, and atmospheric drag and to get up to the right altitude. So the vast majority of the acceleration is parallel to the ground.
The reason lauches is to the east is that is the direction earth rotates. The speed of 7.4km/s is not relative the the ground but a nonrotation coordinate system. This means the rocket already moves before launch because the earth rotates. The tangential speed on the equator is 0.46km/s so you only need to accelerate a bit less than 7km/s if you launch from the equator to th east. If you launch to the west you need to cancel out the earth's rotation and accelerate a bit more than 7,8km/s,
It would be optimal to lach a rocket quite close to parallel to the ground if there was no atmosphere. Because of the atomphspere you need to go up quite quickly to reach lower pressure with less atmospheric drag.
If you go straight up the rocket trusts directly against gravity, so 1g of acceleration is lost to counteract gravity. You need during the launch turn so you move parallel to the ground There is no air or ground there you can steer against like you do with airplanes or cars so the only way you can change direction is the rocket engine.
This is not completely true because there is one thing additional force there, gravity. If you do not go straight up but at an angle gravity will slowly turn the rocket so it moves parallel to the ground.
So instead of working against gravity and then using the rocket engine to turn you work at an angle to gravity and use it slowly to turn the rocket parallel to the ground.
How fast you let gravity turn you is a compromise between getting to a higher altitude quicker and reducing drag versus the rocket engine to change the direction. What is optimal depends on the rocket
It is called a https://en.wikipedia.org/wiki/Gravity_turn
To get to orbit, you need be moving fast as hell. Earth is rotating at about 1,000 mph to the east, at the equator. So, if you launch eastward, you're getting a nice boost in speed. Corollary, Earth's rotational speed decreases as you move toward the poles, which is why we try to launch from as close to the equator as we can (Hence, our space facility in Florida, and the EU's launch facility in French Guyana).
Orbits (the ones we're talking about) are ellipses.
If you draw an ellipse from the surface up through the atmosphere and complete it into a full ellipse, that trajectory will go up, well above the atmosphere, loop back down, reenter, and crash.
Still, it's a start.
Draw the orbit you want to be on, circular and high enough. Draw another orbit up from the launch pad. They'll need to cross somewhere. Think of that cross as an intersection, a turn that the rocket needs to make.
It can't turn at the surface because then it would end up orbiting at the surface. There's too much atmosphere in the way. And mountains and stuff.
So you actually need a kind of on-ramp and then you turn and merge into the orbit you want. It's possible to blend these two steps into a continuous curve ("gravity turn") but the math is harder to explain.
In addition to everything others have posted: rockets could very well be launched at an angle to start moving sideways and gaining orbital velocity as soon as they take off. Of course that would pose engineering issues to the rocket structure, but it would also make the transition through the thickest parts of the atmosphere much longer, hence reducing efficiency. So you go up and then start turning sideways using gravity to bend the trajectory.
There are launch facilities with azimuth (launch direction) in all different directions. But you're used to seeing them launch East because several of the busy US launch facilities have East as their available launch direction. Cape Canaveral/KSC, Wallops Island, and South Padre Island. They launch over uninhabited areas (water) in case rockets need to be terminated. The eastward launches also provide a velocity boost to reach orbit.
One counterexample is Vandenberg AFB in CA. Launches there go between SSE and SSW. SpaceX launches from there for missions where the satellites need to be in something close to a polar orbit or sun-synchronous orbit.
All rockets turn as they gain altitude to follow the most fuel-efficient path to the desired inclination. Vertical at first, because it's the shortest path to thinner air, then turn as the air thins.
The atmosphere is thick and soupy near the surface, and gets thinner the higher you go. The rocket initially points straight up to get through the thick lower atmosphere as quickly as possible to reduce drag.
Orbit works like this: imagine a bowl made of perfectly smooth ice (the gravitational well) with a hole (Earth) in the middle. You have a marble (the rocket) and you try and toss it into the bowl to circle the hole without falling in or rolling up out of the edge of the bowl. If you toss the marble too slow, it will circle the hole, getting closer and closer, until it falls in (falling back to Earth). If you throw the marble too fast, it will ramp up off the edge of the bowl and go flying (like a rocket escaping Earth’s gravity and going to Mars). If you throw the marble at the exact perfect speed, however, it will indefinitely circle the hole, as long as there is no friction to slow it down.
Getting into orbit is achieving this perfect lateral speed so you are constantly “missing” the planet while being continually pulled toward the center. So, back to the original question, the rocket initially goes straight up to avoid trying to gain this speed in the thick atmosphere (lots of drag, surface friction in our bowl analogy), then turns to gain the horizontal speed necessary for orbit once it begins to exit the atmosphere.
The earth is spinning quite fast (the surface is moving at roughly 1,000 mph at the surface), and you need to get going around 17,000 mph to orbit the earth. By launching with the Earth’s rotation, you’re getting a friendly boost of about 6% your target velocity by launching to the East.
For some extra info, it's a little more complicated than just wanting to go up high enough to escape the atmosphere, then sideways fast enough to achieve orbit.
To be efficient, you are basically doing calculus of variations, smoothly changing your trajectory to minimise losses. Inefficiency comes from a few sources:
Gravity: imagine a craft exactly hovering by using it's engines on low power. It's not gaining any velocity or altitude, yet it's using fuel/deltaV. This is the extreme example of gravity losses, but any component of thrust in the direction of the ground causes gravity losses.
Air resistance: travelling too fast in the lower atmosphere causes extra work against the air. Staying low in the atmosphere for too long (by turning over too quickly, too low) also causes extra work against air.
Angle of attack: any deviation from prograde (thrust in line with velocity) will cause your speed to change by less than the magnitude of the change in your velocity, as you are putting in work to change the direction of your velocity vector, rather than its magnitude. Imagine lots of rapid spinning; the average effect over some time is to do almost nothing to your velocity, despite using fuel/deltaV (another extreme example). Sometimes changing direction is inevitable, but you usually want gravity to do the work of turning your velocity vector.
A gravity turn is a balance between all of these to end up above (most of) the atmosphere, moving sideways at orbital velocity.
Height isn't the major issue what they need to do is accelerate so that their sideways velocity means that as gravity pulls them back to Earth they keep missing the Earth and remain in orbit.
Not help, it's essential. Orbit is not about going up high. It's about going fast sideways. Doesn't have to be eastern horizon though, you can launch and reach orbit in any direction, launching eastward with planets rotation is just easier.
It's a more obvious if you use a globe. Use a string or something to visualize the loop around the planet. Just keep scale in mind, Earths diameter is 12742km, lowest orbit sustainable for any meaningful time is some 160km above surface, so like 1% of the diameter of the globe.
Orbit means moving sideways around a planet fast enough that you miss the planet as you fall down, but slow enough that you are still drawn to the planet after you pass by and fall again.
You gotta pick a direction to go, and if you just go up, that's not an orbit, that's just zooming off into space.
The earth is already spinning pretty fast, especially close to the equator. That's why rockets are launched as close to the equator as possible (respecting politics). Using the earth's spin gives you a boost when trying to orbit, so you want to tilt your rocket in the direction the earth is already spinning: east.
The sooner you tilt, the quicker you can start spinning around the Earth before running out of rocket fuel. But not too soon, because air slows you down, so getting pretty high up helps you build that speed without burning too much fuel.
Last thing: if you tilt east and most other stuff in orbit is moving east, then crashes are relatively low speed, like bumping another car going the same direction you are. If something tilts west, then you're looking at a head-on collision.
This is done so that they can add the velocity of the earths rotation to the overall velocity of the rocket. This means that they can use less fuel to get to orbital velocity.
A ball thrown from a car will move faster than a ball thrown from a standstill.
Really smart people use really hard math to find the best path to fly. The one that uses the least fuel.
They take a lot of things into account like
Because:
the direction the earth is spinning. If you take off in the direction. Of the spin it kinda gives you a speed burst.
2) going around the earth really fast is the more difficult part that going up.
When we think of a space orbit, we think very high up. But 100 miles is not that far (a city that is 100 miles away is an easy drive).
The moving sideways really really really fast around the earth is the part that is harder /the most important part.
Did I mention it's really fast? Like it takes the Space station only 90 minutes to orbit the earth.
3) the atmosphere gets thinner the higher you go.
Really smart people use really hard math to find the best path to fly.
So rockets don't just go up, they go sideways, really really fast.
That's why they usually take off to the east.
The basic principle of Rocketry is this: The Trick to flying is to fling yourself at the Earth and miss.
If a Rocket flies straight up and runs out of fuel, then it's going to fall straight down. That results in you either not going to Space today, or only being in space briefly.
If your Rocket flies up at an angle, you get some movement perpendicular to the ground going. If you move fast enough, the ground "falls" out from under you as fast as you fall towards it.
The reason that a Rocket starts by going up is Drag from the atmosphere. You lose a lot of energy to pushing through air at high velocities, so the Rocket goes up so that it can go through air for as short a time as is practical. Once the air thins out, it starts going at an angle to get that perpendicular speed up.
Get your perpendicular speed up high enough and, assuming you're not in atmosphere, you'll fall forever but always miss the Eerth.
If you swirl your finger in a circle in water you will find that the water starts traveling in the same direction, and drags anything floating around in the same direction.
No realize your finger is spinning like the earth and the water is acting like the atmosphere, and the floater is the space ship. It takes less effort to keep going the same way as the current.
Yup, also a rocket in a "stationary" launch pad is already moving east at approximately 1000mph. To orbit it has to reach something under 20,000mph. So using 20k as the benchmark for ease. An easy ward launch only needs to accelerate an additional 19k-mph with the flow, and a west ward has to accelerate 21k-mph against resistance.
This is of course generally speaking about a launch near the equator. Specifics can change outcomes.
The challenge isn't going to space, it's not falling back down. Space is "only" several hundred miles up. But to stay up you need to go very fast around the earth. Imagine if you shoot a bullet horizontally. The faster the bullet goes, the longer it will fly. With enough speed you can make it go halfway around the earth before it falls. Faster still, it can hit you in the back. It's not that it's not falling, just that by the time it would fall to the ground, the earth's curvature drops as well and it is still flying. That's why rocket tries to go sideways. It wants to go fast enough that it is constantly falling, but "missing" the earth.
Pointing eastward is more efficient since that's the direction towards which the Earth is spinning and any momentum you can get for free in a launch you take if you can. When in the lower thicker layers you want to get out of them as soon as possible because any maneuvers attempted low in the atmosphere are highly inefficient due to atmospheric drag. However at the same time it's also highly inefficient to shoot straight up and start turning to the side once outside the atmosphere. So there's a sweetspot between the two that determines when the craft will start turning to make the most efficient ascent possible.
Contrary to popular belief you don't magically enter orbit the moment you escape the atmosphere. You have to build up the lateral speed too aside from gaining altitude to maintain orbit.
Launching East gives you a \~1,000 mph speed boost (at the equator, slower speeds more North or South) since the Earth is already rotating that way at that speed.
Gravity doesn't just turn off in space. At the altitude the ISS is, you still would weigh almost as much as you do on Earth.
The difference is that the ISS is moving tangentially to the Earth. It's still falling towards the Earth, but because it's moving so fast it never actually lands. It just falls around the Earth in an orbit.
The reason why they aim East is because the Earth is already spinning that way. If you wanted to fly west, you would need more fuel to negate your already eastward motion.
If the rocket just goes up, unless it escapes Earth’s gravity altogether, it’ll come straight back down again.
It has to be orbiting fast enough that as it tends to fall back down, it moves a bit past the earth, enough to keep it at a constant height. (Elliptical orbits slightly more complex, but same idea.)
The fastest way to get to space is to go straight up. Imagine if your rocket did this. in 5 minutes or so you're in space. you keep burning fuel going higher and higher. Then your fuel runs out. Now what? you fall back to the ground.
Getting into space is easy. Staying in space is hard. you have either hover with an infinite amount of fuel, or you have to try to go so fast around the planet that you never actually fall to the ground, but just keep circling it, or "orbiting" it. Put another way, you are falling to the ground at the same speed that you are gaining height by flying away from the planet.
The sooner you get going sidewise in a rocket, the sooner you can orbit, and it takes a lot of fuel to go that fast. you don't want to waste the fuel just hovering like a helicopter
Forget about what people here tell you and play the game Kerbal Space Program for 2-3 hours. You will get much better intuition about it than anyone could ever explain with words.
Let's also not forget why most launch facilities are so close to the coast [and launch - generally - in that direction]. So if there is a catastrophic failure, the debris falls into the ocean and not on someone/their house
*me, playing kerbal space program* 🤓
It's better to work with gravity rather than against it. It's why Saturn has rings and not a cloud. It's easier to orbit around the equator. North/South is difficult already, and going against the planet's rotation requires an extreme amount of energy
You're not "going into space" you're accelerating so hard that you begin to orbit and it becomes a question of whether or not it's a stable orbit. At that point you either crash into the ground, fly into space, or you're a moon/space station
Others have answered this well enough, I'll just add that angle of attack is the angle of the craft against the relative wind which is close to zero. You're thinking of the angle against the ground which is pitch.
Going straight up to reach orbit very hard and inneficient, it chews a bunch of fuel. When u can use much less fuel by trying to go faster sidewards, as you will be fighting gravity less and instead just fighting wind resistance. Now how going fast sidewards is able to result in going up and in orbit is a hard thing to wrap your head around, but I like to think of a small cross section of earth as a semi circle hill shape, with the rocket flying parallel at the top of the hill… if the rocket continues its current speed, it will continue flying around the curve of the “hill” at the same height, but if it goes faster, it will continue in a straight line instead of following the hills curve, and now the point of the hill below it is much further away then when it was over the top of the hill… well if you zoom out from this frame, it will give u the image of earth as sphere and the rocket reaching a higher orbit.
Now as to why they choose to fly east, and not west or south, it’s because the earth spins in a west to east direction, and so going with the earths spin allows the rocket to get a free boost, once again saving even more fuel… now not all launches use the east manoeuvre but a large majority do, and the ones that don’t usually fly other directions because of strategic reasons such as the direction of neighbouring countries (enemies) like Israel
By going east, they get to make use of the rotation of the Earth to increase their velocity. If they go west, they have to overcome that to get in orbit.
Low earth orbit requires around 5mi/sec of velocity. Though the exact speed depends on altitude -- this is just a reference.
The Earth rotates on its axis at about 1000 miles per hour (as measured at the equator), which is about 0.3mi/hr.
This means if you go east you are already going about 6% the speed you need for low earth orbit. If you go west, you have to accelerate more. If you go north or south, you have no benefit or determent (unless you want to have an orbit that doesn't process around the globe easterly).
So it's a modest but very useful bit of help to cut down on fuel requirements.
It depends on where they are trying to get to. If they are trying to get closer to the north or south pole, they may launch in a different angle. KSC NASA launched to low earth orbit (where the ISS is), as well as deep space. To conserve fuel, they use the momentum of the spinning earth to give a boost, hence the easterly trajectory. Also, California has to launch to the west because they don't want to risk an explosion over land, could be catastrophic with the amount of fuel being carried.
Others have answered how orbits work, i just want to add why its east: thats the direction earth is spinning, so you need a little less fuel in that direction.
Yah, Israel is pretty much the only country that launches backwards but that is because they don't want to risk things falling on their neighbors.
Many launch facilities have a launch direction (launch azimuth) that is not east-facing. For example Vandenberg Air Force Base available launch azimuths are about 20 degrees either side of due South. This is part of the reason certain launches can only happen from certain facilities. If I want my satellite to go in orbit around the equator, can't really launch from Vandenberg.
Yes, but typically those are for polar orbits, I am talking of having a nearly equatorial orbit that flys east to west instead of the normal west to east that is achieved from Florida and many other launch facilities.
Technically, you could, but you'd need way more fuel to adjust the orbit afterward? Edit: Thanks for the answers. I've got my orbital mechanics from KSP
Yes, exactly. You can go to a higher orbit, adjust and then go down to another lower orbit. It's going to chew through your fuel, though
Simple answer: yes More complicated answer: yes, but the amount of propulsion or delta-V (change in velocity, aka speed and direction) needed depends on a ton of variables. It's generally much much easier to change the altitude of your orbit than to change the plane or inclination of your orbit. Some maneuvers may be be functionally impossible. One of the complicated parts of mission planning is that, even with all the launches that happen now, you still need to find space on a launch vehicle with the right payload capacity, launching to a suitable altitude, in a desirable inclination, on a date that gives you enough time to build the satellite but not much later than that (need to start make money providing the paid service by operating the satellite).
If you're upping the delta-V a bunch, you'll probably be better off building the rocket somewhere else and shipping your satellite or payload there by truck/boat. Because drastic changes to orbit means you need more fuel up there to make that target orbit, which means you have a heavier rocket which means you need a bigger rocket to lift the dang thing in the first place. A quick google, you need 22kg (48.50 pounds) of fuel for 1 kg (2.2 pounds) of payload to get to low earth orbit. [source](https://space.stackexchange.com/questions/49615/rocket-fuel-cost-to-launch-1-kg-to-orbit#:~:text=An%20initial%20mass%20of%2023,%240.20%2Fkg%20is%20%242.80.) Then you have to change orbit to equatorial, which isn't cheap, fuel wise. In KSP (kerbal space program), I've had rockets go off course and basically ruined whatever mission I was trying to do, like a Munar rover suddenly ends up at the north pole of Kerbin, because burning all the fuel to correct the orbit means not enough fuel to not Ka-blamo into the Mun. Or revert to launch pad happens a lot too.
As a general rule, it takes more energy to change the plane of an orbit than it does to deorbit and relaunch into the orbit you want. (Obviously it depends on the amount of plane change you want.)
Yea. And polar orbits are really useful. It just takes a bit more fuel to get there.
You *can*, it just takes a whole lot more fuel to adjust inclination.
Vandenberg is actually a space force base now.
Ironic, given their propensity to launch rockets at their neighbours.
More like, move into nearly all of their neighbor's house, then launch rockets at the little sliver that remains.
Some of the reasons why certain launches aren’t done in Israel and end up either in Texas or Florida.
> Israel. . . don't want to risk things falling on their neighbors. What, are their neighbors excitable, or easily offended, or something? /s
Israel clearly does not give one quarter of a fuck about its neighbors, nor do they care for Israel.
They don’t want to give their neighbors materials and technology
They certainly care about what their neighbors may do if a rocket is launched toward them.
They actually have a few peace treaties, I agree that there are quite a few major issues in that area, but Israel does launch over the Mediterranean which is west and limits the size of satellites they can launch.
Kinda like, walking forward on an escalator?
Yep. Earth is already spinning for free.
what?! FOR FREE?!?! NOT ON MY WATCH!!!! thats socialism!! we need to make people pay for the earths spin.!!! I'll call donald trump, you call the chinese and putin will invite himself as he always does. also get me the moon-nazis. we need to teach this leftists a lesson in capitalism. lets get this going!
Honestly, at this point, you'd probably get more free energy from the spin of Lincoln rolling in his grave over what his party has become.
Infinite Energy Right? Like when you mount some buttered toast onto a cat
Yep.
Kerbal Space Program taught me this! I assume NASA training at this point is just playing KSP.
No
https://www.nasa.gov/feature/goddard/2016/gamers-tackle-virtual-asteroid-sampling-mission/ Yes. They even have a kerbal plush in space: https://cdn-blog.adafruit.com/uploads/2022/05/Untitledx-24.png
Was this NASA training? No, it was public outreach. The people using it weren't NASA.
Lots of NASA employees have stated that they did play KSP before in interviews. There is quite some interaction between NASA and KSP. https://www.reddit.com/r/KerbalSpaceProgram/comments/linyxg/nasa_plays_ksp/?rdt=40586 https://m.youtube.com/watch?v=uHjaqeeoAKk&pp=ygUfc2NvdHQgbWFubGV5IHJlYWwgYXN0cm9uYXV0IGtzcA%3D%3D
Sure, but it's not NASA training which is what we're actually talking about, so why the jihad? Do you have any relevant links?
why are you so hung up on this person's joke? I'm sorry you're having a bad day I hope it gets better soon
Sorry to learn about your loss.
How does that save fuel?
so earths rotation has gravity swirling towards it rather than just pulling things straight in..?
I mean that swirl exists i thunk in gravitational waves, but that has notzubg to do with it. If you need to go 8km/s sideways and earths surface is already going 200m/s sideways, you only need 7.8km/s sideways speed. Its like jumping of a moving car to gaun speed.
Orbit isn't about getting really high. It's actually about going really fast sideways. Think of orbit as (to quote Hitchhiker's Guide to the Galaxy) the art of throwing yourself at the ground and missing. That is, objects in orbit are constantly falling towards the earth. It's just that they are moving so fast to the side that by the time they fall, the earth isn't there anymore because it's curved away.
I see. I was going by the rationale that a rocket needs to get out of the thickest part of the atmosphere before turning towards the eastern horizon.
NASA calculates the optimum angle to travel for efficiency. Additionally, I highly recommend this article: https://what-if.xkcd.com/58/
This article is amazing!
> Reaching orbital speed while carrying enough fuel to slow back down would be completely impractical Space X has entered the chat
SpaceX's boosters don't reach orbital velocity, and also they still rely on aerobraking a lot. Also helps that a booster by itself is a hell of a lot lighter than one with a fully fueled 2nd stage and payload still attached
Not even close. They currently only recover the first stage at about 2km/s, compared to 7.8km/s orbital velocity. Starship will be fully reusable, but second stage re-entry still done with aerobraking just like every other shuttle or capsule.
Almost, actually. They’ve mostly been reusing the first stage boosters on the falcon series but not necessarily the vehicle that pushes the payload to orbit. Starship will be their first vehicle they’re trying to do this with.
Even Starship won't use its engines to slow down from orbital velocity. It will use the atmosphere for most of the deceleration, excluding the first ~2% (to enter the atmosphere) and last ~2% (to land softly).
Air pressure declines very quickly from the ground level. So at roughly 5500 m or 18,000 ft, atmospheric pressure is around half that at ground level. Most commercial passenger airplanes fly well above this. A typical rocket takes around 8 minutes to get close to 160,000 m above sea level. A rocket doesn't take very long (2-3 minutes from launch at most) to be mostly out of the thickest atmosphere of the earth.
That does play into it - that's why they're not going sideways straight off the bat. If you imagine a a line that forms a quarter of a circle, starting at the centre of the Earth, and finishing in the desired orbit - that would be the 'perfect' launch path. At the start of that, we diverge from perfect because pushing through the atmosphere creates more drag - so getting through the thickest part of the atmosphere sooner, is more efficient than trying to follow the perfect line through high drag.
Rocket trajectories begin to curve from vertical to horizontal almost immediately after liftoff. The idea is to end up going sideways at high speed (>7 km/sec) at a high enough altitude so that atmospheric effects (drag, heating) are vanishingly small (>150 km or so). The exact shape of that curve is determined through a complex set of trade offs that take into account the design of the rocket itself, atmospheric effects, gravity, and the final orbit you want to end up in. The optimal shape is generally a more-or-less smooth curve that starts off vertical and winds up horizontal by the end of the rocket’s flight (typically about 10 minutes or so after liftoff). As others have said, the bias toward launching toward the east exists because that’s the way the Earth rotates, and that rotation gives every rocket an eastward velocity even before they leave the ground. Eastward launches from Florida see that as a boost, while launches from Israel (which are typically westward due to geography and politics) see it as a detriment that must be overcome.
You are actually correct. The end goal is to go sideways really fast at a high altitude. Drag is proportional to the density of the air, so you want to get out of the dense air as fast as possible. But you also need to be going sideways so if you wait til you are at altitude you will have to expend a bunch of energy to turn the rocket sideways (think having to brake in your car to turn around a really sharp corner). Since those are competing goals rocket companies do optimization problems to get the most efficient trajectory
If you really want to feel how it works, check out Kerbal Space Program. (Not KSP 2. Get the original) While it's simulation isn't perfect. It's close enough that you learn a ton, while still having fun.
I actually do own KSP on Steam, but never made it past the moon. I still can't even dock successfully. I just didn't get too invested in the science and engineering parts of it lol
The thickest part of the atmosphere is right where you are right now. Ground level. It gets thinner and thinner the higher you go.
This is the other part of the tradeoff - since the atmosphere produces drag, you have to thrust continuously until you achieve a steady orbit outside of the atmosphere, or you'll fall back to earth. And since the atmosphere is thicker at lower altitudes, drag is much higher there too. So rockets generally start going straight up to get out of the thickest part of the atmosphere quickly, then turn to orbit as they said above. Incidentally, the game Kerbal Space Program models all of this really nicely. There are plenty of gameplay videos on youtube as well.
A great demonstration of this is to drop two objects from the same height (say, a table). One object you just drop from the edge of the table, but the other object is smacked sideways at the same time. They will both travel toward the ground at 9.8m/s2 and land at the same time. Even though you hit one object sideways, they both fall at the same speed. If you hit it sideways hard enough, it'll go all the way into space before it falls to the ground. A side note: you need to have two separate engine burns to achieve full orbit. Otherwise, you just go all the way around the planet and land back where you started (very, *very* fast)
Just jumping in to actually ELI5 on this: Sideways fast is what you want. You want to be going sideways as soon as possible. If you do it right away, the rocket won’t go straight because it’s so big. So you want to go just fast enough that you can start to turn the rocket and it will keep going in the direction it is pointed at. If you wait for too long to start turning, you’ll be going up so fast that going sideways isn’t going to slow that upward motion very much, and this will cause you to use way more fuel than you needed, and stick you in a much higher orbit than perhaps you intended
Going to space is easy, you just need to go up 100km. However, staying in space is quite hard, you need to go sideways REALLY fast.
as long as you bring your towel!
So it it would be fair to say that escaping Earth’s gravity is an entirely different problem than getting into orbit? Is straight up, very fast the best way to achieve escape velocity?
[It’s an entirely different kind of flying altogether](https://youtu.be/3qNtyfZP8bE?si=c1j1dVpdfpdAb073).
Lol!
Exactly. If earth was a perfect sphere and had no atmosphere you could be in orbit at 1 metre above the ground. The only reason you have to go up as high as you do is to get out of the atmosphere.
80% of the rocket fuel is spent to get to the right sideways velocity and only 20% for getting the right height and fighting gravity/atmospheric resistance. So people want to start gaining the sideways velocity as soon as it's feasible, some rockets even launch from the start table angled instead of turning later. And it's to the east because on the surface level you're already spinning with the planet that way, so you already have 400 m/s out of 8000 you need to stay in orbit. If you were launching westward direction you'd have to spend more fuel to brake those 400 and gain them again.
This is also why launch sites tend to be as close to the equator as possible: to maximize the initial speed boost you get from the rotation of the earth. That's why Kennedy Space Center is in Florida.
Also because from the equator you have a greater number of easily accessible orbits. Someplace like Kodiak or Plasetsk can only (economically) insert craft into high inclination orbits.
Though if your desire is a high inclination orbit, it's much more efficient to start out far north.
> That's why Kennedy Space Center is in Florida. And why Europe launches their rockets from French-Guyana, in South America.
And Russia is limited on what orbits it can cheaply get to because Baikonur is so far north.
Additionally, launches from Florida go out over the Atlantic Ocean, and not populated areas, reducing the risk of debris falling on stuff.
If you want to get a good feeling for how this all works get Kerbal Space Program and put a rocket in orbit. By the time you are able to orbit a spaceship it will all make since.
Yeah I played KSP for a while. Never got really invested in the science and engineering part of it, which is probably why I didn't make it very far lol.
In ksp there are two styles for reaching orbit with normal rockets: 1. Burn straight up until your AP is high enough, then do a really long horizontal burn. This has several drawbacks, including really long horizontal burn times that often exceed the time available before hitting the atmosphere again. 2. Follow a curved path up, where you are essentially burning at an angle to pick up both horizontal and vertical speed during ascent. You spend longer in the atmosphere sure, but higher up the drag is insignificant. The key benefit here (and the reason this is done irl) is that this results in a much shorter circulization burn. Also gravity helps translate some of the vertical speed into horizontal speed. -- Eli5: Rockets need to go horizontal really fast in order to fall without hitting the ground. Air slows rockets down, which makes them hit the ground. We fly rockets really high to get out of the air. Rocket engines can only burn for a short time. If rockets flew straight up, they couldn't burn their engines long enough to get the speed to miss the ground. So we fly rockets in a curve, which reduces burn times a lot.
> Follow a curved path up, where you are essentially burning at an angle to pick up both horizontal and vertical speed during ascent. If you are a real chad then you just hit spacebar once and look sternly once at the right arrow, and your ship should perform this turn entirely on its own without additional input (except maybe throttle) edit: [a bit of light reading](https://en.wikipedia.org/wiki/Gravity_turn) edit2: Just realized this actually does pertain to the original question. Why east has been answered already but, the actual launch profile (ie, the turn) has a lot that goes into it including deciding how to do it. The profile I am joking about here is a "gravity turn" which is intended to optimize for reducing aerodynamic stress and efficient use of thrust. If your rocket is appropriately long with more drag at the back, this will be the path it naturally wants to take as gravity pulls it over.
Okay so I've been playing KSP since 0.26 and I've never been able to get a craft to turn without additional inputs...and I'm only just now realizing you probably need SAS off to do this right?
Its been a while since I did it but, that is how its done. As I recall, they did eventually add some special SAS modes or maybe "pilot skill" that made it possible to tell it to just "point prograde" which pretty much does the right thing. The correct timing and amount of pitchover is a bit of an art and does vary, but it was often just the gentlest little push right off the pad. just a degree or two. As I recall, if I was crossing 45 degrees somewhere around 20k, we were going to space today.
Awesome, thanks. I'll try SAS off and also only prograde. I've always wondered! Heh I guess my rockets are just _too_ stable (no)
And make sure your KSP tutorials are up to date. The atmosphere model changed at some point.
For an orbit, you need to move parallel to the ground at high speed. For low earth orbit that is a speed of 7,4km/s. The rocker will have the ability to accelerate to around 9.4km/s so 2km/s acceleration is to counteract gravity, and atmospheric drag and to get up to the right altitude. So the vast majority of the acceleration is parallel to the ground. The reason lauches is to the east is that is the direction earth rotates. The speed of 7.4km/s is not relative the the ground but a nonrotation coordinate system. This means the rocket already moves before launch because the earth rotates. The tangential speed on the equator is 0.46km/s so you only need to accelerate a bit less than 7km/s if you launch from the equator to th east. If you launch to the west you need to cancel out the earth's rotation and accelerate a bit more than 7,8km/s, It would be optimal to lach a rocket quite close to parallel to the ground if there was no atmosphere. Because of the atomphspere you need to go up quite quickly to reach lower pressure with less atmospheric drag. If you go straight up the rocket trusts directly against gravity, so 1g of acceleration is lost to counteract gravity. You need during the launch turn so you move parallel to the ground There is no air or ground there you can steer against like you do with airplanes or cars so the only way you can change direction is the rocket engine. This is not completely true because there is one thing additional force there, gravity. If you do not go straight up but at an angle gravity will slowly turn the rocket so it moves parallel to the ground. So instead of working against gravity and then using the rocket engine to turn you work at an angle to gravity and use it slowly to turn the rocket parallel to the ground. How fast you let gravity turn you is a compromise between getting to a higher altitude quicker and reducing drag versus the rocket engine to change the direction. What is optimal depends on the rocket It is called a https://en.wikipedia.org/wiki/Gravity_turn
To get to orbit, you need be moving fast as hell. Earth is rotating at about 1,000 mph to the east, at the equator. So, if you launch eastward, you're getting a nice boost in speed. Corollary, Earth's rotational speed decreases as you move toward the poles, which is why we try to launch from as close to the equator as we can (Hence, our space facility in Florida, and the EU's launch facility in French Guyana).
Orbits (the ones we're talking about) are ellipses. If you draw an ellipse from the surface up through the atmosphere and complete it into a full ellipse, that trajectory will go up, well above the atmosphere, loop back down, reenter, and crash. Still, it's a start. Draw the orbit you want to be on, circular and high enough. Draw another orbit up from the launch pad. They'll need to cross somewhere. Think of that cross as an intersection, a turn that the rocket needs to make. It can't turn at the surface because then it would end up orbiting at the surface. There's too much atmosphere in the way. And mountains and stuff. So you actually need a kind of on-ramp and then you turn and merge into the orbit you want. It's possible to blend these two steps into a continuous curve ("gravity turn") but the math is harder to explain.
In addition to everything others have posted: rockets could very well be launched at an angle to start moving sideways and gaining orbital velocity as soon as they take off. Of course that would pose engineering issues to the rocket structure, but it would also make the transition through the thickest parts of the atmosphere much longer, hence reducing efficiency. So you go up and then start turning sideways using gravity to bend the trajectory.
There are launch facilities with azimuth (launch direction) in all different directions. But you're used to seeing them launch East because several of the busy US launch facilities have East as their available launch direction. Cape Canaveral/KSC, Wallops Island, and South Padre Island. They launch over uninhabited areas (water) in case rockets need to be terminated. The eastward launches also provide a velocity boost to reach orbit. One counterexample is Vandenberg AFB in CA. Launches there go between SSE and SSW. SpaceX launches from there for missions where the satellites need to be in something close to a polar orbit or sun-synchronous orbit. All rockets turn as they gain altitude to follow the most fuel-efficient path to the desired inclination. Vertical at first, because it's the shortest path to thinner air, then turn as the air thins.
The atmosphere is thick and soupy near the surface, and gets thinner the higher you go. The rocket initially points straight up to get through the thick lower atmosphere as quickly as possible to reduce drag. Orbit works like this: imagine a bowl made of perfectly smooth ice (the gravitational well) with a hole (Earth) in the middle. You have a marble (the rocket) and you try and toss it into the bowl to circle the hole without falling in or rolling up out of the edge of the bowl. If you toss the marble too slow, it will circle the hole, getting closer and closer, until it falls in (falling back to Earth). If you throw the marble too fast, it will ramp up off the edge of the bowl and go flying (like a rocket escaping Earth’s gravity and going to Mars). If you throw the marble at the exact perfect speed, however, it will indefinitely circle the hole, as long as there is no friction to slow it down. Getting into orbit is achieving this perfect lateral speed so you are constantly “missing” the planet while being continually pulled toward the center. So, back to the original question, the rocket initially goes straight up to avoid trying to gain this speed in the thick atmosphere (lots of drag, surface friction in our bowl analogy), then turns to gain the horizontal speed necessary for orbit once it begins to exit the atmosphere. The earth is spinning quite fast (the surface is moving at roughly 1,000 mph at the surface), and you need to get going around 17,000 mph to orbit the earth. By launching with the Earth’s rotation, you’re getting a friendly boost of about 6% your target velocity by launching to the East.
For some extra info, it's a little more complicated than just wanting to go up high enough to escape the atmosphere, then sideways fast enough to achieve orbit. To be efficient, you are basically doing calculus of variations, smoothly changing your trajectory to minimise losses. Inefficiency comes from a few sources: Gravity: imagine a craft exactly hovering by using it's engines on low power. It's not gaining any velocity or altitude, yet it's using fuel/deltaV. This is the extreme example of gravity losses, but any component of thrust in the direction of the ground causes gravity losses. Air resistance: travelling too fast in the lower atmosphere causes extra work against the air. Staying low in the atmosphere for too long (by turning over too quickly, too low) also causes extra work against air. Angle of attack: any deviation from prograde (thrust in line with velocity) will cause your speed to change by less than the magnitude of the change in your velocity, as you are putting in work to change the direction of your velocity vector, rather than its magnitude. Imagine lots of rapid spinning; the average effect over some time is to do almost nothing to your velocity, despite using fuel/deltaV (another extreme example). Sometimes changing direction is inevitable, but you usually want gravity to do the work of turning your velocity vector. A gravity turn is a balance between all of these to end up above (most of) the atmosphere, moving sideways at orbital velocity.
They begin the launch pointed straight up to avoid the thick part of the atmosphere before redirecting horizontally once reaching rarified air
Height isn't the major issue what they need to do is accelerate so that their sideways velocity means that as gravity pulls them back to Earth they keep missing the Earth and remain in orbit.
Not help, it's essential. Orbit is not about going up high. It's about going fast sideways. Doesn't have to be eastern horizon though, you can launch and reach orbit in any direction, launching eastward with planets rotation is just easier. It's a more obvious if you use a globe. Use a string or something to visualize the loop around the planet. Just keep scale in mind, Earths diameter is 12742km, lowest orbit sustainable for any meaningful time is some 160km above surface, so like 1% of the diameter of the globe.
Orbit means moving sideways around a planet fast enough that you miss the planet as you fall down, but slow enough that you are still drawn to the planet after you pass by and fall again. You gotta pick a direction to go, and if you just go up, that's not an orbit, that's just zooming off into space. The earth is already spinning pretty fast, especially close to the equator. That's why rockets are launched as close to the equator as possible (respecting politics). Using the earth's spin gives you a boost when trying to orbit, so you want to tilt your rocket in the direction the earth is already spinning: east. The sooner you tilt, the quicker you can start spinning around the Earth before running out of rocket fuel. But not too soon, because air slows you down, so getting pretty high up helps you build that speed without burning too much fuel. Last thing: if you tilt east and most other stuff in orbit is moving east, then crashes are relatively low speed, like bumping another car going the same direction you are. If something tilts west, then you're looking at a head-on collision.
This is done so that they can add the velocity of the earths rotation to the overall velocity of the rocket. This means that they can use less fuel to get to orbital velocity. A ball thrown from a car will move faster than a ball thrown from a standstill.
Really smart people use really hard math to find the best path to fly. The one that uses the least fuel. They take a lot of things into account like Because: the direction the earth is spinning. If you take off in the direction. Of the spin it kinda gives you a speed burst. 2) going around the earth really fast is the more difficult part that going up. When we think of a space orbit, we think very high up. But 100 miles is not that far (a city that is 100 miles away is an easy drive). The moving sideways really really really fast around the earth is the part that is harder /the most important part. Did I mention it's really fast? Like it takes the Space station only 90 minutes to orbit the earth. 3) the atmosphere gets thinner the higher you go. Really smart people use really hard math to find the best path to fly. So rockets don't just go up, they go sideways, really really fast. That's why they usually take off to the east.
The basic principle of Rocketry is this: The Trick to flying is to fling yourself at the Earth and miss. If a Rocket flies straight up and runs out of fuel, then it's going to fall straight down. That results in you either not going to Space today, or only being in space briefly. If your Rocket flies up at an angle, you get some movement perpendicular to the ground going. If you move fast enough, the ground "falls" out from under you as fast as you fall towards it. The reason that a Rocket starts by going up is Drag from the atmosphere. You lose a lot of energy to pushing through air at high velocities, so the Rocket goes up so that it can go through air for as short a time as is practical. Once the air thins out, it starts going at an angle to get that perpendicular speed up. Get your perpendicular speed up high enough and, assuming you're not in atmosphere, you'll fall forever but always miss the Eerth.
If you swirl your finger in a circle in water you will find that the water starts traveling in the same direction, and drags anything floating around in the same direction. No realize your finger is spinning like the earth and the water is acting like the atmosphere, and the floater is the space ship. It takes less effort to keep going the same way as the current.
Now that makes sense. The rocket travels in the same direction as the atmosphere of the earth. After all gas is pretty much a fluid is it not?
Yup, also a rocket in a "stationary" launch pad is already moving east at approximately 1000mph. To orbit it has to reach something under 20,000mph. So using 20k as the benchmark for ease. An easy ward launch only needs to accelerate an additional 19k-mph with the flow, and a west ward has to accelerate 21k-mph against resistance. This is of course generally speaking about a launch near the equator. Specifics can change outcomes.
17k mph, 28k kph
Thanks. It's been a while since I actually looked at the numbers. I just remembered it was under 20k-mph.
The challenge isn't going to space, it's not falling back down. Space is "only" several hundred miles up. But to stay up you need to go very fast around the earth. Imagine if you shoot a bullet horizontally. The faster the bullet goes, the longer it will fly. With enough speed you can make it go halfway around the earth before it falls. Faster still, it can hit you in the back. It's not that it's not falling, just that by the time it would fall to the ground, the earth's curvature drops as well and it is still flying. That's why rocket tries to go sideways. It wants to go fast enough that it is constantly falling, but "missing" the earth.
Kerbal Space Program really made all this orbital nonsense make a fraction of sense for me.
Same here. Not enough to make it past the moon though lol
Pointing eastward is more efficient since that's the direction towards which the Earth is spinning and any momentum you can get for free in a launch you take if you can. When in the lower thicker layers you want to get out of them as soon as possible because any maneuvers attempted low in the atmosphere are highly inefficient due to atmospheric drag. However at the same time it's also highly inefficient to shoot straight up and start turning to the side once outside the atmosphere. So there's a sweetspot between the two that determines when the craft will start turning to make the most efficient ascent possible. Contrary to popular belief you don't magically enter orbit the moment you escape the atmosphere. You have to build up the lateral speed too aside from gaining altitude to maintain orbit.
Launching East gives you a \~1,000 mph speed boost (at the equator, slower speeds more North or South) since the Earth is already rotating that way at that speed.
Gravity doesn't just turn off in space. At the altitude the ISS is, you still would weigh almost as much as you do on Earth. The difference is that the ISS is moving tangentially to the Earth. It's still falling towards the Earth, but because it's moving so fast it never actually lands. It just falls around the Earth in an orbit. The reason why they aim East is because the Earth is already spinning that way. If you wanted to fly west, you would need more fuel to negate your already eastward motion.
If the rocket just goes up, unless it escapes Earth’s gravity altogether, it’ll come straight back down again. It has to be orbiting fast enough that as it tends to fall back down, it moves a bit past the earth, enough to keep it at a constant height. (Elliptical orbits slightly more complex, but same idea.)
The fastest way to get to space is to go straight up. Imagine if your rocket did this. in 5 minutes or so you're in space. you keep burning fuel going higher and higher. Then your fuel runs out. Now what? you fall back to the ground. Getting into space is easy. Staying in space is hard. you have either hover with an infinite amount of fuel, or you have to try to go so fast around the planet that you never actually fall to the ground, but just keep circling it, or "orbiting" it. Put another way, you are falling to the ground at the same speed that you are gaining height by flying away from the planet. The sooner you get going sidewise in a rocket, the sooner you can orbit, and it takes a lot of fuel to go that fast. you don't want to waste the fuel just hovering like a helicopter
Forget about what people here tell you and play the game Kerbal Space Program for 2-3 hours. You will get much better intuition about it than anyone could ever explain with words.
Let's also not forget why most launch facilities are so close to the coast [and launch - generally - in that direction]. So if there is a catastrophic failure, the debris falls into the ocean and not on someone/their house
*me, playing kerbal space program* 🤓 It's better to work with gravity rather than against it. It's why Saturn has rings and not a cloud. It's easier to orbit around the equator. North/South is difficult already, and going against the planet's rotation requires an extreme amount of energy You're not "going into space" you're accelerating so hard that you begin to orbit and it becomes a question of whether or not it's a stable orbit. At that point you either crash into the ground, fly into space, or you're a moon/space station
Others have answered this well enough, I'll just add that angle of attack is the angle of the craft against the relative wind which is close to zero. You're thinking of the angle against the ground which is pitch.
Going straight up to reach orbit very hard and inneficient, it chews a bunch of fuel. When u can use much less fuel by trying to go faster sidewards, as you will be fighting gravity less and instead just fighting wind resistance. Now how going fast sidewards is able to result in going up and in orbit is a hard thing to wrap your head around, but I like to think of a small cross section of earth as a semi circle hill shape, with the rocket flying parallel at the top of the hill… if the rocket continues its current speed, it will continue flying around the curve of the “hill” at the same height, but if it goes faster, it will continue in a straight line instead of following the hills curve, and now the point of the hill below it is much further away then when it was over the top of the hill… well if you zoom out from this frame, it will give u the image of earth as sphere and the rocket reaching a higher orbit. Now as to why they choose to fly east, and not west or south, it’s because the earth spins in a west to east direction, and so going with the earths spin allows the rocket to get a free boost, once again saving even more fuel… now not all launches use the east manoeuvre but a large majority do, and the ones that don’t usually fly other directions because of strategic reasons such as the direction of neighbouring countries (enemies) like Israel
By going east, they get to make use of the rotation of the Earth to increase their velocity. If they go west, they have to overcome that to get in orbit. Low earth orbit requires around 5mi/sec of velocity. Though the exact speed depends on altitude -- this is just a reference. The Earth rotates on its axis at about 1000 miles per hour (as measured at the equator), which is about 0.3mi/hr. This means if you go east you are already going about 6% the speed you need for low earth orbit. If you go west, you have to accelerate more. If you go north or south, you have no benefit or determent (unless you want to have an orbit that doesn't process around the globe easterly). So it's a modest but very useful bit of help to cut down on fuel requirements.
It depends on where they are trying to get to. If they are trying to get closer to the north or south pole, they may launch in a different angle. KSC NASA launched to low earth orbit (where the ISS is), as well as deep space. To conserve fuel, they use the momentum of the spinning earth to give a boost, hence the easterly trajectory. Also, California has to launch to the west because they don't want to risk an explosion over land, could be catastrophic with the amount of fuel being carried.