eli5: I’ve heard orbit described as continuously falling past or missing the Earth, how then do objects in geosynchronous orbit above a single point not fall out of the sky?
In: 2204
From KSP2
For geostationary, the altitude is picked to keep the angular speed equal to a spot on the ground. Other good technical descriptions in the comments.
From KSP2
For geostationary, the altitude is picked to keep the angular speed equal to a spot on the ground. Other good technical descriptions in the comments.
Picture a top that’s spinning (rotating) fast and also drifting aross the table.
To orbit, you need to be moving fast enough and in the right direction to “miss” the top as it travels across the table.
The rotation of the top doesn’t affect the orbit, but it is possible to sync up the orbit around the top to match the rotation.
Picture a top that’s spinning (rotating) fast and also drifting aross the table.
To orbit, you need to be moving fast enough and in the right direction to “miss” the top as it travels across the table.
The rotation of the top doesn’t affect the orbit, but it is possible to sync up the orbit around the top to match the rotation.
Picture a top that’s spinning (rotating) fast and also drifting aross the table.
To orbit, you need to be moving fast enough and in the right direction to “miss” the top as it travels across the table.
The rotation of the top doesn’t affect the orbit, but it is possible to sync up the orbit around the top to match the rotation.
Imagine a tug-of-war rope between you and a friend, and you’re both facing each other. And you stay in one place in the middle because you’re much bigger than your friend. And your friend is running around you in circles as fast as he can, but you’re both holding on.
Geo-synchronous orbit is kind of like that, except your friend doesn’t have to keep expending energy running the whole time, since in space there’s no “ground” (or gravity) acting along the plane of the orbit for him to have to fight friction against.
The Earth and the satellites are “holding on” to each other, just the right amount of gravity to balance it perfectly, meanwhile they are spinning “around” each other, while facing each other. But really, the Earth is so big and the satellite is so tiny, that we barely notice the effect of the satellite on Earth’s movement — Whereas the effect of the Earth on the satellite’s movement is so strong, it keeps the satellite locked in the sky in the same position relative to the ground “beneath” it, and the Earth drags the satellite along as the Earth moves in a circle around the sun.
This is why Geosynchronous orbit is **only possible** at a **specific height/altitude.** For Earth, that altitude is 37,000 km. Below or above that, the “speed” required to maintain orbit is not equal to the speed at which the Earth spins, so it’s not possible to have a stable orbit which maintains its position relative to a spot on the ground beneath. (For heavier planets, the single geosync altitude would be higher and farther away… For lighter planets, it would be lower and closer to the planet.)
Imagine a tug-of-war rope between you and a friend, and you’re both facing each other. And you stay in one place in the middle because you’re much bigger than your friend. And your friend is running around you in circles as fast as he can, but you’re both holding on.
Geo-synchronous orbit is kind of like that, except your friend doesn’t have to keep expending energy running the whole time, since in space there’s no “ground” (or gravity) acting along the plane of the orbit for him to have to fight friction against.
The Earth and the satellites are “holding on” to each other, just the right amount of gravity to balance it perfectly, meanwhile they are spinning “around” each other, while facing each other. But really, the Earth is so big and the satellite is so tiny, that we barely notice the effect of the satellite on Earth’s movement — Whereas the effect of the Earth on the satellite’s movement is so strong, it keeps the satellite locked in the sky in the same position relative to the ground “beneath” it, and the Earth drags the satellite along as the Earth moves in a circle around the sun.
This is why Geosynchronous orbit is **only possible** at a **specific height/altitude.** For Earth, that altitude is 37,000 km. Below or above that, the “speed” required to maintain orbit is not equal to the speed at which the Earth spins, so it’s not possible to have a stable orbit which maintains its position relative to a spot on the ground beneath. (For heavier planets, the single geosync altitude would be higher and farther away… For lighter planets, it would be lower and closer to the planet.)
Imagine a tug-of-war rope between you and a friend, and you’re both facing each other. And you stay in one place in the middle because you’re much bigger than your friend. And your friend is running around you in circles as fast as he can, but you’re both holding on.
Geo-synchronous orbit is kind of like that, except your friend doesn’t have to keep expending energy running the whole time, since in space there’s no “ground” (or gravity) acting along the plane of the orbit for him to have to fight friction against.
The Earth and the satellites are “holding on” to each other, just the right amount of gravity to balance it perfectly, meanwhile they are spinning “around” each other, while facing each other. But really, the Earth is so big and the satellite is so tiny, that we barely notice the effect of the satellite on Earth’s movement — Whereas the effect of the Earth on the satellite’s movement is so strong, it keeps the satellite locked in the sky in the same position relative to the ground “beneath” it, and the Earth drags the satellite along as the Earth moves in a circle around the sun.
This is why Geosynchronous orbit is **only possible** at a **specific height/altitude.** For Earth, that altitude is 37,000 km. Below or above that, the “speed” required to maintain orbit is not equal to the speed at which the Earth spins, so it’s not possible to have a stable orbit which maintains its position relative to a spot on the ground beneath. (For heavier planets, the single geosync altitude would be higher and farther away… For lighter planets, it would be lower and closer to the planet.)
The key to understanding geosynchronous orbit is that it’s no different than any other orbit. It’s just an object orbiting a massive body like any other. All the same rules apply.
One of those rules is that the closer you are to a massive object, the faster you have to go to stay in orbit. The further you are the slower you have to go to avoid shooting off. So the orbital speed is directly related to the distance from whatever you’re orbiting. In other words, the higher the altitude, the slower the orbital speed.
Last piece: the earth is spinning at a certain speed. This doesn’t impact orbital issues at all. But if a satellite’s orbital speed happens to be the same speed that the earth is be spinning, well happy coincidence: it’ll *appear* to be stationary from the ground. But it’s not, it’s just that you and the satellite are going around the earth’s center at the same speed.
The key to understanding geosynchronous orbit is that it’s no different than any other orbit. It’s just an object orbiting a massive body like any other. All the same rules apply.
One of those rules is that the closer you are to a massive object, the faster you have to go to stay in orbit. The further you are the slower you have to go to avoid shooting off. So the orbital speed is directly related to the distance from whatever you’re orbiting. In other words, the higher the altitude, the slower the orbital speed.
Last piece: the earth is spinning at a certain speed. This doesn’t impact orbital issues at all. But if a satellite’s orbital speed happens to be the same speed that the earth is be spinning, well happy coincidence: it’ll *appear* to be stationary from the ground. But it’s not, it’s just that you and the satellite are going around the earth’s center at the same speed.
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