If there are many satellites orbiting earth, how do space launches not bump into any of them?
In: 2066
Space,” it says, “is big. Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.
The simplest possible explanation: “space” is called like that for a very good reason.
People calculate carefully each launch to avoid colliding with other bodies, but it isn’t too difficult to find a reasonable compromise, because there’s so much space available.
“Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”
Basically besides the fact that every satellite is tracked, it’s hard to conceive just how much space there is up there. As we launch more and more it will become a bigger issue though.
Space-launches tend to not stay in low-earth orbit or the belt of geo-stationary objects for very long. So the larger debris can be tracked and avoided, and the smaller debris can be shielded against. And space really large and so on. But impacts are happening, and it is an increasing concern. Not in the least because – or so Kesslers theory goes – if debris fields get to dense, there might be a cascading effect as the pieces start hitting each other, spreading out in a massively larger area. While the pieces are still on their way for burning up or falling down many years into the future.
“Space is big. Really big. You just won’t believe how vastly hugely mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist, but that’s just peanuts to space.”
The earth is enormous, and many satellites orbit so high up that the circumference of their orbit is significantly bigger than the Earth’s circumference. On top of this, satellites orbit at different altitudes.
If you were to go up into space, you would not see any satellites or space junk at all. Similarly, if you were out directly I’m the middle of the asteroid belt, you most likely wouldn’t see a single asteroid at all. Space is BIG.
Hitting a satellite would be equivalent to flying in a straight line around the earth and just happening to collide with a specific parrot living in a remote jungle in an Indonesian island. Or a bird migrating from Uruguay to Hawaii. It’s simply so unlikely that we don’t need to worry.
But still, we track all satellites and most space junk larger than a few centimeters across. Just to be on the safe side 🙂
The sky is big. Like, really really big. It’s hard to convey just how big it is. Also it’s a 3D space, and it’s hard to hit things in a 3D space when you are trying to.
“Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.
Douglas Adams, The Hitchhiker’s Guide to the Galaxy (Hitchhiker’s Guide to the Galaxy, #1)
We track them all. A lot of it is just keeping a database up to date of the different orbits. The us government NORAD program has a fence across the earth that they use to detect objects in space and track them. We then made a standard to exchange that information. It describes the orbit of the object. It’s fairly simple math.
https://www.n2yo.com/satellites/
https://celestrak.org/NORAD/documentation/gp-data-formats.php
http://gpredict.oz9aec.net
But regardless, space is mostly empty. Even if we didn’t know where they are, hitting them by accident just won’t happen. The main reason we track sats is so we know where to point our antennas to talk to them.
Space is *big*. And, more importantly, space *isn’t flat*.
If you’re drawing lines on a piece of paper, then, Euclidean geometry and all, any pair of lines which aren’t parallel *must* intersect. But this is *not* true in three dimensions. Pedestrian bridges go over roads, highways cross over other highways, metro tunnels run under city streets, etc. For two things to collide in space their trajectories have to intersect, and for *that* to happen, the two lines have to be more or less coplanar. I mean, what are the odds that 4 randomly chosen points in three dimensional space will *all* cleanly lie on the same flat plane? There’s also the matter of time: It’s not enough for two trajectories to intersect, the objects themselves have to both be at that shared point at the exact same time, quite literally down to the millisecond. If an object half a meter across is traveling at one thousand meters per second, then it has travelled twice its own diameter in a single millisecond. If two half meter objects are on a collision course at those speeds, then a delay of 0.001 seconds is all it takes to turn a hit into a [very] near miss, and real satellites are moving *a lot* faster than that. Once again, space is *big*, so the odds of two satellites bumping into each other are very very low.
…But *not* zero. [Collisions *do* happen](https://en.wikipedia.org/wiki/2009_satellite_collision), just not very often ([until it’s too late](https://en.wikipedia.org/wiki/Kessler_syndrome), anyway).
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