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Comment by Rooster61 | Hacker News Reader

Thank you for the article, but it really doesn't answer my question. That thread's answers assume that we are talking about the current situation we have around the Earth. We have no precedent for this many satellites orbiting at the same altitude, but at different latitudes/longitudes (which negates the safeguard that they are moving at the same speed, it doesn't matter if they can intersect). The satellites would all need to be moving at both the same speed AND the same direction to not have a risk of collisions (which would of course be a circle, useless to this application).

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First, check out the video explaining the orbits: https://www.youtube.com/watch?feature=youtu.be&v=AdKNCBrkZQ4...

Doing some quick math, the shell in which they'll be orbiting has a surface area of 373,367,808km. With ~7000 satellites, an even distribution would leave them 533,382 km between satellites. All the satellites have station keeping thrusters to keep them in LEO with drag. Keeping them from running into each other is probably pretty simple, in comparison to the other challenges they'll need to solve.

Sure, but this assumes nothing ever collides with one and causes debris to be introduced to the web. The web itself will clearly be ok as long as it remains intact, but if something does cause one of these to RUD catastrophically, we now have debris following a similar, but just different enough orbit to be dangerous.

You won't find an answer to your question because you don't seem willing to drop your alarmist attitude.

There is just far too much space for 100k objects, let alone 10k to ever run the risk of collission. These satellites are all meant to be in line-of-sight. They will communicate with optics as opposed or in conjunction to radio.

You fear unforseen space particles destroying one and causing a chain reaction. Why don't you hold that same fear for existing satelittes which typically operate at an orbit with far lower decay rate? The orbit for StarLink is very low, small particles would not sustain their energy long enough to be a risk factor. The StarLink sats maintain orbit with fuel, everything else without fuel in that orbit will fall. The chance that a particle will end up in the same orbit, on the same plane, at the same time is astronomically low.

Your comments just echo the same type of delusions of people who think in their brillance they've found problems others have not foreseen. SpaceX is really just full of amateurs you ought to submit your findings.

> There is just far too much space for 100k objects, let alone 10k to ever run the risk of collission.

No, there isn't. Satellites can and do collide despite the vast amount of space in a given orbit. It is improbable, but likely enough to warrant at least some concern.

> Why don't you hold that same fear for existing satelittes which typically operate at an orbit with far lower decay rate?

I do, as does the FCC. This is evident in the fact that they now require any body wishing to launch a spacecraft guarantee that the craft can be put into a graveyard orbit.

> Your comments just echo the same type of delusions of people who think in their brillance they've found problems others have not foreseen. SpaceX is really just full of amateurs you ought to submit your findings.

I'm genuinely sorry this post made you feel this way. If I already had the brilliance to answer this question as I'm sure many bright minds at SpaceX do, I would not have asked the question and rebutted the responses to begin with.

> Satellites can and do collide despite the vast amount of space in a given orbit.

Excluding planned collisions, or collisions during failed docking, I found 4 instances of collisions between satellites and space debris. Ever. Now, a couple of things:

* Yes this larger constellation will increase those odds in the future.

* No, a catastrophic doomsday scenario did not occur when those happened.

* SpaceX will have complete control of these satellites through their operational lifespan (excluding collisions or malfunctions).

* Orbital decay for debris at the altitude they're operating at is ~10 years.

Also, have to ask... is all this concern a result of reading Seveneves? :)

I'm afraid I haven't heard of Seveneves before today, although it does look like an interesting read.

My concern is just from a general interest in spaceflight. More of a wish to protect a resource rather than a Chicken Little fear of the sky literally falling out.

Satellites don't just cross their paths by magic. If their orbits don't intersect, they can't collide. Satellites don't collide with each other, it has never happened.

Satellites do collide with debris, but that's a different issue. Furthermore, they don't need a guarantee that they can be put into a graveyard orbit - the proposed satellites (and even any debris, if they'd explode for whatever reason) will be in a graveyard orbit from day one until they stop being pushed up and deorbit.

> Satellites don't collide with each other, it has never happened.

Actually, they do, and it has indeed happened before (https://en.wikipedia.org/wiki/2009_satellite_collision). Far from a Kessler syndrome scenario, but certainly something that should be examined.

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