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SpaceX just got FCC approval to launch 7,518 satellites

fastcompany.com

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Re: SpaceX just got FCC approval to launch 7,518 satellites

#51

Post by TimTheTinker »

bargl wrote: post #33

This is such a cool problem. We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. These satellites will actually have a ton of limitations in how much data they can send around and how they'll have to balance out their signals. Geo are easier to point to because, well they don't move. But these are going to be moving and changing all the t…

> Think about switching your router every 10 minutes.

Cellular and WiFi AP roaming are solved problems. For SpaceX, this will be rather straightforward as the design specifies fixed ground stations that will handle negotiating/maintaining upstream connection(s).

> Or you get a rainy day and your signal clarity goes down.

That's more likely to be an issue, but having multiple satellites overhead, plus the fact that the constellation will be located in LEO (thus higher signal strength due to proximity) will help mitigate signal attenuation due to clouds/precipitation.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#52

Post by dr_orpheus »

tgtweak wrote: post #45
bargl wrote: post #33

This is such a cool problem. We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. These satellites will actually have a ton of limitations in how much data they can send around and how they'll have to balance out their signals. Geo are easier to point to because, well they don't move. But these are going to be moving and changing all the t…

With about a thousand being in your horizon at any given time I don't think it'll be an issue to roam between them. In a Metropolitan area it's not rare to be around dozens of cell sites. Likewise cellular roaming is quite transparent.

Yes, but your cell tower aren't moving around relative to each other. And in order to get the data rates that they need at the speed they need, the signals between the satellites will be more focused rf or laser communication. So all of the satellites have to constantly know which satellite is closest to them and how to point antennas and/or lasers.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#53

Post by Rooster61 »

This scares me a bit. The idea of having LEO internet is great and all, but the idea of quadrupling the number of functioning satellites, all operating in different orbits but at a similar altitude seems incredibly dangerous to me.

The article mentions the movie Gravity, which is a bit unrealistic as it portrays multiple large bodies in orbit all being at about the same altitude (which isn't the case in reality). That is not the case with this web of satellites. If a chain reaction of collisions does occur, it would cause a field of tiny, fast, deadly debris all orbiting on a similar orbital "plane". It would pretty much blanket the planet. Wouldn't this cause a large issue for anything attempting to reach orbit? What am I missing here?

EDIT: A lot of replies here mentioning the fact that LEO spacecraft decay more quickly than higher orbits. Please note that not all LEO orbits are low enough to guarantee a quick decay without powered retrograde thrust. Stuff can hang up there in LEO a long, long time depending on the actual altitude.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#54

Post by ryanmarsh »

bargl wrote: post #33

This is such a cool problem. We already have a ton of Geo sat which can do this kind of communication but they are super expensive and have a limited bandwidth. These satellites will actually have a ton of limitations in how much data they can send around and how they'll have to balance out their signals. Geo are easier to point to because, well they don't move. But these are going to be moving and changing all the t…

My knowledge of satellite internet is circa 2004 when I was in the desert of Iraq.

For the client premises equipment it's a hard problem but entirely solvable. Frequency hoping radios have been around a long time. Link bonding has been around a long time. Which satellites will be in view, where, and when is knowable. I think the harder part will be the backhaul... in space.

I'm curious if they'll use beam shaping antennas for CPE. Surely they won't ship antennas with moving parts right? Also I'm curious about the power requirements of the CPE.

Another problem will be security. This is a known problem with satellite uplinks. They basically spray everyone's traffic all over God's green Earth and if you listen in you used to be able to grab lots of data right out of the sky. These days it should all be encrypted, even then some of the encryption was easily cracked.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#55

Post by detritus »

toomuchtodo wrote: post #44
detritus wrote: post #41

This is probably a stupid thing to ask, but: Could this setup be hacked to provide a loose form of GPS?

Not stupid. Sort of. The term you're looking for multilateration (edit: i'm twisting the term a bit for my own use here, it's not exactly multilateration but it's not exactly triangulation either). Without looking at the RF specd in the FCC docs or the satellite hardware part list, I'm not sure if you could do it on the receiver, but it would be straightforward for the constellation visible to the receiver to triangu…

Thanks! I didn't know the term ( https://en.wikipedia.org/wiki/Multilateration ).

I was thinking of WW2 radio pinging when I asked. I'm sort of imagining a software simulation that has real-time updates of sat positions - I assume more than 3 in any useful domain - that checks delay/ping against where the sats actually are.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#57

Post by DowsingSpoon »

airnomad wrote: post #38

Why do they need approval for this? It's not like Space is owned by anyone?

The radio spectrum is limited, and belongs to the people. Careful regulation ensures it remains usable. Likewise, regulating orbits is important. For example, to limit potential damage from space debris.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#58

Post by Rooster61 »

airnomad wrote: post #38

Why do they need approval for this? It's not like Space is owned by anyone?

Why do owners of airplanes need approval to fly? It's not like the air is owned by anyone?

Just because someone doesn't own something doesn't mean you can just launch stuff up there with no regard for other such things to be launched/already in the air. Things can and do collide, and the ramifications of that are actually much more dangerous when you don't have an atmosphere to pull the pieces down in the event of a collision.

Re: SpaceX just got FCC approval to launch 7,518 satellites

#59

Post by [deleted] »

detritus wrote: post #55
toomuchtodo wrote: post #44

Earlier quoted context omitted.

Not stupid. Sort of. The term you're looking for multilateration (edit: i'm twisting the term a bit for my own use here, it's not exactly multilateration but it's not exactly triangulation either). Without looking at the RF specd in the FCC docs or the satellite hardware part list, I'm not sure if you could do it on the receiver, but it would be straightforward for the constellation visible to the receiver to triangu…

Thanks! I didn't know the term ( https://en.wikipedia.org/wiki/Multilateration ). I was thinking of WW2 radio pinging when I asked. I'm sort of imagining a software simulation that has real-time updates of sat positions - I assume more than 3 in any useful domain - that checks delay/ping against where the sats actually are.

[deleted]

Re: SpaceX just got FCC approval to launch 7,518 satellites

#60

Post by ryanmarsh »

dr_orpheus wrote: post #52
tgtweak wrote: post #45

Earlier quoted context omitted.

With about a thousand being in your horizon at any given time I don't think it'll be an issue to roam between them. In a Metropolitan area it's not rare to be around dozens of cell sites. Likewise cellular roaming is quite transparent.

Yes, but your cell tower aren't moving around relative to each other. And in order to get the data rates that they need at the speed they need, the signals between the satellites will be more focused rf or laser communication. So all of the satellites have to constantly know which satellite is closest to them and how to point antennas and/or lasers.

Yes, but your cell tower aren't moving around relative to each other.

Depends on the observer. If you move in a circle around a set of radios (driving around town) either you're stationary and the other radios are spinning or vice versa. Also, many satellites will share the same orbit, they will be stationary as far as each other are concerned.

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