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SpaceX just got FCC approval to launch 7,518 satellites

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

#71

Post by ryanmarsh »

dr_orpheus wrote: post #48
Filligree wrote: post #31

Earlier quoted context omitted.

> Traditional satellite internet uses satellites in geostationary orbits, or 35,786km high above the equator. This is great because satellites in that orbit are stationary relative to the ground, so you just need a parabolic antenna pointed at a specific point in the sky to get great reception. But it's also terrible for latency because the signal takes 120ms just to get up, and another 120ms to get down. Assuming yo…

The latency from the distance light travels does not vary that much. The rest of the ~600 ms latency is caused by the same thing as latency on ground systems (routers, etc.). And the processors on spacecraft are not particularly fast.

Who builds routers that go in space? Cisco? That's got to be some crazy hardware.

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

#72

Post by zw123456 »

Tuna-Fish wrote: post #27
zw123456 wrote: post #13

Earlier quoted context omitted.

The amount of BW is based on how much spectrum you have (see Shannon's Law). I am not sure how much they have. Also, I am not sure they will have enough power to provide in building service.

> Also, I am not sure they will have enough power to provide in building service. The issue for that is the wavelengths they are using. Their properties basically completely rule out any kind of in-building service, there needs to be a clear uninterrupted path between the receiver and the transmitter. (But they penetrate water well, so should not have a problem with clouds.)

FCC-18-38A1.pdf say 10.7Ghz - 12.7Ghz, that's a lot of spectrum. Depending on the SINR they get, which depends on the power, antenna sizes etc. you could get some pretty good speeds, probably above 100Mbps. But at those frequencies not likely to have any in car or in building. You can penetrate a building with higher frequencies if you have high enough power levels, but not from a satellite. So to use it you will have to install an antenna on the roof of your house.

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

#73

Post by ryanmarsh »

jacquesm wrote: post #25
wongarsu wrote: post #17

Earlier quoted context omitted.

"Regular old satellite internet" is very high latency because it's few satellites in high orbit. SpaceX is doing many satellites in low orbit, resulting in much shorter paths and low latency. Latency for medium to long distances could be better than regular fiber, both because of straigher paths and because speed of light in the relative vacuum of the satellites' orbits is higher than speed of light in fiber. We don'…

I'd expect the first and easy goal to be to sell high speed access to airline passengers.

Considering how hard it is to get a cell signal inside a plane on the ground, and that these will require special CPE, and the airlines can't change the equipment on a plane without a ruling by the FAA, I wouldn't bet on it.

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

#74

Post by dr_orpheus »

ryanmarsh wrote: post #60
dr_orpheus wrote: post #52

Earlier quoted context omitted.

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.

True, the satellites within the orbital plane will remain close to stationary to each other. There will be some perturbations, but generally will be stationary relative to each other. In one of the plans I saw floating around the inter-satellite links within the orbital plane will basically be stationary laser links between the satellites. And the cross-links between the orbital planes will be done with phased array antennas so they can be electrically steered instead of physically steered.

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

#75

Post by zackbloom »

Rooster61 wrote: post #53

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). Tha…

Think how big the Earth is. How hard it would be to find a Xerox machine in the Amazon or the middle of the Atlantic if someone stuck it there. Space is much, much, bigger.

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

#76

Post by ryanmarsh »

tomatotomato37 wrote: post #70
ilrwbwrkhv wrote: post #2

i think the price should be around 35 dollars per month

For a ~$10 billion constellation with an individual satellite lifespan of 5 years, the system would need to average ~$170 million per month for something resembling break-even. Current US satellite internet adoption is at 6.7% percent; push that up to 10% so I have some number to work with when accounting for market penetration and the rest of the world, and you’re looking at 32.5 million users, which sets an absolut…

Current US satellite internet adoption is at 6.7% percent

Current US satellite adoption doesn't matter in this case because the new product would not suck. Satellite internet is not a viable competitor today for the various reasons others have stated here. Starlink however would compete directly with my DSL service and since I (and pretty much everyone else) hate our telco, the sky is the limit as they say.

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

#77

Post by Rooster61 »

wufufufu wrote: post #61
Rooster61 wrote: post #53

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). Tha…

This is a well informed answer to your question: https://www.quora.com/Why-dont-satellites-crash-into-each-ot...

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).

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

#78

Post by thinkcontext »

The fact that SpaceX can piggyback on its own customers' launches to put these in orbit is a significant advantage over competing communication constellations.

Depending on the cost of their satellites it might make sense to use launching them as a means of testing the upper limits of reusability of their rockets. IE, they might not want to risk a customer payload on a rocket that has made 10 launches. But if they are going to build 7,518 satellites the marginal cost is likely to be rather low so it might be worth it to push the risk threshold to stretch the number of trips per rocket. Also, it could be a good opportunity to clear out their inventory of pre-block 5 Falcon 9s.

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

#79

Post by Rooster61 »

zackbloom wrote: post #75
Rooster61 wrote: post #53

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). Tha…

Think how big the Earth is. How hard it would be to find a Xerox machine in the Amazon or the middle of the Atlantic if someone stuck it there. Space is much, much, bigger.

I'm no stranger to the vast physical space at play here (amateur astronomer, here). I'm aware there is a LOT of room for this stuff to move around, but there is still a threshold, however high, to where the amount of debris would become dangerously numerous.

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

#80

Post by vkou »

airnomad wrote: post #38

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

When nobody owns something, we collectively own it. This means that we need to make sure that one bad, or reckless actor does not ruin it for everyone else. [1]

[1] https://en.wikipedia.org/wiki/Kessler_syndrome

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