SpaceX Wants Permission To Test Satellite Internet

An anonymous reader writes: SpaceX has filed documents with the FCC asking for permission to begin testing a project to serve internet access from space. "The plan calls for launching a constellation of 4,000 small and cheap satellites that would beam high-speed Internet signals to all parts of the globe, including its most remote regions." This follows news that Facebook and Google had stepped back their efforts in that arena. SpaceX could prove to be a better fit for the project, given that they need only rely on themselves for launching satellites into orbit. "The satellites would be deployed from one of SpaceX's rockets, the Falcon 9. Once in orbit, the satellites would connect to ground stations at three West Coast facilities. The purpose of the tests is to see whether the antenna technology used on the satellites will be able to deliver high-speed Internet to the ground without hiccups."

Comments

Re:Internet signals to all parts of the globe,

[JaredOfEuropa]

They are planning to test the concept in a few locations in the US. The FCC license they seek covers this test.

Re:There's already satellite internet

[pla]

It wouldn't take much to beat these. Both in speed and the bandwidth caps.

It would take a way to break the speed of light - Pretty tricky problem, that one!

As a former Hughesnet customer, yes, the cap sucks, but overall the system has acceptable bandwidth. The real problem? The god-awful latency.

Nothing any ISP can do will ever solve the basic limitation of physics that a satellite somewhere around 40,000km has a round-trip time over half a second (130ms per trip, times a minimum of four trips - Request from me to satellite, from satellite to ground, then the response from ground to satellite, finally from satellite to me).

Never mind making many games unplayable, this makes SSL all but unusable. Add a little bit of ground-based latency into the picture, and literally a quarter of the time the connection would time out before it could finish the several rounds of handshaking.

Viable satellite internet doesn't need more bandwidth or lower caps, it needs faster radio waves.

Challenges...

[rew]

Google and facebook have realized that some problems are not (economically) surmountable.

The problems are the following: The closer you fly your satelite to the earth, the more resistance it has from the atmosphere. The density of the atmosphere reduces by a factor of 100 each 46 km of height. So at "100km", you have about 10000 times less air than at the surface. Some people call that space. At 200km the air pressure is about 100 million times less than what it is over here. That is enough to have a reasonable decay rate of weeks/months/years. "skylab" came down after a few decades, right?

The further away you fly your satellites, the longer the travel times will be for the signals. This equates to ping-times. Hmm. 200km is 0.6 ms, quite acceptable. Both ways. 1.3ms. Still fine. Double the distance to 400km for slower decay times, and you're still about 10 times faster than a normal ADSL line. Acceptable. Not a problem. (the problem here is the same for everybody. The satellites will then play "pass the hot potato" to one that's flying above the ground station and beam your packet down to earth. Assuming your halfway around the globe, that will be about 10000 km. That's with 66ms (round trip) already more than what you get with a residential ADSL line. Still not too shabby.)

The problem with putting satellites high is that the distance to the user becomes large. You want them as close as possible.

The closer you put them, the more you need. -> 4000 of them. This however is not just a one-time investment: because they are low, their orbits decay and they fall back to earth on relatively short notice. If you need 4000 of them, they are not going to be large. So they are small. If you have a cubesate (10cm cubed) weighing 1kg, its orbit will decay just like a 100kg satellite of 10x100x100cm (flying the wrong side towards the front). But a bigger satellite is likely to be 100x100x100cm and weigh not 100, but 1000kg. The extra weight helps keep it in orbit, the extra size in the flying direction does not make a big difference. So the small satellites decay fast as well!

Re:Challenges...

[DerekLyons]

At 200km the air pressure is about 100 million times less than what it is over here. That is enough to have a reasonable decay rate of weeks/months/years. "skylab" came down after a few decades, right?

Depending on the satellite's drag and ballistic coefficient, below around 200km you're talking hours to days, at 300km - days to weeks at the outside. Unboosted, anything between (roughly) 300 to 350km is essentially gone within a year. That's why Skylab was and ISS is, higher still - in the 400km range.

Skylab's second stage (seperated after the station was in it's final orbit) re-entered after only two years, while the station itself was reboosted on several occasions by docked Apollo spacecraft. Skylab's post occupation lifetime was extended by giving it a larger than normal reboost before the final manned mission departed, and subsequently by carefully maintaining it in a low drag orientation.

The ISS requires regular reboosts to maintain altitude.

Re:4000

[taiwanjohn]

I saw a video of the announcement in Seattle a few weeks ago, and I'm pretty sure he mentioned the number 1,100 km when asked about the altitude. But since then I've heard 6~700 km from another source. Anyway, the idea is to be high enough so that you can join any two points on the globe in only 3~5 hops. He said this would be faster than terrestrial backbone, where you typically have 15 or 20 hops between A and B, each of which adds latency in the form of processing time, not to mention that light travels almost twice as fast in vacuum as it does in fiber.

Re:4000

[taiwanjohn]

Just re-watching the video: He gets into the specs at around 3:30, citing a goal of 1Gbps @20~30ms latency a couple of minutes later. At around 9:30 he specifically mentions 1100 km for the altitude.