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Comment by mattcoles | Hacker News Reader

Do we have space in orbit for this? This is a lot of satellites and I also don't get how the latency can be so much lower than current satellite ISPs?

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1) Space is huge. This is a little like asking if there's enough space left in earths oceans to float a few thousand pingpong balls.

2) Present internet satellites are all in mostly geostationary orbits that are much further away then the proposed leo's. Realistically the ones we have now introduce a whopping 650ms. This will be a huge improvement.

> Present internet satellites are all in mostly geostationary orbits that are much further away then the proposed leo

What about the LEO systems such as Iridium, etc. (I forget which is owned by whom and what their statuses are)?

Iridium is in LEO, but the comms hardware itself is pretty slow (1 to 2+ seconds latency). The throughput is also very low (2 to 4 kbit/s).

Iridium is a great low-cost, low-bandwidth network though.

> This is a little like asking if there's enough space left in earths oceans to float a few thousand pingpong balls.

I'd be pretty nervous about throing 10k pingpong balls into the atlantic IF the collision of two pingpong balls was disastrous :)

Obviously these satellites will be carefully placed NOT to collied - but the effect of a collision is pretty bad. The problem is that any one of them might collide with some tiny piece of junk, turning it 1000 pieces of junk (which is now 1000x more likely to collide with something, and impossible to control). These satellites won't tip the scales, but it's a nightmare scenario that comes ever closer with every satellite launched.

Remember that space is 3d. Not only do you have the surface area of the entire earth + the area from where LEO starts. You can then stack layers on top of that.

No, collisions are a very real risk. In fact, they've already happened. In 2009, an Iridium satellite accidentally collided with a Russian satellite. Space-X is talking about quadrupling the number of existing satellites, so collisions will be more likely and the resulting debris increases the chances of subsequent collisions much more. This escalating effect is know as Kessler Syndrome (https://en.wikipedia.org/wiki/Kessler_syndrome).

To get an impression I think it's a good idea to start with these pictures taken from the ISS [0], which is at about 400 km altitude (it varies a bit but not that much)

- https://twistedsifter.files.wordpress.com/2015/04/nasa-earth...

- Spain: https://twistedsifter.files.wordpress.com/2015/04/nasa-earth...

Note that they are to the side, straight down you would see a much smaller area!

So the SpaceX satellites would be three times higher. Still, you can see you may need quite a few stations on the ground, and also why you need so many satellites. They will fly over the area very quickly and by then the communication will already have to have been handed over to the next one. There is so much earth to cover, with satellites much higher up you cover a much wider area and you can have them in a stationary orbit. Earth has a diameter of 12,742 km, I have to keep reminding myself that even the ISS is barely above the surface if you were to look at earth from a distance.

[0] Source: http://twistedsifter.com/2015/04/earth-day-gallery-by-nasa/

The 4,425 satellites will "operat[e] in 83 orbital planes (at altitudes ranging from 1,110km to 1,325km)," and "require associated ground control facilities, gateway Earth stations, and end-user Earth stations," Cooper said. By contrast, the existing HughesNet satellite network has an altitude of about 35,400km, making for a much longer round-trip time than ground-based networks

Yes, until some of the thousands of small satellites about to be launched (not just by SpaceX) star breaking down and creating space junk that will become a serious problem to the launch of new satellites and spacecraft

http://www.telegraph.co.uk/news/2017/04/20/mega-constellatio...

The SpaceX sats at least are planned to be in very LEO. Their orbit will degrade very quickly if left to their own devices. Heck, that might even be the plan. If sats are cheap enough to launch and produce, then each sat can crash into earth after say 2 years.

1,110km to 1,325km is actually a fairly high orbit. Estimated lifetime is 1000 years.

Well seeing as any future business in either rockets or satellite internet both depend on not creating space junk, I think they are pretty motivated to not let that happen.

Humanity is not so good at doing things in their best interests. We have over utilized any natural resource we have ever consumed often to our own determent.

Exactly. Evolution has not primed us with reward mechanisms linked to long term goals relating to pollution or over-utilisation of natural resources. Also financial incentives are often misaligned with these long term goals. As a result we have a tendency to create a mess - on land, in the oceans, in space, wherever we spread

My understanding is that all new satellites have plans for deorbiting when they reach the end of their lifespan.

That's the plan - but when you have thousands or tens of thousands of satellites malfunctions can happen. Also, lots of existing space debris orbiting the earth that can hit satellites

These low orbits aren't stable though, I think they only have a lifetime of 10-20 years before their lateral velocity decays and they de-orbit on their own, it's not like will just be stuck up there.

No, with orbit altitudes of 1,110km to 1,325km we're talking about many hundreds of years: https://www.nasa.gov/news/debris_faq.html - "Debris left in orbits below 370 miles (600 km) normally fall back to Earth within several years. At altitudes of 500 miles (800 km), the time for orbital decay is often measured in decades. Above 620 miles (1,000 km), orbital debris normally will continue circling Earth for a century or more. "

Ah, I was under the impression that to achieve 25ms latency you would need something very low but it seems to be almost anywhere in LEO would give you close to those speeds.

I was thinking of older speculative articles where HN discussions seemed to think they would only be 300-500 kilometers up, this article states otherwise.

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