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Comment by throwaway_yy2Di | Hacker News Reader

How close are we to space-based laser ISPs? I imagine that you squeeze terabits of optical bandwidth into a single mirror "dish"..

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The big problem is getting through the Earth's Atmosphere. Space observatories are nearly exclusively located on mountains or areas with little atmospheric 'pollution'. I'd imagine even the OPALS system can only be used when it's not too cloudy/rainy.

This technology does exist on land however. Free Space Optics[1] has been around for a while but hasn't taken off in a big way because it's less reliable than sending light down a fibre cable, even though it is cheaper.

[1] http://en.wikipedia.org/wiki/Free-space_optical_communicatio...

imagine a world where this was the norm. You wouldn't need to worry about outages due to falling trees or utility poles exploding or people screwing with your wires.

Then you step outside to look up at the sky and you lose your eyesight

Day of triffids scenario aside, no you won't lose your sight from a 2.5W laser pointing downwards from 260 miles up. The power level is too small.

People think that lasers produce a parallel beam. They don't - they are diffraction limited by the width of the beam. The narrower the beam, the more it spreads out. For example, a 1cm wide beam produced by a perfect laser would spread out to around 20m wide when it hits the ground from 260 miles away. That's assuming visible green light - if it's infra-red (or even just red) then the spread will be wider.

But it wouldn't work on a cloudy day, presumably.

Latency is a real problem. Distances to satellites in orbit are very long. Also, there is a scalability problem. How many ground targets can a satellite simultaneously provide service to? My guess is, not a lot.

This could be an incremental bandwidth (but not latency) upgrade over existing satellite internet service to remote areas (by transmitting to a single ground receiver that serves a local area), but that's about it.

"Distances to satellites in orbit are very long."

That's not a fundamental limit. Existing satellites have high latency, because they're sited at insanely high altitude -- ~36,000 km (6 earth radii; 120 light-milliseconds (-> 240 ms minimum round trip)). This is for engineering and economic reasons which aren't solid: one, because geostationary [0] orbits allow dumb dishes that can't track moving objects; and two, because it allows small satellite networks -- i.e. one satellite covering a whole continent -- commensurate with the small size of the market.

If instead you had a network of satellites at say 500-1,000 km (unjustified guess), the latencies could be no worse than a direct optical fiber.

edit: Here's a sophisticated diagram, https://i.imgur.com/t1SOVpZ.png

[0] https://en.wikipedia.org/wiki/Geosynchronous_orbit#Geostatio...

What you're describing is essentially a data version what the Iridium network provides. Iridium is a constellation of 66 satellites at 450 miles up. Unfortunately, when Iridium was launched, forward thinking wasn't part of the plan -- data is stuck at around ancient dialup modem speeds.

There were plans for similar services, such as Teledesic, which went nowhere. I guess that enough land-based internet covers the majority of the target market, so there isn't enough market left over to justify the cost of a high speed satellite data provider. Remember, in LEO orbit, the satellites have to be replaced after about 5 years or so (atmospheric drag, and they run out of booster fuel).

Lower cost to launch via Space-x reusable rockets may change the cost equations though.

Solar powered boosters and spaceodynamic lifting bodies.

If you're talking lasers though, don't forget to factor in the time needed to reacquire a new satellite in once the existing one goes over the horizon. The shorter the orbit, the more often you'd have to do this.

Fuck everything, we're doing five (simultaneous) lasers.

and we are using drones to deliver them, whether you like it or not

I actually have zero idea how such a thing could work, which is why I'm asking here. :)

If they had a way to have almost unlimited ground targets (maybe using a rotating mirror, or something like https://www.kickstarter.com/projects/117421627/the-peachy-pr...), I could deal with the not so bad ~240ms lag for most of my communications (if you aren't gaming), especially if it's faster then my slow cable connection....

Speed of light: ~299,792 km / s Geostationary orbit distance from earth: ~35,786 km

A grid of sats designing for blanketing the earth in comms is going to be at most 400 miles up, most of my packets go way further than 800 miles, so no, latency won't be an issue.

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