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The First Detailed Look at How Elon Musk's Space Internet Could Work (newscientist.com)
SpaceX has been granted permission by the Federal Communications Commission (FCC) to set up a vast network of thousands of low Earth orbit communication satellites. But the company has been tight-lipped about the project, known as Starlink. Mark Handley, University College London built a simulator based on public details from the FCC filings to understand the latency properties of the network. New Scientist reports: Although Musk has said he wants more than half of all internet traffic to go through Starlink -- Handley's simulation suggests that the project will be most appealing to high-frequency traders at big banks, who might be willing to fork out large sums for dedicated, faster connections. To create the simulation, Handley took what information he could from SpaceX's public FCC filings and combined this with his knowledge of computer networks. Initially, Starlink will consist of 4425 satellites orbiting between 1100 and 1300 kilometres up, a greater number of active satellites than are currently in orbit. There is only one way to arrange this many in a configuration that minimises collisions, says Handley. So he is confident that his simulation reflects what SpaceX is going for.
When sending an internet message via Starlink, a ground station will begin by using radio waves to talk to a satellite above it. Once in space, the message will be fired from satellite to satellite using lasers until it is above its destination. From there, it will be beamed down to the right ground station using radio waves again. Between distant places, this will allow messages to be sent about twice as fast as through the optical fibres on Earth that currently connect the internet, despite having to travel to space and back. This is because the speed of the signal in glass is slower than it is through space.
When sending an internet message via Starlink, a ground station will begin by using radio waves to talk to a satellite above it. Once in space, the message will be fired from satellite to satellite using lasers until it is above its destination. From there, it will be beamed down to the right ground station using radio waves again. Between distant places, this will allow messages to be sent about twice as fast as through the optical fibres on Earth that currently connect the internet, despite having to travel to space and back. This is because the speed of the signal in glass is slower than it is through space.
Solving the worlds problems, step by step.
No sig today...
Just dropping by to mention that, while existing fiberoptic networks have index of refraction around 1.7 (so signal speed is c/1.7) , there is a relatively new thing referred to as "holey fiber." It's essentially analogous to microwave hollow guides, with the hole pattern sized to match the TE/TM modes of the injected light. The speed thru these waveguides is close to the vacuum limit.
https://app.box.com/WitthoftResume Code: https://github.com/cellocgw
High speed trading looking for a timing edge has already upgraded to shortwave which traverses an even shorter distance (bouncing through the lower atmosphere) right at the speed of light.
https://sniperinmahwah.wordpress.com/2018/05/07/shortwave-trading-part-i-the-west-chicago-tower-mystery/
Iridium et al. Just a bunch of space junk now.
Is it? Iridium's problem was lack of customers who needed the service and had money to pay for it. Prices where so high that few people in areas that didn't have cellular service already could afford to pay the subscription fees. Their business model wasn't viable.
In this case, there is actually a different business model and possible paying customers who actually have money and a need for internet service. Are there enough of them who have enough money to make this viable? Maybe... Given Musk's access to exceptionally low cost launch rates, this might just work out this time. I'd not bet on it either way myself.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
SpaceX's revised FCC filing calls for about 1.6k of the initial 4.4k constellation to be at 550km orbit. Brings the minimum latency down to 15ms, instead of 25-35ms.
https://www.theverge.com/2018/...
https://forum.nasaspaceflight....
"'Tis great confidence in a friend to tell him your faults, greater to tell him his." --Poor Richard's Almanac
Iridium's problem was...
Actually, AMONGST Iridium's problems was that it was not designed as a data transport system, and the horrible data capabilities that they offered were based on running a modem over their voice lines.
Iridium Next will expand those offerings to 128 kb/s to mobile, 1.5 Mb/s to marine and 8 Mb/s to fixed land stations.
This leaves a lot of room for improvement and Musk might force iridium's hand to provide faster upgrades than their 20 year turn around on iridium to Iridium Next
Problem is, fiber on the ground is faster as the distance is shorter.
Only true in general for relatively short trips with fixed destinations.
Unless you live in some remote place that depends on geo-stationary satellites for internet, you are better off going along the ground, at least where latency is concerned.
A) These are not geo-stationary satellites SpaceX is proposing. Geostationary orbit is about 35,700km away versus the 1200km being proposed here. That difference is very significant. B) Ground is only faster in some use cases but not all and the longer the transmission the less advantage it has.
The lower latency could be useful for games, too.
Probably not, because the potential savings scale with distance. Halfway across the world and back is 40000 km/300000 km/s = 133 ms at light speed, at c/1.7 it's 226 ms so at most 93 ms to save. But I wouldn't try to play a twitch game at those ping rates while at reasonable gaming ping times the gains are mostly eaten up by the base latency. Unless you really desperately want to play with your guild from another continent, it's not going to matter much. It mainly matters for HFT where your buy/sell orders arrive a few milliseconds before the competition.
Live today, because you never know what tomorrow brings
Who gave them the authority to do that? They should probably only be allowed to have a say about the airspace above the US.
Yes, I'm left. You have a problem with that?
I still prefer the notion of a network of ocean line-dancing sharks supporting a mesh net of laser beams just skimming the surface.
The training and fish bill is high, and this network facilitates phishing too, but you can't have everything.
Rgds
Damon
http://m.earth.org.uk/
Glass is 31% slower, not a rounding error. Speed of light through air is much closer to matching your description. While this article from 2013 talks about using air-based conduits, I don't think it's reached full deployment yet.
Fortunately, I have them.
Space Communications Protocol Specifications
Consultative Committee for Space Data Systems
CCSDS Technical Specifications
Space Assigned Numbers Authority
Spacecraft ID list and manual
Disruption Tolerant Networking
Exploration and Space Communications at NASA
Free Space Optical Communication
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Rule of thumb: light does:
* 1 m / 3 ns - signal in vacuum
* 1 m / 4 ns - signal in copper wire
* 1 m / 5 ns - signal in fiber optic cable
It's a lot slower in in a bent fiber optic cable, of course, but long runs are effectively straight.
Socialism: a lie told by totalitarians and believed by fools.
Handley's simulation suggests that the project will be most appealing to high-frequency traders at big banks, who might be willing to fork out large sums for dedicated, faster connections.
Well that's just dumb. High frequency traders at big banks merely locate their data center / computing presence in close physical proximity to the point where the trades occur. Relying on a massive, expensive space network to come into existence just for high frequency trading is absurd.
This will most appeal to the millions of people that do not have broadband. The money to be made is in the masses, not in "high-frequency traders at big banks".
Better known as 318230.