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Building a Space-Based ISP

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Re: Building a Space-Based ISP

#31

Post by ncmncm »

HALtheWise wrote: post #22
azernik wrote: post #11

Earlier quoted context omitted.

Essentially: They have one address range for shared (i.e. subject to syncing across all replicas) memory, and a separate one for non-shared (single-replica) memory. Cross-replica data is presumably subject to their agreement algorithm, checking that the different computers reach the same (within some error bars) results; you want to arrange things so that there are frequent checkpoints at which the conflict resolutio…

That makes sense. One part I'm still not clear on is how you accomplish a "restore" to fix the broken state of a process with a bitflip. Is it enough to simply copy all the shared state memory over as a block and jump into executing it? That seems like it would require the invariant that shared memory never references private memory, and I'm not sure how to statically enforce that.

You probably have hardware that watches ECC flags. For a correctable one-bit flip, it triggers a read-and-then-write. For a two-bit flip, it might just kill and restart the process, or reset the whole machine. As long as it doesn't happen too often, it's fine: the whole system (constellation and ground nodes) are designed to accommodate such events.

Re: Building a Space-Based ISP

#32

Post by benlivengood »

kevin_thibedeau wrote: post #24
Diederich wrote: post #5

Earlier quoted context omitted.

> Starlink is fundamentally not about providing broadband to anyone. This reply brought to you over a robust, fast, low latency and reliable Starlink connection.

Wait til you have 1000 neighbors vying for bandwidth.

The most pessimistic estimate I've seen paid for by the cable industry is here: https://ecfsapi.fcc.gov/file/10208168836021/FBA_LEO_RDOF_Ass...

Only if each subscriber is using an average of 15-20 Mbps during peak times will about 50% of subscribers see some throttling.

Interestingly they only showed a single graph of average bandwidth over time from a cable company to estimate needs for SpaceX. No clue if they actually separated it out by time zone for each coverage area in their actual analysis.

Re: Building a Space-Based ISP

#33

Post by nynx »

lutorm wrote: post #25
nynx wrote: post #3

Starlink is super exciting from an emerging technologies perspective —— (relatively) cheap satellite production, commercialized laser links, commercialized phased-array tx/rs, among others. These open up very interesting possibilities down the road. These posts always have a thread about people wanting to work for spacex, but because of my pseudo-anonymity, I don’t feel bad about starting it: Does anyone know if spac…

https://www.spacex.com/internships/

Unfortunately, it still says summer 2021.

Re: Building a Space-Based ISP

#34

Post by cryptonector »

ctdonath wrote: post #26
mnd999 wrote: post #2

Puff piece. Starlink is fundamentally not about providing broadband to anyone. It’s landgrabbing a finite resource - low-earth orbit space - before it’s worth is recognised by those who should be regulating it. The broadband itself might be nice or it might be awful. It doesn’t actually matter because that was never the point.

Right, it's not about taking a major share & expansion of a trillion-dollar industry with payout starting immediately, it's about staking out a thin fraction of (literally) empty space and waiting decades for others to start needing small portions of it. Because $99/month * 12 months * 10 years * 1,000,000,000 customers = $11.88T isn't the point to a man who literally needs a trillion dollars to pull off the grandest…

It's not clear what you're saying. Are you saying that SpaceX will end up consuming too much of a precious resource? Or something else?

Anyways, I don't buy that SpaceX will end up consuming too much of a precious resource. Even if it were so, what would be a fair way to share that resource, and who even with?! There's only one announced competitor to Starlink at this time, and they're not even remotely close to being operational. What makes SpaceX able to put up Starlink at such low cost (compared to its earning potential) is that SpaceX has lowered launch costs for itself (and others) by a lot, and they're working to lower those costs even more. What is "fair" when a company works so hard to lower costs and increase availability? Is it to punish them so others get a chance to compete at higher costs??

Re: Building a Space-Based ISP

#35

Post by nonameiguess »

ncmncm wrote: post #23
cute_boi wrote: post #7

"Starlink is currently in orbit at 340 miles" Can we please stop using miles etc :( I am tired when people makes mistake like this.

Yes, the useful unit is light-milliseconds: $ units You have: 340 mi You want: light ms * 1.8251859 / 0.5478894 So, 3.6 ms round-trip. In practice, the route will be slanted, so could just exceed 5 ms. $ sudo apt install units Once the constellation is mature, certain very-high-paying subscribers will get the packets forwarded from one satellite to the next via laser links, across oceans, before being downlinked, and…

Military already has this: https://en.wikipedia.org/wiki/Wideband_Global_SATCOM

The SpaceX edge here is making this kind of thing cheaper and scalable to the point that a global community of hundreds of millions of users can multiplex signals on it, but for a sufficiently well-funded organization with fewer users, it was already possible.

Re: Building a Space-Based ISP

#36

Post by Diederich »

kevin_thibedeau wrote: post #24
Diederich wrote: post #5

Earlier quoted context omitted.

> Starlink is fundamentally not about providing broadband to anyone. This reply brought to you over a robust, fast, low latency and reliable Starlink connection.

Wait til you have 1000 neighbors vying for bandwidth.

Starlink isn't about directly competing against high density fiber connected internet. It's about everyone else.

Re: Building a Space-Based ISP

#37

Post by cryptonector »

lutorm wrote: post #28
krapht wrote: post #16

Earlier quoted context omitted.

People who get irritated over units of measure are themselves irritating. It is not so hard to round, double it 4 times and then divide by 10.

For practical purposes, I get by 99% of the time with 1 (statute) mile == 1.5km.

The conversion factor is very close to the golden number, so if you just remember the Fibonacci sequence up to around 89 you'll be able to do mental conversions easily enough.

E.g., what's 65mph in kmh? Well, the nearest Fibonacci number to 65 is 55, so 65 == 55 + 10, and the next Fibonacci number to 55 is 89, so 65mph will be 89kmh + ??, now we turn to 10mph and notice it's 8 + 2, so it's really 13kmh + 3kmh, which brings us to 65mph ~= 89kmh + 13kmh + 3kmh = 105kmh. My calculator says the actual conversion of 65mph to kmh is 104.60736, so... that's really close!

This is a very fun little mental exercise to do. Obviously it works in both directions.

Let's apply it to 340mi. The bracketing Fb numbers are 233 and 377. 377 - 340 == 33. Next after 377 is 610, so 377mi ~= 610km. Next after 33 is 55, so 340mi = 377mi - 33mi ~= 610km - 55km = 555km. My calculator says it's 547.17696km. Close!!

Re: Building a Space-Based ISP

#38

Post by skissane »

krapht wrote: post #16
azernik wrote: post #12

Earlier quoted context omitted.

Kilometers. If they're writing for a US audience and absolutely need miles, put one or the other in parens after the "main" one.

People who get irritated over units of measure are themselves irritating. It is not so hard to round, double it 4 times and then divide by 10.

When US-based companies put things in US measurements and don't provide metric conversions, it makes me (as a non-American) feel like they aren't thinking about their non-US customers. It appears parochial.

Miles I can roughly convert in my head, but I have really no idea what a gallon or a fluid ounce is. I remember a pound is a bit under 500 grams but can't remember how many ounces in a pound. Fahrenheit to Celsius, I know there is a 5/9 and a 32 involved, but I don't remember exactly what to do with them.

What makes it worse here is that the original measurement was in kilometres – kilometres are the standard unit for measuring orbital altitudes in the space industry, even in the US-based space industry – and someone has gone to the trouble of converting that to miles and then omitting to include the original measurement.

Re: Building a Space-Based ISP

#39

Post by ctdonath »

cryptonector wrote: post #34
ctdonath wrote: post #26

Earlier quoted context omitted.

Right, it's not about taking a major share & expansion of a trillion-dollar industry with payout starting immediately, it's about staking out a thin fraction of (literally) empty space and waiting decades for others to start needing small portions of it. Because $99/month * 12 months * 10 years * 1,000,000,000 customers = $11.88T isn't the point to a man who literally needs a trillion dollars to pull off the grandest…

It's not clear what you're saying. Are you saying that SpaceX will end up consuming too much of a precious resource? Or something else? Anyways, I don't buy that SpaceX will end up consuming too much of a precious resource. Even if it were so, what would be a fair way to share that resource, and who even with?! There's only one announced competitor to Starlink at this time, and they're not even remotely close to bein…

Sorry about the mess, that comment was dripping with sarcasm.

1. There's a lot of room up there, and actually claiming & using it is a normal process for civilizing frontiers.

1b. Handwaving about "underappreciated precious resources" is a waste of opportunity. I get the sentiment, but belongs in the 3rd part of the aphorism "lead, follow, or get out of the way."

2. Saying "SpaceX isn't in it for the money" is ridiculous, considering they could gross >$10T in the next decade with it, at ridiculously low expenditure.

2b. In that timeframe, other businesses would be just barely starting to seek out a small fraction of that "precious resource".

Re: Building a Space-Based ISP

#40

Post by izend »

nonameiguess wrote: post #35
ncmncm wrote: post #23

Earlier quoted context omitted.

Yes, the useful unit is light-milliseconds: $ units You have: 340 mi You want: light ms * 1.8251859 / 0.5478894 So, 3.6 ms round-trip. In practice, the route will be slanted, so could just exceed 5 ms. $ sudo apt install units Once the constellation is mature, certain very-high-paying subscribers will get the packets forwarded from one satellite to the next via laser links, across oceans, before being downlinked, and…

Military already has this: https://en.wikipedia.org/wiki/Wideband_Global_SATCOM The SpaceX edge here is making this kind of thing cheaper and scalable to the point that a global community of hundreds of millions of users can multiplex signals on it, but for a sufficiently well-funded organization with fewer users, it was already possible.

The military system is orbiting at 32,000km, the latency is much higher than Starlink.
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