Building a Space-Based ISP • Hacker News Board

Re: Building a Space-Based ISP

#51

Post by Robotbeat » Thu, May 13, 2021, 2:10 AM UTC

marsokod wrote: post #14

p1mrx wrote: post #10

Earlier quoted context omitted.

I think the most exciting part is their use of electric ion propulsion to maintain low earth orbit. If SpaceX ever goes bankrupt or something, the satellites will passively deorbit within 5 years or so.

No need for that actually. They will deorbit within a year if left completely dead, and within a couple of month if they have a single button "start deorbiting" that uses the electric propulsion. But more importantly, their propulsion allows them to launch at a very low orbit. This is a very good method for a constellation as they can see all the early failures (the beginning of the bathtub curve) happen at a very lo…

Yup, and I think this could be improved further by using even lower orbits. Improves latency, debris, and reduces visible time (i.e. closer and closer to only visible during twilight... plus the closer distance increases apparent angular speed and thus reduces dwell time per pixel) for ground telescopes. Requires a bigger propulsive burden, but this is worth it, IMHO.

Re: Building a Space-Based ISP

#52

Post by ctdonath » Thu, May 13, 2021, 2:28 AM UTC

giantrobot wrote: post #50

ctdonath wrote: post #47

Earlier quoted context omitted.

Additional napkin math: If we’re going to take the “precious resource” argument seriously, let’s. One Starlink satellite can earn ~$25M/year, setting the value of that slot. This seems a reasonable value for LEO “homesteading”; if someone wants it, that’s a fair price to pay. And I do mean fair, seeing as it’s SpaceX inventing the technology, building the satellites, staking claims, and otherwise being first-mover an…

The whole "orbital slot" thing is absurd. Space is really big. Like, really big. And orbital mechanics being what it is, you could launch a satellite in the exact same orbit as a Starlink satellite but trailing a few miles behind and they'll never impact one another. If they are using totally different uplink and downlink frequencies they'll be effectively invisible to ground stations of competing services. That bein…

Agreed. It was an attempt to take the issue as raised and see what the consequential ballpark numbers are.

Re: Building a Space-Based ISP

#53

Post by new_realist » Thu, May 13, 2021, 2:47 AM UTC

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…

You forgot about the latency of going through the atmosphere, and the Manhattan distance between the satellites.

Re: Building a Space-Based ISP

#54

Post by ncmncm » Thu, May 13, 2021, 5:01 AM UTC

new_realist wrote: post #53

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…

You forgot about the latency of going through the atmosphere, and the Manhattan distance between the satellites.

I cited the latency going through the atmosphere, 1.8 to 2.5 ms, in the very post you clicked "reply" on, very evidently without, you know, reading it. (Not reading saves time, but you know what else does? Not posting.)

And there is no "manhattan distance". Satellites (will) have a laser pointing to the next one in their orbit, and one pointing back. That's all.

Re: Building a Space-Based ISP

#55

Post by hackeraccount » Thu, May 13, 2021, 11:20 AM UTC

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.

I agree with that. Also I used to run road races so I know 10K is 6.2 miles - it also helps because I have a feel for just what 10K means if you follow.

Also - drive around and you more or less know what 100kph is in a car.

But mainly - I understand the point but the reasonable complaining gets mixed up - in a frankly counter-productive way - with political signaling.

Re: Building a Space-Based ISP

#56

Post by giantrobot » Thu, May 13, 2021, 3:57 PM UTC

ctdonath wrote: post #52

giantrobot wrote: post #50

Earlier quoted context omitted.

The whole "orbital slot" thing is absurd. Space is really big. Like, really big. And orbital mechanics being what it is, you could launch a satellite in the exact same orbit as a Starlink satellite but trailing a few miles behind and they'll never impact one another. If they are using totally different uplink and downlink frequencies they'll be effectively invisible to ground stations of competing services. That bein…

Agreed. It was an attempt to take the issue as raised and see what the consequential ballpark numbers are.

Yeah sorry I wasn't trying to call you out just point out an additional complexity to the numbers. If Starlink was going to sell an "slot" to a competitor (not that they would need to), they'd be selling an orbital plane rather than a single satellite's position. The cost of that plane wouldn't be some fixed value but the gross revenue from all the subscribes covered by that plane.

The planes that cover mostly empty ocean would be far less valuable than ones that covered subscriber-dense populations. But of course that's in a world where somehow a competitor needs to buy a "slot" from Starlink and not just orbit a few miles higher in the same plane.