Author Topic: Starlink : General Discussion - Thread 1  (Read 1217390 times)

Online ZachF

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2560 on: 03/08/2019 12:05 am »
This thread estimates with downrange landing Block 5 can put 17.1t to LEO parking orbit. FCC filing shows each Starlink weights 386kg, so maximum # of satellites on this launch is 44.

The rocket could be volume constrained.

What is the max it could do with RTLS? Then we'll have a min/max range if it's doing ASDS.
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Offline PM3

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2561 on: 03/08/2019 01:32 am »
This thread estimates with downrange landing Block 5 can put 17.1t to LEO parking orbit. FCC filing shows each Starlink weights 386kg, so maximum # of satellites on this launch is 44.

What is that 386 kg?

- Dry mass?
- Wet mass for 340 km orbit?
- Wet mass for 550 km orbit, where the first batch of sats will go?
- Wet mass for 1110-1325 km orbit?

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Offline su27k

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2562 on: 03/08/2019 01:56 am »
This thread estimates with downrange landing Block 5 can put 17.1t to LEO parking orbit. FCC filing shows each Starlink weights 386kg, so maximum # of satellites on this launch is 44.

What is that 386 kg?

- Dry mass?
- Wet mass for 340 km orbit?
- Wet mass for 550 km orbit, where the first batch of sats will go?
- Wet mass for 1110-1325 km orbit?

I believe it's the wet mass for 1110-1325 km orbit

Offline Zed_Noir

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2563 on: 03/08/2019 06:08 am »
If each stack of 4 is about 2m high then the faring holds about 4 stacks, so 16 sats. About 7 tons of sats+dispenser. Seems like a reasonable payload for a first try.

SpaceX built the dispenser I would say it could hold 5 sats per stack for an even 20 sats. But depending on hight clearances, Payload guide says 13.1m so it could go an extra stack for 25 sats.

According to 2019 SpaceX Falcon user guide on page 37.

The main usable volume within the SpaceX payload fairing is a cylinder 4.6 meter in diameter and 6.7 meter high. Which I reckon that you can stacked 5 to 8 sats in 2 or 3 tiers.

There is room for 2 or 3 more sats on top of the dispenser stack.

So SpaceX can have between a low of 12 sats or a high of 27 sats inside the payload fairing. My guess is 15 sats in 3 tiers of 5 for the inaugural Starlink launch.

Offline Tomness

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2564 on: 03/08/2019 02:43 pm »
When do you guys think SpaceX will complete phase I of Starlink constellation? I am in the condrum of having horrible phone service for high speed internet, just little beyond rual fiber internet (I know!) & getting ViaSat or Hughes. I won't be able to game until Starlink or Rual Fiber. So I've been leanning to ViaSat with 2 year contract :( I am see if I can get to a 1 year with fiber or Starlink on the horizon

Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2565 on: 03/08/2019 07:49 pm »
If each stack of 4 is about 2m high then the faring holds about 4 stacks, so 16 sats. About 7 tons of sats+dispenser. Seems like a reasonable payload for a first try.

SpaceX built the dispenser I would say it could hold 5 sats per stack for an even 20 sats. But depending on hight clearances, Payload guide says 13.1m so it could go an extra stack for 25 sats.

According to 2019 SpaceX Falcon user guide on page 37.

The main usable volume within the SpaceX payload fairing is a cylinder 4.6 meter in diameter and 6.7 meter high. Which I reckon that you can stacked 5 to 8 sats in 2 or 3 tiers.

There is room for 2 or 3 more sats on top of the dispenser stack.

So SpaceX can have between a low of 12 sats or a high of 27 sats inside the payload fairing. My guess is 15 sats in 3 tiers of 5 for the inaugural Starlink launch.

22 satellites per launch would be a sweet spot because they are launching 66 satellites per orbit for the first constellation.  More is better of course...

Offline WormPicker959

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2566 on: 03/09/2019 08:09 pm »
If each stack of 4 is about 2m high then the faring holds about 4 stacks, so 16 sats. About 7 tons of sats+dispenser. Seems like a reasonable payload for a first try.

SpaceX built the dispenser I would say it could hold 5 sats per stack for an even 20 sats. But depending on hight clearances, Payload guide says 13.1m so it could go an extra stack for 25 sats.

According to 2019 SpaceX Falcon user guide on page 37.

The main usable volume within the SpaceX payload fairing is a cylinder 4.6 meter in diameter and 6.7 meter high. Which I reckon that you can stacked 5 to 8 sats in 2 or 3 tiers.

There is room for 2 or 3 more sats on top of the dispenser stack.

So SpaceX can have between a low of 12 sats or a high of 27 sats inside the payload fairing. My guess is 15 sats in 3 tiers of 5 for the inaugural Starlink launch.

22 satellites per launch would be a sweet spot because they are launching 66 satellites per orbit for the first constellation.  More is better of course...

Given that it's relatively easy to change planes, why would the number of satellites per launch be wedded to the number of eventual satellites per plane? (I'm making the assumption that it is easy to change planes, and I could be wrong about that)

In addition, 66/plane is the eventual goal - but in order to first operate a "minimum viable product", what is the minimum number of sats/plane that will allow a full mesh? Whatever that minimum is, that seems like the number to aim for per launch, if the plane change is more difficult than I'm assuming. Then you would only need one launch per plane (assuming all planes are necessary for a minimum mesh) to start service. I imagine they could get away with both fewer populated planes (12 maybe?) and planes with lower populations, but I could be very wrong about this.

Offline Roy_H

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2567 on: 03/09/2019 08:18 pm »
I don't think it is trivial to change planes. Also I don't know what the minimum number of satellites per plane is but the minimum number of satellites for operation is 812 IIRC.
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Offline Barrie

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2568 on: 03/09/2019 08:39 pm »
I don't think it is trivial to change planes. Also I don't know what the minimum number of satellites per plane is but the minimum number of satellites for operation is 812 IIRC.

AIUI it is changing inclination which is hard; moving between planes with the same inclination is more straightforward (Iridium did quite a bit of it).  I think Starlink was going to use 2 or 3 inclinations, but I'm lost on current state of play

Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2569 on: 03/09/2019 09:27 pm »
It takes time and propellant to change orbits.
The mission is designed around a balance including duration and how much propellant (mass) it carries these 5 to 7 year missions.
These 550 km orbits have more atmospheric drag than the higher orbits so they require more help from the engines.


Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2570 on: 03/09/2019 09:39 pm »
If each stack of 4 is about 2m high then the faring holds about 4 stacks, so 16 sats. About 7 tons of sats+dispenser. Seems like a reasonable payload for a first try.

SpaceX built the dispenser I would say it could hold 5 sats per stack for an even 20 sats. But depending on hight clearances, Payload guide says 13.1m so it could go an extra stack for 25 sats.

According to 2019 SpaceX Falcon user guide on page 37.

The main usable volume within the SpaceX payload fairing is a cylinder 4.6 meter in diameter and 6.7 meter high. Which I reckon that you can stacked 5 to 8 sats in 2 or 3 tiers.

There is room for 2 or 3 more sats on top of the dispenser stack.

So SpaceX can have between a low of 12 sats or a high of 27 sats inside the payload fairing. My guess is 15 sats in 3 tiers of 5 for the inaugural Starlink launch.

22 satellites per launch would be a sweet spot because they are launching 66 satellites per orbit for the first constellation.  More is better of course...

Given that it's relatively easy to change planes, why would the number of satellites per launch be wedded to the number of eventual satellites per plane? (I'm making the assumption that it is easy to change planes, and I could be wrong about that)

In addition, 66/plane is the eventual goal - but in order to first operate a "minimum viable product", what is the minimum number of sats/plane that will allow a full mesh? Whatever that minimum is, that seems like the number to aim for per launch, if the plane change is more difficult than I'm assuming. Then you would only need one launch per plane (assuming all planes are necessary for a minimum mesh) to start service. I imagine they could get away with both fewer populated planes (12 maybe?) and planes with lower populations, but I could be very wrong about this.

Someone calculated minimum number of satellites at 550 km and 35 degrees above the horizon... as I recall it was 11.

Offline WormPicker959

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2571 on: 03/09/2019 09:54 pm »

Someone calculated minimum number of satellites at 550 km and 35 degrees above the horizon... as I recall it was 11.

11 per plane? 11 total planes? 11 total sounds implausible, but I'd love to see the math.

Offline jketch

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2572 on: 03/09/2019 10:05 pm »

Someone calculated minimum number of satellites at 550 km and 35 degrees above the horizon... as I recall it was 11.

11 per plane? 11 total planes? 11 total sounds implausible, but I'd love to see the math.

If all you care about is having a satellite visible at all times, you really don't need too many. Iridium manages to achieve complete global coverage with only 66 satellites. They're at 775km, so you'd need somewhat more at 550km but it could probably be done with around 100. The bandwidth you could deliver to end users would probably be pretty low though.

Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2573 on: 03/09/2019 10:08 pm »

Someone calculated minimum number of satellites at 550 km and 35 degrees above the horizon... as I recall it was 11.

11 per plane? 11 total planes? 11 total sounds implausible, but I'd love to see the math.

If all you care about is having a satellite visible at all times, you really don't need too many. Iridium manages to achieve complete global coverage with only 66 satellites. They're at 775km, so you'd need somewhat more at 550km but it could probably be done with around 100. The bandwidth you could deliver to end users would probably be pretty low though.
Sorry I meant 11 per plane.

Offline Robotbeat

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2574 on: 03/10/2019 03:47 am »
When do you guys think SpaceX will complete phase I of Starlink constellation? I am in the condrum of having horrible phone service for high speed internet, just little beyond rual fiber internet (I know!) & getting ViaSat or Hughes. I won't be able to game until Starlink or Rual Fiber. So I've been leanning to ViaSat with 2 year contract :( I am see if I can get to a 1 year with fiber or Starlink on the horizon
I would bet you a beer that SpaceX won't be offering Starlink internet to consumers for the next two years, so don't let Starlink stop you. When your contract is up, Starlink may just be starting operations, optimistically.
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Offline AC in NC

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2575 on: 03/10/2019 02:37 pm »
When do you guys think SpaceX will complete phase I of Starlink constellation? I am in the condrum of having horrible phone service for high speed internet, just little beyond rual fiber internet (I know!) & getting ViaSat or Hughes. I won't be able to game until Starlink or Rual Fiber. So I've been leanning to ViaSat with 2 year contract :( I am see if I can get to a 1 year with fiber or Starlink on the horizon
I would bet you a beer that SpaceX won't be offering Starlink internet to consumers for the next two years, so don't let Starlink stop you. When your contract is up, Starlink may just be starting operations, optimistically.

And based on OneWeb's sellout of their initial capacity, early Starlink sales may be exclusively to business-class, high-value applications.

Offline WormPicker959

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2576 on: 03/10/2019 11:14 pm »

Someone calculated minimum number of satellites at 550 km and 35 degrees above the horizon... as I recall it was 11.

11 per plane? 11 total planes? 11 total sounds implausible, but I'd love to see the math.

If all you care about is having a satellite visible at all times, you really don't need too many. Iridium manages to achieve complete global coverage with only 66 satellites. They're at 775km, so you'd need somewhat more at 550km but it could probably be done with around 100. The bandwidth you could deliver to end users would probably be pretty low though.
Sorry I meant 11 per plane.

Thanks for the clarification. Do you know how many planes are required, minimally? I know they're aiming for 24 in the end, but could they get away with halving that at first? 11/plane, 12 planes is 132 sats. This could be accomplished in less than ten flights, and would allow a minimum network to be achieved. This could be accomplished fairly quickly - if they can produce the sats fast enough, by the end of the year I would imagine.

Would there be a benefit to build out a MVP with limited bandwidth like this? Start attracting customers, test along the way, setup ground stations/terminals? Once they start being able to demonstrate capability and take in revenue, it will go along way to shoring up investor support (if that's even necessary) and developing a customer base. On the other hand, launching a lackluster product might backfire or give it a reputation for sloth or low quality.

Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2577 on: 03/11/2019 12:19 am »

Someone calculated minimum number of satellites at 550 km and 35 degrees above the horizon... as I recall it was 11.

11 per plane? 11 total planes? 11 total sounds implausible, but I'd love to see the math.

If all you care about is having a satellite visible at all times, you really don't need too many. Iridium manages to achieve complete global coverage with only 66 satellites. They're at 775km, so you'd need somewhat more at 550km but it could probably be done with around 100. The bandwidth you could deliver to end users would probably be pretty low though.
Sorry I meant 11 per plane.

Thanks for the clarification. Do you know how many planes are required, minimally? I know they're aiming for 24 in the end, but could they get away with halving that at first? 11/plane, 12 planes is 132 sats. This could be accomplished in less than ten flights, and would allow a minimum network to be achieved. This could be accomplished fairly quickly - if they can produce the sats fast enough, by the end of the year I would imagine.

Would there be a benefit to build out a MVP with limited bandwidth like this? Start attracting customers, test along the way, setup ground stations/terminals? Once they start being able to demonstrate capability and take in revenue, it will go along way to shoring up investor support (if that's even necessary) and developing a customer base. On the other hand, launching a lackluster product might backfire or give it a reputation for sloth or low quality.

Calculating the minimum satellites per plane is straight forward you know the altitude and minimum degrees above the horizon. 
The satellites other planes all changing with respect to each other. 

Mark Handley video 

Assuming F9 can carry 24 or more satellites per launch I think Spacex will split them across two planes (1,12,6,18,...)


Online oldAtlas_Eguy

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2578 on: 03/11/2019 07:59 pm »
One of the questions going forward is the Sat build rate. If SpaceX ramped build rate after firing the Starlink senior management in October a launch in May would be about right for the build rate to have gotten to about 2 satellites per week. But even at that rate launches would be spaced about 3 months apart. Such that for 2019 there would be at most 2 more Starlink launches.

To increase the launch cadence build rates would need to increase. To get to 1 launch per month you would need to build 7 or 8 satellites per week.

It is possible that this first launch would be half full. Just to get a handful of the production satellites on orbit to do production design validation. If no issues requiring redesign, then the next launch would be a full complement sometime this fall toward end of year.
« Last Edit: 03/11/2019 08:00 pm by oldAtlas_Eguy »

Offline DistantTemple

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Re: SpaceX - now a satellite manufacturer (Starlink)
« Reply #2579 on: 03/11/2019 10:21 pm »
once they have a design to run with.... it doesn't look hard to ramp up production.... we're not talking 5000 per week here!!! But with many hundreds to make setting up a "production line" and quality control procedures properly will will be essential.... I bet there is a drive to keep the cost down and to keep them as simple as possible. - and designed for manufacture...
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