Author Topic: Starlink v2 mini satellites  (Read 67119 times)

Offline FutureSpaceTourist

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Re: Starlink v2 mini satellites
« Reply #20 on: 02/26/2023 08:06 pm »
https://twitter.com/spacex/status/1629948869239873538

Quote
Argon Hall thruster tech specs:
- 170 mN thrust
- 2500 s specific impulse
- 50% total efficiency
- 4.2 kW power
- 2.1 kg mass
- Center mounted cathode

Offline Zed_Noir

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Re: Starlink v2 mini satellites
« Reply #21 on: 02/26/2023 08:11 pm »
Stupid question: How many per launch? This has a huge impact on concerns regarding space debris and astronomical impact.

Stack looks to be 20 high but it's not clear if there are multiple satellites in each layer.
SpaceX tweeted 21 per launch:

https://twitter.com/SpaceX/status/1629898239066480640?t=mNgtxYvARzRcMzgET8K5rA&s=19
The PLF volume wise can support 30 sats but mass wise will be around 20 depending upon factors such as launch site, launch azimuth and targeted inclination and seasonal weather.

They might upgrade to Extended Fairing with Recovery.
That would necessitate using Falcon Heavy as the combined payload stacks' wet mass is the constraint not the fairing. The stack is 9 minis short of the of the v1.0 stack height which was two parallel stacks of 30 totalling 60.

FH every month until Starship is launching would be wild.

It is even wilder. Considering that the Falcon Heavy for the Starlink v2 mini should be fully recoverable except for the upper stage. In theory one Falcon heavy core set could sustain the month launch rate for Starlink v2 mini.

The question is how many Starlink v2 mini in the Falcon extended payload fairing that  still allows the recovery of the cores?

Offline Robotbeat

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Re: Starlink v2 mini satellites
« Reply #22 on: 02/26/2023 08:25 pm »
2000W/kg is REALLY good specific power, I think?

The Busek 600W hall thruster is 2.6kg. 230W/kg, around an order of magnitude less.
https://www.busek.com/bht600
« Last Edit: 02/26/2023 08:32 pm by Robotbeat »
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Offline ZachF

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Re: Starlink v2 mini satellites
« Reply #23 on: 02/26/2023 08:35 pm »
2000W/kg is REALLY good specific power, I think?

The Busek 600W hall thruster is 2.6kg.

All the stats are pretty impressive considering argon fuel.

SpaceX is getting good at building them, not a surprising development factoring in the gigantic numbers of them they must build now. (Must be multiples the rest of the world combined?)
« Last Edit: 02/26/2023 08:37 pm by ZachF »
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Online oldAtlas_Eguy

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Re: Starlink v2 mini satellites
« Reply #24 on: 02/26/2023 09:03 pm »
2000W/kg is REALLY good specific power, I think?

The Busek 600W hall thruster is 2.6kg.

All the stats are pretty impressive considering argon fuel.

SpaceX is getting good at building them, not a surprising development factoring in the gigantic numbers of them they must build now. (Must be multiples the rest of the world combined?)
Overall it does better using argon than the Busek does using Xenon fuel. Plus its ISP increase over that of an Xenon Hal thruster will need 30% less fuel for same total Delta-V.

added: Correction For the V2 sats. That is >50% less fuel for same DV. From the Isp*9.8*LN(wet/dry) where using argon only 20% of V2 sat mass is fuel.

The V2 will be a "lively" as in highly and quickly maneuverable sat vs the V1's due to the much higher acceleration rates even with same number of thrusters and 2X the total mass. Giving the V2s about 2X the acceleration over that of V1 for same number of thrusters.
« Last Edit: 02/26/2023 09:33 pm by oldAtlas_Eguy »

Offline Zed_Noir

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Re: Starlink v2 mini satellites
« Reply #25 on: 02/26/2023 09:28 pm »
Wonder if SpaceX consider a Xenon version of their new Argon thruster for high performance usage?

Come to think of it, maybe their new Argon thruster is a derated variant of a Xenon thruster that SpaceX was working on. Until they realized the very limited availability of Xenon even before the Russians invaded Ukraine.

Offline Robotbeat

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Re: Starlink v2 mini satellites
« Reply #26 on: 02/26/2023 09:47 pm »
No, there is not nearly enough Xenon, and itís way too expensive to use Xenon.
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Online oldAtlas_Eguy

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Re: Starlink v2 mini satellites
« Reply #27 on: 02/26/2023 09:57 pm »
No, there is not nearly enough Xenon, and itís way too expensive to use Xenon.
A 3000 to 1 price difference per kg. The V2Mini sat holds 150kg of fuel so $150 for Argon and $450,000 for the same amount of Xenon.

Online oldAtlas_Eguy

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Re: Starlink v2 mini satellites
« Reply #28 on: 02/26/2023 10:06 pm »
An implication of use of this thruster is that with higher thrust it enables a quicker reaching of the orbital operational position. Instead of up to 3 months to reach its operations orbit after launch. It could be considerably shorter as in a month or even less depending on how much fuel usage is the optimum use amount for sat lifetime.

Online M.E.T.

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Re: Starlink v2 mini satellites
« Reply #29 on: 02/26/2023 10:33 pm »
We knew the v2 full sized satellites will have 4x the bandwidth of the v1.5 satellites. Guess I am a little surprised that v2 mini's have 4x the bandwidth.  Guess it makes sense,  other than the antennas which are half the size,  everything else in the payload is the same.  Smaller antennas just means they don't have the sensitivity and beam forming capabilities of their larger brothers.

Can not wait to see them in orbit... or not see them if the new coatings work.

Elon said the V2 sats would have ďalmost an order of magnitudeĒ more capacity than the V1.5ís. People interpreted that as meaning about 8 times more. So the miniís having 4 times more (or half that of the full size V2ís) seems about right.
« Last Edit: 02/26/2023 10:41 pm by M.E.T. »

Offline Robotbeat

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Re: Starlink v2 mini satellites
« Reply #30 on: 02/26/2023 10:38 pm »
No, there is not nearly enough Xenon, and itís way too expensive to use Xenon.
A 3000 to 1 price difference per kg. The V2Mini sat holds 150kg of fuel so $150 for Argon and $450,000 for the same amount of Xenon.
whatís your source for 150kg of propellant for V2Mini? I spitballed 20%, but it was totally made up.
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Offline Robotbeat

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Re: Starlink v2 mini satellites
« Reply #31 on: 02/26/2023 10:44 pm »
BTW, the reason why, ignoring price, Xenon is better than Krypton which is better than Argon is:
1) the higher atomic mass means higher density, easier to store with lower dry mass tanks and plumbing.
2) lower ionization energy per unit atomic mass, which means greater efficiency.

You have to ionize the gas in order to accelerate it typically but that ionization energy is typically totally lost. You can adjust the ISP to be as high as you want, but too low of an ISP means it takes a lot longer to reach your destination for a given input power. However generally, the efficiency increases with ISP as you already paid for the energy to ionize it so you can accelerate it as fast as you want and so the denominator of the loss ratio gets bigger, reducing the relative loss.

Xenon has the lowest per atom ionization energy of all the stable noble gases. It also is the heaviest. So it will be the most energy efficient to use. 131.2 amu for Xe, 83.8 amu for Kr, 40.0 amu for Argon.

If we assume we accelerate each of those atoms to 20km/s (about 2000s Isp), then theyíll have a kinetic energy of 272, 174, and 83eV, respectively.
12.13eV, 14.00eV, 15.76eV first ionization energy respectively. So if everything else is totally efficient, Xenon can be 96% efficient, Kr 92.6%, and Argon 84%. Or you can operate at higher Isp, so ionization losses become even less important.
« Last Edit: 02/27/2023 12:13 am by Robotbeat »
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Offline InterestedEngineer

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Re: Starlink v2 mini satellites
« Reply #32 on: 02/27/2023 03:31 pm »
I'm curious why bandwidth is the constraining metric.

The more subscribers (uplinks) you have the less likely all will be using bandwidth at the same time. 

I suspect that number of uplink connections per satellite is the constraining metric.  I guess that is kept as a trade secret.

Subscribers pay the bill, not bandwidth


Offline InterestedEngineer

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Re: Starlink v2 mini satellites
« Reply #33 on: 02/27/2023 03:32 pm »
are there any specs on the solar power system?  Can't find any

Online DigitalMan

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Re: Starlink v2 mini satellites
« Reply #34 on: 02/27/2023 03:35 pm »
I'm curious why bandwidth is the constraining metric.

The more subscribers (uplinks) you have the less likely all will be using bandwidth at the same time. 

I suspect that number of uplink connections per satellite is the constraining metric.  I guess that is kept as a trade secret.

Subscribers pay the bill, not bandwidth

I think ISP's in the EU had the same opinion. However they are currently trying to get the likes of Amazon and Netflix to pay for their network upgrades.

Offline DanClemmensen

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Re: Starlink v2 mini satellites
« Reply #35 on: 02/27/2023 03:41 pm »
I'm curious why bandwidth is the constraining metric.

The more subscribers (uplinks) you have the less likely all will be using bandwidth at the same time. 

I suspect that number of uplink connections per satellite is the constraining metric.  I guess that is kept as a trade secret.

Subscribers pay the bill, not bandwidth
The beams almost certainly share bandwidth using TDMA on the uplink and some sort of packet tags in the downlink. This allows for an effectively unlimited number of simultaneous users per beam, limited only by the bandwidth, unless the protocol designers made some extremely short-sighted decisions.

Offline FutureSpaceTourist

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Re: Starlink v2 mini satellites
« Reply #36 on: 02/27/2023 04:37 pm »
https://twitter.com/lrocket/status/1630260581658923009

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Wow, they've com a long way since my original spreadsheet!

Offline Asteroza

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Re: Starlink v2 mini satellites
« Reply #37 on: 02/28/2023 12:33 am »
An implication of use of this thruster is that with higher thrust it enables a quicker reaching of the orbital operational position. Instead of up to 3 months to reach its operations orbit after launch. It could be considerably shorter as in a month or even less depending on how much fuel usage is the optimum use amount for sat lifetime.

That recent research on overdriven thrusters made me think, for orbit placement could the thrusters be fed by the full power of the solar arrays in some sort of overdrive mode, then do maintenance propulsion with a smaller energy budget when the sat is transmitting?

Offline kevin-rf

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Re: Starlink v2 mini satellites
« Reply #38 on: 02/28/2023 02:13 am »
While Shell 4 satellites took up to three months to reach operational altitude,  they filled multiple orbital planes each launch and had to spend time drifting. The Shell 3 satellites which only filled one plane per launch reached operational altitude in two months.

Launching 21 satellites per launch it is reasonable to expect v2 mini's to all go to the same plane without needing to drift.  So, we should expect v2 mini's on station less than two months after each launch.
« Last Edit: 02/28/2023 02:24 am by kevin-rf »
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Online gongora

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Re: Starlink v2 mini satellites
« Reply #39 on: 02/28/2023 02:18 am »
Lots of changes.  The mirror film over the phased arrays, the deployment rods staying attached to the second stage.  Can't tell what the fold-out pieces on top of the solar arrays are.

https://twitter.com/elonmusk/status/1630394434847227909

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