Jump to content

Starlink and other megaconstellations (updates and concerns). The Crowded Sky or how to summon Kraken IRL.


kerbiloid
 Share

Recommended Posts

From wiki.

Phase Orbit shells (km) Number of satellites Inclination

(degrees)

Half size contractual completion time Full size contractual completion time Current completion (23 May 2019)
1
550 1,584 53 March 2024 March 2027 62[43]
1,110 1,600 53.8 0
1,130 400 74 0
1,275 375 81 0
1,325 450 70 0
2
335.9 2,493 42 November 2024 November 2027 0
340.8 2,478 48 0
345.6 2,547 53 0

So, they distinguish 335, 340, and 345 km orbit, and as well 1110 and 1130.
They also distinguish 53° and 53.8°, i.e. 0.2° = 12' ~= 12 nm ~= 22 km.
So, this gives us a mesh step ~= 5..20 km in their sat pattern.

Total area of a sphere of radius:
330 km = 4 * pi * (6370+330)2 ~= 564 mln km2
1330 km = 4 * pi * (6370+1330)2 ~= 745 mln km2

So,
564*106 * ((345+5) - (335-5)) / 7500 = 1.5 mln km3/sat in 340 km orbits.
745*106 * 20 / 4400 = 3.4 mln km3/sat in higher than ISS orbits.

A 340 km orbit length = 2 * pi * (6730 + 340) ~= 44 400 km.
A 480 km orbit length (ISS) = 2 * pi * (6730 + 480) ~= 45 300 km.
So, say, our orbit is ~45 000 km long.

Say, our cross-section area is 20 x 20 m ~400 m2 = 4*10-4 km2. (A large sat, a spaceship + upper stage, or else).
Total volume of the orbital torus = 45 000 * 4 * 10-4 ~= 18 km3.
So, the probability of a sat crossing our way is roughly:
~18 / 1.5*106 ~=1.2 * 10-5, 1 chance per ~80 000 orbital turns in LEO.
~18 / 3*106 ~= 0.6 * 10-5, 1 chance per ~160 000 orbital turns in typical OS 480 km orbit (ISS, Mir), when the sats orbit get significantly decayed.

1 day = 24 / 1.5 = 16 turns.
Chances to hit a sat spending in 340 km orbit
a day = 1-(1 - 1.2*10-5)16 = 0.0002 = 1:5000
a week = 1-(1 - 0.0002)7 = 0.0014 = 1:700
a month = 1-(1 - 0.0002)30 = 0.006 = 1:160
a year = 1-(1 - 0.006)12 = 0.07 = 1:14

Chances to hit a decaying orbit sat spending in 480 km orbit
a year = 1-(1 - 0.6*10-5)16*365 = 0.034 = 1:30

***

Say, a sat lifespan is ~15 years.
This means that every year they should deliver ~1/15 of total sats amount = ~800 sats/year.
Probably they are going to deorbit the failed sats, so ~800 sats are going to deorbit.

But as a launch vehicles are ~0.98 reliable, and the sats to be deorbited are by definition out of service,
we can presume that ~20% of sats will stay in orbit as garbage.
So, +160 sats every year.

Twenty years later there will be ~3000 additional dead sats plus to the initial amount.

***

Plus kesslerization of this

Say that 15 years long Starlink sat.
Say, its cross-section is ~5 m2 (including the solar panel)

Its orbital torus volume ~ 45 000 * 5*10-6 ~= 0.2 km3.
At 1.5 mln km3/sat around, the probability to hit another Starlink sat is ~ 0.2/1.5*106 ~= 1.3*10-7 per turn.
Per year = 1-(1-1.3*10-7)16*365 ~= 0.00076 = 1:1300.
So, we can expect ~5..10 Starlink collisions per year.

Every collision creates, say, 10 debris, so +several hundred objects per year.

Of course, most of them will deorbit, but while deorbiting they can hit a Starlink sat in a lower shell.

***

So, if the Starlink had been raised, 30-40 years later there will be no safe orbit below the radiation belts for anything bigger than a Starlink sat.

Spoiler

Chances to hit a sat spending in 340 km orbit
a day = 1-(1 - 1.2*10-5)16 = 0.0002 = 1:5000
a week = 1-(1 - 0.0002)7 = 0.0014 = 1:700
a month = 1-(1 - 0.0002)30 = 0.006 = 1:160
a year = 1-(1 - 0.006)12 = 0.07 = 1:14

Chances to hit a decaying orbit sat spending in 480 km orbit
a year = 1-(1 - 0.6*10-5)16*365 = 0.034 = 1:30

Edited by kerbiloid
Link to comment
Share on other sites

Also the Starlink idea itself is an antithesis to the reusable rocket idea itself.
They are just opposite to each other.

Currently For decades there are just small rockets, up to ~20 t.
They launch small sats, up to ~15 t, or even 2..3 t in high orbits.

The sats are tiny, the place onboard is overexpensive. And there is no way to replace, support, or resupply damaged equipment.
Thus, the satellite equipment manufacturers are forced to make electronics as compact and durable as possible, and this makes the satellites cost like they are made of brilliants.

Can a reusable rocket solve this problem?

If it has 20 t of payload like Falcon - definitely, no. Because a sat anyway costs like several reusable rockets at once.

Say, a reusable rocket gets 100-200 t capable.
The things wouldn't change, as it would be silly to change sat making technology just to put twice as more sats than now.

But if the annual lifted mass starts being counted in thousands tonnes, the things should dramatically change.
In this case you don't need a 15 years living individual sat. You build a big orbital data-center full of standard cheap equipment, and instead of miniaturization and making the equipmentt live for 15 years, you just fill it with cheap electronic garbage from online shops and replace 10% of your equipment per year.

Instead of puny 1 m antennas you use 10 m wide ones.
Instead of high-tech radiators you bring moar water for cooler.
And by using thick hull made of steel you protect your cheap electronic rubbish from radiation and vacuum.

Then you lease it for low price, and nobody needs overexpensive, overdurable, overreliable vacuum rad-protected electronics. Arduino and Raspberry is enough.

The sats get much cheaper, several huge orbbital platforms are serviced and resupplied easily, just send a brigade of engineers once per month.
On Dragon. No. On a big reusable shuttle launched by the big reusable rocket. Puny Dragons are just for ISS (until the first collision with Starlink cloud, lol).

As we can see, the situation when sats get cheap and widely available, and reusable rockets start being self-supported:
1) absolutely opposite to Starlink
2) makes sense when reusable rockets are not second-hand cigarettes like Falcon, but proper large things like Nexus.

Size matters.

Edited by kerbiloid
Link to comment
Share on other sites

2 hours ago, kerbiloid said:

Also the Starlink idea itself is an antithesis to the reusable rocket idea itself.
They are just opposite to each other.

Currently For decades there are just small rockets, up to ~20 t.
They launch small sats, up to ~15 t, or even 2..3 t in high orbits.

The sats are tiny, the place onboard is overexpensive. And there is no way to replace, support, or resupply damaged equipment.
Thus, the satellite equipment manufacturers are forced to make electronics as compact and durable as possible, and this makes the satellites cost like they are made of brilliants.

Can a reusable rocket solve this problem?

If it has 20 t of payload like Falcon - definitely, no. Because a sat anyway costs like several reusable rockets at once.

Say, a reusable rocket gets 100-200 t capable.
The things wouldn't change, as it would be silly to change sat making technology just to put twice as more sats than now.

But if the annual lifted mass starts being counted in thousands tonnes, the things should dramatically change.
In this case you don't need a 15 years living individual sat. You build a big orbital data-center full of standard cheap equipment, and instead of miniaturization and making the equipmentt live for 15 years, you just fill it with cheap electronic garbage from online shops and replace 10% of your equipment per year.

Instead of puny 1 m antennas you use 10 m wide ones.
Instead of high-tech radiators you bring moar water for cooler.
And by using thick hull made of steel you protect your cheap electronic rubbish from radiation and vacuum.

Then you lease it for low price, and nobody needs overexpensive, overdurable, overreliable vacuum rad-protected electronics. Arduino and Raspberry is enough.

The sats get much cheaper, several huge orbbital platforms are serviced and resupplied easily, just send a brigade of engineers once per month.
On Dragon. No. On a big reusable shuttle launched by the big reusable rocket. Puny Dragons are just for ISS (until the first collision with Starlink cloud, lol).

As we can see, the situation when sats get cheap and widely available, and reusable rockets start being self-supported:
1) absolutely opposite to Starlink
2) makes sense when reusable rockets are not second-hand cigarettes like Falcon, but proper large things like Nexus.

Size matters.

The problem is space junk will accumulate over time anyway. You can bash Falcon for being small and puny as much as you want but it's its second stage that actually deorbits itself to keep space as clean as possible.

Now, as I said, space junk will build up anyway. You can either accept it and keep leaving spent second stages in stable orbits (because it's better to boost that extra 200-300kg to its final orbit than deorbit the upper stage), or fight it with big stuff like Starship that could probably act as a space garbage truck collecting all those upper Atlas stages.

Either way, I agree. Size matters.

Link to comment
Share on other sites

 

Regarding the long @kerbiloid post, I miss the point? Sats cost more than rockets? GEO sats certainly do right now, but smallsats don't. I'd imagine that the total cost of all the 60 launched Starlinks on that one flight exceed the retail cost of F9, but honestly, I'd be surprised if SpaceX wasn't trying to get their actual cost for those down in the "expensive car" range. There's no reason why spacecraft need to cost 100s of millions.

I agree that bigger reusables make a difference, because cheaper launch costs (once there is competition to reduce costs) and/or larger volumes can mean cheaper, and more long lasting spacecraft.

Assume Starship works, and that it is reusable enough that the SpaceX cost of launch is on the order of Falcon 1. SpaceX could retail a Starship launch for what they charge for a F9 right now, 60M$, and they'd profit 54M on that flight. If you launch a single 2019 type sat, you've gained nothing as the customer---but if you made that single sat vastly larger, more survivable, with large prop reserves, etc, ad nauseum, you've gained quite a bit. That's a way SpaceX could transition to SS without leaving money on the table.

Link to comment
Share on other sites

38 minutes ago, tater said:

SpaceX could retail a Starship launch for what they charge for a F9 right now, 60M$

Not the launch cost itself. But maximum total mass which can be delivered into orbit in one piece, inside one hull, without orbital construction works.

Instead of spamming the sky with tens thousands small satellites which cannot be serviced, repaired, upgraded, resupplied, and which raise collision chances up to the enormous values.
And should be made of vacuum-resistant and radiation-protected electronics.
And should contain each its own propulsion system (to deorbit), power source, SAS, cooling system and so on.

When you have several tens heavy platforms with thick pressurized steel hulls, you can place all these sats equipment inside, make it from cheap electronic components from trash can, use single power and cooling system for all of them at once. They are already protected from the radiation and the vacuum. (Yeah, the Soviet school with pressurized command module! Huzzah!)
You can easily repair, replace, upgrade, resupply the equipment, or switch off the currently unused ones until somebody rents it.
You can use nice big antennas of proper shapes and configurations, not just what could be packed into a small sat.
You can make this platform crewless but habitable for engineers visiting it from time to time, and the engineers work in usual clothes, not in spacesuits.

And this is a question of the rocket payload. The rocket should be reusable and big.
Falcons add nothing here, as their payload is tiny compared to, and their landing technologies unlikely can be used in really big rockets.
BFR/Starship brings probably not much more, as the idea of 150 engines in a rocket 2 times smaller than Nexus mostly looks like a dead end in ideas.

Upd.
The same about Bigelow's balloon aerial circus.
When you have a big steel cystern in sky, who needs these inflatable ponies.

Edited by kerbiloid
Link to comment
Share on other sites

The problem is, the whole point of Starlink is the widely distributed physical network. Like the terrestrial internet, this adds redundancy and bandwidth. It also cuts down on lightspeed delays from going all the way out to geostationary orbit.

This is the same reason why Iridium has a fleet of 76 sats (plus spares) rather than one or two.

You can question whether one company should be allowed to profit by simply taking so much of a common resource (orbital space). But saying they should just build a few big satellites ignores what they are trying to do.

53 minutes ago, Wjolcz said:

could probably act as a space garbage truck

Reminds me of:

 

Link to comment
Share on other sites

8 hours ago, Wjolcz said:

Looks to me like the hinge part we've seen before.

I agree, though the better view suggests strongly that it is a movable piece within a larger flaperon, and the landing legs themselves are somehow fixed.

I never liked the idea of a single failure point that takes out both maneuverability and landing capability.

8 hours ago, Technical Ben said:

Seems others are reporting it's one of the dead SpaceX sats. So, "dead".

I guess SpaceX still have some work to iron out with their designs. Also "chance of collision", so it's for safety, and not necessarily and emergency.

SpaceX chose three satellites -- either ones that weren't operating perfectly well, or some other approach -- to test passive decay. Avoidance of Kessler syndrome requires that the satellites will passively decay if left without control. These three sats are being used for this purpose, to show that even if SpaceX completely lost control, they will all fall out of the sky on their own in a controlled fashion.

In this case, SpaceX likely rejected any suggestion that a collision was likely and accordingly declined to move their sat, as doing so would ruin its data. Even an inclination change would alter numerous factors (like insolation, exospheric temperature, etc.) and make the whole thing harder to work out. ESA was free to move its satellite if it was concerned...which, evidently, it was.

6 hours ago, kerbiloid said:

Say, a sat lifespan is ~15 years.
This means that every year they should deliver ~1/15 of total sats amount = ~800 sats/year.
Probably they are going to deorbit the failed sats, so ~800 sats are going to deorbit.

But as a launch vehicles are ~0.98 reliable, and the sats to be deorbited are by definition out of service,
we can presume that ~20% of sats will stay in orbit as garbage.
So, +160 sats every year.

Twenty years later there will be ~3000 additional dead sats plus to the initial amount.

Sats are low enough that they decay on their own without control input within a few years. So, not a problem.

6 hours ago, kerbiloid said:

The sats are tiny, the place onboard is overexpensive. And there is no way to replace, support, or resupply damaged equipment.
Thus, the satellite equipment manufacturers are forced to make electronics as compact and durable as possible, and this makes the satellites cost like they are made of brilliants.

Can a reusable rocket solve this problem?

If it has 20 t of payload like Falcon - definitely, no. Because a sat anyway costs like several reusable rockets at once.

More likely, Falcon 9 or FH drops off a stack of replacement sats with larger propellant reserves directly in an eccentric MEO (perhaps with a slightly higher apogee). The cluster of sats would hang around up there until they were needed, at which point they could use their onboard propellant to adjust inclination at apogee to match plane with the derelict sat's former orbit. This is dV-cheap, since it is done at a high apogee. Then, they lower their perigee just enough to use atmospheric braking to circularize. The replacement sats wouldn't have quite the same lifetime as a brand new one dropped off directly in the desired orbit, but that's fine.

Link to comment
Share on other sites

1 minute ago, Technical Ben said:

*If not controlled*. They have fuel to boost for their assumed useful lifespan.

This.

And as the 12 000 objects constellation is presumed to be permanently existing, the argument of orbit decay is not applicable.
This cloud of floating contact mines will be existing and make low orbits as dangerous as a minefield.

Edited by kerbiloid
Link to comment
Share on other sites

3 hours ago, Technical Ben said:
3 hours ago, kerbiloid said:

So, the whole 12 000 constellation will be lost in several years? Great.

*If not controlled*. They have fuel to boost for their assumed useful lifespan.

Exactly. They carry onboard fuel to adjust trajectory and stay in space, and enough to perform a rapid deorbit if there was a problem. The only time that they will deorbit passively is if they somehow lose electrical power and become junk. They are probably programmed to do a rapid deorbit if they lose comms as well.

Link to comment
Share on other sites

Just now, sevenperforce said:

Exactly. They carry onboard fuel to adjust trajectory and stay in space, and enough to perform a rapid deorbit if there was a problem.

So, 12 000 sats raising risk of collision up to percents per year are always in orbit.
If one dies and deorbits, they launch a replacement to keep the cloud same dangerous.

Link to comment
Share on other sites

2 minutes ago, kerbiloid said:

This.

And as the 12 000 objects constellation is presumed to be permanently existing, the argument of orbit decay is not applicable.
This cloud of floating contact mines will be existing and make low orbits as dangerous as a minefield.

Just like all those cars, boats and aircraft... oh wait!

Link to comment
Share on other sites

1 minute ago, Technical Ben said:

Just like all those cars, boats and aircraft... oh wait!

Cars, boats, and aircrafts can maneuver and stop.

If 12 000 sats start maneuvering in evasive action, the chaos just gets absolutely chaotic.

Edited by kerbiloid
Link to comment
Share on other sites

2 minutes ago, Rakaydos said:

Spacecraft can dodge.

They can make a torus-like satellite, to let another one pass through the opening.

Just now, Technical Ben said:

Can cars evade?

Can cars move 8 km/s? (Except Tesla).

1 minute ago, Technical Ben said:
Quote

1. Are they going to?
2. Will they evade each close satellite?

Yes, they cannot.

Me: 

What proof?

What proof they are going?

Link to comment
Share on other sites

3 minutes ago, kerbiloid said:

They can make a torus-like satellite, to let another one pass through the opening.

Can cars move 8 km/s? (Except Tesla).

What proof they are going?

So. You are saying we need to take every car off the road. Boat out of the sea. And aircraft out the sky... because:

"What proof they are going?" to avoid collisions?

 

Quote

Can cars move 8 km/s? (Except Tesla).

Yes, if you put it in orbit.

Edited by Technical Ben
Link to comment
Share on other sites

3 minutes ago, Technical Ben said:

So. You are saying we need to take every car off the road. Boat out of the sea. And aircraft out the sky... because:

"What proof they are going?" to avoid collisions?

The false analogies with slow-moving and maneuverable crafts are pointless.

3 minutes ago, tater said:

Some were intended to be deorbited from the start to demonstrate/test that capability.

To be immediately replaced with new ones.
The problem is in the cloud density itself.
It's overdangerous even if use aviation safe distances between trajectories.

Edited by kerbiloid
Link to comment
Share on other sites

1 minute ago, kerbiloid said:

The false analogies with slow-moving and maneuverable crafts are pointless.

To be immediately replaced with new ones.
The problem is in the cloud density itself.

You are saying the satellites are not maneuverable. Have you played KSP? Is it a false analogy?

Quote

To be immediately replaced with new ones.

Really, did they just launch? I missed that one.

Quote

The problem is in the cloud density itself.

Possibly. But other arguments are nonsensical currently. :/

Link to comment
Share on other sites

1 minute ago, kerbiloid said:

The false analogies with slow-moving and maneuverable crafts are pointless.

To be immediately replaced with new ones.
The problem is in the cloud density itself.

It's a LEO constellation.

They cannot have fewer, bigger sats, as the point is to have them above people all the time, and the ground stations as not supposed to be major installations.

Fewer, larger sats with bigger antennas is a 1-way solution, else you need much more powerful ground stations.

Link to comment
Share on other sites

13 minutes ago, kerbiloid said:

Cars, boats, and aircrafts can maneuver and stop.

If 12 000 sats start maneuvering in evasive action, the chaos just gets absolutely chaotic.

Just for comparison, on average there are around 12,000 aircraft in the air at any given time*, which are much bigger than Starlinks, in a much smaller “shell” of space. They are highly regulated, and very rarely hit each other at altitude. 

The whole Kessler syndrome thing is way overblown. People forget that space is big. Really, really, big. And the farther out you go the bigger it gets. And most things that aren’t far out don’t stay up forever. 

 

*And as high as 19,000 at once, I recall reading. 

Edited by CatastrophicFailure
Link to comment
Share on other sites

9 minutes ago, Technical Ben said:

You are saying the satellites are not maneuverable. Have you played KSP? Is it a false analogy?

1. Are you aware that infinite fuel onboard is a cheating? Especially in low orbits.
2. So, one craft passing through the cloud makes a hundred of sats start maneuvering to evade collisions with closest neighbors?

9 minutes ago, Technical Ben said:

Really, did they just launch? I missed that one.

Aren't they going to keep 12 000 in orbit?

9 minutes ago, Technical Ben said:

Possibly. But other arguments are nonsensical currently. :/

When I hear such "nonsense" arguments, I see that the opponent is out of rational arguments.

8 minutes ago, tater said:

They cannot have fewer, bigger sats, as the point is to have them above people all the time, and the ground stations as not supposed to be major installations.

Fewer, larger sats with bigger antennas is a 1-way solution, else you need much more powerful ground stations.

So, they should consider the grounds stations as a rational alternative.
As well they can't just cover the sky with foil to keep the signal available everywhere. Probably it should be solved by a combination of 1000 km and GSO sats, and the ground signal distribution equipment.
 

7 minutes ago, CatastrophicFailure said:

Just for comparison, on average there are around 12,000 aircraft in the air at any given time*, which are much bigger than Starlinks, in a much smaller “shell” of space. They are highly regulated, and very rarely hit each other at altitude. 

Now have a look at the airlines map and compare it to the straight line of orbit.
You can't command to a sat: "Please, pass from TIKOL to POLIK, then turn to NETAM and follow to RATAM"

7 minutes ago, CatastrophicFailure said:

The whole Kessler syndrome thing is way overblown.

As I've calculated above, the cloud is the Kessler from its appearance. Debris are not required.

Edited by kerbiloid
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...