Starlink Thread (split from SpaceX)

[tater]

3 hours ago, Terwin said:

You are assuming that the starlink sat thrusts in a random direction and keeps traveling in that direction.

Actually, I was assuming any failure would likely be them not having propulsion at all, which would tend to drop the orbit over time. The primary collision concern is crossing the other 22 planes. I would assume that each plane is a very slightly different alt, so some must be higher than others, and the decaying sats would (briefly) be a collision concern.

[Guest]

2 hours ago, mikegarrison said:

Your faith in in the inviolability of Starlink orbital space is charming, but (IMO) misplaced.

Why? Even during Cold War nations have generally looked to make sure their satellites won't crash into each other. Ensuring the inviolability of Starlink orbital space is as simple as not launching anything into it. Which, quite frankly, is not very difficult given where they'll fly. Nobody would be stupid enough to violate it unless they wanted to deliberately mess with the sats, and if you believe that, there's no hope for you. Things in space move in a very predictable manner. Failed satellite do, too, usually a failure means loss of a propulsion system, which means the sat will stay put, in the orbit it had before failing. It's rather trivial to keep clear of that.

Space is big. Outside of GEO, there's plenty of room for everyone. 

Edited September 4, 2019 by Guest

[mikegarrison]

19 minutes ago, Dragon01 said:

Space is big. Outside of GEO, there's plenty of room for everyone. 

https://en.wikipedia.org/wiki/2009_satellite_collision

It. Really. Already. Has. Happened.

Edited September 4, 2019 by mikegarrison

[Guest]

You sound like a broken record. You're quoting the only sat-to-sat collision in the recorded history. This happened once, between two satellites which orbital altitudes were matched very closely, but not quite. In short, a very special case. In fact, the collision was entirely avoidable. That it happened was an error on part of human planners. Space is big, but that doesn't stop you from putting two things next to one another in it. My point was that you usually have an option of not doing it.

[mikegarrison]

1 minute ago, Dragon01 said:

You sound like a broken record.

Yeah, because in my world, facts trump theory. Iridium has 80-some sats (76 plus spares) in orbit. They got hit. Just once, mind you (so far), but it actually happened.

Starlink is 12000 satellites. 150x as many opportunities.

[Guest]

Just now, mikegarrison said:

Yeah, because in my world, facts trump theory.

Then get your bloody facts straight! Does Starlink have a single satellite in its area with which one of its sats could collide? 

In case you don't know, the answer is: no, it doesn't. And if you want to come up with some "alternative facts" to that, better follow it up with evidence. I cannot point to anything that's at risk of collision with the proposed constellation.

[tater]

35 minutes ago, Dragon01 said:

Then get your bloody facts straight! Does Starlink have a single satellite in its area with which one of its sats could collide? 

In case you don't know, the answer is: no, it doesn't. And if you want to come up with some "alternative facts" to that, better follow it up with evidence. I cannot point to anything that's at risk of collision with the proposed constellation.

Any Starlink that is at its target altitude that subsequently fails will be effectively crossing every single orbit below it (all the polar sats, for example) as it drops.

9/60 (15%) are in variant orbits (plus 4 pieces of debris). Some of the failed ones are in circular orbits (triangles together that make a diamond), others are eccentric.

Wonder what % in larger production will fail? Surely less than 15% (1800) by then 1.5% failure rate (180)?

[Guest]

43 minutes ago, tater said:

Any Starlink that is at its target altitude that subsequently fails will be effectively crossing every single orbit below it (all the polar sats, for example) as it drops.

True, but that should be much easier to avoid, and the trajectories are still predictable. Even assuming a 1.5% failure rate, those will not fail at the same time. We've learned enough from the 2009 collision to give them a wide berth. TBH, I think that failure rate will be less than 1.5%. Sats falling at that rate would cause problems with pieces hitting people on the ground (contrary to popular belief, reentering satellites seldom burn up completely) before they strike another satellite.

[Terwin]

3 hours ago, tater said:

Any Starlink that is at its target altitude that subsequently fails will be effectively crossing every single orbit below it (all the polar sats, for example) as it drops.

9/60 (15%) are in variant orbits (plus 4 pieces of debris). Some of the failed ones are in circular orbits (triangles together that make a diamond), others are eccentric.

Wonder what % in larger production will fail? Surely less than 15% (1800) by then 1.5% failure rate (180)?

If I remember correctly, all of the failed starlink sats failed before moving up to the shared orbital altitude, so even if 15% fail, almost all of those should have the same failure mode as the failures we have already seen(failing before they move to their designated orbits), which means they are already below all functional satellites and will quickly de-orbit due to the low altitude.  (It is almost like SpaceX is expecting some of them to fail and is taking measures to make sure those failures don't cause any problems)

 

To be  danger to anything in orbit, they will need to fail after they climb to their desired orbit, and we have not yet seen any failures that late.

[Brotoro]

10 hours ago, tater said:

...I suppose they could put a grapple of sorts on Starlink sats, and if one fails in a concerning way they could move a neighbor to deorbit it....

This is the Best Idea. Because...

a) Failures WILL eventually happen to Starlink sats in operational orbits, some of which will involve loss of command control or propulsion system failure,

b) The extra 'janitor' sats can be functional Starlink sats in the meantime, and you wouldn't need specialized janitor sats,

c) It would be cool.

[sevenperforce]

13 hours ago, Brotoro said:

Failures WILL eventually happen to Starlink sats in operational orbits, some of which will involve loss of command control or propulsion system failure...

But operational-orbit failures will be rare, and failures which involve the loss of comms will be only a fraction of those, and failures which involve propulsion system failure will be an even smaller fraction. The tiny, tiny number of Starlink sats with prop failure will be quickly identified and their decay rate can be simulated well in advance, based on existing measurements of decay as provided by the tests they're currently running. There will be plenty of time to look at their descent path and figure out if other satellites need to perform avoidance maneuvers.

[Technical Ben]

10 hours ago, Brotoro said:

This is the Best Idea. Because...

a) Failures WILL eventually happen to Starlink sats in operational orbits, some of which will involve loss of command control or propulsion system failure,

b) The extra 'janitor' sats can be functional Starlink sats in the meantime, and you wouldn't need specialized janitor sats,

c) It would be cool.

Oooh. Yeah, dockbump slam the other sat into re-entry!

[Nightside]

Everyone is assuming that the failure rate has been low, because spacecraft typically have a low failure rate. But this is a new age of cheap access to space. (Especially cheap if the launcher company = payload company.)

Because access is cheap, there is no need to build quadruple-redundant spacecraft that can operate for decades. Instead, launch thousands, and hope that ~90% work well enough. This is mass production (for comparison, iphones had a failure rate of 3-22% in the last 2 years). For Starlink, the redundancy is in the shear number of pieces in the system. There is no way that all 60 of the first batch of Starlinks received the same care and technical oversight that a GPS, KH, or NASA probe gets. 

In addition to Starlink and the 2 other similar systems planned, it is access is now cheap enough to send all sorts of art projects, space urns, university projects, tech demonstrations, etc - will all these be controlled and tracked as a communication network? I don't think so.

1 hour ago, sevenperforce said:

There will be plenty of time to look at their descent path and figure out if other satellites need to perform avoidance maneuvers.

What if neither sat has control?

Edited September 5, 2019 by Nightside

[sevenperforce]

4 hours ago, Nightside said:

5 hours ago, sevenperforce said:

There will be plenty of time to look at their descent path and figure out if other satellites need to perform avoidance maneuvers.

What if neither sat has control?

That's going to be an exponential decrease in likelihood. A very low probability times another very low probability is a much, much lower probability.

Also, remember that satellites don't decay "up" in space. Starlink sats will decay in five years without control input. If an uncontrolled, decaying Starlink sat is descending, anything in its path is going to have active propulsion, or it wouldn't have stayed in that orbit. The 2009 collision happened at nearly 800 km, in a region where atmospheric drag is virtually nonexistent.

[ment18]

Ill just leave this here: https://en.wikipedia.org/wiki/Project_West_Ford

There are currently several hundred million tiny needles in a high polar orbit, and they have been there since the beginning of space travel.

[magnemoe]

1 hour ago, sevenperforce said:

That's going to be an exponential decrease in likelihood. A very low probability times another very low probability is a much, much lower probability.

Also, remember that satellites don't decay "up" in space. Starlink sats will decay in five years without control input. If an uncontrolled, decaying Starlink sat is descending, anything in its path is going to have active propulsion, or it wouldn't have stayed in that orbit. The 2009 collision happened at nearly 800 km, in a region where atmospheric drag is virtually nonexistent.

But down in starlink orbits it drag, also the body will be flat in the direction of travel, solar panels will be as flat as they can be while giving enough power and might be oriented to reduce drag while in shadow. 
This is not true for an dead satellite who will tumble, you typically set a satellite up to rotate once each orbit this way the solar panels will always point to towards the sun but drag and solar sail effects will disrupt this if not under control. Belive this is something SpaceX is testing with the offending satellite. The second deorbit mode is orient it to maximize drag, might rotate solar panels 90 degree on body so you will be an high drag object even of losing control.

[tater]

2 hours ago, sevenperforce said:

The 2009 collision happened at nearly 800 km, in a region where atmospheric drag is virtually nonexistent.

Almost 3000 Starlinks are supposed to be in a few shells over 1100km. A bunch are to also be lower, at 350 I think.

[sevenperforce]

4 hours ago, ment18 said:

Ill just leave this here: https://en.wikipedia.org/wiki/Project_West_Ford

There are currently several hundred million tiny needles in a high polar orbit, and they have been there since the beginning of space travel.

There are only forty remaining clumps of needles remaining. All the lone needles have long since been deorbited by sunlight pressure, and the forty clumps that remain are tracked as they also deorbit.

3 hours ago, tater said:

Almost 3000 Starlinks are supposed to be in a few shells over 1100km. A bunch are to also be lower, at 350 I think.

The first shell that will be deployed goes at 550 km. Those are the ones that will decay within 5 years if left uncontrolled, and which are unlikely to cross the path of any uncontrolled debris on their way down since any uncontrolled debris below them will also decay rapidly.

Subsequent shells at 1150 km and 340 km will not be placed until later in the program; the bulk (7500 of them) will go to 340 km, where the decay time is even shorter and the risk of collision with uncontrolled debris is dramatically less. 

The 2800 sats that will go to 1100 km are the tricky ones, yes. They are the potential Kesslers.

[tater]

Have there been stories regarding laser comms between sats, and the current status of that?

[magnemoe]

2 hours ago, tater said:

Have there been stories regarding laser comms between sats, and the current status of that?

Think its pretty much required for starlink system fully deployed. Assume the 1200 km birds are relays / routers. Lower satellites uses them as relays to reach other satellites and because they higher orbits the relays can service more satellites. 
An P2P system is faster but also more complex and require each starlink satellite to carry lots of satellite to satellite communication systems while they only need to link to one to a couple relays. 

[tater]

1 hour ago, magnemoe said:

Think its pretty much required for starlink system fully deployed. Assume the 1200 km birds are relays / routers. Lower satellites uses them as relays to reach other satellites and because they higher orbits the relays can service more satellites. 
An P2P system is faster but also more complex and require each starlink satellite to carry lots of satellite to satellite communication systems while they only need to link to one to a couple relays. 

Yeah, it got me wondering why they applied for the 30,000 more sats... is there a solution using low power omni antennas for sat to sat relay vs lasers that is easier, or are they for added capability, or are they for replacements, etc.

[mikegarrison]

4 minutes ago, tater said:

Yeah, it got me wondering why they applied for the 30,000 more sats... is there a solution using low power omni antennas for sat to sat relay vs lasers that is easier, or are they for added capability, or are they for replacements, etc.

They are planning to hold space itself hostage until they are paid one MILLION dollars!

 

[tater]

9 minutes ago, mikegarrison said:

They are planning to hold space itself hostage until they are paid one MILLION dollars!

That's about as good a guess as any, frankly, LOL.

[G'th]

Topics like these make me wish Gravity was about literally anything else. 

As noted earlier Kessler Syndrome is a vastly overblown non-issue. Even in the most catastrophic scenario, any debris cloud would be -easily- avoidable by any given rocket launch, especially if its in a relatively low orbit like Starlink would be. 

And even in the most Gravity-like sci-fi disaster film nonsense scenario, at worst Earth can't launch rockets for a couple years while the debris cloud de-orbits naturally. 

In other words, we handle it by not handling it. 

[kerbiloid]

9 hours ago, tater said:

it got me wondering why they applied for the 30,000 more sats... i

Probably because the project in whole was well thought out and perfectly engineered. So, they just have to increase it a little, just 4 times.

9 hours ago, mikegarrison said:

They are planning to hold space itself hostage until they are paid one MILLION dollars!

One million to launch every sat. A hundred billion to cancel the project.

Spoiler

 

9 hours ago, G'th said:

In other words, we handle it by not handling it.

They launched 60 and already had one incident, lol.

Edited October 19, 2019 by kerbiloid