SpaceX F9 : Starlink v0.9 : May 23, 2019 - DISCUSSION

[Alexphysics]

Launch weather forecast has improved to 80% GO but upper level winds have worsened:

Launch day probability of violating launch weather constraints: 20%
Primary concern(s): Cumulus Cloud Rule
 
Delay day probability of violating launch weather constraints: 20%
Primary concern(s): Cumulus Cloud Rule

Upper level winds are not an issue, it's the upper-level wind shear that is an issue, which I don't believe these forecasts capture.

Well, at 110knots I think the actual speed and not only the wind shear may also count, that seems to be too high for launch.

[jongoff]

Just a note.
Because of using electric thrusters for the orbit maneuvers, the time frame is month to months to get the sats to final orbit. Such that sats could be dispersed to any position in any plane just as easily as getting them all to a single plane. Only the inclination and initial sunlight to start the sats up and get them going hence the launch window so that sats are deployed in sunlight at the beginning of the sun side transit.

If it had be chemical thrusters optimal would be nearly same plane or close planes. This is because time frame is days to get to final orbit. A few days is insufficient to do drifts to most of the other planes.

I don't think this is true for these satellites because they're going to a 550km operating altitude. What altitude are they launching to? If you were talking about launching to 500km and then spiraling out to 1100-1200km what you're saying would be a lot more true. But when your starting and ending altitudes are so similar, I'm not sure how well that would actually work in practice (read: I could do the math, and am pretty sure it wouldn't work, but am too lazy to do the math).

~Jon

[oldAtlas_Eguy]

Using an orbit calculator the drift rate between the release orbit of 350km and final orbit of 550km is only 1 degree per day. So yes realistically at most a plane dispersion of 30 degrees or less. There are about 5 planes that can be reached final orbit in just 2 months. So likely 3 planes every other plane with 20 per plane.

Added:
Thinking about this more from the organised population t ion to achieve first minor coverage with 6 launches then moderate with 12, it would be best as 2 planes every 5th and 30 per plane. Resulting minor with 12 planes and 30 / plane and moderate of 24 planes and 30/ plane.

[acsawdey]

I going to wait to 1) see if it really works and 2) see how much it costs, because I expect it will be pricey.  Isn't this really aimed for the smaller towns and rural areas, where existing options are already limited and costly?
 - Ed Kyle

If Starlink can meet the proposed performance targets (1Gbps and 15ms latency) it will be of great interest everywhere. 

The latency in particular is very optimistic. For comparison, I have fiber-to-the-premises internet at my home and typically get 6ms latency in my tests. For 15 years prior I had cable broadband with 20-30ms latency).

The question is, 6ms to where? The theoretical advantage of starlink is that c in vacuum is much larger than c in fiber so if your packets transit starlink and exit somewhere near the destination the overall latency may be reduced compared to traversing the terrestrial internet.

[rakaydos]

The telescope shown in the Goddard Space Center tweet (Luivor? I've probably got it wrong) has a manipulator arm that pivots the telescope off the large sunshade.

I'm wondering if the flat-pack satellite might have something similar- a large solar array, and an antenna that pivots to keep the solar panels in the light while pointing at earth.

[ludovic_f]

I think the Starlink value proposition is more geared toward "shorter + more diverse paths" than anything else.

I deal with Internet connections around the world at work, and I can tell you that a "space" route from, for example, Paris to Sao Paulo would be (easily) way better than the current Paris -> NY > Miami > Brazil route.

And how about going from Brazil to South Africa, or from India to Russia etc?

[rakaydos]

I think the Starlink value proposition is more geared toward "shorter + more diverse paths" than anything else.

I deal with Internet connections around the world at work, and I can tell you that a "space" route from, for example, Paris to Sao Paulo would be (easily) way better than the current Paris -> NY > Miami > Brazil route.

And how about going from Brazil to South Africa, or from India to Russia etc?

I saw some simulations awhile back suggesting that the orbits would be optimized for east-west communication, and that north-south communication would zigzag more than optimum.

[launchwatcher]

How does this "drifting" actually work ? I assume, if you have a bunch of sats in different planes with the same inclination, all sats in all planes  encounter roughly similar precession, so relatively little corrections would be needed to keep the plane and phase distances constant relative to each other. You just need to compensate atmospheric drag.

Changing plane propulsively seems way too expensive . You could do it with multiple inclination changes, or one massive 9ne at the point of intersection, but that seems horribly inefficient.

So what's drifting? Increase apoapsis into a more excentric orbit that encounters less/more precession, then recircularise?

Equations here if you want to work through the math: https://en.wikipedia.org/wiki/Nodal_precession.

You need the inclination, semi-major axis, orbital period, and eccentricity.   

[Semmel]

Do we have a ground path for the satellites after launch and deployment? I have a small telescope waiting to cool down for some observation in 10 minutes or so and if the clouds behave, I could just point it at the right place to see a string of satellites pass by. Launch is 3:30 am here, so pretty dark but since its almost mid summer, sats will likely be in sunlight when passing overhead and if they are not too far north. I am based in Berlin, Europe. Anyone has any predictions?

[Comga]

Static Fire! Wait for SpaceX to confirm good test after quick look review.

Without knowing if it was a successful static fire, it's apparent it wasn't a really bad one.

[PM3]

https://twitter.com/SpaceX/status/1128134469972447232

This is somewhat historic: First F9 static fire with attached payload since September 2016! Can't wait to see the first reused fairing, but consensus seems to be that it will happen on a later Starlink flight.

[Bananas_on_Mars]

https://twitter.com/SpaceX/status/1128134469972447232

This is somewhat historic: First F9 static fire with attached payload since September 2016! Can't wait to see the first reused fairing, but consensus seems to be that it will happen on a later Starlink flight.

That‘s not correct, last static fire with payload attached was January 24th of this year.

[Nomadd]

Do we have a ground path for the satellites after launch and deployment? I have a small telescope waiting to cool down for some observation in 10 minutes or so and if the clouds behave, I could just point it at the right place to see a string of satellites pass by. Launch is 3:30 am here, so pretty dark but since its almost mid summer, sats will likely be in sunlight when passing overhead and if they are not too far north. I am based in Berlin, Europe. Anyone has any predictions?

I`ll help by staying out of town.

[snowball445]

Do we have a ground path for the satellites after launch and deployment? I have a small telescope waiting to cool down for some observation in 10 minutes or so and if the clouds behave, I could just point it at the right place to see a string of satellites pass by. Launch is 3:30 am here, so pretty dark but since its almost mid summer, sats will likely be in sunlight when passing overhead and if they are not too far north. I am based in Berlin, Europe. Anyone has any predictions?

Flightclub.io might be able to help you there - particularly if you can get access to the Photohrapher toolkit. But with details scarce on the mission profile, the trajectory may not be completely accurate.

[gtae07]

I know it’s a long shot but... from the update thread it looks like OCISLY has taken up station due east of Savannah.  Do we expect any part of the boost or reentry phase to be visible from the Savannah area?  The weather looks to be clear and I have a decent view to the east/northeast from the second floor...

[leetdan]

Do we expect any part of the boost or reentry phase to be visible from the Savannah area?

GTO reentry burns are visible just over the horizon from the Cape Canaveral area.  According to Raul's map, ASDS looks to be closer than that to you.  If you're at the beach or over the tree line, you've got a good shot.

[Semmel]

Do we have a ground path for the satellites after launch and deployment? I have a small telescope waiting to cool down for some observation in 10 minutes or so and if the clouds behave, I could just point it at the right place to see a string of satellites pass by. Launch is 3:30 am here, so pretty dark but since its almost mid summer, sats will likely be in sunlight when passing overhead and if they are not too far north. I am based in Berlin, Europe. Anyone has any predictions?

I`ll help by staying out of town.

No-clouds high five! 

I just played around with the distance measuring tool in google maps. It follows the curvature of earth and you use it to roughly find a path, assuming it is straight. Given the OCISLY location, the path should be close to Berlin. As a metric, if the ground path misses the coast of Newfoundland, it will go south of Berlin. If it goes over the land it will be slightly north. Ill have about 15 minutes of warning (8000km), which is pretty tight to go and setup either north-viewing or south-viewing but should be possible. Hope the deployment sequence is going to be in full swing by then. Guess, I will set my alarm early.

[guckyfan]

Launch is 4:30 CEST, not 3:30.

[Semmel]

Launch is 4:30 CEST, not 3:30.

Ohh thank you! 2:30am UTC is 2 hours difference this time of the year. Thats just before sunrise, probably too bright to see satellites.. too bad.

[Bananas_on_Mars]

Launch is 4:30 CEST, not 3:30.

Ohh thank you! 2:30am UTC is 2 hours difference this time of the year. Thats just before sunrise, probably too bright to see satellites.. too bad.

Gruß aus München.

Anyhow, IMO they are doing a circularisation burn with stage 2 prior to deployment, about half an orbit after launch, so you would only be able to see stage 2 with the satellites still attached. But that would mean you can watch the groundtrack on the webcast during the coast phase and determine when it should be visible and just step outside.