SpaceX F9 : Starlink v1.0 L7 : June 3/4, 2020 : Discussion

[FlattestEarth]

Rod deployment https://ytcropper.com/cropped/y45ed85734143f3

[anield]

The curved bit in the middle looks like a mass to pull the rod outwards due to the deployment spin.

[Comga]

Does anyone have a prediction for visibility for the first two passes over the US?
Particularly Denver

[Thorny]

Does anyone have a prediction for visibility for the first two passes over the US?
Particularly Denver

Saw nothing from west Texas. Expected Starlink very low in the SW, but the moon is very bright this evening.
The morning passes on Thursday and Friday look much more favorable.

[Lars-J]

With the mechanism as shown, I'm a bit surprised they did not design them to stay attached to the upper stage through a plain hinge. But on the other hand, perhaps there is a risk they could bounce back and re-contact the stack... And there are no doubt other concerns. I have no illusions about seeing things that did not occur to the team.  And this is cheap, and works.

[mn]

WOW. They actually showed the deployment this time :-) So fascinating

I wonder if the fact that OneWeb as the main competitor has gone bankrupt has anything to do with it. Probably not, they never had the architecture to even try and adapt to this. Blue Origin possibly could, if Kuiper eventually becomes reality, but then again by the looks of it Starlink will probably be on-line and serve customers before Blue Origin makes their first successful orbital launch.

I think, when your technological lead has become far enough that even a fast follower would take years to get to where you are now, you can show your tricks safely, knowing that by the time someone could duplicate them, you wont need them anymore.

Specifically in this case, by the time Kuiper sats could benefit from a bulk deployer on top of New Shepperd Glenn SpaceX would already shovel them out of Starships cargo hold in bulk quantities with an entirely different method.

If this deployer has been compared to a dump truck dumping its load versus individual offloading of palettes, then what Starlink might be doing could be closer to pressure pumping concrete through a construction pipeline...

I must admit, I briefly considered the "hey Oneweb just went bankrupt" angle as well, but I'll stick with "unexpected interference due to shock/moving metal that they've only just worked around" for now.

It's equally possible that someone is in really hot water now because they forgot to push the 'generate interference' button.

[geza]

Watching how relatively quickly the deployment rods decay and reenter, that idea never really made sense to me, but whatever reason (technical, procedural, or managerial) we finally got to see the deployment, I'm stoked.  Now I'm trying to work out how the deployment is actuated.  (Watching it repeatedly, you can see the deployment rods "slacken" before swinging out and releasing.)

It seems that there is a pusher (in white) in operation at the near end of the rod. Something like this must operate at the far end  also, as the rod starts to move upward parallelly. I  guess the pusher just contain a spring. A latching mechanism should keep it compressed before the commanded release. Also, the satellite stack seems to be pushed away by something. However, the stack is released only after the rod separation is complete. Therefore, stack release is either mechanically connected to rod release, or commended separately.

[jacobmarley]

Does anyone have a prediction for visibility for the first two passes over the US?
Particularly Denver

According to n2yo, overnight around 4:50 AM(denver time) from NW to SE or tomorrow at 21:05 PM from SW to NE !

[wxmeddler]

I tried looking from here in Fargo at 23:38 local. This works this time of year because of our latitiude. Even with a 67 deg max elevation, didn't see anything. Usually can see ISS at ~420 km till midnight, but not sure with how low the stack (perigee 230) is if that is enough.

[CorvusCorax]

Watching how relatively quickly the deployment rods decay and reenter, that idea never really made sense to me, but whatever reason (technical, procedural, or managerial) we finally got to see the deployment, I'm stoked.  Now I'm trying to work out how the deployment is actuated.  (Watching it repeatedly, you can see the deployment rods "slacken" before swinging out and releasing.)

It seems that there is a pusher (in white) in operation at the near end of the rod. Something like this must operate at the far end  also, as the rod starts to move upward parallelly. I  guess the pusher just contain a spring. A latching mechanism should keep it compressed before the commanded release. Also, the satellite stack seems to be pushed away by something. However, the stack is released only after the rod separation is complete. Therefore, stack release is either mechanically connected to rod release, or commended separately.

Do not forget the entire stack is under tension due to the stage rotation around y axis.

Being not in the center of gravity, the satellites want to drift away from each other and the stage as opposed to remaining in rotation around a joint center of mass. A centripetal force acts through the rod, pulling the stack together. The moment the rods let lose, the sats will separate from each other and the stage simply by momentum already imparted to them.

Ultra simple, ultra effective. Part count: zero.

[niwax]

I tried looking from here in Fargo at 23:38 local. This works this time of year because of our latitiude. Even with a 67 deg max elevation, didn't see anything. Usually can see ISS at ~420 km till midnight, but not sure with how low the stack (perigee 230) is if that is enough.

If they already use the new orientation for ascent, we might see very little of these satellites if anything with the naked eye.

[Jcc]

Watching how relatively quickly the deployment rods decay and reenter, that idea never really made sense to me, but whatever reason (technical, procedural, or managerial) we finally got to see the deployment, I'm stoked.  Now I'm trying to work out how the deployment is actuated.  (Watching it repeatedly, you can see the deployment rods "slacken" before swinging out and releasing.)

It seems that there is a pusher (in white) in operation at the near end of the rod. Something like this must operate at the far end  also, as the rod starts to move upward parallelly. I  guess the pusher just contain a spring. A latching mechanism should keep it compressed before the commanded release. Also, the satellite stack seems to be pushed away by something. However, the stack is released only after the rod separation is complete. Therefore, stack release is either mechanically connected to rod release, or commended separately.

Do not forget the entire stack is under tension due to the stage rotation around y axis.

Being not in the center of gravity, the satellites want to drift away from each other and the stage as opposed to remaining in rotation around a joint center of mass. A centripetal force acts through the rod, pulling the stack together. The moment the rods let lose, the sats will separate from each other and the stage simply by momentum already imparted to them.

Ultra simple, ultra effective. Part count: zero.

I was just wondering where the center of mass is for the stage2-starlink stack with mostly empty prop tanks. Estimates are that stage 2 has a mass of 4.5 tones at burnout. The starlink sats are more than that, so the axis of spin should be inside the starlink stack somewhere. So, a pusher mechanism to separate them from stage 2 is essential.

[XenIneX]

I was just wondering where the center of mass is for the stage2-starlink stack with mostly empty prop tanks. Estimates are that stage 2 has a mass of 4.5 tones at burnout. The starlink sats are more than that, so the axis of spin should be inside the starlink stack somewhere. So, a pusher mechanism to separate them from stage 2 is essential.

Not at all.  Stop thinking in an S2-centric reference frame; it's a loosely-associated collection of objects, each with their own inertia.  If the second stage is outside the center of mass -- and thus the center of rotation -- it goes flying when the retention mechanism lets go, just like the satellite on the opposite end does.


Awful text art:

STAGE2
   ⬆
   ⬆   sat
   ⬆    ⬆  sat     (center of mass/rotation)
   ⬆    ⬆   ⬆    ↙
STAGE2 sat sat >< sat sat sat sat sat sat
                   ⬇   ⬇   ⬇   ⬇   ⬇   ⬇
                  sat  ⬇   ⬇   ⬇   ⬇   ⬇
                      sat  ⬇   ⬇   ⬇   ⬇
                          sat  ⬇   ⬇   ⬇
                              sat  ⬇   ⬇
                                  sat  ⬇
                                      sat

[geza]

It seems that there is a pusher (in white) in operation at the near end of the rod. Something like this must operate at the far end  also, as the rod starts to move upward parallelly. I  guess the pusher just contain a spring. A latching mechanism should keep it compressed before the commanded release. Also, the satellite stack seems to be pushed away by something. However, the stack is released only after the rod separation is complete. Therefore, stack release is either mechanically connected to rod release, or commended separately.

Do not forget the entire stack is under tension due to the stage rotation around y axis.

Being not in the center of gravity, the satellites want to drift away from each other and the stage as opposed to remaining in rotation around a joint center of mass. A centripetal force acts through the rod, pulling the stack together. The moment the rods let lose, the sats will separate from each other and the stage simply by momentum already imparted to them.

Ultra simple, ultra effective. Part count: zero.

This is not exactly what we see on the video. The stack of satelites separates together from the stage with a definite push, which is definitely delayed relative to the jettisoning of the rod.

[rsdavis9]

Do we know the rotation is end over end?
I always assumed it was a roll.

[kdhilliard]

This is not exactly what we see on the video. The stack of satellites separates together from the stage with a definite push, which is definitely delayed relative to the jettisoning of the rod.

That's what I thought at first, but looking again closely it appears that they start moving as soon as the rod is free, but with the upper satellites in the stack separating moving away more quickly than the lower ones.

_{Edit: Clarity}

[eriblo]

This is not exactly what we see on the video. The stack of satelites separates together from the stage with a definite push, which is definitely delayed relative to the jettisoning of the rod.

That's what I thought at first, but looking again closely it appears that they start moving as soon as the rod is free, but with the upper satellites in the stack separating more quickly than the lower ones.

I do not see any sign of a push either. Remember that the second stage center of mass is many meters back from the center of rotation while those of the satellites are only separated by the thickness of the satellites. You would therefore expect the stage to separate much more rapidly from the closest satellite than the satellites separate from each other.

[kdhilliard]

Do we know the rotation is end over end?
I always assumed it was a roll.

You can see the moon passing by in last night's mission about ten seconds before deployment, but the flat spin is even more visible in daylight.  Here is during March's Starlink 6 keyed to T+00:13:36.  The spin is visible for 70 seconds before the 30 second deployment cutaway.  Post-deployment, you can see the stage stabilize itself.

[allins]

It seems that there is a pusher (in white) in operation at the near end of the rod. Something like this must operate at the far end  also, as the rod starts to move upward parallelly. I  guess the pusher just contain a spring. A latching mechanism should keep it compressed before the commanded release. Also, the satellite stack seems to be pushed away by something. However, the stack is released only after the rod separation is complete. Therefore, stack release is either mechanically connected to rod release, or commended separately.

Do not forget the entire stack is under tension due to the stage rotation around y axis.

Being not in the center of gravity, the satellites want to drift away from each other and the stage as opposed to remaining in rotation around a joint center of mass. A centripetal force acts through the rod, pulling the stack together. The moment the rods let lose, the sats will separate from each other and the stage simply by momentum already imparted to them.

Ultra simple, ultra effective. Part count: zero.

This is not exactly what we see on the video. The stack of satelites separates together from the stage with a definite push, which is definitely delayed relative to the jettisoning of the rod.

Is there any RCS capability to "tap the brakes"?

[whitelancer64]

It seems that there is a pusher (in white) in operation at the near end of the rod. Something like this must operate at the far end  also, as the rod starts to move upward parallelly. I  guess the pusher just contain a spring. A latching mechanism should keep it compressed before the commanded release. Also, the satellite stack seems to be pushed away by something. However, the stack is released only after the rod separation is complete. Therefore, stack release is either mechanically connected to rod release, or commended separately.

Do not forget the entire stack is under tension due to the stage rotation around y axis.

Being not in the center of gravity, the satellites want to drift away from each other and the stage as opposed to remaining in rotation around a joint center of mass. A centripetal force acts through the rod, pulling the stack together. The moment the rods let lose, the sats will separate from each other and the stage simply by momentum already imparted to them.

Ultra simple, ultra effective. Part count: zero.

This is not exactly what we see on the video. The stack of satelites separates together from the stage with a definite push, which is definitely delayed relative to the jettisoning of the rod.

Is there any RCS capability to "tap the brakes"?

Yes, but it's not needed for deployment. Second stage stabilizes itself after separation, then deorbits some time later.