Author Topic: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION  (Read 133992 times)

Offline DAZ

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #320 on: 12/17/2017 04:57 PM »
2 things I noticed:  First, the first stage flip after staging was extremely fast, making for an efficiently timed boostback burn.

Noticed that one too, and went back to find comparison. Side-by-side with NROL-76: http://youtubedoubler.com/mqCH

[edit for shorter URL]

Super quick turn and burn.  Seems SpaceX is getting the timing refined. 

It will be interesting to see how fast the FH side boosters can do the boost back burn since they peel off the side versus axial separation.

That's a neat way to compare videos, but I can't resolve any real difference in the interval between MECO and the start of the boostback burn.  Did anyone do a more careful comparison, perhaps going frame by frame?

I agree. It may have been the different angle of the shot, but it seems that NROL-76 did not have to rotate as far (loftier trajectory?), so rotated slower. The boost-back engine start of each looked to be at the same time.

From what I remember, from viewing the other Falcon 9 launches, all the cold gas thruster bursts came from the top of the booster.  Presumably, these are from the kit installed in the 1st to 2nd stage adapter along with the grid fins.  On this launch, I saw something that to me looked distinctly different.  It looks like not only where there cold cast thrusters being fired from the top of the booster but if I'm not mistaken even more thruster bursts from the bottom of the booster.  I do not remember ever seeing bursts from the bottom of the booster before.  Could this be a new kit that has been installed that allowed for not only a quicker turnaround but more accuracy on the final touchdown?

Online envy887

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #321 on: 12/17/2017 05:02 PM »
2 things I noticed:  First, the first stage flip after staging was extremely fast, making for an efficiently timed boostback burn.

Noticed that one too, and went back to find comparison. Side-by-side with NROL-76: http://youtubedoubler.com/mqCH

[edit for shorter URL]

Super quick turn and burn.  Seems SpaceX is getting the timing refined. 

It will be interesting to see how fast the FH side boosters can do the boost back burn since they peel off the side versus axial separation.

That's a neat way to compare videos, but I can't resolve any real difference in the interval between MECO and the start of the boostback burn.  Did anyone do a more careful comparison, perhaps going frame by frame?

I agree. It may have been the different angle of the shot, but it seems that NROL-76 did not have to rotate as far (loftier trajectory?), so rotated slower. The boost-back engine start of each looked to be at the same time.

From what I remember, from viewing the other Falcon 9 launches, all the cold gas thruster bursts came from the top of the booster.  Presumably, these are from the kit installed in the 1st to 2nd stage adapter along with the grid fins.  On this launch, I saw something that to me looked distinctly different.  It looks like not only where there cold cast thrusters being fired from the top of the booster but if I'm not mistaken even more thruster bursts from the bottom of the booster.  I do not remember ever seeing bursts from the bottom of the booster before.  Could this be a new kit that has been installed that allowed for not only a quicker turnaround but more accuracy on the final touchdown?
All I see is smoke coming off the legs and the base of the stage.

Offline OneSpeed

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #322 on: 12/17/2017 08:01 PM »
From what I remember, from viewing the other Falcon 9 launches, all the cold gas thruster bursts came from the top of the booster.  Presumably, these are from the kit installed in the 1st to 2nd stage adapter along with the grid fins.  On this launch, I saw something that to me looked distinctly different.  It looks like not only where there cold cast thrusters being fired from the top of the booster but if I'm not mistaken even more thruster bursts from the bottom of the booster.  I do not remember ever seeing bursts from the bottom of the booster before.  Could this be a new kit that has been installed that allowed for not only a quicker turnaround but more accuracy on the final touchdown?
All I see is smoke coming off the legs and the base of the stage.

I think DAZ means this transient plume, at T+ 2:42 in the webcast, which is just before the outer 2 S1 engines restart for boostback. Edit: perhaps it is gas generator exhaust being diverted by the already running centre engine?
« Last Edit: 12/17/2017 08:15 PM by OneSpeed »

Offline DAZ

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #323 on: 12/17/2017 09:47 PM »
From what I remember, from viewing the other Falcon 9 launches, all the cold gas thruster bursts came from the top of the booster.  Presumably, these are from the kit installed in the 1st to 2nd stage adapter along with the grid fins.  On this launch, I saw something that to me looked distinctly different.  It looks like not only where there cold cast thrusters being fired from the top of the booster but if I'm not mistaken even more thruster bursts from the bottom of the booster.  I do not remember ever seeing bursts from the bottom of the booster before.  Could this be a new kit that has been installed that allowed for not only a quicker turnaround but more accuracy on the final touchdown?
All I see is smoke coming off the legs and the base of the stage.

I think DAZ means this transient plume, at T+ 2:42 in the webcast, which is just before the outer 2 S1 engines restart for boostback. Edit: perhaps it is gas generator exhaust being diverted by the already running centre engine?

Yes, that is exactly what I am talking about.  I don't remember ever seeing that before.


Offline ZachF

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #324 on: 12/17/2017 10:42 PM »
Some good footage from this launch



Offline OneSpeed

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #325 on: 12/18/2017 01:02 AM »
Yes, that is exactly what I am talking about.  I don't remember ever seeing that before.

I've gone back through the RTLS launches, and many are at night, so the plumes are not visible. Of the daylight RTLS launches, many show the S1 camera view from near the top of the stage. This makes it hard to discern exactly where the plumes all emanate from, but CRS-11 at T+ 2:46 is the best example I can find. However, the NROL-76 broadcast shows a very similar plume to CRS-13 at T+ 2:43.

Offline sevenperforce

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #326 on: 12/18/2017 06:17 PM »
Was it just an odd angle, or did the first stage do a horizontal-plane flip? It looked very different.

In all prior flips I've seen, it looked like the first stage fired the nitrogen thruster pointing at the ground, causing the nose to head up toward radial and then back toward retrograde. In this flip, it looked like one of the lateral forward thrusters fired, causing the nose to yaw toward normal (or perhaps antinormal?) before rotating around toward retrograde. Is this really a change? If so, why?

One possible reason, if this is a new change, might be that they are going to do horizontal-plane flips for the side boosters on Falcon Heavy rather than vertical-plane flips, to put more distance between the two boosters, and so this was an early practice run.

Offline old_sellsword

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #327 on: 12/18/2017 06:23 PM »
From what I remember, from viewing the other Falcon 9 launches, all the cold gas thruster bursts came from the top of the booster.  Presumably, these are from the kit installed in the 1st to 2nd stage adapter along with the grid fins.  On this launch, I saw something that to me looked distinctly different.  It looks like not only where there cold cast thrusters being fired from the top of the booster but if I'm not mistaken even more thruster bursts from the bottom of the booster.  I do not remember ever seeing bursts from the bottom of the booster before.  Could this be a new kit that has been installed that allowed for not only a quicker turnaround but more accuracy on the final touchdown?
All I see is smoke coming off the legs and the base of the stage.

I think DAZ means this transient plume, at T+ 2:42 in the webcast, which is just before the outer 2 S1 engines restart for boostback. Edit: perhaps it is gas generator exhaust being diverted by the already running centre engine?

Yes, that is exactly what I am talking about.  I don't remember ever seeing that before.

It's LOX bleed coming out of the octaweb. You can see it kick into full flow at T-2:10 (~21:00) during CASSIOPE.

https://www.youtube.com/watch?v=Rj4C9bydkX8?t=21m
« Last Edit: 12/18/2017 06:25 PM by old_sellsword »

Online ugordan

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #328 on: 12/18/2017 06:52 PM »
Was it just an odd angle, or did the first stage do a horizontal-plane flip? It looked very different.

In all prior flips I've seen, it looked like the first stage fired the nitrogen thruster pointing at the ground, causing the nose to head up toward radial and then back toward retrograde. In this flip, it looked like one of the lateral forward thrusters fired, causing the nose to yaw toward normal (or perhaps antinormal?) before rotating around toward retrograde. Is this really a change? If so, why?

One possible reason, if this is a new change, might be that they are going to do horizontal-plane flips for the side boosters on Falcon Heavy rather than vertical-plane flips, to put more distance between the two boosters, and so this was an early practice run.

On this launch you were looking though a camera that has its detector rotated 90 degrees away from up. This HD camera viewing setup goes back to the latter days of the Shuttle and I guess the rationale was that, since launch vehicles are taller than they are wide, they might as well rotate the view so it makes better use of the 16:9 aspect ratio during initial ascent. I'm personally not a fan of the setup as it makes the vehicles appear to execute weird maneuvers left to right, especially during first stage descent.

Also, nothing I've seen indicates to me that there was anything different about this flip than the previous ones, neither their speed nor the timing of the boostback burns. People tend to make big conclusions from low resolution and two different vantage points (specifically the NROL-76 stage sep seemed to be from a camera further north than they typically use so it was more of a side-on than an aft view).

Offline sevenperforce

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #329 on: 12/18/2017 07:18 PM »
On this launch you were looking though a camera that has its detector rotated 90 degrees away from up. This HD camera viewing setup goes back to the latter days of the Shuttle and I guess the rationale was that, since launch vehicles are taller than they are wide, they might as well rotate the view so it makes better use of the 16:9 aspect ratio during initial ascent. I'm personally not a fan of the setup as it makes the vehicles appear to execute weird maneuvers left to right, especially during first stage descent.

Also, nothing I've seen indicates to me that there was anything different about this flip than the previous ones, neither their speed nor the timing of the boostback burns. People tend to make big conclusions from low resolution and two different vantage points (specifically the NROL-76 stage sep seemed to be from a camera further north than they typically use so it was more of a side-on than an aft view).
Hmm, thanks.

It does get me thinking, though. Ideally, they'd want as much separation between the two side boosters as possible, to prevent any possible interactions. Flipping horizontally and firing up the three boostback engines mid-flip would push the boosters as far away from each other as possible; then they'd be following a trajectory such that their closest approach would be the landing burn itself.

Offline cscott

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #330 on: 12/18/2017 07:48 PM »
Yaw flip would push the engine sides of the booster towards each other, and point the hot flamey bits at the other booster during engine startup as well.  Don't think that will happen.

Offline mheney

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #331 on: 12/18/2017 08:02 PM »
Please note that there are FH threads to discuss Falcon Heavy; the CRS-13 Discussion thread should be ... discussing CRS-13.

Thank you.

Offline kerogre256

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #332 on: 12/20/2017 02:22 PM »
Strange look like my post with question regarding some item falling off from inside second stage disappear, will post again... anyone know what is item falling from secon stage at 26:06 - 26:11.
https://www.youtube.com/watch?v=OPHbqY9LHCs?t=1566  26:06 26:11.
« Last Edit: 12/20/2017 02:35 PM by kerogre256 »

Offline drnscr

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #333 on: 12/20/2017 02:25 PM »
Strange look like my post with question regarding some item falling off from inside first stage disappear, will post again... anyone know what is item falling from first stage at 26:06 - 26:11.
https://www.youtube.com/watch?v=OPHbqY9LHCs?t=1566  26:06 26:11.


Not being snarky but the first stage separated LONG before the items you’re asking about.  That is dragon separating from the second stage

Offline kerogre256

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #334 on: 12/20/2017 02:37 PM »
Strange look like my post with question regarding some item falling off from inside first stage disappear, will post again... anyone know what is item falling from first stage at 26:06 - 26:11.
https://www.youtube.com/watch?v=OPHbqY9LHCs?t=1566  26:06 26:11.


Not being snarky but the first stage separated LONG before the items you’re asking about.  That is dragon separating from the second stage

yeh my mistake  second not first stage. Thx.

Online envy887

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Re: SpaceX Falcon 9 : CRS-13 : Dec 15, 2017 : DISCUSSION
« Reply #335 on: 12/20/2017 04:28 PM »
Strange look like my post with question regarding some item falling off from inside first stage disappear, will post again... anyone know what is item falling from first stage at 26:06 - 26:11.
https://www.youtube.com/watch?v=OPHbqY9LHCs?t=1566  26:06 26:11.


Not being snarky but the first stage separated LONG before the items you’re asking about.  That is dragon separating from the second stage

yeh my mistake  second not first stage. Thx.

This was beaten to death upthread. Read earlier comments.

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