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#680
by
cscott
on 28 Jun, 2019 18:58
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#681
by
Paul_G
on 28 Jun, 2019 20:55
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During the booster boostback burn there was something "flying around" with a gaseous "tail" in the plume interactions. It can be seen in the IR view from T+02:45 to 02:50 (from 27:43 in the Youtube video). Does anyone know what it was?
I'm not suggesting that anything went wrong, I'm just curious.
I noticed that - it definitely looked (to the untrained eye) like something spinning around and gassing out - in my snapshot it doesn't look much, but for the second or so that it is visible in the video stream, it looked significant. Perhaps it was something from the side booster ejection mechanism - during the pre launch chat on the video stream, the separation mechanism was described as using high pressure gas.
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#682
by
gongora
on 28 Jun, 2019 21:08
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Are you sure you're not just looking at the exhaust from the center engine on the core that's still burning?
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#683
by
Paul_G
on 28 Jun, 2019 21:17
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Are you sure you're not just looking at the exhaust from the center engine on the core that's still burning?
It doesn't look like the exhaust - in the video stream it definitely looks an object spinning, rather than the core engine thrust impinging on the boosters. Perhaps its just the result of the Infra Red video.
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#684
by
Robotbeat
on 28 Jun, 2019 23:31
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Are you sure you're not just looking at the exhaust from the center engine on the core that's still burning?
It doesn't look like the exhaust - in the video stream it definitely looks an object spinning, rather than the core engine thrust impinging on the boosters. Perhaps its just the result of the Infra Red video.
it’s a phenomenon in the exhaust itself.
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#685
by
OneSpeed
on 28 Jun, 2019 23:49
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Are you sure you're not just looking at the exhaust from the center engine on the core that's still burning?
It doesn't look like the exhaust - in the video stream it definitely looks an object spinning, rather than the core engine thrust impinging on the boosters. Perhaps its just the result of the Infra Red video.
gongora is correct, it is a downstream Mach disk formed by the interaction of the exhaust plumes from the core stage. There is an excellent explanation of this phenomenon in the video 'The flames of the rockets, part 2 of 2' by 'French Space Guy' starting at:
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#686
by
intrepidpursuit
on 29 Jun, 2019 08:54
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During the booster boostback burn there was something "flying around" with a gaseous "tail" in the plume interactions. It can be seen in the IR view from T+02:45 to 02:50 (from 27:43 in the Youtube video). Does anyone know what it was?
I'm not suggesting that anything went wrong, I'm just curious.
It's basically the high altitude version of a Mach diamond. It's normal and can be seen with many kerolox rockets, here's an example on a Saturn V
Recent F9 launch seen pretty much from sideways, starting at around 30 seconds in:
This guy must be from LA. If the boosters landed in Vandenberg now THAT would be impressive.
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#687
by
ugordan
on 29 Jun, 2019 11:16
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#688
by
mlindner
on 29 Jun, 2019 17:29
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Here is a plot of the second stage telemetry. It took a while to process the 350,000 odd frames from the webcast, but it is interesting to note the low acceleration implied by the raw data, less than 1g for all burns. This distortion would have been caused by the high yaw angle used for the plane changes, which resulted in a much lower measured ΔV than actually occurred.
Correction for those reading the plot here, 980 cm/s^2 is 1g so all the burns were all over 1g.
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#689
by
mark_m
on 29 Jun, 2019 18:49
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Here is a plot of the second stage telemetry. It took a while to process the 350,000 odd frames from the webcast, but it is interesting to note the low acceleration implied by the raw data, less than 1g for all burns. This distortion would have been caused by the high yaw angle used for the plane changes, which resulted in a much lower measured ΔV than actually occurred.
Correction for those reading the plot here, 980 cm/s^2 is 1g so all the burns were all over 1g.
I took it to mean the raw data implied a (misleading) less-than-1g set of burns, which became the final greater-than-1g values after accounting for the high yaw angle.
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#690
by
Alexphysics
on 29 Jun, 2019 20:57
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23 objects tracked now, including Falcon upper stage. LightSail should still be inside Prox-1, and Tepce may not have split yet, so this could be all.
DSX and PSat-2 are identified.
NORAD Name NSSC ID Type Country Period Incl. Apo Peri
44339 OBJECT A 2019-036A TBA TBD 99.13 24.00 725 709
44340 OBJECT B 2019-036B TBA TBD 99.12 24.00 725 708
44341 OBJECT C 2019-036C TBA TBD 99.12 24.00 725 708
44342 OBJECT D 2019-036D TBA TBD 99.11 24.00 725 707
44343 OBJECT E 2019-036E TBA TBD 99.10 24.00 725 707
44344 DSX 2019-036F PAYLOAD US 316.92 42.21 12035 6005
44345 FH R/B 2019-036G R/B US 306.86 42.24 11936 5449
44346 OBJECT H 2019-036H TBA US 96.27 28.52 853 307
44347 OBJECT J 2019-036J TBA US 96.24 28.53 850 307
44348 OBJECT K 2019-036K TBA US 96.23 28.52 852 304
44349 OBJECT L 2019-036L TBA TBD 99.10 24.00 724 707
44350 OBJECT M 2019-036M TBA TBD 99.10 24.00 724 707
44351 OBJECT N 2019-036N TBA TBD 99.09 24.00 724 706
44352 OBJECT P 2019-036P TBA TBD 96.23 28.53 849 307
44353 OBJECT Q 2019-036Q TBA TBD 99.09 24.00 724 706
44354 OBJECT R 2019-036R TBA US 96.19 28.53 847 305
44355 OBJECT S 2019-036S TBA US 96.19 28.53 847 305
44356 OBJECT T 2019-036T TBA US 96.15 28.52 847 301
44357 PSAT2 2019-036U PAYLOAD US 96.17 28.53 845 306
44358 OBJECT V 2019-036V TBA US 99.09 24.00 725 705
44359 OBJECT W 2019-036W TBA US 96.14 28.52 847 300
44360 OBJECT X 2019-036X TBA US 96.12 28.53 848 297
44361 OBJECT Y 2019-036Y TBA US 96.12 28.52 848 297
Now it seems the FH second stage ended up in a bit different orbit than the DSX after all so it could probably be that the earlier orbit estimate was not very good and now with a better estimate it really shows some difference between both orbits. If that's the case, maybe there was a propulsive passivation after all.
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#691
by
OneSpeed
on 30 Jun, 2019 02:00
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Here is a plot of the second stage telemetry. It took a while to process the 350,000 odd frames from the webcast, but it is interesting to note the low acceleration implied by the raw data, less than 1g for all burns. This distortion would have been caused by the high yaw angle used for the plane changes, which resulted in a much lower measured ΔV than actually occurred.
Correction for those reading the plot here, 980 cm/s^2 is 1g so all the burns were all over 1g.
My mistake. I should have said 'for all of the first burn' (SES2). From the telemetry, the ΔV was 7022 - 6963 = 59m/s, over a 23 second burn. That's an average of 2.6 m/s², or 0.26g, much less than the Merlin engine could deliver with that gross mass. E.g. if the engine was actually producing a 4g burn, then the yaw angle must have been cos-1(0.26/4) = 86.27°.
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#692
by
ThatOldJanxSpirit
on 01 Jul, 2019 11:25
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23 objects tracked now, including Falcon upper stage. LightSail should still be inside Prox-1, and Tepce may not have split yet, so this could be all.
Now it seems the FH second stage ended up in a bit different orbit than the DSX after all so it could probably be that the earlier orbit estimate was not very good and now with a better estimate it really shows some difference between both orbits. If that's the case, maybe there was a propulsive passivation after all.
I’m estimating that to be a 145 m/s manoeuvre at around apogee. If they lit the engine it would have consumed about 200kg of propellant which would seem to be a very tight margin. Most likely they just dumped everything through the nozzle as shown in the animation. Assuming the same Isp as an N2 CGT (70s) then a tonne of propellant would have been vented, so this seems quite credible.
Likely that cruising for an extra two and a half hours then demonstrating that the vehicle was still controllable and fluids could still flow was an adequate demonstration to the USAF that it was capable of relighting for GEO insertion.
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#693
by
Comga
on 04 Jul, 2019 03:03
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https://twitter.com/spacex/status/1146546495241371649
View from the fairing during the STP-2 mission; when the fairing returns to Earth, friction heats up particles in the atmosphere, which appear bright blue in the video
Super cool
The reentry seems remarkably stable
The fairing looks almost empty in the distorted view of the fisheye lens.
What’s that ring that appears faintly around 0:15 and strongly at the end?
The video is under one minute.
Is it sped up, edited?
The chute just appears. Any deployment action is hard to see.
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#694
by
Vettedrmr
on 04 Jul, 2019 03:06
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The video is under one minute.
Is it sped up, edited?
The chute just appears. Any deployment action is hard to see.
Edited, yes. But it doesn't look like it runs at anything other than normal speed.
Have a good one,
Mike
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#695
by
ThatOldJanxSpirit
on 04 Jul, 2019 07:01
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https://twitter.com/spacex/status/1146546495241371649
View from the fairing during the STP-2 mission; when the fairing returns to Earth, friction heats up particles in the atmosphere, which appear bright blue in the video
Super cool
The reentry seems remarkably stable
The fairing looks almost empty in the distorted view of the fisheye lens.
What’s that ring that appears faintly around 0:15 and strongly at the end?
The video is under one minute.
Is it sped up, edited?
The chute just appears. Any deployment action is hard to see.
I also note there is a lot of thruster activity during entry.
Is it me, or have they mounted the fairing sideways. Both the entry and Ms Tree videos seem to show it flying sideways on. Iirc in all previous videos it has flown pointy end first.
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#696
by
cscott
on 04 Jul, 2019 11:51
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I also note there is a lot of thruster activity during entry.
Is it me, or have they mounted the fairing sideways. Both the entry and Ms Tree videos seem to show it flying sideways on. Iirc in all previous videos it has flown pointy end first.
There's further discussion in the fairing reuse thread:
https://forum.nasaspaceflight.com/index.php?topic=37727.msg1962801.msg#1962801I agree the landing is "sideways" but the re-entry video seems to be looking aft from a nose-mounted camera re-entering nose first. To me, at least.
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#697
by
matthewkantar
on 10 Jul, 2019 14:25
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Rewatching the fairing reentry video, this time on a desktop instead of my phone. Definitely one of the best space vids I have ever seen.
I have a question, not sure if it has been answered here: Is the little bit of thermal protection we have seen on the tip of the fairing protection for the ascent, or for the descent?
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#698
by
Alvian@IDN
on 10 Jul, 2019 15:20
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I have a question, not sure if it has been answered here: Is the little bit of thermal protection we have seen on the tip of the fairing protection for the ascent, or for the descent?
The former. Although the fairing reenter even faster than the center core, it's (relatively) lightweight, the air pushes the fairing like a piece of paper falling down instead of like a pencil (okay, maybe not that light, because it still need parafoil)
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#699
by
codav
on 11 Jul, 2019 10:53
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I have a question, not sure if it has been answered here: Is the little bit of thermal protection we have seen on the tip of the fairing protection for the ascent, or for the descent?
The former. Although the fairing reenter even faster than the center core, it's (relatively) lightweight, the air pushes the fairing like a piece of paper falling down instead of like a pencil (okay, maybe not that light, because it still need parafoil)
I strongly disagree and say it's the latter, for two reasons.
First, rocket speeds through ascent aren't high enough to really heat up the fairing tip so much that it needs any additional protection. No other rocket using expendable fairings have this extra protection.
Second, SpaceX only recently added this extra metal protection to the tip to fairings which were planned to be recovered. The recent RADARSAT launch, for example, didn't sport the thermal protection cap. And in the reentry video, you can clearly see sparks coming from the tip, which is the area where air compression is highest as the fairing is moving very fast horizontally as it hits the upper atmosphere tip-first. The camera has a large field of view, it's a fisheye lens, so it is not clearly visible.