Author Topic: SpaceX Falcon 9 CRS/SpX-10 Dragon - Feb. 19, 2017 - Discussion  (Read 325919 times)

Offline rpapo

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It's either ice or pieces of TPS coming off during the M1D chilldown/purge before restart. Watch the technical webcast *really* carefully and you can see pieces coming off after the reentry burn, too, but the drag is so high at that point that the pieces only show up as dark spots in single frames in the video.
Another thing you don't know is the scale of those things.  They could be close and small, or far and larger, but with a single camera you have no real perspective.
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Offline Rei

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It's either ice or pieces of TPS coming off during the M1D chilldown/purge before restart. Watch the technical webcast *really* carefully and you can see pieces coming off after the reentry burn, too, but the drag is so high at that point that the pieces only show up as dark spots in single frames in the video.

I agree.  Which would reduce the relative velocity and size of the debris vs. if it were something just being passed.  It looks like they pass the top of the stage at around 3 seconds after they break off.  The stage is 42,6m long. With constant acceleration they would be passing the top of the stage moving at 28,4 m/s.  The only obvious protrusions being at risk being the grid fins anyway, which aren't all the way at the top, so a bit slower there.  Probably no threat at all.

On the other hand, it'd probably be worse if something sizeable broke off at the landing burn, I'd imagine it'd move at significantly greater velocity due to the higher wind resistance.  I wonder how heavy these things are?  Note that I watched in slow motion and I didn't see your dark spots.  I saw some well before the burn but they appeared more to be rain.

Those grid fins are some pretty sturdy structures.  I imagine they could take a reasonable-sized strike.
« Last Edit: 02/20/2017 01:08 PM by Rei »

Offline Steven Pietrobon

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Watching the hosted webcast, they gave some more details about the TVC issue. The primary TVC was working fine, but the backup secondary TVC was not working properly. A similar thing happened with the Apollo 16 CSM while orbiting the Moon. With Apollo 16, they decided to continue since the secondary system could still be used. As we all know now, SpaceX decided to scrub the launch at T-13 seconds and perform some replacements of the TVC system. That was the right call in my opinion since if the primary system failed during flight, the secondary system could probably not be relied upon to do its job.
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Offline Bob Shaw

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Looks like there *was* a camera on the LUT - still, but the brief video shot during the countdown suggests there may be video to come as well.
« Last Edit: 02/20/2017 09:47 AM by Bob Shaw »

Offline ugordan

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Looks like there *was* a camera on the LUT - still, but the brief video shot during the countdown suggests there may be video to come as well.

There is a video camera on the tower, it was shown on the hosted webcast at T-57sec and at T+5sec, but it's located at a lower level than the photo above. I'm guessing the latter is one of Ben Cooper's remote cameras.

Offline old_sellsword

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Do we have an exact launch time ?
Ed Kyle :14:38
http://www.spacelaunchreport.com/

14:38:59
http://www.orbita.zenite.nu/

14:39:00
http://forum.nasaspaceflight.com/index.php?topic=8184.1240

16:38
http://prehled-druzic.blogspot.de/2017/02/2017-009.html#yA

It was originally 14:38:59 going into Sunday, but they updated it to exactly 14:39:00 a few hours before launch.

Offline Jim

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Is it just me or did the rainbirds activate awfully late?
Visible on this clip: https://streamable.com/v9zjg

Here's a Youtube link to the same moment; you can slow it down to 1/4-time to get a better look at the water plume.

It looks to me like they never quite reached the platform, rather were missing it.  But that is based on this one camera angle and zero experience.

The rainbirds are for sound suppression.   The peak sound is usually occurs after the vehicle is few hundred above the pad.  And it is the sound reflected of the pad structure that is the issue.  This when the rainbirds need to be at their full volume and not at T-0.  That how it was with the shuttle.

Online DanseMacabre

Is it just me or did the rainbirds activate awfully late?
Visible on this clip: https://streamable.com/v9zjg

Here's a Youtube link to the same moment; you can slow it down to 1/4-time to get a better look at the water plume.

It looks to me like they never quite reached the platform, rather were missing it.  But that is based on this one camera angle and zero experience.

The rainbirds are for sound suppression.   The peak sound is usually occurs after the vehicle is few hundred above the pad.  And it is the sound reflected of the pad structure that is the issue.  This when the rainbirds need to be at their full volume and not at T-0.  That how it was with the shuttle.

You can see the rainbirds at full throttle at this point of the webcast: https://www.youtube.com/watch?v=giNhaEzv_PI?t=19m59s

When the shot goes a bit wider, you can see the rainbirds really ramp up after the rocket clears them.

Offline Alter Sachse

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Do we have an exact launch time ?
Ed Kyle :14:38
http://www.spacelaunchreport.com/

14:38:59
http://www.orbita.zenite.nu/

14:39:00
http://forum.nasaspaceflight.com/index.php?topic=8184.1240

16:38
http://prehled-druzic.blogspot.de/2017/02/2017-009.html#yA

It was originally 14:38:59 going into Sunday, but they updated it to exactly 14:39:00 a few hours before launch.
Thank you !
*some are now corrected
« Last Edit: 02/20/2017 05:04 PM by Alter Sachse »

Offline edkyle99

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SECO seemed to happen about 20 seconds late, any explanation?
Some, if not all of that, is webcast latency.  There was, for example, a 10 second delay between ground and on-board views of the first stage landing on the SpaceX split-screen.  I would guess that the second stage view has 10 seconds or more of delay.  The on-screen mission elapsed time clock does not have the same delay.

 - Ed Kyle

Offline Johnnyhinbos

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This debris really looks like birds as they "flap" past the camera... Of course, its much too high up in the atmosphere to be actual birds flying there, but could it be that there were birds (or bats?) which somehow hiked a ride on the first stage (weren't there stories about bats and birds clinging to the main tank of several space shuttle flights?), died outside the atmosphere and were only shaken loose once the first stage started to re-enter the denser parts of the atmosphere?
Cork
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Offline rsdavis9

This debris really looks like birds as they "flap" past the camera... Of course, its much too high up in the atmosphere to be actual birds flying there, but could it be that there were birds (or bats?) which somehow hiked a ride on the first stage (weren't there stories about bats and birds clinging to the main tank of several space shuttle flights?), died outside the atmosphere and were only shaken loose once the first stage started to re-enter the denser parts of the atmosphere?
Cork

I should know this... What sections of the exterior is the cork exactly?
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Offline envy887

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This debris really looks like birds as they "flap" past the camera... Of course, its much too high up in the atmosphere to be actual birds flying there, but could it be that there were birds (or bats?) which somehow hiked a ride on the first stage (weren't there stories about bats and birds clinging to the main tank of several space shuttle flights?), died outside the atmosphere and were only shaken loose once the first stage started to re-enter the denser parts of the atmosphere?
Cork

I should know this... What sections of the exterior is the cork exactly?

Most of the interstage and part of the octaweb are insulated with cork.

Offline toruonu

Congrats to Buzz Aldrin, who made it to another launch. (Had a conversation with him!  He praised a mutual colleague, touted some of his own inventions, and told a chiding and affectionate story about Neil Armstrong.  It was another amazing few minutes.)

Can we please have those stories retold here? :)

Online Jarnis

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There was a delay on the onboard views for sure, but it doesn't fully explain the difference vs. press kit times. I assume the press kit was wrong, unless some other information comes up.

Offline ugordan

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Going back to CRS-8 and CRS-9 webcasts to compare, curiously, SECO was significantly *later* on CRS-8 with the ASDS landing than on CRS-9, a RTLS flight. One might have expected the opposite to be the case, given lower delta V requirements for ASDS, even despite CRS-8 apparently carrying 900 kg more cargo.

CRS-10 falls in the middle in terms of SECO timing.
« Last Edit: 02/20/2017 03:24 PM by ugordan »

Offline clegg78

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Could there be a weight difference in the loading of Dragon on the different flights.  From what I understand even small changes in weight up there have pretty noticeable changes in burn times, etc...
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Offline mvpel

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I wonder what caused the plume that appeared at the upper stage umbilical area on the TEL as it was leaning back? Seems like those propellant lines should be purged by that point. Maybe exhaust glare reflecting from a LOX cloud?
« Last Edit: 02/20/2017 03:39 PM by mvpel »
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Offline russianhalo117

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I wonder what caused the plume that appeared at the upper stage umbilical area on the TEL as it was leaning back? Seems like those propellant lines should be purged by that point. Maybe exhaust glare reflecting from a LOX cloud?
residual prop igniting or TEL LOX are the usual culprits
« Last Edit: 02/20/2017 04:49 PM by russianhalo117 »

Offline Thorny

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I wonder what caused the plume that appeared at the upper stage umbilical area on the TEL as it was leaning back? Seems like those propellant lines should be purged by that point. Maybe exhaust glare reflecting from a LOX cloud?

I think that's just a reflection of the engine plume off vented LOX.

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