SpaceX Falcon 9 CRS/SpX-10 Dragon - Feb. 19, 2017 - Discussion

[Rei]

Just a bit more... reentry burn begins at around 70km (correct?)  so that was passed at just above 70km. 

Does anyone know the velocity at the time of the reentry burn?  Running the free-fall numbers from ~200km I get around 1600 m/s velocity (not taking into account air resistance, so that's a maximum).  Aka, it was moving fast when it passed the debris.

[Herb Schaltegger]

It hadn't even done its entry burn yet (the entry burn started immediately after the debris).

The audio loop was about 1-2 seconds ahead of the video from the descending stage. I think it almost a certainty that whatever it was, it was liberated from the lower part of the vehicle as a result of the startup sequence for the entry burn.

[SpaceX_MS]

On behalf of the teams, thank you for the kind words and your amazing support! We still have Dragon to complete arrival at the ISS of course.

[RotoSequence]

Ice ? Hard to figure out it's size given the position of the camera.

bird

Clearly not ice or a bird.  Far too large for either, far too high up for a bird, and clearly tumbling in free fall with a periodic rotation.

The stage was moving at hundreds of meters per second in free fall at that point.  It was still far above the cloud deck.  It hadn't even done its entry burn yet (the entry burn started immediately after the debris).

Even if it's just some sort of insulation, nobody likes a strike at high speeds.  :Þ

The debris almost looks like a broken impeller, but I honestly have no idea what it is. 

[Llian Rhydderch]

FWIW, the press conference Q&A was where that info on the TVC actuator being completely replaced was first mentioned.  There is a full video of the press conference in the UPDATES thread.

[rocketguy101]

"Picking up some dust..."

[gongora]

FWIW, the press conference Q&A was where that info on the TVC actuator being completely replaced was first mentioned.  There is a full video of the press conference in the UPDATES thread.

Some of the press new beforehand:
Tweet from William Harwood (CBS) before launch

F9/CRS10: For the record, SpaceX PAO says company is 'go' for launch after replacing parts in the 2nd stage TVC steering system

[Jcc]

Ice ? Hard to figure out it's size given the position of the camera.

bird

Clearly not ice or a bird.  Far too large for either, far too high up for a bird, and clearly tumbling in free fall with a periodic rotation.

The stage was moving at hundreds of meters per second in free fall at that point.  It was still far above the cloud deck.  It hadn't even done its entry burn yet (the entry burn started immediately after the debris).

Even if it's just some sort of insulation, nobody likes a strike at high speeds.  :Þ

The debris almost looks like a broken impeller, but I honestly have no idea what it is. 

Maybe just a random gap in the clouds. Notice the shape of the "wing" (if it were a bird) follows the same curvature as the surrounding puffs of cloud.

[speedevil]

Maybe just a random gap in the clouds. Notice the shape of the "wing" (if it were a bird) follows the same curvature as the surrounding puffs of cloud.

It moves at significant velocity, so no.

[NotOnImpact]

I haven't seen it mentioned, but I was very excited to see the boostback burn start from the perspective of the second stage.  The call wasn't synchronized with the visual of the burn - but it was obviously lit on camera.   Might just be me - but I think that is the quickest rotation after separation that I've witnessed, and for sure it is the first time I have seen the first stage light up so close to the second stage. 

[ChrisC]

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.

[Lars-J]

The water in the rain birds did not flow at full pressure until just after liftoff. That may have been by design.

[Jdeshetler]

Video focusing on F9 CRS-10's 1st Stage w/ Tech Audio.

[toruonu]

Looking again at the video, the two pieces of debris appear around T+6:30, the call out for entry burn is at T+6:35 and we see the engine come on at T+6:38 so the video is ~3+ seconds delayed.

But the debris became visible about 8 or so seconds before the entry burn. What could cause such an event that much before the engine startup. As I've understood most of the startup stuff happens within a few seconds before ignition so 8s seems quite a long time.

[Alter Sachse]

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

[Bynaus]

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?

[Lars-J]

It is clearly some debris thrown loose during the Merlin restart. Why look for rube goldberg solutions when the obvious answer is staring you in the face?

[ugordan]

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.

[rpapo]

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.

[Rei]

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.