Author Topic: SpaceX Falcon 9 - CRS-8 Dragon - NET April, 2016 - DISCUSSION  (Read 397423 times)

Offline meekGee

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In the airborne video



I see the right leg deploy after the others - I assumed that all legs deploy at the same time. Is it sequential deployment, or just a sticky leg?

I keep seeing the same thing (right leg late), and given how close to touch down everything deploys, it's really scary to watch.

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Offline TomH

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Amazing! And this is why FH is late. The importance of this far exceeds FH's maiden flight. Now when FH flies, three stages will be recoverable rather than three thrown away. I think now we will begin to see rapid progress on other fronts: in-flight abort, FH, Dragon V2, Raptor. For awhile I was feeling that progress in space was simply coming to an end. Today, I feel the kind of optimism I felt in 1968.

Offline CyndyC

With my limited knowledge I don't think RP-1 would do that, so that leaves LOX. The only other fluid on board. Helium is pressed in gas form in the COPVs, wouldn't crystallize to my knowledge. So it has to be LOX venting, instantly puffing into ice. Clinging to the piping until a gimbal or vibration knocks it off. Probably means nothing. It's also got to be some insanely small amount, like measured in ml's. I think that's a safe bet what do you think?

I'll say none of the above and go outside the box, I mean outside stage 2. It's ultimately melting formerly frozen nitrogen gas from the RCS thrusters at the top of stage 1, when stage 1 was moving max plaid to get out of the way of the stage 2 plume at separation.

Edit: Or maybe hydraulic fluid from the pushers for stage separation.
« Last Edit: 04/09/2016 04:22 am by CyndyC »
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Offline CyndyC

In the airborne video I see the right leg deploy after the others - I assumed that all legs deploy at the same time. Is it sequential deployment, or just a sticky leg?

I keep seeing the same thing (right leg late), and given how close to touch down everything deploys, it's really scary to watch.

Is it not possible the legs can be operated independently just as the grid fans can? The legs are designed to contribute to drag, so even though most talk is about slowing down the stage, you probably don't want to slap on the brakes too hard either.
"Either lead, follow, or get out of the way." -- quote of debatable origin tweeted by Ted Turner and previously seen on his desk

Offline Brovane

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I would think they would want all the legs to come out at the same time, for aerodynamic reasons.  But, that said, I think on every flight thus far where we've seen the legs deploy, one has come down a touch later than the others.

As long as the staggered deployment doesn't spin the stage out of control (which it obviously didn't), and as long as they are all down and locked at touchdown, I guess it doesn't really matter.

Oh, and BTW, how great was it that SpaceX decided to share their drone view of the landing (in HD, no less) with us this time?  Maybe it has something to do with the fact that it was a NASA mission being launched, and as such had its feed going out over the satellite system via NASA TV.  Sort of a "now, let's all look nice for the camera" kind of moments... ;)

Maybe now they will share the video from the SES-9 mission.  I always love explosions. 
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Offline Herb Schaltegger

Maybe now they will share the video from the SES-9 mission.  I always love explosions. 

That would be nice. So would OCISLY onboard video from this afternoon.
« Last Edit: 04/09/2016 04:34 am by Herb Schaltegger »
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Offline meekGee

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With my limited knowledge I don't think RP-1 would do that, so that leaves LOX. The only other fluid on board. Helium is pressed in gas form in the COPVs, wouldn't crystallize to my knowledge. So it has to be LOX venting, instantly puffing into ice. Clinging to the piping until a gimbal or vibration knocks it off. Probably means nothing. It's also got to be some insanely small amount, like measured in ml's. I think that's a safe bet what do you think?

I'll say none of the above and go outside the box, I mean outside stage 2. It's ultimately melting formerly frozen nitrogen gas from the RCS thrusters at the top of stage 1, when stage 1 was moving max plaid to get out of the way of the stage 2 plume at separation.

Edit: Or maybe hydraulic fluid from the pushers for stage separation.
Ideally, yes.

But - the fins are controlled by mechanism that can move them at will - back and forth, and proportionally.  It is part of a servo system.

The legs in comparison are ginormous, and are not so efficient as control surfaces.  They are operated by a one-time push-only system that barely has enough oomph to get them open, going all out.

Being able to control the legs with finesse would take a much heavier actuator.

They were talking about improving the legs, but the end goal, I believe, is just enough power to be able to deploy them earlier during the landing.

My 2c.

Edit: using legs as air brakes was mentioned by Musk a long time ago.  It may no longer be the plan.

One problem: if the legs open before the engine starts, and do so asymetrically, you only have the grid fins to keep the rocket straight, and that's not a lot.
« Last Edit: 04/09/2016 05:21 am by meekGee »
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Offline jimbowman

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The 4k landing footage ain't too bad  ;D

Online Steven Pietrobon

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Some captures I made soon after launch, but only now have the time to post them.

SpaceX LCC showing grid fin deployed in top left screen.

Series of captures showing the "white stuff" whatever it is. The first three showing it in position and then falling away. The next two showing the stuff reappearing.

View inside the Dragon trunk.

SpaceX LCC showing the Stage 2 LOX tank on the left screen and the first stage on OCISLY on the right screen.

Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline daver

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My son and I watched from A1A.
Truly amazing.
Thank You SpaceX

Online Steven Pietrobon

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Some screen capture from the full SpaceX webcast.

Our presenters and control centres.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Steven Pietrobon

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Talking about Dragon.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Steven Pietrobon

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Spacecraft clean room and performing testing.
« Last Edit: 04/09/2016 06:37 am by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Steven Pietrobon

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Rare view of base of second stage.

Dragon 2.
« Last Edit: 04/09/2016 06:40 am by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Steven Pietrobon

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Talking about BEAM.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Ben the Space Brit

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Is this the second stage?

Yes it is! Cool find; I've never seen a discarded stage from the spacecraft so long after S/C separation before!
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Online Steven Pietrobon

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Dragon late load.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Steven Pietrobon

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Mission profile. They show the second stage splitting in two and Dragon being grabbed by the nose!
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Steven Pietrobon

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Some pre launch and launch shots. The nozzle looks like it is back to using the old style thin partial rings to hold the nozzle in place.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online Steven Pietrobon

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The beautiful landing!
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

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