Author Topic: SpaceX Falcon 9 - CRS-9 Dragon - NET July 18, 2016 - DISCUSSION  (Read 173759 times)

Offline LouScheffer

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It also might slide before tipping.  Static coefficient of friction of .5 to .25. 
Well, the downward force is about 265 kN.  Tipping force is about 80 kN to 113 kN depending on the wind direction with respect to the legs.

So if the coefficient of fraction is < 0.3, it always slides before it tips.  If >0.43, it always tips before it slides.  In between, it could either slide or tip depending on the direction of the wind.

I'm sure SpaceX would prefer this stay a thought experiment.

Online ugordan

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Impressive new video from SpaceX

If that video is real time (and it looks like it might be), there's indication that at 8 seconds in either the outer two engines were started only just then or all 3 abruptly throttled up. I'm leaning toward the former explanation as it looks near-instantaneous. A brightening of the engine glow and the shock bubble puffed up at the same time.

Offline Elmar Moelzer

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Impressive new video from SpaceX

If that video is real time (and it looks like it might be), there's indication that at 8 seconds in either the outer two engines were started only just then or all 3 abruptly throttled up. I'm leaning toward the former explanation as it looks near-instantaneous. A brightening of the engine glow and the shock bubble puffed up at the same time.
Full video on youtube says it is "high speed footage".
https://www.youtube.com/channel/UCtI0Hodo5o5dUb67FeUjDeA

Offline Steven Pietrobon

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Here's the direct link.

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

Offline JamesH65

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Impressive new video from SpaceX

If that video is real time (and it looks like it might be), there's indication that at 8 seconds in either the outer two engines were started only just then or all 3 abruptly throttled up. I'm leaning toward the former explanation as it looks near-instantaneous. A brightening of the engine glow and the shock bubble puffed up at the same time.

High speed footage, filmed at 200fps or more (guess), then played back at 30fps, giving a slow motion view.

I particularly like the footage of the single engine landing burn - shows how harsh the environment is whilst landing.

Online ugordan

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High speed footage, filmed at 200fps or more (guess), then played back at 30fps, giving a slow motion view.

I don't think that instagram video is *that* much different from realtime speed. Some of the stuff in that other youtube video is certainly not high speed footage, but regular footage like the long ascent plume, and the staging sequence so clearly the "high speed" caption does not apply to all segments.

If the instagram bit *is* slow motion, I'd wager it's at most 60 fps progressive original video (which is what I believe the CCAFS tracking cameras use nowadays) played back at 30 fps (instagram) and 24 fps (youtube version). Look at the motion of stars that show up in the background, now imagine how it would look if it was played at your "original" 200 fps. The plume filament dynamics roughly match what I've seen in other amateur videos, although they weren't zoomed in as much, which is why I'm thinking this is (near)realtime speed. Closer to realtime than 7x slow motion at least.
« Last Edit: 08/10/2016 10:52 AM by ugordan »

Offline JamesH65

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High speed footage, filmed at 200fps or more (guess), then played back at 30fps, giving a slow motion view.

I don't think that instagram video is *that* much different from realtime speed. Some of the stuff in that other youtube video is certainly not high speed footage, but regular footage like the long ascent plume, and the staging sequence so clearly the "high speed" caption does not apply to all segments.

If the instagram bit *is* slow motion, I'd wager it's at most 60 fps progressive original video (which is what I believe the CCAFS tracking cameras use nowadays) played back at 30 fps (instagram) and 24 fps (youtube version). Look at the motion of stars that show up in the background, now imagine how it would look if it was played at your "original" 200 fps. The plume filament dynamics roughly match what I've seen in other amateur videos, although they weren't zoomed in as much, which is why I'm thinking this is (near)realtime speed. Closer to realtime than 7x slow motion at least.

Sorry, only some bits of the linked YouTube video are slowed right down. Other bits are real time. Meant to come back and modify my post to make that clear, but did actual work instead.

Offline mvpel

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Here's the direct link.

Interesting feature on the flexible boot around the engine here - does this show infrared hot spots, burning on the surface of the boot, or visible flames in the interior of the engine compartment through a hole in the boot?
« Last Edit: 08/11/2016 04:28 PM by mvpel »
"Ugly programs are like ugly suspension bridges: they're much more liable to collapse than pretty ones, because the way humans (especially engineer-humans) perceive beauty is intimately related to our ability to process and understand complexity. A language that makes it hard to write elegant code makes it hard to write good code." - Eric S. Raymond

Offline hrissan

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Here's the direct link.

Interesting feature on the flexible boot around the engine here - does this show infrared hot spots, burning on the surface of the boot, or visible flames in the interior of the engine compartment through a hole in the boot?
They are very stable - might they be reflections of the main flame in some metallic stage features?

BTW: If this inferno around engines happens during [early phase of?] landing burn, then how does braking burn look? :):):)
Wow just wow...
« Last Edit: 08/11/2016 10:15 PM by hrissan »

Offline mn

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CRS-9 Dragon will be heading into Entry Interface (EI) at this time, protected by her PICA-X heat shield.



On the Dragon return UPDATES thread, chris posted this image of reentry - which is of course just an artist drawing.

I was wondering if a reentry was ever recorded by the ISS? is it even possible to arrange the reentry to occur while the ISS is overhead to record?

Offline eriblo

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CRS-9 Dragon will be heading into Entry Interface (EI) at this time, protected by her PICA-X heat shield.

[...]
On the Dragon return UPDATES thread, chris posted this image of reentry - which is of course just an artist drawing.

I was wondering if a reentry was ever recorded by the ISS? is it even possible to arrange the reentry to occur while the ISS is overhead to record?
Both launches and reentries can often be seen from the ISS - haven't heard of a Dragon having that timing yet (with regard to the ISS and the sun) but here are some quick google results:

Soyuz TMA-17M contrail
Progress 42P
Final shuttle landing
« Last Edit: 08/26/2016 04:58 PM by eriblo »

Offline eriblo

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If you think about it seems unlikely the we will see one for Dragon or any crewed capsules anytime soon: If you are going to recover something you want to maximize the amount of daylight to do so in, i.e. land early in the (local) day. Meaning you vill reenter in daylight...  The shuttles landed on a specified runway so they had other concerns/could show off ;)

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