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#400
by
Mongo62
on 12 Jun, 2017 17:08
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Further note: I won't enter the discussion of it being a caliper or not, but it seems weird for a piece of ice to drift off camera in that direction (being first obscured by the S2-Dragon interface ring) and, a few seconds later, *reappear* on the same trajectory and with the same shape, receding into the distance.
I am referring to T+10:34 to 10:40.
Agreed. If that object seen at 10:34 is the same object, I can't imagine any trajectory for it that would have originated from the ROSA area deep in that trunk. I can imagine trajectories that originate at the S2/trunk interface area, specifically where all the other separation debris comes from normally. I suspect that "caliper" is smaller and much closer to the camera than the video makes it seem.
Edit: It's a big IF on that being the same object but it sure looks very similar.
It would be possible to determine how far away the object is from the camera by looking for perspective effects. Its apparent motion would increase by more, if it's closer to the camera at its closest point.
In other words, if it genuinely emerged from the trunk, its apparent motion across frame should not change too much, but if it's actually significantly closer than the trunk when it is picked up, there should be a larger difference in its apparent rate of motion -- it should appear to slow down more as time passes than if it were further away at the start.
This matters because if it is indeed closer to the camera when it is first picked up, then it quite possibly is just a piece of ice from the LOX dome on the second stage.
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#401
by
cscott
on 12 Jun, 2017 17:44
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And, to be clear, the preponderance of evidence at this point is that it is ice. All is quiet, both in public and L2: no NASA anomaly investigation, no worries from SpaceX, not a peep of anything unusual being looked into.
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#402
by
woods170
on 12 Jun, 2017 17:59
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Do we know the specs of the trunk with regards to temperature and humidity control? Is it advertised as being temperature and humidity controlled?
This is SAGE-III pre Dragon integration processing. It is in a clean tent within a clean room. Do you think they are not going to want temperature and humidity control?
I'm aware of a few Delta launches where the same was required but never actually achieved.
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#403
by
russianhalo117
on 12 Jun, 2017 18:14
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Do we know the specs of the trunk with regards to temperature and humidity control? Is it advertised as being temperature and humidity controlled?
This is SAGE-III pre Dragon integration processing. It is in a clean tent within a clean room. Do you think they are not going to want temperature and humidity control?
I'm aware of a few Delta launches where the same was required but never actually achieved.
AFAIU, their is a double ring seal on the mating plane between the capsule and the trunk as well as between the trunk and the Dragon PAF on the PAF side.
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#404
by
ennisj
on 12 Jun, 2017 18:21
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Here's one that I followed after it came to rest.
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#405
by
russianhalo117
on 12 Jun, 2017 18:28
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Here's one that I followed after it came to rest.
I believe I heard that it is steel plating.
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#406
by
kevin-rf
on 12 Jun, 2017 20:06
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Here's one that I followed after it came to rest.
I believe I heard that it is steel plating.
Dang...
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#407
by
cscott
on 13 Jun, 2017 00:48
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Makes sense. I'd said earlier that if the conductive paint worked out, they'd probably want to upgrade to steel plates or denser rebar for the future. Looks like securing steel plates to the pad isn't quite as simple as it may appear.
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#408
by
kevin-rf
on 13 Jun, 2017 01:18
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Makes sense. I'd said earlier that if the conductive paint worked out, they'd probably want to upgrade to steel plates or denser rebar for the future. Looks like securing steel plates to the pad isn't quite as simple as it may appear.
Maybe they didn't secure them and thought the plates weight alone would keep it in place. If they had bolted them down with some concrete anchors and the bolts shear or pulled out, that would be some serious forces.
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#409
by
guckyfan
on 13 Jun, 2017 06:51
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Makes sense. I'd said earlier that if the conductive paint worked out, they'd probably want to upgrade to steel plates or denser rebar for the future.
I hope so. That red cloud ring looks pretty but not like this should happen every landing.
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#410
by
cscott
on 13 Jun, 2017 13:32
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Makes sense. I'd said earlier that if the conductive paint worked out, they'd probably want to upgrade to steel plates or denser rebar for the future. Looks like securing steel plates to the pad isn't quite as simple as it may appear.
Maybe they didn't secure them and thought the plates weight alone would keep it in place. If they had bolted them down with some concrete anchors and the bolts shear or pulled out, that would be some serious forces.
Bernoulli's law: high velocity flow lowers pressure above the surface. Any gas left at std atm pressure under the plate is going to create a strong force across a large area.
They may need to engineer explicit jet blast deflectors, now that they are fairly confident of landing in the center of the pad. Or just take extra care sealing the edges of the plate.
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#411
by
LouScheffer
on 13 Jun, 2017 14:51
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Makes sense. I'd said earlier that if the conductive paint worked out, they'd probably want to upgrade to steel plates or denser rebar for the future. Looks like securing steel plates to the pad isn't quite as simple as it may appear.
Maybe they didn't secure them and thought the plates weight alone would keep it in place. If they had bolted them down with some concrete anchors and the bolts shear or pulled out, that would be some serious forces.
Bernoulli's law: high velocity flow lowers pressure above the surface. Any gas left at std atm pressure under the plate is going to create a strong force across a large area.
Both the Bernoulli forces pulling the plate up, and the force on the flat plat once it's pulled up, go (to first order) like the dynamic pressure, which is 1/2*rho*v^2, where rho is the density of air and v is the wind speed. A 2 cm thick steel plate, at a density of 8, masses 160 kg/m^2, so the downward pressue is g times that, or about 1600 N/m^2. According to
this wind force calculator you can get this force at a wind speed of a little over 50 m/s (about 112 mph) at sea level. This explains both why regular road construction sites don't worry about this, and why a flat steel plate on the landing pad might go flying.
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#412
by
JoerTex
on 13 Jun, 2017 17:27
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Makes sense. I'd said earlier that if the conductive paint worked out, they'd probably want to upgrade to steel plates or denser rebar for the future. Looks like securing steel plates to the pad isn't quite as simple as it may appear.
Maybe they didn't secure them and thought the plates weight alone would keep it in place. If they had bolted them down with some concrete anchors and the bolts shear or pulled out, that would be some serious forces.
Bernoulli's law: high velocity flow lowers pressure above the surface. Any gas left at std atm pressure under the plate is going to create a strong force across a large area.
They may need to engineer explicit jet blast deflectors, now that they are fairly confident of landing in the center of the pad. Or just take extra care sealing the edges of the plate.
Or, use steel grids so there's little 'trapped' air. The same forces are on the concrete, which has lousy tensile strength, so the lifting may be due to the edges of the plates - if they lift even a little, they're flying.
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#413
by
Comga
on 14 Jun, 2017 15:01
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Published on 14 Jun 2017
Was a loose wrench left in Dragon's trunk?
Watch at end of video, from about 2:49:
Extensively discussed
two pages back
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#414
by
punder
on 14 Jun, 2017 15:35
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Makes sense. I'd said earlier that if the conductive paint worked out, they'd probably want to upgrade to steel plates or denser rebar for the future. Looks like securing steel plates to the pad isn't quite as simple as it may appear.
Maybe they didn't secure them and thought the plates weight alone would keep it in place. If they had bolted them down with some concrete anchors and the bolts shear or pulled out, that would be some serious forces.
Bernoulli's law: high velocity flow lowers pressure above the surface. Any gas left at std atm pressure under the plate is going to create a strong force across a large area.
Both the Bernoulli forces pulling the plate up, and the force on the flat plat once it's pulled up, go (to first order) like the dynamic pressure, which is 1/2*rho*v^2, where rho is the density of air and v is the wind speed. A 2 cm thick steel plate, at a density of 8, masses 160 kg/m^2, so the downward pressue is g times that, or about 1600 N/m^2. According to this wind force calculator you can get this force at a wind speed of a little over 50 m/s (about 112 mph) at sea level. This explains both why regular road construction sites don't worry about this, and why a flat steel plate on the landing pad might go flying.
Maybe it was an experiment of some kind. For example, nail down a few plates with different types of anchors and see what happens.
Otherwise, I can't imagine why they'd leave loose steel plates lying around on the F9 landing pad.
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#415
by
kevinof
on 14 Jun, 2017 20:29
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THIS is why I love this friggin site! Learn something new every day.
Makes sense. I'd said earlier that if the conductive paint worked out, they'd probably want to upgrade to steel plates or denser rebar for the future. Looks like securing steel plates to the pad isn't quite as simple as it may appear.
Maybe they didn't secure them and thought the plates weight alone would keep it in place. If they had bolted them down with some concrete anchors and the bolts shear or pulled out, that would be some serious forces.
Bernoulli's law: high velocity flow lowers pressure above the surface. Any gas left at std atm pressure under the plate is going to create a strong force across a large area.
Both the Bernoulli forces pulling the plate up, and the force on the flat plat once it's pulled up, go (to first order) like the dynamic pressure, which is 1/2*rho*v^2, where rho is the density of air and v is the wind speed. A 2 cm thick steel plate, at a density of 8, masses 160 kg/m^2, so the downward pressue is g times that, or about 1600 N/m^2. According to this wind force calculator you can get this force at a wind speed of a little over 50 m/s (about 112 mph) at sea level. This explains both why regular road construction sites don't worry about this, and why a flat steel plate on the landing pad might go flying.
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#416
by
Ben the Space Brit
on 17 Jul, 2017 14:23
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SpaceX @SpaceX
Stage 2 returns the favor.
https://twitter.com/spacex
SpaceX @SpaceX
Dragon photobombs stage 2 before heading to the @Space_Station earlier this month.
https://twitter.com/spacex
What I like about both these pictures (and maybe this is a visual record of two uncrewed spacecraft, both still under control, whilst in close formation. A rare enough thing to see, I think.
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#417
by
jcm
on 13 Aug, 2017 19:20
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Let's look back to CRS-11: has there been any accurate post-mission figure been given for the downmass returned on CRS-11? On landing day reports were saying around 4100 lb (1860 kg) and earlier values
expected were around 1900 kg but I think these values were planned, not actual. Any definitive, more accurate value?