Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3  (Read 807521 times)

Offline thor1872

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #280 on: 03/27/2016 04:11 PM »
Octaweb ?

https://imgur.com/a/aYUJY 1:Gif 4.5Mo 2: picture
« Last Edit: 03/27/2016 04:14 PM by thor1872 »

Offline OxCartMark

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #281 on: 03/27/2016 05:25 PM »
Octaweb ?

Nice find.  You clearly have a case.  But its also the case that we believe the rocket was coming down tail first, the octaweb is at the tail end, and something did serious damage to the 9/16" (14mm) steel deck.  Hmmm.

Perhaps in addition to finding a way around the drone ban (such as taking Disney cruises) we also need a tarp penetrating microwave imager.

Online cscott

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #282 on: 03/27/2016 05:49 PM »
The *nozzles and chamber and turbopumps* are at the tail end.  The octoweb is above that.  I think there's plenty of opportunity for the business end of the rocket to do serious damage to the deck without disrupting the integrity of the octoweb.  The combustion chamber has to be a pretty strong chunk of metal, considering the pressures it must contain.
« Last Edit: 03/27/2016 05:50 PM by cscott »

Offline OxCartMark

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #283 on: 03/27/2016 06:37 PM »
Which brings up the question, what is this octaweb we all talk of?  Images are hard to come by.  Here is the closest thing found on the first page of a google image search.  To me the octaweb is a structure consisting of plate aluminum stock which extends from the engine throat to the bottom dome of the fuel tank in which all structural members are aligned with the long axis of the rocket.  There is a circular member around the perimeter which aligns with tank walls but only goes partway down.  There are radial members which go between engines for both structure and to contain an engine failure or fire to one compartment. These go to the bottom of the octaweb at the engine throat. I presume each of these radial members align directly under one of the tank weld seams but not necessarily so.  The radial members need to join at the center for structural reasons but there is also an engine at the center and the tank bottom bulges down at the center so I expect the vertical dimension of the octaweb has been trimmed there and doublers have been added.  This is one of two reasons the center engine is lower than the other engines, the other reason being that the center one needs to gimbal fully while the others sleep.  I don't think there is much horizontal structure to it, that the engines somehow impart their thrust forces into the vertical walls directly.  The only horizontal panels I think are there are the panels at the bottom of the octaweb which probably don't have much structural function, but serve to contain fires surrounding an individual engine and to keep out re-entry heat.  In other words, I see the bottom of the octaweb as being at the throat of the engine and the top of the octaweb extending only the minimum possible distance above the tops of the engines.  With respect to the impact, I see the nozzles hitting first, then the bottom of the octaweb, followed very quickly by the combustion chambers as the octaweb shortens then the pumps.  I don't see the octaweb surviving and the engines not or the other way around.
« Last Edit: 03/27/2016 06:42 PM by OxCartMark »

Offline Ohsin

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #284 on: 03/27/2016 06:41 PM »
What do you think the circled feature is?
if the part we see is the bottom of the tank, the feature is the attachment of leg's telescopic cylinder.
I cannot think to another feature passing "through" the wall of the tank this way.

Attachment point is way above on RP1 tank from bottom it can't be that.

http://forum.nasaspaceflight.com/index.php?topic=33788.msg1370037#msg1370037

Attaching top view of stage for reference on what that feature could be. Also a relevant view from recovered stage.

https://c2.staticflickr.com/2/1476/24175842475_57833a78ff_o.jpg
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Offline cambrianera

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #285 on: 03/27/2016 06:53 PM »

Attachment point is way above on RP1 tank from bottom it can't be that.

http://forum.nasaspaceflight.com/index.php?topic=33788.msg1370037#msg1370037


Thanks, these pictures shows clearly that the attachment point is about two meters above the bottom of the tank (and no, not way above).
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Offline cambrianera

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #286 on: 03/27/2016 06:55 PM »
Which brings up the question, what is this octaweb we all talk of?

This.
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Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #287 on: 03/27/2016 08:35 PM »
Regarding the grid fin, IIRC, its outer shape is not rectangular.  The side away from the rocket is, but the side near the body (where the attachment stem is) has two large chamfers to it.

Does this match what we see under the tarp?
« Last Edit: 03/27/2016 10:55 PM by meekGee »
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Offline CyndyC

Below is a classic Saturday Night Live skit from 1979 titled "What the Hell Is That?", with a much younger Bill Murray and Steve Martin. Please don't take it the wrong way, after awhile I just couldn't help but think of it, having no more theories of my own to add to the current discussion.

http://www.liveleak.com/view?i=872_1313749431
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Offline Ohsin

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #289 on: 03/27/2016 10:22 PM »

Attachment point is way above on RP1 tank from bottom it can't be that.

http://forum.nasaspaceflight.com/index.php?topic=33788.msg1370037#msg1370037


Thanks, these pictures shows clearly that the attachment point is about two meters above the bottom of the tank (and no, not way above).

I think its more than 3 meters which is a lot. Also don't forget the riveted seam, rest of interstage which is under tarp and the other grid fin most of which I think is sheared off. Attached a comparison with features that are somewhat similar to me(visible when enlarged).

Edit: '3' is just about part not orientation of it.
« Last Edit: 03/27/2016 10:59 PM by Ohsin »
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Offline CyndyC

Regarding the grid fin, IIRC, its outer shape is not rectangular.  The outer side is, but the side near the body (and the near the attachment stem) has two large chamfers to it.

Does this match what we see under the tarp?

No. Ohsin's closeups don't either.
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Offline Comga

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #291 on: 03/27/2016 10:56 PM »
Which brings up the question, what is this octaweb we all talk of?  Images are hard to come by.  Here is the closest thing found on the first page of a google image search.  To me the octaweb is a structure consisting of plate aluminum stock which extends from the engine throat to the bottom dome of the fuel tank in which all structural members are aligned with the long axis of the rocket..... (snip)

IIRC the Octoweb is made of titanium.  Musk discussed the thrust structure of the Falcon 1 as being made of titanium and being sufficiently expensive that its recovery would have by itself justified attempting to recover the first stage.

(Kudos to anyone with sufficiently heightened google-fu to be able to locate that quote, which is from more than a decade ago.

A titanium structure just might be able to survive intact, but not undamaged, from an impact with steel like this.
« Last Edit: 03/27/2016 10:57 PM by Comga »
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #292 on: 03/27/2016 10:58 PM »
Regarding the grid fin, IIRC, its outer shape is not rectangular.  The outer side is, but the side near the body (and the near the attachment stem) has two large chamfers to it.

Does this match what we see under the tarp?

No. Ohsin's closeups don't either.
So either this is a grid fin in a misleading orientation, or a partial grid fin, or something else.

One possibility is that this is a never seen before core of a composite leg sandwich....  But for the skin to be laminated like that, it would take a very odd application of force.

My money is still on a grid fin, but I'm noting the discrepancy...
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Offline Ohsin

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #293 on: 03/27/2016 11:10 PM »
Regarding the grid fin, IIRC, its outer shape is not rectangular.  The outer side is, but the side near the body (and the near the attachment stem) has two large chamfers to it.

Does this match what we see under the tarp?

No. Ohsin's closeups don't either.
So either this is a grid fin in a misleading orientation, or a partial grid fin, or something else.

One possibility is that this is a never seen before core of a composite leg sandwich....  But for the skin to be laminated like that, it would take a very odd application of force.

My money is still on a grid fin, but I'm noting the discrepancy...

Grid Fin in background has its under side facing us , mangled Grid Fin under interstage is rotated 180 and folded 'up'. Another Grid Fin could be under tarp in its normal folded position. Also I have no clue about the walls of lox tank does it have layers that could peel away?

Edit: Mangled fin could have been in deployed position just jutting out when whole upper portion of stage crashed upon it that would explain it being mangled and being buried.
« Last Edit: 03/27/2016 11:19 PM by Ohsin »
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Offline CyndyC

So either this is a grid fin in a misleading orientation...

That's what it is, I can see it now. One of the corners of the fin that is normally lopped off at an angle closer to the rocket body is the angle top left in the wreckage photo. Looking closely you can see the actual grid that runs perpendicular to that angled edge. It helps to compare to a good closeup of a normal fin. Now I'm thinking it's still attached too. Edited to add crop of Apirie98's photo, with angle in ref at bottom of his red circle.

         
« Last Edit: 03/28/2016 12:07 AM by CyndyC »
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Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #295 on: 03/28/2016 02:18 AM »
So either this is a grid fin in a misleading orientation...

That's what it is, I can see it now. One of the corners of the fin that is normally lopped off at an angle closer to the rocket body is the angle top left in the wreckage photo. Looking closely you can see the actual grid that runs perpendicular to that angled edge. It helps to compare to a good closeup of a normal fin. Now I'm thinking it's still attached too. Edited to add crop of Apirie98's photo, with angle in ref at bottom of his red circle.

         

Playing with the contrast, the cross-hatch pattern is clear, as well as the two parallel long ribs.

What I perceive as lack of chamfers is perspective.  If I use the grid pattern to figure out the viewing angle (note that they are close to perpendicular, which means that find is more "face on" than I'd assumed) then suddenly the chamfer is obvious.

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Online cscott

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #296 on: 03/28/2016 02:25 AM »
Which brings up the question, what is this octaweb we all talk of?  Images are hard to come by.  Here is the closest thing found on the first page of a google image search.  To me the octaweb is a structure consisting of plate aluminum stock which extends from the engine throat to the bottom dome of the fuel tank in which all structural members are aligned with the long axis of the rocket.  There is a circular member around the perimeter which aligns with tank walls but only goes partway down.  There are radial members which go between engines for both structure and to contain an engine failure or fire to one compartment. These go to the bottom of the octaweb at the engine throat. I presume each of these radial members align directly under one of the tank weld seams but not necessarily so.  The radial members need to join at the center for structural reasons but there is also an engine at the center and the tank bottom bulges down at the center so I expect the vertical dimension of the octaweb has been trimmed there and doublers have been added.  This is one of two reasons the center engine is lower than the other engines, the other reason being that the center one needs to gimbal fully while the others sleep.  I don't think there is much horizontal structure to it, that the engines somehow impart their thrust forces into the vertical walls directly.  The only horizontal panels I think are there are the panels at the bottom of the octaweb which probably don't have much structural function, but serve to contain fires surrounding an individual engine and to keep out re-entry heat.  In other words, I see the bottom of the octaweb as being at the throat of the engine and the top of the octaweb extending only the minimum possible distance above the tops of the engines.  With respect to the impact, I see the nozzles hitting first, then the bottom of the octaweb, followed very quickly by the combustion chambers as the octaweb shortens then the pumps.  I don't see the octaweb surviving and the engines not or the other way around.
I think you are confusing the bottom of the containment structure with the octogrid.  The octogrid carries the thrust loads, hence the "strong part" is above the combustion chamber.

Or am I wrong? Is it actually the nozzle, not the combustion chamber, which is the source of the thrust force?

Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #297 on: 03/28/2016 02:50 AM »
Which brings up the question, what is this octaweb we all talk of?  Images are hard to come by.  Here is the closest thing found on the first page of a google image search.  To me the octaweb is a structure consisting of plate aluminum stock which extends from the engine throat to the bottom dome of the fuel tank in which all structural members are aligned with the long axis of the rocket.  There is a circular member around the perimeter which aligns with tank walls but only goes partway down.  There are radial members which go between engines for both structure and to contain an engine failure or fire to one compartment. These go to the bottom of the octaweb at the engine throat. I presume each of these radial members align directly under one of the tank weld seams but not necessarily so.  The radial members need to join at the center for structural reasons but there is also an engine at the center and the tank bottom bulges down at the center so I expect the vertical dimension of the octaweb has been trimmed there and doublers have been added.  This is one of two reasons the center engine is lower than the other engines, the other reason being that the center one needs to gimbal fully while the others sleep.  I don't think there is much horizontal structure to it, that the engines somehow impart their thrust forces into the vertical walls directly.  The only horizontal panels I think are there are the panels at the bottom of the octaweb which probably don't have much structural function, but serve to contain fires surrounding an individual engine and to keep out re-entry heat.  In other words, I see the bottom of the octaweb as being at the throat of the engine and the top of the octaweb extending only the minimum possible distance above the tops of the engines.  With respect to the impact, I see the nozzles hitting first, then the bottom of the octaweb, followed very quickly by the combustion chambers as the octaweb shortens then the pumps.  I don't see the octaweb surviving and the engines not or the other way around.
I think you are confusing the bottom of the containment structure with the octogrid.  The octogrid carries the thrust loads, hence the "strong part" is above the combustion chamber.

Or am I wrong? Is it actually the nozzle, not the combustion chamber, which is the source of the thrust force?

I think both.  The nozzle is pushing upwards (remember that in addition to just pressure, the flow accelerates as it expands, awkwardly, so there's got to be a reaction back on the nozzle wall to counter that) and the chamber certainly generates a force (simple vee-m-dot).  All are channeled to the engine structure though, which in turn pushes on the octoweb, which distributes it to the tank structure.
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Offline OxCartMark

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #298 on: 03/28/2016 03:02 AM »
I think you are confusing the bottom of the containment structure with the octogrid.  The octogrid carries the thrust loads, hence the "strong part" is above the combustion chamber.

Or am I wrong? Is it actually the nozzle, not the combustion chamber, which is the source of the thrust force?
Golly we're wandering from ASDSing and I think I started it.  Whether the thrust is generated here or there in the engine the engine mounts are toward the top of the chamber and their connection to the octaweb is above that level.  The interface with the throat area is only a flexible blanket material.  But what you are calling containment structure may or may not be one and the same as the octaweb and could carry load (and be containment) even if its far below the engine attachment point and far below the tank.  Or not.
« Last Edit: 03/28/2016 03:07 AM by OxCartMark »

Offline meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #299 on: 03/28/2016 03:42 AM »
I think you are confusing the bottom of the containment structure with the octogrid.  The octogrid carries the thrust loads, hence the "strong part" is above the combustion chamber.

Or am I wrong? Is it actually the nozzle, not the combustion chamber, which is the source of the thrust force?
Golly we're wandering from ASDSing and I think I started it.  Whether the thrust is generated here or there in the engine the engine mounts are toward the top of the chamber and their connection to the octaweb is above that level.  The interface with the throat area is only a flexible blanket material.  But what you are calling containment structure may or may not be one and the same as the octaweb and could carry load (and be containment) even if its far below the engine attachment point and far below the tank.  Or not.

I believe the barge structure and the octoweb can be considered as a single entity now...
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