Author Topic: Building BFR  (Read 72534 times)

Offline woods170

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Re: Building BFR
« Reply #20 on: 04/09/2018 05:30 pm »

Interesting that they not using the big robot arm approach used by NASA/Boeing/Janicki.  I assume it's since they're attaching the domes after, this giant tube is simpler.

I'm assuming, in ignorance, that the outer tube will allow them to cure it in place (Also assuming out of autoclave).

I suggest do not assume anything. The image shared by Elon shows just the lay-up mould, resting on its supports, housed in a temporary facility. The tent is NOT where actual manufacturing of BFS will be done. This is just an image of recently arrived tooling sitting in temporary storage.

The stands the cylinder is sitting on seem to be more substantial than SpaceX would build simply to store a bit of tooling. They look like tooling.

Yes, they are part of the tooling. No better way to hold the mandrel than having it sit on its own rollers. But still, this is just storage for now.

Offline aero

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Re: Building BFR
« Reply #21 on: 04/09/2018 05:33 pm »
I expect the stands are more than just stands, too. Likely they are rollers, but I imagine their purpose to be simply to rotate the mandrel while it is sitting to avoid deformation of the mandrel. The bearing in the visible end is the support point around which the mandrel rotates, for use when the tool is completed and the composite is being laid up.

The mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight. And if you have ever tried to move a railroad car using a wheel jack, you will know what I mean. Before college, I worked one summer at a concrete ready-mix plant where the dry cement arrived in hopper cars. They had to be manually moved along the siding to the storage bins and bottom dumped. The longer a loaded car sat, the harder it was to start it moving. That was because the steel wheels, track and wheel bearings deformed over time as the weight of the load pressed them together.
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Offline Slarty1080

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Re: Building BFR
« Reply #22 on: 04/09/2018 05:45 pm »
The stands I believe are more than just stands - they are rollers - some driven and some passive. Meaning that there are no end domes, rather the composite wraps around the mandrel to form a barrel section. This means that the barrel section doesn't go to the ends of the mandrel (where the rollers are). I would also go so far as to say that the near side end may have air injectors and the far side has a taper to allow the mandrel to be removed from the composite barrel segment when complete. This would make it some amount less than the assumed 15M in length.

(I've annotated, with what looks like a four year old's ability, the image to point out the ends of the actual composite barrel and possible air injectors at the near end).

Also, the outer diameter of the mandrel is of course the inside diameter of the barrel section of the BFS (and perhaps BFR as well?). Any guesses as to how thick the actual composite / insulation / etc will be?

Very curious as to how they intend on mating the three dome sections (including the common inside dome between the two tanks).

Woods170 gave a nice photo of the Dragon trunk barrel section being wound - quite possible this will utilize a similar process.
My guess on the thickness of the shell is 3mm.

On the matter of mating the dome sections and the internal components, is there any way to access / inspect the interior of the tank post manufacture?
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Offline OxCartMark

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Re: Building BFR
« Reply #23 on: 04/09/2018 06:03 pm »
The stands I believe are more than just stands - they are rollers - some driven and some passive.
I'll buy that and further add that the things that look like control stations below the rollers may actually be control stations for the rollers.  However it could be that those rollers and stands are leftovers from the process of fabricating the mandrel in place there, not the ones that will be used to lay on carbon.  Assuming for a second that the rollers and stands are for the laying on of carbon I'd guess you wouldn't store them under the mandrel because they would have come on a truck on a pallet and you'd leave them on the pallet until they were brought to the production floor and they'd have to be installed on the production floor before the mandrel drum would be moved there which is made more difficult by the fact that they are currently supporting the drum in this location and there is no overhead crane (without disassembling the tent).  And notice that they are not on pallets or railroad ties or similar, they are directly on the floor type surface in the tent.

Any guesses as to how thick the actual composite / insulation / etc will be?
We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.

The mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight.
I'm not buying that steel deforms at stresses significantly below its yield strength at room temperature over an extended period of time.  There doesn't seem to be any theoretical basis for that to occur. Perhaps the phenomenon you describe is due to the oil film in the bearings being crushed out or due to cold welding.
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Offline Wolfram66

Re: Building BFR
« Reply #24 on: 04/09/2018 06:13 pm »
A little tweaking in photoshop express shows a little more detail of the inner workings of the mandrel

This piece of kit will now be known as Barbra ... Mandrel #Snarkasm
« Last Edit: 04/09/2018 07:24 pm by Wolfram66 »

Offline Rabidpanda

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Re: Building BFR
« Reply #25 on: 04/09/2018 06:18 pm »
The stands I believe are more than just stands - they are rollers - some driven and some passive.
I'll buy that and further add that the things that look like control stations below the rollers may actually be control stations for the rollers.  However it could be that those rollers and stands are leftovers from the process of fabricating the mandrel in place there, not the ones that will be used to lay on carbon.  Assuming for a second that the rollers and stands are for the laying on of carbon I'd guess you wouldn't store them under the mandrel because they would have come on a truck on a pallet and you'd leave them on the pallet until they were brought to the production floor and they'd have to be installed on the production floor before the mandrel drum would be moved there which is made more difficult by the fact that they are currently supporting the drum in this location and there is no overhead crane (without disassembling the tent).  And notice that they are not on pallets or railroad ties or similar, they are directly on the floor type surface in the tent.

Any guesses as to how thick the actual composite / insulation / etc will be?
We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.

The mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight.
I'm not buying that steel deforms at stresses significantly below its yield strength at room temperature over an extended period of time.  There doesn't seem to be any theoretical basis for that to occur. Perhaps the phenomenon you describe is due to the oil film in the bearings being crushed out or due to cold welding.

This phenomenon is called Creep and is generally only a consideration for metals when they are exposed to a continuous load at very high temperatures. So not applicable to rail cars or this tooling.

Offline DistantTemple

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Re: Building BFR
« Reply #26 on: 04/09/2018 06:25 pm »
All of you are talking as if the OUTER cylinder is the mandrel. Most of you have mentioned rotating it on the shown rollers when winding the carbon.

I am quite certain that its the INNER cylinder that is the mandrel. The inner one is mounted on bearings, and has an inner structure to keep it rigidly circular. Its also the right diameter.

Between the two is an annular 1m, enough for a custom auto wind head to traverse the surface on tracks.

The outer cylinder could be the beginning of an oven or autoclave. Why steel - if thats what it is? Could be pressurised, if that would benefit curing. Why rollers... don't know.
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Offline butterwaffle

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Re: Building BFR
« Reply #27 on: 04/09/2018 06:29 pm »
The stands I believe are more than just stands - they are rollers - some driven and some passive.
I'll buy that and further add that the things that look like control stations below the rollers may actually be control stations for the rollers.  However it could be that those rollers and stands are leftovers from the process of fabricating the mandrel in place there, not the ones that will be used to lay on carbon.  Assuming for a second that the rollers and stands are for the laying on of carbon I'd guess you wouldn't store them under the mandrel because they would have come on a truck on a pallet and you'd leave them on the pallet until they were brought to the production floor and they'd have to be installed on the production floor before the mandrel drum would be moved there which is made more difficult by the fact that they are currently supporting the drum in this location and there is no overhead crane (without disassembling the tent).  And notice that they are not on pallets or railroad ties or similar, they are directly on the floor type surface in the tent.

Any guesses as to how thick the actual composite / insulation / etc will be?
We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.

The mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight.
I'm not buying that steel deforms at stresses significantly below its yield strength at room temperature over an extended period of time.  There doesn't seem to be any theoretical basis for that to occur. Perhaps the phenomenon you describe is due to the oil film in the bearings being crushed out or due to cold welding.

This phenomenon is called Creep and is generally only a consideration for metals when they are exposed to a continuous load at very high temperatures. So not applicable to rail cars or this tooling.

Given how much empty space is inside the mandrel, I agree. But I know they _do_ need to rotate similar-diameter steam turbine blades when _not_ in service at power plants in order to prevent deformations that lead to imbalance and bad resonance when they power up again.

Offline Johnnyhinbos

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Re: Building BFR
« Reply #28 on: 04/09/2018 06:33 pm »
The stands I believe are more than just stands - they are rollers - some driven and some passive.
I'll buy that and further add that the things that look like control stations below the rollers may actually be control stations for the rollers.  However it could be that those rollers and stands are leftovers from the process of fabricating the mandrel in place there, not the ones that will be used to lay on carbon.  Assuming for a second that the rollers and stands are for the laying on of carbon I'd guess you wouldn't store them under the mandrel because they would have come on a truck on a pallet and you'd leave them on the pallet until they were brought to the production floor and they'd have to be installed on the production floor before the mandrel drum would be moved there which is made more difficult by the fact that they are currently supporting the drum in this location and there is no overhead crane (without disassembling the tent).  And notice that they are not on pallets or railroad ties or similar, they are directly on the floor type surface in the tent.

Any guesses as to how thick the actual composite / insulation / etc will be?
We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.

The mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight.
I'm not buying that steel deforms at stresses significantly below its yield strength at room temperature over an extended period of time.  There doesn't seem to be any theoretical basis for that to occur. Perhaps the phenomenon you describe is due to the oil film in the bearings being crushed out or due to cold welding.

This phenomenon is called Creep and is generally only a consideration for metals when they are exposed to a continuous load at very high temperatures. So not applicable to rail cars or this tooling.

Given how much empty space is inside the mandrel, I agree. But I know they _do_ need to rotate similar-diameter steam turbine blades when _not_ in service at power plants in order to prevent deformations that lead to imbalance and bad resonance when they power up again.
It’s my guess that this mandrel is fabricated from invar, which is highly dimensionally and thermally stable. Not your father’s mandrel, this...
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Offline kraisee

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Re: Building BFR
« Reply #29 on: 04/09/2018 06:46 pm »
It’s my guess that this mandrel is fabricated from invar, which is highly dimensionally and thermally stable. Not your father’s mandrel, this...

Invar is certainly the norm, and SpX have used it for a number of other parts already on both F9 and Dragon.   But it should also be noted that Janicki specializes in making composite layup tooling too, so a composite mandrel is a definite possibility here.

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Offline Lar

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Re: Building BFR
« Reply #30 on: 04/09/2018 07:03 pm »
I am buying the larger diameter thing as outer shell. Either its supports unbolt or the other end is arranged differently, else the newly wound shell can't be withdrawn after it's laid up (and cured, possibly)
« Last Edit: 04/09/2018 07:05 pm by Lar »
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Offline Slarty1080

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Re: Building BFR
« Reply #31 on: 04/09/2018 07:29 pm »
Any guesses as to how thick the actual composite / insulation / etc will be?

Quote
We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.

Elon Musk said that they had tested the O2 tank to its design pressure and then "a little bit more" the video of the O2 tank rupture states that the tank was tested to 2.3 atmospheres.
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Offline OxCartMark

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Re: Building BFR
« Reply #32 on: 04/09/2018 07:47 pm »
I didn't understand until Wolfram's photo tweaking that there was an inner and an outer.  I'm of the opinion that (as stated above) a custom winding head works the inner drum and the outer provides a clean environment for winding and an autoclave enclosure.  So if its the inner we're talking about then I don't think the photo scaling that someone did above applies anymore.  Which takes away much of the need to move it indoors, it is indoors in many of the ways that count.  But just out of curiosity, do any of you with photo tweaking skills see bolts into the floor?

Kinda looks like one of the rotating sets that Hollywood uses to film space scenes.  But this one's for making a scene in space.
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Offline speedevil

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Re: Building BFR
« Reply #33 on: 04/09/2018 07:57 pm »
I didn't understand until Wolfram's photo tweaking that there was an inner and an outer.  I'm of the opinion that (as stated above) a custom winding head works the inner drum and the outer provides a clean environment for winding and an autoclave enclosure.  So if its the inner we're talking about then I don't think the photo scaling that someone did above applies anymore.

The inner drum is very visible in the photo.

Offline sanman

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Re: Building BFR
« Reply #34 on: 04/09/2018 08:09 pm »
How do you get the mandrel out, once you've wrapped the composite around it?

Offline Johnnyhinbos

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Re: Building BFR
« Reply #35 on: 04/09/2018 08:28 pm »
How do you get the mandrel out, once you've wrapped the composite around it?
From what I've read, there are many ways, depending on your manufacturing process. For instance, you can inject air between the outside of the mandrel and the inside of the composite structure and use that air bearing to slide the structure off - that was what I was alluding to in my earlier post. Or you can cool the mandrel to fractionally reduce it's diameter (either from active heating during manufacture and allow to cool, or active cooling post manufacture). Then there are release agents. And some mandrels are meant to disassemble into smaller sections. When I toured the OrbitalATK facility in Promontory, UT prior to the QM-1 test fire of the SLS SRB, I _believe_ the mandrels used to cast the segments used this last technique - though not 100% positive I'm remembering this correctly...
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Offline Robotbeat

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Re: Building BFR
« Reply #36 on: 04/09/2018 09:38 pm »
The outer surface is almost certainly what is being built on as the mandrel surface. You’re not going to fit a robot in that tight space between the two. The inner one is probably just reinforcement.
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Offline Navier–Stokes

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Re: Building BFR
« Reply #37 on: 04/09/2018 09:39 pm »
Great article  from vaporcobra with pictures of additional tooling: SpaceX’s BFR factory abuzz with work activity and giant rocket tooling

Offline Robotbeat

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Re: Building BFR
« Reply #38 on: 04/09/2018 09:40 pm »
How do you get the mandrel out, once you've wrapped the composite around it?
From what I've read, there are many ways, depending on your manufacturing process. For instance, you can inject air between the outside of the mandrel and the inside of the composite structure and use that air bearing to slide the structure off - that was what I was alluding to in my earlier post. Or you can cool the mandrel to fractionally reduce it's diameter (either from active heating during manufacture and allow to cool, or active cooling post manufacture). Then there are release agents. And some mandrels are meant to disassemble into smaller sections. When I toured the OrbitalATK facility in Promontory, UT prior to the QM-1 test fire of the SLS SRB, I _believe_ the mandrels used to cast the segments used this last technique - though not 100% positive I'm remembering this correctly...
And if you do both heating and cooling, you can get up to a percent of size difference for aluminum.

If you’re using the differential temperature method, the last thing you want the mandrel made of is invar.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline rory

Re: Building BFR
« Reply #39 on: 04/09/2018 10:26 pm »
Worth noting that Ascent Aerospace retweeted an article about their hybrid Invar/composite layup tooling two hours before they tweeted about the BFR tooling, in their first tweets in weeks:

Quote from: Mike Richardson, Aero Mag
Hey you, listen up! Read my latest @JECComposites interview article with Colin Birtles of @AscentAerospace regarding the company's launch of its HyVarC hybrid Invar and composite mould solutions

https://twitter.com/aero_mag/status/982263038903382016

Quote from: Ascent Aerospace on Twitter
@SpaceX showing off the main body tool for the BFR 🤩🤩🤩

https://twitter.com/AscentAerospace/status/983382489035980800

https://www.aero-mag.com/tooling-mould-die/

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