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#1500 by roma847 on 29 Jun, 2018 15:13
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Absolutely I'll be contacting you with questions here and there about what sort of products you found for some of the details (eyewash bowl, lamp ferrules, etc). Being a CAD engineer I'm tentatively considering sizing up the LVM sets and etching new parts for my tower, and the RSS resin parts to be sized up to 1:144 and 3D printed.
Hi Mike,
cool idea, but keep in mind that LVM has adapted all their detail kit parts to the Revell Launch Tower kit (4911), which is a mix of different scales.
Only the RSS Payload Bay is 1/144, so that the Shuttle (1/144) fits in.
BTW, what do you think about a solution for the mysterious wavelike SOFI texture on the STS-6 ET-8 surface, have you any ideas?
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#1501 by roma847 on 29 Jun, 2018 23:34
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Hi everybody,
after my successful Ultrasonic cleaning of my FUD-IT I am currently on one of my obligatory voyages of discovery, still looking for the origin of this wavelike SOFI structure of the first generation of ETs, which one can see both on this photo of the ET-33 (STS-36) by George Gassaway,
Source: georgesrockets.com
as well as on the LO2 tank (ET-137) in this video (5:14) before Discovery's last mission ( STS-133).
In the meantime, I was following the traces concerning the ET production, which are known to lead directly to the Michoud Assembly Facility (MAF ), popularly NASA's Rocket Factory.
Although I have not found any photos of the SOFI Cells, a friend from NSF forum (psloss) has posted an interesting hint to drawings from the assembly process of the tank production.
And they come from the PDF Space Shuttle/External Tank System Definition Handbook SLWT, Volume II/2, among others. also this picture here.
On it one can see the manufacturing and assembly cells, in which both the priming (Prime) and the SOFI Application of the LH2- and LO2 tanks, as well as the Intertanks took place.
From there all ET parts went into the Cell A, where they were assembled vertically. And of this largest cell at that time, I also found an impressive picture by Jester, namely this one, which is linked to the Hi-Res. image, in which one can see a plate at the lower right corner with Cell A.
Source: forum.nasaspaceflight.com (Jester)
This success made me even more curious, and since I really wanted to find these special SOFI Cells of the MAF, I searched further.
The difficulty lies in the fact that Google-searching for SOFI Application & MAF lead almost without exception to actual photos of their equipment there, but it must be noted that in the MAF after the end of the Shuttle-Program 2012/13 all former equipment was dismantled or modified for the bigger tanks of the SLS program, which does not help me much.
But in this context, I finally found what I was looking for and found this great photo-combination on which the Cell B & C in Building 110 see before (top) as well as after (below) the dismantling, in which the LH2 tanks got their SOFI-TPS.
Source: blogs.nasa.gov
Since then, at this lace is standing the new Vertical Assembly Center (VAC) with the world's largest Friction Stir Weld Machine for the production of the larger SLS tanks.
So far, so good, but that still left the answerless question of the explanation of the typical wavy SOFI structure of the ETs.
As far as I know by now, 90% of the total ET-SOFI insulation was applied with an Automatic Gun Spray System, and only 10% by hand, as can be seen here on the connecting flange between the Intertank and the LO2 tank.
Source: NASA
But how this automatic system worked in the SOFI cells and how and why this wave-like structure was created during coating still remains a mystery, but which I still want to solve it somehow,
why the search goes on ... 
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#1502 by Starbase101 on 29 Jun, 2018 23:50
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cool idea, but keep in mind that LVM has adapted all their detail kit parts to the Revell Launch Tower kit (4911), which is a mix of different scales. Only the RSS Payload Bay is 1/144, so that the Shuttle (1/144) fits in.
Yes, I know. Dumb of Revell to do that, but at this point it is what it is. I expect portions of the Revell tower will be usable, and most of it scratch-built using the EDU parts for reference. The LVM parts will be useful as references for making new parts in the correct scale, and then afterwards I'm sure I can sell the original LVM sets considering how rare and collectible they are.BTW, what do you think about a solution for the mysterious wavelike SOFI texture on the STS-6 ET-8 surface, have you any ideas?
This one is indeed a pickle. I've been thinking on it for about a week now and actually do have a couple ideas besides just 3D printing it. (And honestly, if we 3D printed everything then why buy a model kit?) I should make a drawing to help explain the idea. Maybe I'll have time for that on the weekend. -
#1503 by roma847 on 29 Jun, 2018 23:57
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I'm really looking forward to that and already curious.
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#1504 by Starbase101 on 30 Jun, 2018 04:57
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Okay, this might sound odd but maybe it could work. First add thin plastic, metal, or heavy paper strips around the tank. For the conical top section these will probably need to be cut as arcs for them to lay properly. Then apply a high-viscosity adhesive over them to "round off" the corners. You could maybe add tissue over the adhesive in a sort of decoupage to help smooth the contours and provide a texture. Or, perhaps just primer and paint over the strips might be enough to round them out at this scale. I would test out the concept on a prototype for working out the strip size and spacing. You'll want to keep this very thin to not increase the tank size too much. (See attached image for graphical representation of the concept.)
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#1505 by roma847 on 30 Jun, 2018 13:47
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Hi Mike,
the same method I have already considered and have thought of 1 mm wide thin masking tape. The smallest Evergreen strips would be even better because they are narrower, e.g. 0.75 mm wide. But unfortunately, they are 0.25 mm thick, what would be too much and increase the tank too much.
And over these stripes then will be applied the "Flour technique" by a friend of mine in the Raumcon Forum, who had this cool idea for simulating the foam structure.
And this is the amazing result, a great looking SOFI structure.
Meanwhile, I learned from an ET specialist, Vincent Morales (Sr. Staff QA Engineer), Lockheed Martin, that the distance between the wavy rings (Peak to Valley) in the Barber Pole SOFI mode should have been about 5'' (130 mm), which roughly confirms the distance of about 1 mm (1:144) that I estimated.
Starting from this Peak-to-valley width of about 5'' = 127 mm = 0,9 mm (1:144) I have designed the following sketch (1:2) to show the profile of this wave structure, as I could imagine. 
Considering that the average SOFI thickness on the ET is approx. 1'' (25,4 mm), I have drawn a profile whose peak height I assumed with about 0,5'', which rounded up to approx. 0,1 mm in 1/144, what would be very flat.
Or maybe Vincent meant the Peak-to-peak width of 5'', which would be similar to a profile that would look something like the ones I drew in my first draft.
Now it would be important to find out how big this peak height of the foam insulationactually was at that time.
Let's see if or how Vince Morales will comment on that, because he should actually remember it.
BTW, in your picture the valleys seem to me too sharp, especially if we see this STS-6 image.
Source: nasaspaceflight.com (woods170)
Therefore, I think that they should be slightly bent, as I have indicated by the red arcs.
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#1506 by mike robel on 30 Jun, 2018 16:20
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There is a tool somewhere for armor modelers for the simulation of Zimmerent anti-mine coating on WWII Germany tanks.
I used to do it with a thin layer of body putty, then I would use the small Xacto chisel blade to make the cells. I think someone came out with a "comb" to do it. Such a tool might work with an effect suggested by Starbase101 above. -
#1507 by Starbase101 on 30 Jun, 2018 16:49
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It was just a simple sketch to help communicate the idea, not at all intended to be in scale with anything. Obviously, as drawn it is much too thick. That's why making the ribs from something very thin prior to spraying with texture would be appropriate.
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#1508 by mike robel on 30 Jun, 2018 20:56
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understood
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#1509 by mike robel on 30 Jun, 2018 20:59
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Heres a link. There are some other ones as well
https://www.amazon.com/Trumpeter-Zimmerit-Application-Tool-5-Piece/dp/B003M2N2LM -
#1510 by roma847 on 30 Jun, 2018 21:45
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Thanks Mike,
and you mean seriously that one can reproducible create this regular pattern at an interval of 1 mm this way over a length of 170 mm?
I do not want to dump my ET afterwards in the waste.
Then I prefer gluing of 200 strips onto the ET and sprinkling flour on it.
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#1511 by roma847 on 30 Jun, 2018 22:05
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It was just a simple sketch to help communicate the idea, not at all intended to be in scale with anything. Obviously, as drawn it is much too thick. That's why making the ribs from something very thin prior to spraying with texture would be appropriate.
No problem, it was a clever approach for finding a suitable method.
Surely you can draw such a radiused profile with your CAD program, right? What 3D-Software do you use?
What do you think of the 3D printing of such a wavelike textured ET?
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#1512 by Starbase101 on 30 Jun, 2018 23:10
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I used TurboCAD Mac Pro and AutoDesk 123Design for modeling, and Meshmixer for .stl cleanup. For slicing I use Simplify3D, and for printers I own a Mass Portal Pharaoh XD30 and a MAKEiT-3D PRO-L. It would probably not be difficult at all to do the CAD work, but there is a reason why I have not started on my own shuttle model project yet.....time! Perhaps I could model one in the future, but right now it just isn't able to happen from me, sorry.
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#1513 by roma847 on 30 Jun, 2018 23:13
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Hello everybody,
back to the question of how the Automatic Gun Spray System had worked in the SOFI cells and how and why this wavelike pattern was created during coating.
I also followed up on exactly this exciting question, and meanwhile I have received a first-hand answer by Craig Capdepon from New Orleans, here during Trimming on ET-122, 
Source: facebook.com
which was flown during the last mission of the Endeavour (STS-134).
Source: NASA
And so we are now close to the SOFI application.
To his Facebook site I came across more or less randomly during my search in the MAF, but thereto later more, because that would lead now too far, especially since I got pretty tired now ... 
... 
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#1514 by Starbase101 on 01 Jul, 2018 01:02
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you mean seriously that one can reproducible create this regular pattern at an interval of 1 mm this way over a length of 170 mm?
It depends on the printer resolution. Definitely Shapeways can do it, as they have some pretty high-end machines. The cheap machines a lot of people buy (because they're cheap) don't perform well on small intricate details. That's why I paid more (a lot more) for higher-quality printers. My machines print at 10-micron resolution (that's 0.01mm layer height) so there would be 100 print layers for each mm on the part ....plenty enough for something that will even be texturized afterwards. So honestly, it's not really a matter of whether a printer is able to reproduce it, it's more an issue with design time for the part. -
#1515 by roma847 on 01 Jul, 2018 07:40
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Thanks Mike,
then you are really well equipped and might outdo everything with your project. Hopefully you'll start with it, I can not wait.
BTW, but I meant the other Mike (mike robel), who proposed the tool for the simulation of Zimmerent anti-mine coatings.
No problem.
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#1516 by mike robel on 01 Jul, 2018 14:02
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Thanks Mike,
and you mean seriously that one can reproducible create this regular pattern at an interval of 1 mm this way over a length of 170 mm?
I do not want to dump my ET afterwards in the waste.
Then I prefer gluing of 200 strips onto the ET and sprinkling flour on it.
Nope. Just throwing out an example of a similar application that might assist in your brainstorming. Goodness knows there are hundreds - even thousands - of tools out there that we don't know about. -
#1517 by roma847 on 05 Jul, 2018 22:43
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Thanks Mike,
that's right, the right tool at the right time can be a great help.
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#1518 by roma847 on 05 Jul, 2018 23:07
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Hello everybody,
BTW, some friends in the Raumcon forum did mean that this flat wavy ring structure was just an optical effect, but this was a three-dimensional effect, as Craig Capdepon has confirmed.
"The SOFI (spray on foam insulation) was applied with automatic spray gun sets on vertical moving rails I think in 3 locations 120 deg. apart around the tank. The tank would rotate and the guns traveled down the rail to apply the desired thickness. The 3 locations were required because the overlap max. time was 45 seconds. We desired the "as sprayed" finished condition because it was more durable when exposed to sunlight and the weather conditions in Florida. There was no attempt to create a "pattern" to the finish. We tried for a smooth uniform finish.
The wave like patterns were unique to each tank as a result of the variations in the spray foam insulation process. The spray guns pattern control tip would accumulate a build up of foam causing a less than perfect pattern. There were engineering drawing requirements limiting the peaks and valleys of this finish. The critical area near the nose cone was often machined to obtain a smooth surface using a tool we nicknamed the "pencil sharpener".
I found this photo, on which one can see this tool during the repair work of the hail damage on the ET-124 during the start preparations for the STS-117, in which he was involved too.
Source: NASA
Of course I had asked further questions, including a term "Barber pole", which I found that characterizes the SOFI mode.
"It was a non-stop procedure. The tank was rotating as the guns started spraying a predetermined amount of SOFI. Carriages holding the spray guns traveled (down the rail) at a set speed until the end of the spray operation.
The correct tank rotation, travel of spray carriages, temperature of SOFI components, pressure of component supplied to guns, substrate temperature, cell environment, (temp. & humidity) and the pattern at the gun pattern control tip all determined the thickness and as sprayed condition of the finished product.
"Barber pole" was a shop term to generally refer to the method. The travel of the gun carriages was slow because of the large area (diameter) of the tank. If a smaller cylinder was sprayed (i.e. feed lines) this same method may produce a "spiral-effect" surface."
That these rings actually have a three-dimensional structure can also be seen in this video (unfortunately without sound) which shows an SOFI piece of the ET-93 used in the fateful last Columbia mission STS-107.
Craig commented about this video:
"This was not an optical effect. I would have to see a larger cross section to know exactly where this piece is from. It looks like part of an automatic spray possibly from the aft dome of the LH2 tank. I see two knit lines and it appears the three passes were approx. 1 inch each. SOFI is pliable for about 5 seconds after components are mixed and exit the spray gun. The rough surface in this picture is an example of "roll over" caused when SOFI is formed by an outside force soon after application such as excessive air movement from the direction of the gun."
Furthermore, I have learned from him, that he has worked on every shuttle that has flown, what I found next to this photo. 
"Endeavor the newest shuttle STS-134 (16.05.2011) on the pad. This is ET-122 - we did the mod in February. I've worked on every shuttle that has flown."
A very interesting contemporary witness from that time, I have met in this way.
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#1519 by Starbase101 on 05 Jul, 2018 23:46
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You are so resourceful!
