Space Shuttle Launch Pad 39A with Challenger STS-6

[Mustermark]

Great work Manfred! You have a good dentist there. Perhaps Shapeways should provide this service on their prints?

[roma847]

Thanks Mark, 

 

they clean their prints already a bit, but they needed to do it more thoroughly, which would take more time, but time is money ... 

[roma847]

Hello everybody,

 

after finally defeating the wretched wax residue of my FUD-IT, now I have to find a solution for the mysterious wavelike SOFI texture on the STS-6 ET-8 surface, what is a further exiting chapter.

 

Source: wikimedia.org

 

And then I'll hope finally to come back to model building ...

[Mustermark]

Looking forward to the next developments. ☺️

[roma847]

Thanks Mark, and 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).

 

 

https://www.youtube.com/watch?v=gD2iT8hSm0k

 

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 ...

[RichO]

Great report Manfred!  Keep looking for us, you'll find the answer.

[roma847]

Thanks Rich, 

 

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 and to your thought later more, because that would lead now too far, especially since I got pretty tired now ...  ... 

[noeyedears]

you take research and detailing to a whole other level. well done that man! 😲

[roma847]

Thanks my friend for looking in on me again, 

 

stay tuned.

[roma847]

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.

[roma847]

Hello everybody,

 

in the meantime another expert and friend of Craig Capdepon has joined our Facebook-Dialog, namely Vince Morales (Sr. Staff QA Engineer) from Louisiana, ie a quality assurance specialist, who among others was also involved in the repair of hail damage at the ET-124 (STS-117) in the KSC.   

 

And he has spontaneously shared more details on my questions.

 

The rotation of the tank varied during sprays depending on the required SOFI thickness and averaged approximately 2 rpm for the LH2 Tank and up to 6 rpm for the upper part of the LO2 Ogive.

 

As he said the peak to valley was about 5 inches due to the tanks being sprayed in a shingle pattern (barber pole style), what did confirm my estimated approx. spacing between the wavy rings of about 1 mm (1:144).

 

BTW, the Pencil sharpener was only applied to the most affected area at the top of the LO2 Tank during the repair work on the damaged by hail  ET-124. 

 

Due to the high density of golf ball-sized holes at this point, the entire area had to be repaired,

 

Source: NASA

 

while the rest of the approx. 1.000-2.000 impacts further down in painstaking detail was repaired hole by hole by hand.

 

Source: NASA

 

This amazing tool, mounted on the Lightning Rod on top of the Composite Nose Cone, was be swung all-around for grinding the hand-sprayed SOFI foam.

 

Source: NASA

 

Viewed from up close, one can see that the device was a kind of Multi-belt sander.  

 

Source: NASA

 

And with this speckled ET the Atlantis stack came back to the pad, seen here from the west side,

 

Source: NASA

 

and here from the south side,

 

Source: NASA

 

and was then ready for launch again.

[roma847]

Hello everybody,

 

at the end of May, my friend Mike (crowe-t) from the ARC Forum asked me, if I could ask Michael Key whether he could also model an Intertank (WSF) for his Airfix STS-135 Shuttle Stack, for what he would have to modify my STS 6-IT only slightly.

 

Since I thought that it would be quite feasible, I asked Michael Key and tried to make it tasty for him, since this would be a useful extension of his store offer and certainly would find even more buyers, since most Shuttle modeler rather would build the later missions.

 

To do this, he would actually only need to remove some details such as the PAL ramps with the Cable trays, as well as the circumferential rings in the Thrust panels, since there were only Ribs, and needs modify the Access door.

 

These changes should make it relatively easy for him to model an IT version for the Super Lightweight Tanks (SLWT) of the later missions from STS-91 (1998), since he has already done the main work.

 

Here is a photo of the ET-138, which was flown at the STS-135, where one can see some of these details,

 

Source: NASA

 

whereby the Access door in the SLWTs was only closed by a Graphite Composite plate ,

 

Source: NASA

 

as can be seen here on the ET-122 at the STS-134.

 

Source: NASA

 

After Michael Key had agreed to it and I had discussed with Mike some detail changes back and forth, it was time, and so you can now after the Airfix Early LWT-IT (1:144)

 

Source: shapeways.com (The Aerospace Place)

 

also order the Airfix Late SLWT-IT (1:144) both in WSF and FUD at Shapeways

 

Source: shapeways.com (The Aerospace Place)

[roma847]

Hi everyone,

 

since I now know from two experts that I chase after no phantom, now a next step for the implementation of this wave-like ring structure on model ET.

 

As I've said already, there are these two discussed possibilities, either by a 3D printing, if Michael Key finally would have time and desire, or by Scratch-building.

 

Since Michael Key for his 3D model but already should know about what shape and especially what dimensions should have this wavy line, I have now tried to draw a first scetch.

 

Starting from the Peak-to-Valley width of about 5'' = 127 mm = 0,9 mm (1:144) specified by Vincent Morales , which roughly matches my previous estimates from photos, I have sketched the following profile (1:2), which should show this wavelike foam structure, how I could imagine it.  

 

 

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 with approx. 0,1 mm in 1/144 would be very flat.  

 

Now it would be important to find out how large this peak-height actually was at that time in the foam insulation.

 

Let's see if or how Craig Capdepon or Vincent Morales will comment on that, since they should actually remember it.

[roma847]

Hello everybody,

 

unfortunately, there is no feedback from the two experts so far, whyever ...

 

If I understood Vincent Morales right, that the Peak-to-Valley 5'' is the spacing from the top of the wavy pattern to the deepest point of the valley, then the Peak-to-Peak is the spacing from one peak to the next one.

 

But somehow my 7th sense tells me that his 5'' can't be quite right, maybe it's a bit to large, or I'm misinterpreting his term Peak-to-Valley so far. 

 

That's why I took a different approach, because ultimately for scratch-building it is crucial, how many rings were on the ET, whereby the difficulty is only to determine this number as accurately as possible, wherefore I used these two Hi-Res photos. 

 

This old photo from the initial phase of the shuttle program I wanted to evaluate anyway, because one can see this wavy ring structure on the LH₂ tank quite clearly.

 

And meanwhile I also know that this photo shows the rollout of the first LWT ET-8 for Challenger's STS-6.

 

Source: forum.nasaspaceflight.com (Jester)

 

However, especially in the front area at the beginning of the LH₂ tank, this photo is simply too fuzzy for an exact counting of the rings, whereby this is made even more difficult by the foreshortening. 

 

Therefore, I have used another photo for this, where one has almost a direct view of this area, namely this one of the discarded ET-121 (STS-114), in which one in Hi-Res-Zoom with a little imagination and a sharp eagle eye it is also possible to count out the rings in this front area.  

 

Source: NASA

 

For better orientation on the tank, I have numbered the 17 Ice/Frost Ramps, in order to find the exact point for continuing the count up to the Aft Dome.

 

And then the counting went off, but first of all, I had to attach a few markings in order not to constantly have to re-count, when my eyes had gone on strike and lost the orientation.

 

Source: NASA

 

And at this first count I came to 64 rings at the rear end of the Ice/Frost Ramp No. 7, although I have to admit that the counting between the first two ramps was extremely difficult.

 

And then it went on in the other photo exactly at this point Ramp 7 (64), where the count was now increasingly easier.

 

 

At the end of the tank I came to a total of 132 Rings.
What is following now from this for the width of the rings, which is actually the center distance of Valley-to-Valley?

 

Luckily, this calculation is now quite simple if I refer it directly to the length of the Airfix-LH₂ tank (without Aft Dome), which is 170 mm, whereby I rounded the number of rings to 130 for the sake of simplicity:

 

170 mm:130 = 1,3 mm per ring, which would be extrapolated 187 mm, which means 7,4'' at the original ET, which is less than the Peak-to-Peak distance (10'') by Vincent Morales.

 

Now only the Peak height is still missing.  But with the distance of 1,3 mm I can now at least determine the best width of the stripes and their distance for my test, possibly 0,75 mm instead of 1 mm with a 0,5 mm tape as a spacer, what I'm going to try on this ET dummy (Ø 50 mm), which I bought at the hardware store.

 

 

Let's see what comes out of it ...

[Mustermark]

Good luck! Good idea for a practice ET... 😜

[roma847]

Thanks Mark. 

[roma847]

Hello Friends of the Rings,

 

since we were just now dealing with counting the rings on the LH2-Tank, here comes with the Aft Dome the still missing ET end.

 

As the trained eye can see on this photo, which has already been shown several times, the rings on the Aft Dome are significantly wider than those on the front part of the LH2-Tank, although their curvature is barely visible, even in Hi-Res.  

 

Source: forum.nasaspaceflight.com (Jester)

 

Nevertheless, I tried to count these rings, whereby I came only with difficulty to 14.

 

 

With the reference dimension of the front ring width of 1,3 mm, this results in a width of the rings on the Aft Dome of around 2 mm. The arrow in this picture indicates a small, but fine detail, which lies on the 4th ring, but what can be identified only in the Hi-Res-Zoom.

 

Therefore, here again in the left part of the picture an enlargement can be seen, on which one can recognize the number 73. And this number reminded me of the already multiply shown photo in the right part of the ET-8 of the STS-6, on which one can see the bulge of the Rings on the Aft Dome very nice, whereby the number 73 is also sitting on the 4th ring. 

 

 

Thereby the counting of the rings  is finished, at least on the LH2-Tank. 

 

But as we know by now, on the LO2-Tank there are also such rings, or bands after my earlier terminology, 

 

Source: georgesrockets.com 

 

which I'm already in the end of May was starting to count,

 

Source: retropaceimages.com (STS-6)

 

what I can now check again from today's perspective, because this would be the starting point for Michael Key's 3D modeling, if he would get still involved with it.

[roma847]

Hi everybody,

 

in my search for more Hi-Res photos of the ET-8, I came across another great rollout photo here in NSF, even though with a laughing and a crying eye.

 

At first glance, one can still see no details at the Intertank in this resolution, but the picture is also from the thread Michoud: Best of External Tank - Hi-Res Images of Jester, and that's why the zoom finally provides information about the so far hidden detail structure of the Thrust Panel, which surprised me quite a bit.

 

Source: forum.nasaspaceflight.com (Jester)

 

Thereon one can clearly see that these panels of the first LWTs had no circumferential rings and bars, how I let them modeled by Michael Key for my IT.  

 

 

 

That means that the Intertank, which was modeled by Michael Key for me and since then offered by Shapeways, is no LWT-IT but an early SLWT-IT.

 

My mistake was that at that time I was too inspired by the 3D Intertank of my ARC friend Bill (niart17) and had not researched thoroughly enough.  

 

Thus, this is another example of the "curse" of the late pictures, one could almost say, what I had already happened one time at the very beginning, only this time with the difference that I have surprised myself.

 

BTW, even in this photo one could already see this Rib structure without the circumferential rings in the zoom.

 

Source: forum.nasaspaceflight.com (Jester)

 

And also my only STS-6 photo with a view of the Thrust Panel actually indicated that already, although I was not sure yet.  

 

Source: forum/nasaspaceflight.com (woods170)

 

Anyway, now I know about it and just have to think about how I handle it now.

 

As you may remember, my two ITs look like that, whereby I really liked these Thrust Panels. 

 

 

But these seven rings and small bars did not exist on the ET-8 at the STS-6 and are therefore out of place.  

 

These rings existed only since the transition to the SLWTs since STS-91, but were then left out again since STS-122. 

 

What is to do now? But anyone who knows me a bit closer, knows that I can not be satisfied with that,   which is why I was looking for a workable solution. And since the grooves between the ribs are very narrow and flat, my mini-saw of CMK (cmkkits.com), was the perfect choice, which is only 0,1 mm thick, 

 

 

With that, I carefully removed the bars between the grooves, which is cumbersome and requires the utmost caution, but is ultimately feasible, which at least my first test on a wasted IT has shown. And with the steel ruler one can then even later smoothen something.  

 

 

In principle, a modification of Michael Key's 3D model would be possible, but the master is currently absent, and if I could get it that way, it would be okay and also cheaper.

 

Consequently I'll probably have to bite the bullet and try to get it right on my Stack-IT, toi, toi, toi!!!  

[RichO]

  I feel another Frankenstein moment coming on!  Good luck with the surgery if you choose that path Doctor.  I just love finding a really good reference photo after I have built something.  It's enough to drive you nuts!  You'll make it look great in the end tho.  Keep digging my friend.

[roma847]

Thanks  for your gallows humor, 

this time it would just be a cosmetic surgery, the modifications to the SRB and SSME Blast Chambers have hurt more at that time ... 

[roma847]

Hello everybody,

 

meanwhile, the 0,75 mm masking tape has arrived, whereby I was lucky and got the last role.

 

 

The 0,5 mm tape is unfortunately not available at this dealer, as it is no longer offered by his source in England, which is why I have ordered it now in the

 

Sockelshop, where even 0,3 mm tape is offered.

 

Then I tried the 0,75 mm tape on the LO₂ Tank to see if or how it sticks to the curved surface.

 

For this I have marked an orientation line and then glued the tape next to it, which is quite feasible, as it clings well to the curvature.  

 

 

If I then have the intended as a spacer 0,5 mm tape, then I can make the test on the ET-dummy, whereby I would need to use 1 mm tape, 

 

 

since the 25 m of the 0,75 mm tape would be needed almost completely for the 130 rings on the LH₂ Tank and are reserved for it.  

[roma847]

Hi everyone,

 

today I glued the first few tape rings of the 1 mm tape onto the ET dummy, but that was not for the faint of heart.  

 

Since I still haven't got the 0,5 mm tape as a spacer, I have taken an Evergreen Strip 0,25 mm x 0,5 mm, whereby the difficulty is to position this very thin strip around the tube, in order to stick the 1 mm tape strip beside it.
After having tested and rejected some holding methods, I came up with this Magnet sling, wherefore I clamped the strip at both ends between two small magnets and put it over the tube, which may seem adventurous,  

 

 

but still have worked.

 

 

 

And in a similar way I would now have to glue 170 of such strips in case of emergency onto the LH₂ Tank, whereby the 0,5 mm tape as a spacer should be a great relief.

 

 

And to such an emergency I really have to adjust myself now, because Michael Key today has given me a knock-back for reasons of time.

 

He means that he has only little time and would need it to spend on projects that are financially worthwhile for him. He would have the feeling that only the front ET part (LO₂ Tank) would take a lot of development time, with the prospect, possibly to be able to sell only a few of them.

 

He had also hoped that the IT for the STS-135 SLWT for my friend Mike (crowe-t) would be a quick and easy conversion, but also that was turned into a time-consuming project with several modifications.

 

Unfortunately, I have to accept his decision, so I will now fully be focused on my Scratch variant with those tape-rings and by using the Flour technique for the SOFI texture.

[Mustermark]

Yet again... fantastic detailed research and ingenious techniques. I will be interested to see details on how you do the flour technique, because that can also be useful for my model railway at the similar scale!

[roma847]

Thanks Mark, 

 

I'm not sure, but I think, that you know how the Flour method works, or not? 

 

I have already shown it sometimes. Here is the link to the Thread of my friend Jörg (inselaner) in our Raumcon Forum.

 

Source: raumfahrer.net/forum (inselaner)

 

Source: raumfahrer.net/forum (inselaner)

[Mustermark]

Thanks Manfred, I have seen the impressive results are just what is needed, but I have not followed how it is done before. I look forward to seeing some pictures from your adventure, accompanied by your excellent narration in very good English.