-
#1520 by EG on 06 Jul, 2018 00:50
-
Looks to me like they made three passes around, one layer above another.
The peaks and valley's were very shallow at the start and building as they went....
Also, it is very uneven in a micro sense, close to the surface, but when obviously you step some yards away you can see a pattern and 20 - 30 yards away it appears as lines circling the tank......
Interesting that they shaved the upper point to a smooth surface.
I still think a comb technique is the way to go......
Or now that I think about it a masking technique could work also.
Mask the lines where you want the depression to be, spray coat it with your texture, pull the masking which gives you the raised parts and then coat it again giving you the foam pattern overall...
Should produce a similar pattern......
Anyway great investigative work......
EG -
#1521 by roma847 on 06 Jul, 2018 11:28
-
Thanks guys,
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.
-
#1522 by roma847 on 15 Jul, 2018 13:16
-
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 (The Aerospace Place)
also order the Airfix Late SLWT-IT (1:144) both in WSF and FUD at Shapeways
Source: Shapeways (The Aerospace Place)
-
#1523 by roma847 on 15 Jul, 2018 22:36
-
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/how Craig Capdepon or Vincent Morales will comment on that, since they should actually remember it.
-
#1524 by roma847 on 17 Jul, 2018 17:39
-
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 ...
-
#1525 by roma847 on 20 Jul, 2018 16:13
-
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 in my Reply #1483 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.
-
#1526 by roma847 on 21 Jul, 2018 16:07
-
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!!!
-
#1527 by Starbase101 on 21 Jul, 2018 22:33
-
If it were me, I'd contact Michael and request a revised model without the ribs. It would be a LOT easier to remove them digitally and print a new part than manually remove them with a saw. He responded promptly to messages when I was talking with him, so maybe he's simply on vacation at the moment?
-
#1528 by Ronpur50 on 22 Jul, 2018 03:37
-
That would be a very delicate surgery, bit if anyone could do it, you could!
-
#1529 by roma847 on 22 Jul, 2018 22:17
-
If it were me, I'd contact Michael and request a revised model without the ribs. It would be a LOT easier to remove them digitally and print a new part than manually remove them with a saw. He responded promptly to messages when I was talking with him, so maybe he's simply on vacation at the moment?
Maybe Michael Key will answer, I'll wait and see ...
-
#1530 by roma847 on 22 Jul, 2018 22:24
-
That would be a very delicate surgery, bit if anyone could do it, you could!
Thanks Ron,
this time it would just be a cosmetic surgery, the modifications to the SRB and SSME Blast Chambers have hurt more at that time ...
-
#1531 by roma847 on 22 Jul, 2018 23:08
-
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.
-
#1532 by roma847 on 23 Jul, 2018 22:20
-
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 ARC friend Michael (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.
-
#1533 by roma847 on 25 Jul, 2018 23:09
-
Hello everybody,
let's go on with the analysis of the SOFI Rings.
Since my first count of the rings on the LO2 Tank on this ET-8 photo seemed to be a bit vague and upto the top was incomplete anyway due to the lack of resolution,
Source: retropaceimages.com (STS-6)
I repeated the count again today on this new (old) photo of the ET-8 because its resolution is much better. 
Source: forum.nasaspaceflight.com (Jester)
For this I had set the zoom mode (MS Word) to 250%, where one can see the rings pretty well, and came up to 66 rings.
And that would have to be roughly the area, where at the Airfix-LO2 Tank, which is 81,5 mm long, the front Nose cone cap is put on, the tip of which unfortunately broken several times and must be replaced.
With this the determination of the ring widths was made, or in slightly more complicated expert wording, the Valley-to-Valley distances:
81,5 mm : 66 = 1,2 mm, which agrees well with the value of 1,3 mm for the rings determined on the LH2 Tank, and would match also from the optical impression.
Unfortunately, in the photo above, the Nose cone is covered with foil, but in the following image one can see different cones on LWTs of the first generation (1988), whose shape is interesting for scratching,
Soure: forum.nasaspaceflight.com (Jester)
and therefore here once more a slightly larger section.
And already thereon you can see that the Nose cones of the LWTs looked a bit different, than one knows them in Graphite composite version from the last missions with SLWTs.
Source: californiasciencecenter.org
-
#1534 by roma847 on 29 Jul, 2018 17:45
-
Hello everybody,
there are enjoyable news.
Fortunately Michael Key had compassion for me and has modified his 3D model of the IT,
so that I can save me the painstaking post-processing of the Thrust Panels by using my mini-saw, which I had tested about a week ago. 
Here is his 3D-Update of the flown STS-6 tank ET-8, which is now to be found at Shapeways under its new name Early LWT.
Source: Shapeways (The Aerospace Place)
Before this action, I noticed still just in time that at his previous model still lacked two small details that I had previously overlooked.
So far I had mostly only ET photos of the side facing the shuttle, but hardly any of the opposite side.
Source: retrospaceimages.com (J. L. Pickering)
There I was always fixated only on the Access Door and the Carrier Plate Assembly.
But also on the back there are exactly opposite the same two items as on the front side, as one can see in this photo from George Gassaway. The pink circle involves the RSS Antenna and the blue circle an aerodynamic Vent.
Source: georgesrockets.com
And exactly these two items were missing on the back of my IT, which of course could not stay that way, wherefore I should have to scratch them if necessary. 
But these two things Michael Key has kindly complemented next to the modification of the Thrust Panel Ribs, so that the IT now is perfectly matching the Early LWT.
Source: Shapeways (The Aerospace Place)
And this IT I have ordered now once more in WSF and will probably use it in this form for my ET.
BTW, the IT modeled for my ARC friend Mike (crowe-t) for his STS-135 (ET-138) Shuttle stack is offered at Shapeways under Late SLWT.
-
#1535 by Hobbes-22 on 08 Aug, 2018 11:30
-
Hi Darren,
do you know what kind of material Shapeways is using?
The material is described in the MSDS:
https://www.shapeways.com/rrstatic/material_docs/msds-frosted.pdf
I use CA to glue this material. -
#1536 by Hobbes-22 on 08 Aug, 2018 11:36
-
So I will either extend the cleaning time still significantly, or sometimes have to try Aceton, or are there any ideas of the Shapeways experts here in the forum?
I use white spirit. Dip the part in white spirit for 5 minutes. For parts with grooves: use a brush to get the wax residue out of the grooves (a paint brush works)
That treatment will leave the part with a slightly rough texture (and it'll be white instead of translucent) so you'll need to sand it afterwards. -
#1537 by roma847 on 08 Aug, 2018 20:58
-
Thanks Hobbes,
I have solved the problem with the FUD-IT and presented the successful technique by using the ultrasonic cleaning with TICKOPUR R60, about 3 hours at 70 °C in my Dental lab in Reply #1487.
BTW, I have ordered the Early LWT-IT in WSF, for what no wax support material is used during printing, therefore I have to clean it only in dish detergent.
-
#1538 by roma847 on 09 Aug, 2018 23:05
-
Hello everybody,
today, still a supplement to the 3D-Intertanks.
Meanwhile, Michael Key still also offers a further modified Airfix-IT. And that is the Early SLWT, which was flown since the STS-91 (ET-96), which here is presented in the new Shapeways Design.
Source: shapeways.com (The Aerospace Place)
For this he only needed to modify a few details on my previous IT,
which he thankfully has done too.
Here once again the front side with the 26 Integral Ribs and the 7 Circumferential Ribs in the Thrust Panels, etc.,
and here the back with the Graphite Composite Access Door and the Vent.
This configuration of the Early SLWTs was flown up to the STS-107 (Columbia disaster), starting with the STS-114 the PAL Ramps were omitted at the Late SLWTs, and from STS-122 then also the 7 Circumferential Ribs.
There are now three versions of the Airfix IT (1:144), my Early LWT, which is now on its way to me, and next to the Early SLWT also the Late SLWT, all of which can be found here both in WSF as well in FUD.
-
#1539 by roma847 on 10 Aug, 2018 16:17
-
Hello everybody,
meanwhile, I did ask my ARC friend Joe (crackerjazz) if he would not even have time and inclination for modeling the Crawler Track Shoes in 1:160, whereupon, to my surprise, he has started right away.
BTW, he did also the 3D design of the Aft Skirt Thermal Curtains (ASTCs) for my SRBs.
And what the CAD expert has delivered with the help of the drawing without further ado, is simply stunning again, I think.
There's nothing like a good technical drawing with measurements, even if they are just so on the limit of readability.
Source: arcforums.com (crackerjazz)
Now he has to downscale the Track shoe "only" still to 1:160, whereon I'm really curious. Hopefully there will be some left over from the details after 3D modeling, especially as one can see based on David Maier's Paper Kit how small these things are in 1:160. 
While the holes in the Pin lugs (Ø 3,3'') with Ø 0,5 mm (1:160) and the 0,4 mm (1:160) wide grooves (green) should still be printable,
the small holes (pink) with Ø 0,2 mm (1:160) should unlikely to be printable, although one should be able to live without them, because later they are hardly recognizable anyway from a normal viewing perspective.
Now I'm curious what my friend Joe is going to say, whereby Shapeways has the last word anyway.
