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
LH[sub]2[/sub] 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
LH[sub]2[/sub] 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-LH[sub]2[/sub] 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 ...
