Saturn V S-IC Engine Fairing-The Real Dimensions
Getting It Right...
(or being really "tedious" about details)
Having collected Saturn V data for over 40 years I grew to expect that the information, particularly dimensional data, can differ from document to document even when the document is from the same source but released at different times and for different reasons. This is not unexplainable as the Saturn V vehicle was an extraordinarily rapidly evolved machine and significant dimensions changed, in many cases, right up to the days before launch. In the course of recent research, it became evident that almost all popularly available data was originally released to the public domain in the form of press releases, articles, drawings, and books in the 1964-1966 timeframe and much of it was based on information rooted at the very start of the Apollo program. Once "Moon Fever" got into full swing in the couple of years preceding the first launch of the Saturn, any new materials that appeared were merely rehashes of older data and didn't pick up new dimensions as the vehicle finally came to be manufactured. This is totally understandable since the dimensional changes tended to be minor with respect to the overall scheme of things and they just didn't matter when it came to information that would eventually find its way to public hands.
When I first began generating drawings to build my Saturn models by, I simply took the data that I had on hand and drafted, using "traditional" drafting tools such as paper, pencils, compasses, triangles, and T-square and penciled the dimensions I took to be "correct" onto the drawings. After a few years, I began to actually calculate the geometry of many of the shapes, particularly the S-IC fairings and fins and came up with various discrepancies as to what the calculated geometries were revealing. I didn't think about it too much but it made me wonder just what was "right." Finally, in the 2003-2005 timeframe, when I could actually get my hands on various Saturn components, I took as many measurements as I could...and discovered that an astonishingly large number of dimensions that I measured didn't agree with ANY "official" data that I had collected over the years.
Measurements From Real Vehicles
I took a number of measurements of the fairings of both of the Saturns at Johnson Space Center in Houston and the U.S. Space and Rocket Center in Huntsville, AL. Specifically, I measured the fin thicknesses at the tips and at the root at the trailing edge of the fin. I measured the offset of the fin from the trailing edge of the fairing. I measured the length of the fairing's titanium aft skirt as well as its circumference. The overall length from the fairing aft edge to its forward tip as well as from the aft edge to the "separation plane" where the fore section of the fairing separates when the S-IC retro rockets are fired. And, I counted and measured the stringers as well as took hundreds of photos of the fairings.
Matching Real-World to Documentation
Over the past couple of years I compared the dimensions that I measured against most of the data and drawings that I have collected over the years and found significant discrepancies. I purchased sets of recent popular drawings, found more books and data, and scoured the Internet. I stumbled across a couple of pages from my earlier paper collections of an aerodynamic study of the Saturn V that included the dimensions of both the fins and the fairings and I was astonished that it agreed, in most cases to within less than .1", to my measurements. I sat down with my trusty CAD software and began to precisely generate these components both as 2D drawings and 3D electronic files and and quickly discovered that I could get perfect matches of EVERY dimension and geometry in my drawings using my measurements as on those two pages I had stumbled across. I could not do this by trying to replicate and reconcile dimensions using other NASA sourced or current commercially available drawings of those components. Finally, I had a (presumably) authentic dimension source that matched the dimensions I took from the real thing.
One of the measurements that I took that told me I was on the right track was of the circumference of the aft end of the fairing of the JSC Saturn. My notebook tells me it measured 314 1/4" (very convenient for the measurement to end up right on the "quarter inch"). I also measured the thickness of the titanium skin (using calipers) at .03" (it turns out that drawings and documents found since that time indicate a skin thickness of .029"...so, getting agreement within .001" is quite good). When I used these dimensions along with the dimensions from the NASA documents, they fell right into place. The NASA document indicated a fairing radius of 100.029". At first this was odd until I realized that the fairing structure had a diameter of exactly 200" and a skin thickness of .029"...a standard thickness. Further, I discovered that the 314.25 measurement was EXACTLY one half the circumference of a 200.058" circle...which is the diameter of the fairings in the NASA document. This told me that the fairing aft edge spanned exactly 180-degrees of a circle...NOT a bit greater as almost every drawing I had come across. It also explained the visible geometry of the fairings aft of the S-IC firewall vs. what drawings indicated.
One other dimension that told me I had zeroed in on the precise geometry of the fairings was the measurement I had taken from the aft edge of the fairing to the very forwardmost tip of the fairing where it touched the S-IC fuel tank. In my notes I show this as 324 3/4" (yes, a non-decimal fraction on my notes) and the actual calculated dimension (via CAD software) as 324.659". The difference is astoundingly small when you consider I was stretching a tape measure along an inconvenient angle almost 40 feet in the air.
In a nutshell, since my measured dimensions agree to within 1/4" (indeed, less than 1/8" in most cases) to those found on that one NASA document, I have taken those on the NASA document as the definitively accurate dimensions for the fairing and are what I base the fairing patterns and dimensions on.
Model Rocketry and Spacemodeling?
Drop us a note!
If you find the information or images here of value, please consider a donation* to keep the Accur8 website going! Donations will be handled securely via PayPal.
*Due to PayPal fees, no donations less than $2.00, please.