Saturn V Small Rectangles On S-II Stage

Question

On the Saturn V there was a line of several small black rectangles running vertically on the upper part of the S-II stage. What were they for?

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here is a picture from the McMahan Photo Archive. I added it to verify these markings did exist on the actual SV-II .

I checked my pictures of the JSC Saturn V but I didn't have a good one of that area. I'm pretty sure they are just paint. I might be able to stop by tomorrow and confirm. — Organic Marble, Feb 16 '20 at 18:29
They are a different black than the nearby writing, and the top one doesn’t have a break for the change of surface there. Could these have been added at some point? — Bob Jacobsen, Feb 16 '20 at 22:46
Never mind. There’s a clear image on this page: http://saturn500f.com/saturn-v — Bob Jacobsen, Feb 16 '20 at 23:00
Ok, thanks for the info. I'll be watching the thread if anyone finds anything else out. — Daknife, Feb 17 '20 at 02:04
@BobJacobsen the image in the question is not sourced. It appears to be computer imagery to me, the top black mark does not conform to the surface. — Organic Marble, Feb 17 '20 at 05:27
@BobJacobsen The direct link to the image of the second stage with the seven rectangles. — Uwe, Feb 17 '20 at 16:28

Organic Marble · Answer 1 · 2022-09-09T22:53:18.467

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This document is for a Saturn 1B but I think it still applies. See below for the Saturn V info.

The vertical bar of black rectangles are called "vertical motion targets".

Source APOLLO/SATURN CONSOLIDATED INSTRUMENTATION PLAN FOR AS-204/LM-1 pp 3-5 & 3-6

Special cameras were pointed at the targets.

4.4.2 FIRST MOTION AND VERTICAL MOTION OPTICAL COVERAGE. This information is provided by 16mm Milliken and 35mm Mitchell cameras. The two Milliken (DBM-4) cameras are located on holddown arms, 180 degrees apart, looking at first-motion targets near the base of the launch vehicle. They will operate at a frame rate of 400 frames per second (fps). A 35mm Mitchell camera will be sited at the 110-foot level of the umbilical tower, centered on the motion targets (Figure 3-3) located on the Position II (Fin 3) centerline of the S-IB/S-IVB interstage. The cameras will provide pictures showing first motion and the first 3 to 5 meters of the vertical movement of the space vehicle.

(emphasis mine)

Once you know what the document is called...here is the same info for a Saturn V (Apollo 15).

One camera at the 160-foot level of the umbilical tower, positioned to include a fixed reference target in the field of view will provide coverage during the first 5 to 7 meters of vehicle ascent. The frame rate is 96 frames per second.

Page 4-4 of APOLLO/SATURN V CONSOLIDATED INSTRUMENTATION PLAN FOR AS-510 (APOLLO 15)

I managed a quick visit to the JSC Saturn V. Here is a personal photo of the targets on its 2nd stage. Obviously it's been repainted over the years but I think they tried to keep it historically accurate.

edited Sep 09 '22 at 22:53

answered Feb 17 '20 at 15:35

Organic Marble

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110 feet is 1320 inches. Station 1206 is 1206 + 116 = 1322 inches above the bottom of the engine nozzle end (see http://heroicrelics.org/info/saturn-v/saturn-v-general.html). I don't know for sure where the umbilical tower base is with respect to the station number references, but it seems to add up with the camera exactly at the top of the topmost marker. – Ludo Feb 17 '20 at 16:28
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I stopped by JSC but the guard told me you now must have a badge to get into the Saturn V building! I blame the pernicious influence of Space Center Houston. – Organic Marble Feb 17 '20 at 18:24
OMG English units! :-) – Carl Witthoft Feb 17 '20 at 20:39
@CarlWitthoft Aviation SE told me to call them "Imperial units". – uhoh Feb 18 '20 at 08:16
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@uhoh be careful -- the British Imperial pint is different from the US pint :-) . Luckily (or not), the inch is the same. – Carl Witthoft Feb 18 '20 at 13:11
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"English units" is correct: https://en.wikipedia.org/wiki/English_Engineering_units But then at the end they throw in "meters of vehicle ascent".... – Organic Marble Feb 18 '20 at 13:33
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@OrganicMarble and yet 1 & 2 – uhoh Feb 18 '20 at 14:05
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@uhoh nuts and bolts are different, I guess. – Organic Marble Feb 18 '20 at 14:26
I've just asked Did the Saturn IB have eight equally spaced fins around its circumference? – uhoh Feb 18 '20 at 21:42

Saturn V Small Rectangles On S-II Stage

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