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enter image description here

For me it looks like water droplets, but I doubt that's the case in space. Also, I don't understand why this should be a craft's surface feature. Wouldn't one aim to design a spacecraft to be as smooth as possible? And even if this is intentionally designed part of the surface, what is this irregularly placed rough stuff intended for?

If it is some environmental phenomenon, what is it and how did it get there?

Here is a contrast-enhanced detail of the Service Module (click on the photo to see the full image):
Apparent bubbling on parts of the Service Module's aluminium skin

No Nonsense
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Zaibis
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  • In space the surface does not matter as there is no atmosphere. Satellites are also not designed to be 'as smooth as possible'. During launch the spacecraft is hidden under 'smooth' fairings of the rocket. – wheeler Aug 02 '16 at 10:47
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    @wheeler: Thats true, but remember we are talking here about the apollo mission. And this is as far as I can tell the orbiter, which was part of reentry(?), in which case the surface would have mattered again. But even if this whole part was covered while leaving atmosphere and not part of the manned reentry section, the question remains as it had a reason why designed this inperiodic and rough way. – Zaibis Aug 02 '16 at 10:53
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    we're looking at the Service Module which didn't reenter. – Hobbes Aug 02 '16 at 11:28
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    Note that this might not be the external surface - the SIM bay cover was ejected several days before so Worden could use the cameras, etc. Those bumps might be on the stuff below, which could be insulation of some sort. (I've been looking for detailed pics of the bay pre-flight, just before closing it up but can't find any close enough.) – Andy Aug 02 '16 at 12:23
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    It is the external skin, above the SIM bay, as seen in this slightly less blurry photo: http://spaceflight.nasa.gov/gallery/images/apollo/apollo17/hires/as17-145-22254.jpg – Leorex Aug 02 '16 at 13:28
  • Great find @Leorex, I edited it into the question. Looks like blistering of the paint, but can't confirm. – Organic Marble Aug 02 '16 at 14:46
  • Apollo SM wasn't under a fairing on ascent, so it would have been directly exposed to blistering friction heat. (The command module was under a conical shroud until LES jettison.) – Russell Borogove Aug 02 '16 at 15:10
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    Any possibility this could be glued layers of foil and heat (from sunlight) has caused bubbling in the adhesive? It vaguely looks like that but of course I have no idea what they really used... – Andy Aug 02 '16 at 15:40
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    I've replaced the added image with a better view of the area of interest (AS17-145-22252) – Leorex Aug 02 '16 at 19:08
  • Any possibility that the paint had not fully cured prior to launch? – amI Feb 26 '18 at 19:48

2 Answers2

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The Apollo Service module was painted with an aluminum paint. Aluminum paint will bubble severely if exposed to temperatures above 747 K, if properly cured. One can only assume the paint was exposed to something close to that temperature at some point in it's lifecycle.

Tracing back, let's see where we can find them. Here's a picture of the SM from the LM after release around the Moon. It's hard to see, but I think I see some evidence of the bubbling near the CM, where there's high glare. This matches the same spot as seen at your image.

enter image description here

The breakdown of the spacecraft is as follows. Note that the image was almost certainly taken from the side hatch.

enter image description here

If I had to venture a guess, I would say it probably happend when the tower was jettisoned, some small flame reached the paint that caused to to boil somewhat.

The next image is at the Rendezvous, post-Lunar mission. There is certainly bubbling seen there.

enter image description here

Martin Schröder
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PearsonArtPhoto
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  • Is there any guess on why exactly that part could have been that close to the temperature, and why expecially the area seems to bea square shaped? – Zaibis Aug 03 '16 at 12:39
  • I've been searching, but haven't found anything. It seems it was unique to Apollo 17, and if there was a review on it, I can't find it. – PearsonArtPhoto Aug 03 '16 at 13:16
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    @Zaibis The square shape is just the shape of the panel. If you look closely you can see some amount of bubbling around the panel as well. It is not perfectly uniform. As to why that panel was exposed more than the rest of the surface, I'm not sure. – called2voyage Aug 03 '16 at 14:15
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Those are bubbles of air, trapped underneath the reflective mylar sheeting that makes up the outermost layer of heat shield for the forward sufaces of the CM. After splashdown, that's the same material that appears ragged, having been shredded by reentry.

C Stuart Hardwick
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