Apollo LM rear panels

[BertieSlack]

Does anybody the identity and purpose of the object on the rear panels of the LM ascent stage?

[onebigmonkey]

As I'm sure you know the panels there cover the aft equipment bay, which housed electronics and cooling gear. It isn't referenced by any document I can find, so I tend to agree with a user on quora that it's an access port used to check those things while on the ground.

[onebigmonkey]

I can also add (thanks to the marvellous book 'Countdown to a moon launch') that those panels were added at the last moment on the launch pad with the LM inside the stack in case anything needed fixing immediately prior to launch. I'd say that it being some sort of connector to jnternal electronics is more likely than access to the glycol lines.

[onebigmonkey]

Happily digging around about this, and one thing that I came across was the Abort Equipment Assembly, part of the Abort Guidance System, that was housed in the Aft Equipment Bay.

What is mentioned in various documents, eg

https://www.hq.nasa.gov/alsj/FP6_OperatingManual.pdf

is that data was uploaded to this prior to launch.

It's a guess, but I would think it possible that you'd want to be able to update that system at the last minute if you needed to, and an access port through the panel would be a good place to do that. It would be nice to have a definite "this is what it is" reference, but it's a start!

[BertieSlack]

It isn't referenced by any document I can find..........

I couldn't find anything either. Thanks for having a look. Electrical access port seems a very solid idea.

[onebigmonkey]

I decided to ask the question in the private Apollo Lunar Module facebook group, and got this response:

The blister covers test ports for the oxygen and helium tanks. This was asked three years ago in another FB group, and the answer came from Frank O'Brien.

along with this picture:



I did see some other suggestions that it was related to the those, but thought it less likely I guess keeping a check on those tanks as long as possible was just as important!

Edit: This doesn't really help, but it's a great little booklet!

https://archive.computerhistory.org/resources/access/text/2019/01/102789077-05-01-acc.pdf

[onebigmonkey]

Blimey it's a can of worms! A few other people have weighed in and suggested that it isn't that. One person suggests that the blister is over the bottom portion of the Rendezvous Radar Electronic Assembly - which is the furthest left (looking face on) on the equipment rack. I did some overlaying of two a couple and that process seems to confirm it, with it sitting over the bit I've circled:



That piece is kit is discussed here

https://www.hq.nasa.gov/alsj/ApolloLMRadarTND6849.pdf

Whether that means it specifically connects to it is another matter! It's possible that every module was connected to it for checking purposes prior to launch and that, if it was the last panel put on, this was the most convenient place for it.

[JayUtah]

Funny, I only ever thought that blister was on LM-5, but I've gone back and seen it in photographs of all the other LMs.  Scott Sullivan (Virtual LM) reproduces it in his model, but doesn't opine what it is.  The geometry has to work out, of course, but if Frank O'Brien is wrong this will be the first time.  Nobody gets a T-shirt off that guy.