Apollo Command Module heatshield tube - what was it for?

Question

I went to the Science Museum in London last year, where I saw (amongst many other wonderful things!) the Apollo 10 CM, Charlie Brown. Looking at the heat shield, I saw two circular indentations with a tube poking through between them.

A hole in the heat shield would be a very bad idea during re-entry, so presumably a cover was ejected after the atmospheric braking.

I asked a member of the museum staff what it was at the time, they didn't know, and I haven't found any information online since. Does anyone know what it is, please?

Answer 1

That is the remnant of one of the attachments between the Command and Service modules (there were three). Here is a cutaway drawing showing the bolt penetrating the heat shield (labeled "tension tie").

From Apollo Experience Report Spacecraft Structure Subsystem

Here's a closer picture showing that the circular areas are not penetrations.

Photo source

The bolts, support structure, and circular pads can be seen in this drawing from the Apollo Spacecraft News Reference (annotations mine)

Answer 2

Service module attachment point

The service module (SM) was attached to the command module (CM) using tension members which pulled the two modules towards each other. The SM used cups that rest on the compression pads on the CM heatshield (also visible in your photo).

This cross section shows the CM on the left, heat shield in the middle and the cups of the SM on the right.

Pictures adapted from Finkbeiner, Joshua & Dunlap, Patrick & Steinetz, Bruce & Daniels, Christopher. (2008). Apollo Seals: A Basis for the Crew Exploration Vehicle Seals. Journal of Spacecraft and Rockets. 45. 900-910.