posted 12-02-2015 12:59 PM
Interesting question and there might be more than one answer. The latch(es) could certainly be the point of failure.
Page 5 of this 1971 Fifth Aerospace Mechanisms Symposium paper makes mention of a 12,000 pound tensile load rating in each latch.
Not sure how this single rating would translate to allowable torquing (roll) or asymmetric forces (pitch/yaw) on the circular latch array. It's probably safe to say that something greater than 12,000 lbf tensile would be required for fail.
It also seems possible that the docking ring or supporting structures might give way first. Force direction and type (linear/shear/rotational) might even be a variable for initial failure points.
This document could be read to imply the docking ring was the main load-bearing element. Of course the ring bears against the surrounding space craft but perhaps it was the most vulnerable:
Docking Ring-This is an aluminum structure bolted to the CM tunnel just forward of the top hatch. It contains seals and the shaped charge for final separation. It also serves as the mounting point for the probe and docking latches. The docking ring must withstand all loads from docking and from course corrections, and must maintain proper alignment of the docked vehicles.
Diagrams from the Apollo 10 Flight Journal detail the charge separation line used for pyro LM ascent stage jettison (I hadn't known about this!). This same region might also be the most mechanically-fragile part of the ring though I can't help with anything quantitative. This research paper describes the design and software behind the Apollo Docking Test Device (ADTD). Seems like the effort would have identified failure forces and mechanisms, but I found no other ADTD references online.
If the failure were outside the ring or latches (i.e. tunnel or airframe), perhaps the LM was the 'lighter built' of the two sides. It's a complex structural question at that point.
posted 11-29-2015 05:36 AM
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