I've always thought that looking at the outside skin of the Lunar Module, and deciding that it's construction is too flimsy was just plain weird. This makes no sense. Do they think their shirt is holding them upright in their chair? No? What about their skin - is that holding them up?
What is important is what's under the skin, so let's have a look at what's under the LM's skin:
Here it is one on the factory floor at Grumman Aviation in Long Island.
To the left is the Descent Stage. Note that it is not actually octagonal, but rather is five box structures welded together, with vertical reinforcements rather like a wine box. This provided fantastic vertical strength for the mass of material used; allowing it to support the weight of the Ascent Stage during Saturn V liftoff, and also for it to serve as a launch pad for the AS when it takes off.
To the right is the Ascent Stage. You can see that the inner skin of the pressurized crew cabin is supported by closely-spaced ribs for maximum strength at minimum weight. One of the ascent fuel tanks is visible to the right.
Here is the Ascent Stage of the LM,viewed from the right-rear. To the right (partially obscured) is the drum-like crew compartment. To the left is the aft electronics bay. You can see the thin stringers from which the outer skin will hang, but don't get them confused with the much sturdier structural framework underneath that you can see supporting the AEB and oxidizer tank.
Here's another view of the Descent Stage, showing its rugged construction. The descent fuel & oxidizer tanks are inside the boxes. The triangular sections between the outer boxes were storage areas for auxiliary tanks and equipment the astronauts would need on the Moon, including tools, science packages and, on the later missions, the folded-up lunar rover.
Grumman, whose
proud engineers built the Lunar Module, also built the best and most durable naval aircraft ever - they didn't do flimsy.
When I first saw pictures like this, I thought that they had formed the skin to the right shape, and then added the ribs, or that they built the rib framework and the attached the inner skin to it, like you would build a ship.
The reality is far more interesting and clever (and stronger): The skin & ribs are a single block of aluminum! They milled-down the sections between the ribs to the desired skin thickness. They did this for each section of hull, then welded the sections together at strong edges.
Here are pictures of the pieces coming together with diagrams of where the sections fit.
Grumman went onto use the same technique to build the F-14 Tomcat.
Hope this helps
