The LEM consisted of an upper pressurized ascent unit whose function was to pilot the whole unit down to the moon using the large rocket motor in the lower unpressurized descent unit. To escape from the Moon, the upper ascent stage would then blast free from the lower part and ferry the Moon-walkers back to orbit to link with the command module. This ugly insect consisted of jutting angles and flat planes. Any first year structural engineering student would know enough to design a pressure vessel as a sphere, but the moron who designed the LEM didn't seem to know this.
So the NASA apologists can't claim that the LEM was not pressurized, we have this statement about the Apollo 11 LEM; "They worked their way to the ladder and squeezed into their "flight deck," and sealed and pressurized their cabin." On page 160, of The Illustrated Encyclopedia of SPACE TECHNOLOGY there is a cut away drawing of the LEM. It has been drawn to scale and from that I determined that there was at least one large flat panel with dimensions of 3 feet across and 4 feet high. Another section of the drawing shows that the ribs are on 6 inch centers. I assume this section to be typical and that the rest of the LEM was ribbed the same way.
Aldrin speaks of the LEM's ribs thusly, "...and there were ominous corrosion cracks in the LM's paper-thin aluminum ribs." 14 A tissue paper thought here raises its thin head. Since the support ribs of vehicles, vessels and structures are always much thicker than their covering, you can imagine what the hull thickness must have been.
Continuing with the dissection at hand, I shall assume that the designers correctly put the ribs across the shortest span. The LEM was pressurized in space to 5.2 pounds. That's the minimal pressure needed to sustain life on a long term basis. Such being the case, and since
there are 144 square inches to each square foot, the hull was under a load of 750 pounds per square foot. Compare this with 30 pounds per square foot allowed, and designed for on the floor of your home, or with the 200 lb/sq ft loading of commercial warehouses.
This simply means that each rib (6 inches on center) had to carry 1100 pounds. In structural engineering, loading is translated into a concept called the Maximum Bending Moment (MBM) which is measured in inch pounds. For a beam (rib) supported on both ends
and carrying a load the formula is W x L / 8, where W is the load in pounds and L is the span in inches. Therefore the Maximum Bending Moment for each rib is 1100 x 36 / 8 or 4,950-inch pounds.
The restraining moment needed to support this load is found by determining a thing called the Section Modulus (SM). This is found by dividing the MBM by the working tensile strength of the material involved. I don't know which particular aluminum alloy was used,
nor do I figure I will live long enough for NASA to answer my letters, but since all aluminum alloys have less strength than steel, I shall pretend that the paper-thin ribs he (Aldrin) spoke of were made of common steel which has a working tensile strength of
20,000 pounds per inch square.
The Section Modulus (SM) needed to hold this load is found by dividing the MBM by the tensile. Then SM = MBM / 20,000 or 4,950 divided by 20,000 which equals .2475. The proper size rib to do that particular job is 2 x 2 x 1/4 inch steel angle iron which has an SM of .25. Would you call a chunk of metal that is 1/4 inch thick paper-thin? Neither would Aldrin! Obviously, whatever ribs he was writing about would never, ever, hold the internal pressure necessary to keep men alive and breathing in space.