The overall design and systems aproach for the lunar module was rapidly arrived at: an ungainly two-stage vehicle, capable f transporting two astronauts to the surface, where the bottom half of the vehicle would remain, after serving as the launch platform for the upper, which would re turn the astronauts to the orbiting command module.
If there was trouble with the descent to the moon, it would be possible to abort and return to the command module. On the lunar surface, failure of the ascent engine would mean the end for two astronauts.
The command module's water was purified with chlorine; the LM's with iodine, making it taste like a little scotch had been added.
On one mission, the lunar module left in lunar orbit after the astronauts returned to the command module failed to respond to a computer command to de-orbit into the moon.
It was later found that the docking radar was not turned off, so the computer was attempting to find the command module at the same time it was calculating descent rates and curves.