Originally Posted by
Dont Hang Up
The lunar lander was of course another story. Scarily lacking in any contingency a long long way from home.
It was basically designed to minimize the risk of failure, rather than to have backups if it did fail. The ascent stage engine, for example, was about as simple as you can make a rocket engine; if I remember correctly, it was pressure-fed and hypergolic, so just a couple of tanks, a couple of valves, and a rocket nozzle.
NASA actually did propose to carry an emergency backup for the LEM ascent stage on later missions which would stay on the Moon for longer periods with a greater risk of failure. Basically just a rocket engine, a couple of fuel tanks that would be filled with enough fuel from the LEM to reach low orbit, and space for two astronauts to stand in their space suits.