> Test exhaustively. > It's notable that this was published before Apollo 13 One of the causes of the Apollo 13 service module explosion was damage caused dur

> Test exhaustively. > It's notable that this was published before Apollo 13 One of the causes of the Apollo 13 service module explosion was damage caused during a pre-flight test. The SM included a pipe whose only role was to drain out oxygen after pre-flight launch-pad tests. It had no in-flight role. The pipe was damaged during assembly (nobody noticed) and failed to drain the oxygen tank. The test team instead decided to drain the tank by heating the oxygen using an in-tank heater and in effect boiling it off. The heater temperature gauge didn't show (it was badly designed) that the heater had in fact got so hot that it had melted electrical insulation on a fan in the oxygen tank. All of this was pre-flight. 56 hours into the mission, the crew used the fan to stir the tank, causing sparks and the eventual explosion.