I once read that NASA used the space pen even for the Apollo program and that this little thing saved the success of the Apollo 11 mission: When Armstrong finished his moon walk and entered the lunar module again, he broke a tiny toggle switch inside, that was most essential for restarting the engines in order to go back home. Armstrong is said to have fixed this by entering the top of his space pen into the casing of the switch and pushed it in the desired position. That's how the story goes..