There has to be a science fiction story where the crew urinates on a platinum rich asteroid to generate enough fuel to get them out of some life threatening predicament.

This was actually how BMW created ultra-hardened combustion chambers. It was discovered that urinating on the engine block hardened the metal:

http://www.autoevolution.com/news/turbocharged-engines-in-fo...

Some of you might wonder how did the engine block resist to such immense detonation inside the combustion chamber. This may not be the answer you were looking for – and most of you might not believe it – but it seems BMW was in fact using seasoned inline 4 cylinder blocks – picked up from several junkyards – for their F1 operations. The interesting part about it was that the blocks were kept out in the cold and urinated upon in order to strengthen their composition.