TIL that NASA lost a $330m Mars Orbiter in 1999, immediately before mars orbit was achieved, because one of the contracted US companies used imperial units instead of metric. ( everydayastronaut.com )
https://www.reddit.com/r/todayilearned/comments/1cukcnv/til_that_nasa_lost_a_330m_mars_orbiter_in_1999/...