Apollo 1
  But in less than 30 months following the Apollo 1 accident, 
  NASA flew five Apollo missions. During the final one of
  those five, Neil Armstrong and Buzz Aldrin stepped onto the
  Moon. Much later, in the last decade of his life, Armstrong
  would reflect on what it took to reach the Moon. “The rate
  of progress is proportional to the risk encountered,” he
  said. “The public at large may well be more risk averse 
  than the individuals in our business, but to limit the
  progress in the name of eliminating risk is no virtue.”

Sadly, Armstrong and his ilk no longer makes the calls at NASA (and haven't for quite some time.)  And so we see no progress.