GPS is fascinating, especially the development period. Due to the complexity of the signal processing (relativity means that the clocks onboard run faster than

GPS is fascinating, especially the development period. Due to the complexity of the signal processing (relativity means that the clocks onboard run faster than on earth) there was much scepticism. The story I heard was that they only let them launch 1 Block 1 satellite to prove that could work, and then the first block of 10 satellites was used to validate the system before spending enough to get the full 24 satellites needed.