On May 18, 1969, NASA astronauts Thomas Stafford, John Young, and Eugene Cernan blasted off from Cape Canaveral aboard the Apollo 10 lunar module, the fourth manned mission in the US Apollo Space program and only the second after Apollo 8 to orbit the moon. Its mission was to circle the moon and thoroughly test the components and procedures to pave the way for the first lunar landing. The mission went flawlessly and without incident — At least that's what everyone believed.