"We must honor their sacrifice by fortifying our commitment to safety and excellence as new generations of space explorers, follow their footsteps." ...
NASA holds a Day of Remembrance to pay respect to the lives lost while working to further the understanding of space. This includes the crews of Apollo 1, Challenger and Columbia.
We’ve come years in our journey to explore the unknown, but none of that would be possible without those who made the ultimate sacrifice towards the exploration.