Throughout the historyhistoryhistory of mankind, humans have endeavored to look beyond the dark shroud of our night sky and unlock the mysteries it holds. For a long time, that effort was limited to ground based observation and an underdeveloped understanding of laws of physics, but it was only in recent decades that we, as a species, harnessed the ability to close the distance between us and the great beyond. In the ages to come, this era of human spaceflight may well be recalled with the same sense of wonder and awe that we now reserve for early man, harnessing fire and bringing light to the darkness.

Unfortunately, however, our effort to pull back that celestial veil hasn’t always been met with success, and even in the United States, where safety is widely considered to be a higher priority than it may be in competitor states like Russia, the story of our path into space has, at times, been a tragic one. On Friday, NASA honored those we’ve lost in the space program since its inception in 1958. These deaths represent technical stumbling blocks, tragic accidents, and the propensity for error that is intrinsic to the human condition – but from a different perspective, they represent something larger, more dramatic, and more meaningful than that: they represent the nobility of man.

We humans are willing to sacrifice for the greater good, whether in a war zone on the other side of the globe or in a capsule zooming in orbit high above it – some people are willing to gamble with the great gift of life, betting on their success in the name of progress. More often than not, when it comes to NASA, we humans win those bets… but the stakes are high, and occasionally, fate steps in to remind us all of just how tenuous a grasp we have on life when attempting to further the reach of our species into a new and unforgiving frontier.

Below are three videos aimed at remembering the brave men and women we lost in the Columbia, Challenger, and Apollo 1 disasters, produced and released by NASA along with their accompanying descriptions.