We’ve been reaching for the heavens since the dawn of man and space pioneers have paid the ultimate price.

Number Five: 1967 Michael Adams earned his pilot wings at Webb Air Force base in Texas and posthumously earned his astronaut wings after his X-15 rocket plane disintegrated during reentry and crashed into the California desert.

His flight passed an altitude of 50 miles—the U.S. definition of space.

Click PLAY to watch “NASA: The Top 5 Space Exploration Disasters”