Simplify the following text for a Grade 13 native English-speaking person.
Original: When the mission finally did lift off the pad , an O-ring seal failure destroyed the shuttle 73 seconds into the flight , killing Scobee and the other six members of the crew ; the tragedy , viewed live on national television , prompted several days of national mourning , as well as a major shakeup at NASA .
Simplified: When they did the mission , an O-ring seal failure destroyed the shuttle 73 seconds into the flight , killing Scobee and the other six members of the crew ; the tragedy was viewed live on national television and prompted several days of national mourning .