>> today is a day for mourning and remembering. the future doesn't belong to the faint-hearted. it belongs to the brave. the "challenger" crew was pulling us into the future. and we'll continue to follow them. there will be more shuttle flights and more shuttle crews, and yes, more volunteers, more civilians, more teachers in space. nothing ends here. our hopes and our journeys continue. >> to honor our fallen, we have to find this and fix it and fly it again. >> it was in a matter of days, we knew it was a solid rocket booster joint that had failed. the o-ring was a flawed design that had led to the loss of the "challenger." >> during the 30 months since the "challenger" accident, there have been hundreds of hardware changes not only to the rocket booster but also to the orbiter