(CBS) The investigation into the disaster that killed all seven astronauts aboard the shuttle Columbia is just starting, but already there are serious concerns being raised about whether the loss was a freak occurrence or accident waiting to happen. 60 Minutes Correspondent Ed Bradley reports an aerospace advisory panel told Congress last year that the repeated postponement of safety upgrades inevitably increased risks of operating the space shuttle. The panel at that time claimed that NASA's approach to safety was planting the seeds for future danger. Marcia Smith, senior analyst for space policy research for the U.S. Congress, says some...