Shuttle disaster: 'Something didn't look right'
In 1984 US President Ronald Reagan announced that Nasa would search for a member of the public to accompany five experienced astronauts on the Space Shuttle Challenger.
The twist was that the person chosen would have to be a teacher.
Thousands of people from across the US applied. Christa McAuliffe was the one selected to join the mission and Barbara Morgan was chosen as her backup.
On 28 January 1986, classrooms and offices around the country ground to a halt as the nation watched the eagerly anticipated take-off.
Soon after the launch, Barbara Morgan and the rest of the crew on the ground realised something was very wrong.
They watched helplessly as the shuttle was destroyed a little more than a minute after take-off.
Barbara Morgan spoke to Witness about that day and the legacy of the Challenger disaster.
Witness is a World Service programme of the stories of our times told by the people who were there.
27 Jan 2016