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On 28 January 1986, people watched in horror as Challenger, one of America's four space shuttles, erupted into a ball of flames just over a minute after lift off, killing everyone on board. "Flight controllers here are looking very carefully at the situation. Obviously a major malfunction," reported the Nasa launch commentator as television screens showed a cloud of smoke and water vapour where Challenger had been, along with debris falling into the Atlantic Ocean.

At Mission Control, the doors were immediately locked and the phones disconnected as flight controllers, following protocol, began backing up the flight data. In the stands near the launch site there were heartbreaking scenes as the astronauts' friends and families reacted with disbelief and shock.

Challenger's crew of seven was led by led by Dick Scobee and included Christa McAuliffe, a 37-year-old social science teacher from New Hampshire, who had been chosen from over 11,000 applicants to become America's first civilian astronaut. Salvage crews spent several weeks bringing up pieces of the shuttle and carefully recovering the remains of the seven astronauts.

A special commission appointed by then President Ronald Reagan to investigate the accident identified a failure in a solid rocket booster joint as the cause for explosion, but also the pointed the finger at problems in Nasa's organisational culture and decision-making processes.

Joining Sue MacGregor round the table to look back on one of Nasa's darkest tragedies are June Scobee Rodgers, the widow of Challenger space shuttle commander Richard "Dick" Scobee; Steve Nesbitt, Nasa chief commentator; astronaut Norman Thagard; and Allan McDonald, former Morton Thiokol director of the Space Shuttle Rocket Booster Project.

(Photo: US space shuttle Challenger lifts off 28 January 1986 at Kennedy Space Center, 72 seconds before its explosion. Credit: Bob Pearson/AFP/Getty Images)