The crew of the space shuttle Endeavour were doing their best to look relaxed for the cameras as they prepared to blast off into space. If tonight’s launch goes ahead this will be Endeavour’s first flight to the International Space Station since the Columbia disaster four and a half years ago. It is a mission full of symbolism. Included in the crew is former primary school teacher Barbara Morgan. She has waited years to get her chance to float in orbit. She originally trained as the replacement for Christa McAuliffe, another teacher who was on board the fateful Challenger flight when it blew up soon after liftoff in January 1986. All seven crew members were killed. The tragic breakup of Columbia in February 2003 is also on engineers’ minds as they prepare the launch. Endeavour has had a complete overhaul since it last flew, and its flanks will be trained with dozens of cameras to spot any potential flying debris. A falling chunk of insulation foam was blamed for damaging the shuttle’s heat shield and causing it to overheat and disintegrate.