Imagine a bomber so fast it could outrun any fighter jet, soaring at Mach 3 speeds across continents. The XB-70 Valkyrie was this dream made real, pushing engineering to new heights. But its path was ...

Part Transformer, part Star Wars stormtrooper and with hands that look like they can crush beer cans, at 1.8 metres tall and weighing 120 kilograms, NASA’s Valkyrie robot is an intimidating figure.