Trying to nudge astronomical objects into new orbits might sound as futile as jousting with windmills, but it's the goal of a new European Space Agency mission, now being planned. It's named, appropriately, "Don Ouijote". Quentin Cooper hears how one spacecraft, Sancho, will look on from a safe distance while Hidalgo lunges at an asteroid at a speed of 10km per second. That's just to prove the concept, but one day it might do a better job of saving the world than Bruce Willis managed in the film Armageddon. Producer Martin Redfern