This week, Nasa is planning to launch the Artemis II mission, sending four astronauts on their way to the Moon. Their voyage around our nearest neighbour will pave the way for a lunar landing and, eventually, a Moon base. Nasa's Artemis programme has taken years of work, involved thousands of people and is estimated to have cost $93bn to date. More than 50 years ago, America's Apollo missions made history when the first people set foot on the lunar surface. With six landings in total, it felt