It's the moment every astronaut dreams of. Tim Peake has been told he'll be exiting the International Space Station (ISS) next week and conducting a spacewalk with NASA astronaut Tim Kopra. The pair have been tasked with replacing a broken Sequential Shunt Unit that transfers power generated by the space station's solar arrays. There are eight of these in total, so the problem isn't too serious, and the European Space Agency (ESA) says it can be removed by undoing a single bolt. Simple!