A stray Falcon 9 rocket part is on course to slam into the moon in August.The expected impact poses no immediate danger, experts say, but warn that it highlights a critical lack of rules for managing debris as lunar activity by the US, China and private companies ramps up.Measuring 13.8 metres (45 feet) long and 3.7 metres wide, the SpaceX Falcon 9 rocket’s upper stage has been drifting through Earth-moon space since it launched a US commercial lander and a Japanese lander in January last...