In Part 1 we looked at the cost of building and launching a “Daedalus” class star-probe, massing some 2,000 tonnes with empty tanks. The original “Project Daedalus” study fuelled the vehicle with a 50,000 tonne mixture of deuterium (worth $25,000/kg) and helium-3 (currently available only in tiny amounts on Planet Earth.) To solve the fuelling [...]