Starflight on the Cheap II: Beating the Fuel Costs

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 problem, the Design Team of “Daedalus” examined the different sources of helium-3, the lightest helium isotope, composed of just 2 protons and one neutron. What makes it rare is what makes it desirable as a star-probe fuel – it can be fused relatively easily. Not as easily as deuterium fusing with itself, or deuterium with tritium, but helium-3’s reaction with deuterium doesn’t make damaging high-energy neutrons like the former two reactions. So helium-3, like deuterium, is rare in the Universe because it fuses too easily relative to plain hydrogen and plain helium-4. (more…)