Fusion power is the technology that is 30 years away, and always will be, according to skeptics, at least. Despite its difficult transition into a reliable power source, the nuclear reactions that power the sun have a wide variety of uses in other fields. The concept fusion drive, called a direct fusion drive (or DFD), is in development at the Princeton Plasma Physics Laboratory (PPPL). Though still under development, the engine itself exploits many of the advantages of aneutronic fusion, most notably an extremely high power-to-weight ratio. The fuel for a DFD drive can vary slightly in mass and contains...