Though it always seems to be 25 years away no matter what calendar you look at, the potential payoff of a practical fusion reactor is so earth-shattering that there is tremendous incentive to pursue the technology. The thing is, the problem isn't just creating a nuclear fusion reaction – any halfway decent physics lab can do that on a benchtop. The real trick is to build a commercial reactor that is net-energy positive and practical.

Aside from coming up with a reactor design that can steadily produce more energy than it consumes, fusion reactors must be able to turn that energy into power. They must also withstand the immense stresses produced by powerful magnetic fields, extreme heat, and the intense neutron radiation caused by the fusion process.