MB has built deuterium-based prototypes as well.Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of planet Earth of approximately one atom in 6500 of hydrogen. Deuterium thus accounts for approximately 0.015% (on a weight basis 0.030%) of all naturally occurring hydrogen (see VSMOW; the abundance changes slightly from one kind of natural water to another). The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common hydrogen nucleus consists only of a proton and no neutrons. The isotope name is formed from the Greek deuteros of which one translation is "two", an obvious reference to the two subatomic particles comprising the nucleus.
Deuterium is useful in nuclear fusion reactions, especially in combination with tritium, because of the large reaction rate (or cross section) and high energy yield of the D-T reaction, and in the even higher-yield D-He3 fusion reaction, though the breakeven is higher than with most other fusion reactions, making it implausible as a practical power source until at least D-T and D-D fusion reactions have been performed. Unlike protium, deuterium undergoes fusion purely via the strong interaction, making its use for commercial power plausible.