The MHD duct is not a complete power plant in itself because, after
leaving the duct, the stream of gas must be compressed, heated, and
returned to the duct. Very high temperature materials and components
must be developed for this kind of service. Moreover, while the duct is
simple in concept, it must operate at very high temperatures in the
presence of the corrosive alkali metals. This presents us with difficult
materials problems. When the problems are solved, probably within the
next decade, MHD power plants should be able to provide reliable power
with high efficiency. They may then serve in large space power plants,
and, most important, they may provide cheaper electricity for general
use through their higher temperatures and greater efficiencies.