In the design of gas turbines, the most important limitation is imposed by the materials of which the combustion chambers, guide vanes, and, most important, the turbine blading are made. Any improvement in the heat resisting properties of the materials used in the construction of these parts will immediately show as an increase in power output.

As Major Halford stated before the Royal Society of Arts in a recent lecture on the gas turbine, a gas temperature of 850°C. at the turbine blade will allow a maximum take-off thrust of 15,000 lb. for one unit, running at 6,200 r.p.m.

The present temperature reached is around 750°C, this being attained after six years of war-time development. From this it will be seen that unless the metallurgist produces a new alloy, the limit with metal blades will soon be reached. Of course, cooling of the blades could be resorted to, but this brings with it the attendant difficulties.