Altitude Performance of a Turbojet Engine Using Pentaborane Fuel

A full-scale turbojet engine having a two-stage turbine was operated with pentaborane fuel continuously for 11.5 minutes at a simulated altitude of 55,000 feet at a flight Mach number of 0.8. The engine incorporated an NACA combustor designed specifically for use with pentaborane fuel. The specific fuel consumption was initially reduced 32 percent below that obtained with gasoline fuel; however, the occurrence of a 25-percent reduction in net thrust after 8 minutes of operation resulted in a subsequent increase in specific fuel consumption to a value only 11.5 percent lower than that for gasoline.