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This paper presents the results of a design study of a low cost Jet Fuel Starter (JFS). The JFS is a small free turbine turboshaft engine with a peak output of 150 horsepower. The design concentrates on high output per unit volume and weight, and on low cost. A low speed, four stage axial compressor design results in a compact, lightweight starter. Die castings and a radial pin construction for both the static structure and the compressor rotor provide the most significant cost savings over conventional gas turbine fabrication methods. The low speed concentric shaft design (approximately 70 percent of usual design practice) permits a simple two bearing shaft suspension for both rotors. The resulting close coupling of the turbines reduces the number of expensive hot end components to only five parts.

Powder metallurgy cold forming processes provide several advantages: economy of material, minimal machining, close tolerances, high density and lower production costs. IN-861 is an air hardenable ferrous alloy of 2% Ni, 1% Mo, 0.7% Mn plus carbon produced from mixed elemental powders. Specimens were alloyed at three carbon levels and sintered at several temperatures in order to relate ductility and workability to alloy composition and preform sintering temperature. Results indicate that increasing carbon content and sintering temperature required increasing preform forming stresses. Also, ductility of the preform increased with increasing sintering temperature and decreasing carbon content. Further additions of manganese raise the forming stresses, however a marked reduction in ductility is noted. Additions of molybdenum appear to have little effect upon strength, but decrease the ductility.