hydraulic fluid, engine oil, accessory drive system oil, the TEB tank and afterburner nozzle actuator control lines. Materials The development of the J58 involved some of the most challenging metallurgical development problems experienced by Pratt & Whitney Aircraft so far, with components operating at unprecedented temperatures and levels of stress and durability. New manufacturing techniques as well as new alloys improved the mechanical properties, and surface coatings had to be developed to protect components. Premature cracking of turbine vanes and blades made from conventionally cast (i.e. equiaxed) Mar-M200, the strongest cast nickel-base alloy, was avoided by the development of directionally solidified parts cast in the same material. Directionally solidified Mar-M200 became the strongest cast turbine material to date and was introduced in production engines. Single-crystal turbine blades cast in Mar-M200, giving further improvement of high temperature resistance, would also be developed through testing in J58 engines. Waspaloy was the most widely used alloy in the engine, from critical high-energy rotating compressor discs to components made from sheet. Although used for turbine discs in other engines, it did not have the required properties for J58 turbine discs. Astroloy, the strongest known nickel-base superalloy in the Western world at that time, was used instead. Waspaloy was also used initially for the diffuser case, the part that joins the compressor to the combustor and that contains the highest pressure in the engine. Diffuser case weld cracking led to the introduction of Inconel 718 for this part. The afterburner liner was sprayed with ceramic thermal barrier coating that, together with the cooling air from the compressor, allowed continuous use of the afterburner with flame temperatures up to . Performance enhancement for NASA NASA was loaned 2 SR-71 aircraft for research work. One was modified to flight-test a Linear Aerospike rocket engine and was fitted with thrust-enhanced J58 engines. Engine thrust was increased by 5% to offset increased aircraft drag. The increased thrust came from a throttle push, or exhaust gas temperature uptrim, of . The increase was limited by the allowable reduction in life of the second-stage turbine blades (the life-limiting component) from 400 to 50 hours. The same thrust-enhancement studies used for this work also looked at an additional 5% thrust from additional afterburner fuel made possible with oxidizer injection (nitrous oxide). The nitrous oxide rate would have been limited by thermal choking of the nozzle. Legacy , the J58 is the only