known aircraft engine certified for 100% continuous afterburner operation. J58 experience was used extensively in the JTF17 engine proposal for a Mach 2.7 SST, due to significant flight time at Mach 2.7 and above. It was also used for subsequent engines developed by Pratt & Whitney, both commercial and military. The next afterburning engine, the TF30 as installed in the F-111, used an airframe-mounted secondary nozzle with free-floating flaps similar to that used on the SR-71. J58 emissions were measured as part of the NASA Stratospheric Wake Experiment, which looked at the environmental impact of using afterburning jet engines for supersonic transports. An engine was tested in an altitude chamber at a maximum condition of full afterburning at Mach 3.0 and 19.8 km altitude. Design Contemporary compressor solutions for Mach 3 flight Alternative solutions to combat the adverse effects of high inlet temperature on the aerodynamic performance of the compressor were rejected by the Pratt & Whitney patentee, Robert Abernethy. One of those solutions was used in a contemporary installation. The GE YJ93/XB-70 used a variable-stator compressor to avoid front-stage stall and rear-stage choking. Another possible solution, pre-compressor cooling, was used on the MiG-25. Water/methanol was injected from a spray mast in front of the compressor to lower the intake temperature for short durations at maximum speed. Pre-compressor cooling was also proposed for a Mach 3 reconnaissance Phantom and the Mach 3+ F-106 RASCAL project. Propulsion system design The propulsion system consisted of the intake, engine, nacelle or secondary airflow and ejector nozzle (propelling nozzle). The propulsive thrust distribution between these components changed with flight speed: at Mach 2.2 inlet 13% – engine 73% – ejector 14%; at Mach 3.0+ inlet 54% – engine 17.6% – ejector 28.4%. Intake The intake had to supply air to the engine with acceptable pressure loss and distortion. It had to do this in all flight conditions. Nacelle airflow and ejector nozzle The ejector, or secondary, nozzle performed the reverse function of the inlet accelerating the turbine exhaust from about Mach 1.0, as it left the primary nozzle, back up to Mach 3. Mach 3 exhaust velocity is higher than Mach 3 flight velocity due to the much-higher temperature in the exhaust. The nacelle airflow from the intake controlled the expansion of the hot engine exhaust in the ejector nozzle. This air flowed around the engine and served also to cool the hot external