I wish to say thank you to Lyman for forcing me to contemplate where I stood in this discussion, and erred I might add. Off line discussion with other contributors are also to be thanked – they know who they are.
How I view it at the moment.
Briefly, the engine, taken in isolation as per Abernethys Patent, is a pure turbojet with afterburner. Just about every axial turbine requires compressor bleed to control stall or surge, and are normally closed when at operating RPM. The J-58 requires compressor bleed to unchoke the compressor when operating above 1.8 to 2.0 Mach. Up to that point it’s your regular pure turbojet with afterburner. It is not a bypass engine in the general understanding of the term.
Even though Abernethy himself says, “Bypass the bleed air around the compressor at high Mach number into the afterburner and it would solve the surge problem, provide cool air to afterburner and increase the mass flow and thrust significantly. Actually it converted the engine into a partial ramjet with capability above Mach 3”, the J-58 taken in isolation, as on the test bed, does not have a ramjet mode, partial or otherwise. Abernethys use of the “ramjet” word I take as being recognition of the type of inlet that would be necessary to make his Patent a viable high supersonic powerplant. When combined with that inlet it does give the J-58 a “partial ramjet” feature.
A ramjet requires the inlet to “start” in order to become operational. The SR-71 inlet “starts” between 1.6 and 1.8 Mach, so once the bleed opens at 1.8 to 2.0 Mach, the J-58 can be said quite correctly to have a “partial ramjet” feature.
Sorry Lyman that we were at cross purposes re the patent. I was viewing the installation in its entirety (inlet, J-58, afterburner, nozzle) rather than the J-58 as a stand alone item. The J-58 was after all, purpose designed for one particular aircraft. If that can be taken as an excuse.
