Re max/cruise Mach. The flight manual quotes
Mach 3.2 is the design Mach number. Mach 3.17 is the maximum scheduled cruise speed recommended for normal operations However, when authorised by the Commander, speeds up to Mach 3.3 may be flown if the limit CIT of 427°C is not exceeded.
Perhaps you can draw some conclusions
Clive from the following numbers (from the flight manual).
Minimum afterburner thrust at sea level is approx 85% of maximum afterburner thrust and approx 55% at high altitude.
Military thrust at sea level is approx 70% of maximum thrust. At high altitude military thrust is approx 28% of the maximum available.
Some temperature and pressure ratio (compared to ambient) engine numbers.
Compressor face
ccccccc427/38.8
Compressor discharge
1ic704/
4th stage bypass tubes
i566/
Combustor
cccccccccci1093/112
Turbine
ccccccccccccic788/35.5
Afterburner
ccccccccc1760/
Ejector secondary
ccccccc/9.1 (flow accelerated from Mach .4 to 3.0)
Exhaust
cccccccccccci649/31.2
Following is a plot of thrust (and drag of the spike) provided by the various engine components at various speeds with max A/B.
It would be interesting to get hold of
Brown, William H. “J58/SR-71 Propulsion Integration,” Studies in Intelligence 26:2 (Summer 1982), 15-23. Probably be able to shed some light.