Lower Mach and mission requirements and so on surely helped, but I thought Concorde's Olympi (or Olympuses or whatever) were ranked as the
most efficient engines ever at pressure recovery - something like 94%. And the inlet design slightly beat the SR-71 by producing 85% of the thrust (vs. 83% for the Blackbird.)
If I have my facts approximately right, SR-71 could sustain Mach 3 for 90 minutes
with afterburners and occasionally supercruise at Mach 1.5 without AB, Concorde could sustain Mach 2.02 in supercruise (no afterburner/reheat thrust) for around 180 minutes (London-Bridgetown, and occasionally, if the winds/weather and weight were right, Caracas-Paris).
The Blackbird was actually the "older technology" (first flight 1964, A-12 1962) although the core strategy (no pun intended) was the same, just different engineering tactics (ramps vs. spikes, etc.), and more or less concurrent with Concorde. And both brilliant.
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