Hi Beagle
My copy of AP129 AL5 Dec55 (and even AP3456 at 2-1-3-1 Page 4) breaks down the forces produced inside a turbojet into thrust and drag elements. Both references show the compressor being the major engine contributor to thrust with only small amounts coming from the combustion cans and the diffuser.
I therefore reason that the amount of compression produced by one of Sir Frank’s lovelies is closely related to the thrust of same. Now add an intake on to the front of the donk and it seems reasonable to apportion the thrust “produced by the intake” and the thrust “produced by the engine” according to the amount of compression produced by each.
As to the numbers relevant to Concorde and Blackbird, I well remember Brian Trubshaw quoting “a bit more than half” the thrust in the cruise comes from the intake. Increase the speed of the aeroplane from M=2 to M=3.2 and that gives the intake a chance to really play the star role.
You might be interested in this quote from Paul Crickmore’s comprehensive article on the A12/YF-12/SR71 story as published in Wings of Fame Vol 8.
“The inlet system created internal pressures which reached 18 psi when operating at M 3.2 and 80,000ft, where the ambient pressure is only 0.4psi. This extremely large pressure differential led to a forward thrust vector which resulted in the forward inlet producing 54 per cent of the total thrust. A further 29 per cent was produced by the ejector, while the J58 engine contributed only 17 per cent of the total thrust”
Not quite the same numbers as you were quoting but yours would likely be correct when going a tad slower.
Regards
JF