Upon measuring off a photograph of an operational version of the JT-11D-20, it became excrutiatingly self-evident that the total cross sectioal area, and, by definition, delivery capability, of the six bypass tubes coming off the compressor just after the fourth stage, was substantially less than the similarly tasked area available with a fully annular bypass duct in a classic turbofan. Which leads to my question: does anyone know what the claimed "bypass ratio" of the JT-11"D" actually was?
When looking at the respective bypass ducts of F-100s, F-110s, and F-135s, measuring the available areas there, dividing by six, then PI, extracting the square root, and multiplying by two, i.e. the reverse figuring for the area of a circle, I came up with tube diameters more than TWICE(!!!) the diameter of those on the J-58, thus exposing the JT-11D as not much more than a "leaky" turbojet, and leaving me to wonder just how useful such an arrangement could ultimately be above mach-3 when ANY(!!!) rotating machinery in the way of ramjet/afterburner airflow is about as desirable as a drag chute?
Agree,
but how else would you get the vehicle up to that speed to begin with where the compresor becomes useless?
It's not the relative efficiency of the parts that's important, it's the mission objective being met