Perhaps it helps, just for a moment, to view the engine as a flow inducer. This is the term used by 'Kelly' Johnson to needle P&W J58 engineers. This merry banter should be seen for what I'm sure it was, just that.
However there is merit in viewing the engine as such since another angle on any issue can only help to get a better picture.
This particular view imo helps to come to terms with the ever-increasing relative contribution of the intake to the total thrust.
At the same time though the engine is producing ever more gross thrust from an ever-increasing release rate in its engine and jetpipe combustors. Everything can be traced back to the fuel. The burning fuel induced the flow which, by virtue of its finer details, must produce forces in some direction or other.
Imagining what's going on in the combustors should help prevent downplaying the loser in the relative stakes.
On a slightly different tack:
Would the inlet momentum drag be zero when the flight speed is the same as the engine entry speed, say M0.5, assuming, of course, that the intake design flow was matched to the engine flow at that flight speed?
After all, if I watch a plane go right to left at M0.5 the compressor face is going left at M0.5 and the air is going right at the same speed, ie is stationary like it was before the plane appeared.
Alternatively, if I'm sitting on the Rosemount probe and looking ahead I see air approaching at 0.5 and if I look behind I see it going away from me into the compressor at 0.5, again no speed change.
Last edited by peter kent; 25th November 2012 at 23:33.
Reason: ification