This is why the SR-71 becomes so damned efficient at Mach 3+... most of its thrust is developed by the pressure differentials. The actual engine thrust (momentum flux) is only like 35% of the total thrust, but it is still needed to set up the velocity fields which generate the pressure differentials. If I recall, most of the SR's thrust at high Mach is from pressure differential across the inlet spike (and a lesser amount across the afterburner funnel). The higher the Mach, the less total thrust that is actually coming from engine thrust.
So someone else's comment about engineer's and physicists both not writing well misses the mark. It was clearly written by a physicist since an Aero Engineer or Mechanical Engineer with a fluids background would not make this mistake.
My favorite (and best) prof of all time was, in fact, a German rocket scientist who worked for von Braun in the Fatherland. He was one of "our Germans," (though he was actually Ukranian) brought to the US after WWII. Every shuttle launch, until he retired, NASA would fly him down to the Cape as a consultant. He came to class, always dressed formally, and had the total 1 hour lecture always memorized, and I'm talking heavy duty equations. "Vir haff dis trust tairm, und vir integreeren dees oober tay-ta won to tay-ta too." I had no problem since my grandparents spoke the same way... sounded perfectly natural zu mir.
He insisted on calling the roll every day (like a Prussian schoolmarm), always butchering the names. One day, one of the students corrects him on the pronunciation, and he repronounces it, exactly as he did the first time. The student corrected him again, telling him that the name was Ukranian. Ol' Prof Hnatiuk got red in the face and said "I'm Ukranian, und eets prro-nounced [blah-blah]".
When we got back our first midterm, a four question test, the grades were given by a number in the 0 to 4 range (most likely 2 or below). Some kids were real interested on how this translated to letter grades, so they asked him what the grading scale was. "Zeero to forr," he replied looking perplexed. When they demanded to know letter grades that corresponded to these numbers, he reeled it off the cuff, saying 4 was an A, 3 = B, 2 = C, "und so weiter" (etc.) A whiner complained "that's not fair, you have to get a perfect paper to get an A." The old professor, never really adjusting to uppity American students got red in the face, and proclaimed "Gott, heez an A; Me? I'm a B. You?" and then he just shook his head with a snicker. He went on to say that if anyone had problems with the grades, you could talk to him after class. I debated it, but decided to just listen to how the early ones went before committing. Not only did he not give out a single additional point, but he actually reduced a few grades upon finding extra mistakes.
Professor Bohdan T. Hnatiuk was definitely "take no prisoners" with undergrads, but he had a soft spot for grad students. I never learned more during a semester than when he manned the chalk. God rest his soul.