You guys were talking about props and supersonic flight? I real rec.aviation.homebuilt daily and Corky Scott, a nice guy and very intelligent one at that, touched on that subject yesterday. Here's part of what he said...
"To me, the big monkey wrench would be the prop. During WWII, a handful of fighters nibbled around the edge of the sonic region but never managed to actually go beyond, despite several who thought they had,
for several reasons.
First, the airfoils themselves were all non swept. Not good when you are trying to exceed the speed of sound. Plus the airfoils (with the exception of the P-51B and up series) were not designed for close to
mach flight. This meant that when the airplane approached Mach 1, the airflow over the wing and other appendages began to develop shockwaves long before the airplane itself actually got there. When this
happened, drag went up to the point where more power was needed, which leads us to.
Second, the prop. Props weren't designed to exceed Mach 1 and as the airplane approached that speed, the prop itself began to build up those same shockwaves that the wings and other surfaces had. This increased the drag of the prop to the point where thrust petered out. So no matter how hard the pilot hammered on the throttle (don't really think anyone did, any pilot in a fighter going this fast was REALLY scared and likely wasn't thinking about going faster) the prop just could not develop any more thrust.
So the fighter had flown up against a wall of drag, and so had the prop.
The way around this, in theory, would be to design a scimitar shaped prop blade and sweep the wings back and design them for Mach + flight."
In summary, that prop is the biggest obstacle as the shock waves set in.
