I have this SAE paper from Moller 900037 wherein it states
the static thrust from the 50 HP at 6500 RPM (or so) engine used 
at the time was 70Kg or 154 pounds.

If the engine was 50 HP or 27500 pound feet/second that would 
make the duct 5.6% efficient at 10 feet per second assuming 
the thrust was the same as it was at static conditions.

At 100 FPS assuming the thrust stayed constant (unlikely) the eff.
would be 56%. Usually the thrust is dropping off at this
point and the eff. is getting better but perhaps not this
much better.

All this jibes with convential wisdom of course :-)

Small diameter high RPM ducted fans just plain don't 
become eff. until you get to 400 MPH or so.

Jeff knows a lot about this engine as he was project engineer
on it. According to the paper it was 32.3 cubic inch 
engine. Here is a picture of the final engine design.

Jeffs-Moller2.jpg

Paul Lamar
 
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