Re: [ERPS] E-D nozzles

[Alex Fraser]

I'm not really knowledgeable about these nozzles, but I do know that at 
least this post is close to doable rocketry. If we don't get talking 
practical stuff, we ain't going to get into space at all. It's been a 
weird long winter, but spring is coming! How high we going this year?

Henry Spencer wrote:

In the latest Armadillo update, John writes:

"I think we are going to fabricate and test an expansion-deflection nozzle
for our bench test 5.5" engine."
I'll be very interested to see how well it works.  Both the Hagemann paper
in the Sept/Oct 1998 JP&P, and the earlier work in NASA TN D-4462 (from
1968), agree that E-D nozzles do not in fact altitude-compensate very
well.  Aspiration effects tend to take their base pressure down well below
ambient.  TN D-4462 says that adding secondary flow from the base didn't
help much.
The interesting question is, why do plug nozzles work (at least, TN D-4462
found that they did) while E-D nozzles fail?  Lots of unexplored corners
here...
                                                         Henry Spencer
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