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From: weverka@spot.Colorado.EDU (Robert T. Weverka)
Newsgroups: sci.military,rec.models.rockets
Subject: Re: Secant Ogive
Message-ID: <1991Jun15.021629.309@amd.com>
Date: 14 Jun 91 13:11:00 GMT
References: <1991Jun13.055308.22899@amd.com> <1991Jun14.080300.20680@amd.com>
Sender: military@amd.com
Organization: University of Colorado, Boulder
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From: weverka@spot.Colorado.EDU (Robert T. Weverka)


deichman@cod.nosc.mil (Shane D. Deichman) writes:
>
>figure is plagiarized from Jeff Berton at NASA Lewis Research Ctr :-)  
>
>                                  o  o  o  ---
>                               o         / o    ---
>                             o          /    o       ---------
>                            o          /      o    Wake
>     Flow                  o      Phi /        o
>     ----->   - - - - - - -o- - - - -/- - - - -o- - - - - - -
>                           o                   o
>                            o                 o
>                             o               o       ---------
>                               o           o    ---
>                                  o  o  o  ---

At low velocities the laminar flow creates greater drage than would a
thin turbulent layer hugging the sphere.  a thin wire ring placed on
the sphere at phi< 90 degrees creates what is called early drag
crisis.  this reduces drag.  Perhaps the golf dimples do something
similar (I know they also conspire with the spin to induce lift).

For a rocket one might attach such a wire on the nose quite easily.

As an engineer I would focus on the greatest contribution to drag
first.  During propulsion this might be the nose, but after burn out I
think most rockets suffer from base drag as the most important drag
contribution.

I have considered, but not implemented:
  
  moving tail cone which gets out of the way during propulsive phase.
  means of bringing air into the wake region from rocket side wall or nose.
  wire near tail to induce early drag crisis in the base drag.

Having no wind tunnel I have no quantitative measure of how my efforts
might help

-- 
Ted
weverka@boulder.colorado.edu