At 07:39 PM 7/2/2002 -0400, Henry Spencer wrote:
>Those are awfully high numbers. Several references show plots more like
>0-15-0.2 at subsonic speed, rising sharply to a peak of 0.5-1.0 just after
>Mach 1, declining smoothly to around the original at about Mach 6. (One
>source adds a comment that an overall average Cd is *not* a good
>substitute for a Mach-dependent one -- even a vague approximation to the
>shape of the curve is much better than trying to pretend it's flat.)
Agreed -- if you're doing first-order trajectory optimization,
which is how this discussion started, anything less would be pointless.
>One caution: there are a lot of variables here. Those plots probably
>assume a traditional rocket shape, long and pointy. Even going from a
>narrow cone to a wide cone on the nose of a cone-cylinder shape raises Cd
>a *lot*. Anderson's "Fundamentals of Aerodynamics" shows experimental
>data on a cone-cylinder shape with a 30deg half-angle in the cone:
>subsonic Cd about 0.5, peak about 1.0, hypersonic limit about 0.6.
Where in the book is this data? I have my copy of second edition
in front of me and I'm not finding it in the index.
-p
Mars or Bust!
www.marssociety.com
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