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Hospital_Rocket

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Is there a link to where I can find some information on nose cone geometry. I'm trying to find out the differences between conical, Ogive, etc. Of course I tell by looking at them, however I'd like to know how the rations in an ogive work, and if there is some information on how different profiles are suited for different flight characteristics.
 

stevem

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Minnesota Rocketry has a newsletter called MASA Planet - the first three issues of 2003 ran a 3 part article on turning your own nosecones. Laying out nose cone geometry was one of the topics covered in the series.

go here and check the January 2003, March 2003, and May 2003 newsletters.
 

powderburner

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Originally posted by Hospital_Rocket
I'd like to know . . . if there is some information on how different profiles are suited for different flight characteristics.
Hospital, what are you designing for? Mid- or high-power rockets, trying to go supersonic? Or just 'sport'-type low-power rockets? Or are you interested in the different shapes as a matter of style?
 

Micromeister

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Hospital:
Look in any edition of G. Harry Stines "Handbook of Model Rocketry" there is an entire section of nose and fin designation and layouts with examples. I understand Bill Stine will be releasing the next edition in April.
 

Hospital_Rocket

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I have a couple of ideas for some scrarch builts that I am tossing around and want to know how geometry affects performance.

I have a Stine on order and will check out the NC section as soon as it arrives.
 

DynaSoar

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Originally posted by Hospital_Rocket
I have a couple of ideas for some scrarch builts that I am tossing around and want to know how geometry affects performance.

I have a Stine on order and will check out the NC section as soon as it arrives.
Send me your phone number at my work address again (lost it, sorry!). We can get together (your hospital, or mine?) for a coffee and I'll bring mine along. I'll bring a pad of paper too. Despite their fine tradition with all things engineered, napkins just don't hold up.
 

powderburner

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Originally posted by Hospital_Rocket
I have a couple of ideas for some scrarch builts that I am tossing around and want to know how geometry affects performance.
In general, nose shapes like conical, ogive, secant ogive, and the other 'pointy' ones are the best choices for transonic and supersonic flight. On the real sounding rockets they want to reach high altitudes efficiently so these shapes are often selected unless a specialized payload requirement steers the design in some other direction. For some missiles (usually military) the nose shape is a radome (cover for the guidance system antennae) and the nose shape is often influenced by seeker-head function and sensitivity.

In general, nose shapes like elliptical, parabolic, hemispherical, and other 'round' configurations are the best choices for subsonic flight. When given a smooth finish these shapes offer the lowest drag coefficients, and a short (~2:1) elliptical NC also minimizes wetted surface area. Serious NAR competition models will frequently use these shapes unless some other design requirement prevails (such as the hinge mechanisms of HD models).

There is nothing inherently wrong with using supersonic shapes in subsonic model rockets. You will pay a small performance penalty for the (unnecessary) extra surface area. If you turn your own NCs out of a relatively heavy wood (basswood, poplar, etc) the added volume will result in a heavier nose cone, unless you perform some additional step to hollow out part of the nose. The nose shape selection is basically just a matter of style. Obviously, if you are making a scale model of a supersonic design then you have to use the original nose shape.

In general, in all cases you would prefer to avoid sharp corners and mathematically-hard lines oriented perpendicular to the airflow. Shapes like the Gemini crew capsule are a perfect example: the flat nose (and sharp corner), the crease where the main capsule shape flares out, and the base of the capsule (another sharp corner to transition to the Titan booster shape) are all 'bad' aerodynamically. (In the case of the Gemini design, it would have been worse to add an aerodynamically optimized fairing over the whole thing because the weight would have reduced performance unacceptably.)
 
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