Flight characteristics

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dr wogz

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A friend & I were talking about our previous launch, and we were wondering about one particular flight path he had. Ideally rocket flights should be straight (or slightly angled into any apparent wind) or will have a slight ‘corkscrew’ as it ascends.

We all know a tail-heavy (under stable) or an under-powered flight is squirrely, if not flipping & tumbling all over the sky. We all know one fin slightly off will cause a visible corkscrew in flight, along the [flight] axis of the rocket..

But what about other flight characteristic that might be hard to explain. Or the cause might not be apparent.

What about a flight in which the tip (tip of the NC) is dead on line, but the tail tends to wobble / rotates / gyrates around the flight axis? Is there a typical cause? A fix? The rocket checks out per sims & a balance test..

What about if the midpoint of the rocket or the CG point does the same? (The CG or a point along the BT is dead on the flight axis, but the tip & tail tend to wobble / gyrate as it ascends?) Probable cause? Fix? The rocket checks out per sims & a balance test..

Could either the above be a thrust vectoring? A mass shift? uneven drag on one side?

If a pod is added to the side of an airframe (camera shroud for instance), is there a rule of thumb as to how much it stick out? Its frontal area? How far up or down the BT it should be before it causes any instability issues..
 

Rex R

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a wobble about the cg might be caused by fins that don't have quite enough semi-span(they don't stick out far enough from the air frame) and are blanketed by turbulent air flow from the nose/ airframe. fix add some more span.
Rex
 

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