Aspect ratios

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TNmike

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A couple questions concerning aspect ratios, that is, rocket length versus body tube diameter (20" OAL rocket, 1" BT = 20:1 AR). And I am asking these questions looking at only single stage, constant BT diameter rockets.

1) What aspect ratio do you consider to be the most aesthetic? This is purely subjective from individual to individual, and things like fin and nose cone shapes are also a factor.

2) When going for altitude or mach, what aspect ratio(s) do you believe are optimum, if any? Obviously a thousand criteria affect this, just looking for your thoughts.

Thanks
 

watheyak

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For altitude, speed, or any time the least amount of drag is what you want, the smallest possible diameter in the shortest possible rocket.
 

LithosphereRocketry

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Not necessarily... Below Mach, short stubby rockets have issues with dynamic stability. Longer rockets can also get away with smaller fins, making them more efficient. Above Mach, you start to worry about wave drag, so you want a long nose cone with stubby fins that have a long root edge. I'm not sure if BT length makes too much difference, but it probably helps.

As to the best aspect ratio, Wikipedia says that for small airplanes it's typically 6-8, but airplanes have much more drag than rockets, so that may make a difference.

I'm not an expert on this though... I'd be interested to hear what everyone else has to say.
 

blackjack2564

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For altitude, speed, or any time the least amount of drag is what you want, the smallest possible diameter in the shortest possible rocket.

.......you forgot......"with the largest possible motor"!!! LOL
That pretty much sums it up.
Now how you GET there, is where the choices come in.

Use the motor as airframe.Carbon,Fiberglass, Aluminum, Kevlar tubes.
Optimum weight for altitude.
Light as possible for speed.
Nose cone shape, Conical, Von Karmon,Parabolic. This IS rocket science. 6 -1 & 7-1 cones have proven best performance so far. [with what I'm involved in]

For 1. anything goes,it's a matter of what you like.

2. you build rocket around a given motor.
 
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