Calculating CP/CG with Strapons

[ClusterNut]

I did several searches and didn't see anything that quite matched my question. I am trying to find information on computing CP/CG/stability of a rocket with strapon boosters. I have used the old Estes and Centuri manuals in the past and OpenRocket more recently for simpler rockets but now I want to try something a little more complex. Any one have a pointer or reference, including a thread I missed?

Thanks. And sorry if it turns out that the question is answered elsewhere.

 

[troj]

Are they boosters you plan to have permanently attached? Or will they be dropped mid-flight?

If the former, OpenRocket may be able to do it, though I know RockSim 9 can. If the latter, RockSim 9 is the only program I know of that can do it.

I don't know any formulas, but on our Delta III several years ago, because the boosters were high enough in number to basically form a tube around the tube, so I ran two simulations -- one with a rocket with a body the diameter of the outside of the boosters, and a transition at the nosecones down to the actual diameter of the body.

The second simulation was the main body, without the boosters.

Once I knew it was stable in both configurations, we were good to go.

-Kevin

 

[ClusterNut]

The strapons will be permanent. One configuration is like the Viking II in my profile picture. (Love that old bird! ) I want to experiment with different things and it would be great to test the ideas out "on paper" first. RockSim is a bit expensive but I may consider it if necessary. I don't mind doing the calculations myself. I even remember what slide rule is! :jaw:

 

[troj]

The strapons will be permanent. One configuration is like the Viking II in my profile picture. (Love that old bird! ) I want to experiment with different things and it would be great to test the ideas out "on paper" first. RockSim is a bit expensive but I may consider it if necessary. I don't mind doing the calculations myself. I even remember what slide rule is! :jaw:

Looks like there are two tubes alongside the main. I'd do it this way...

Calculate the surface area of the three tubes, for the length of the bodies of the pods. Then, derive from that a single tube with the same surface area. For simulation purposes, that's now the diameter of the rear of the rocket. Then do a transition, the length of the pod nosecones, down to the main body diameter, and keep the rest of the rocket the same.

-Kevin