rocksim... strange nose cone

I just recently aquired a "argosy" (...???) I believe thats what it was called... 4" nose cone. It is very much like a conical but has a cockpit shape, like an X15 rocket-plane. Best way to simulate in rocksim? Conical of the same length?

Also, how will it perform at high speeds? Will the strange shape cause instability problems?

Lastly, is rocksim accurate with models that have 2 pairs of fins, each pair with a different shape/size? It seems to work but I dont know how accurate or correct it is.

I think most of you can tell where this rocksimin' is goin' ... nothing scale but I would like to make a rocket plane style rocksim file and see how it performs.

I've tried using different nose cones in Rocksim and never found it to predict anything different in terms of performance. Try a few different shapes and see for yourself.

-Ben

I need some input on the fins... barrowman says the rocket is stable, rocksim says it is way unstable. Is rocksim accurate when simulating a rocket with 2 small fins and 2 large fins? I would assume if barrowman says its stable it will be, thats the old trusted method. The largest issue may be a slight coneing... is the rocksim method accurate?

One thought is that barrowman is combining the surface area of the fins, and rocksim is actually looking at the effects that the two smaller fins will have on stability, is this a possibility?

Ill try playing around a bit more but input would be great...

Originally posted by jraice
I need some input on the fins... barrowman says the rocket is stable, rocksim says it is way unstable. Is rocksim accurate when simulating a rocket with 2 small fins and 2 large fins? I would assume if barrowman says its stable it will be, thats the old trusted method. The largest issue may be a slight coneing... is the rocksim method accurate?

One thought is that barrowman is combining the surface area of the fins, and rocksim is actually looking at the effects that the two smaller fins will have on stability, is this a possibility?

Ill try playing around a bit more but input would be great...

Click to expand...

RockSim is more accurate since it takes into account some of the dynamic stability effects that the Barrowman equations don't. RockSim also looks at the CP and CG versus wind angle; click on the "Stability Analysis.." under the "Rocket" menu. I simulate a cockpit as 3 thick fins the middle fin the profile of the cockpit and the two side fins as the the half height of the cock pit. The thickness of all three fins totals up to the frontal area of the cockpit. For the SR-71 Black Bird I did the cockpit portion of the nose cone that way and added two fins to either side to take into account the flattened shape of the nose cone.

I attached my simulation of the Estes Argosy so you can see how I did this.

Bruce S. Levison, NAR #69055

That file and nose cone tip helps a lot! Actually I am thinking about going with a 4" upscale argosy. Saw a picture of one in a sport rocketry mag and it is a very nice looking bird! Plus the cone I have is a 4" argosy nose cone...