04-18-2006, 08:32 PM
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BARCLONE Rocketry
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Join Date: Mar 2005
Location: Mobile, Alabama
Posts: 5,357
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Originally Posted by Chris_Timm
Will rocsim detect a design that is stable in the cg/cp sense, but unstable in the fin placement sense?
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That's really the whole idea of stability -- the correct relationship between the CG and the CP. As long as the CG remains ahead of the CP, no matter how the fins are placed, the rocket should fly, even if it looks like it ought to do cartwheels. Consider the "big boys" down at the cape -- they fly without fins, but the CG/CP relationship remains the same (or close to it). They just use thrust vectoring to accomplish the same job as the fins.
I recall seeing the footage of a Delta II that lost its main engine before the solids kicked off due to a fuel leak. The computer shut down the main and the verniers. Immediately the rocket swapped ends and broke up.
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Would it recognize the unstability of a maple-seed style rocket?
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You mean a rocket with a single fin, or asymetric fins? No. This is perhaps something that needs to be addressed in a future version. Currently, it will simply calculate the total fin area and how that total relates to the rest of the design.
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How about a design with the motor-mount offset to one side of a bt-70?
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Again, sadly, no. I just tried a sample using some PML 2.7 parts and a BT-50 motor tube. It flew with the motor mount 0.5" and 0.75" off-center, and didn't show any results of the asymetry. This also needs some addressing. Being able to have asymetric fins with equally asymetric thrust positioning would make for some wildly interesting designs. |