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Other OR sim inputs
Not a huge effect for pressure and temp but did weather analysis and used for cycle2.0-2.2 conditions testing.
Fin shape with flutter considered
Looked at increasing the length of tip chord in order to get better flutter characteristics and there was slight benefit to it but did not end up increasing this due to drag and not hugely increased flutter qualities.
Increasing fin thickness vs area for flutter resistance
It appears that changing fin area does not affect flutter FOS nearly as much as changing fin thickness so thickness changes will be used for weather studies.
Launch rail being shorter if want
As the limiting factor on stability is still off rail for most of the simulations we don’t really want to lower the launch rail size but we also don’t really need it longer as we are very close to not having off rail be the worst stability. Launch tower team suggested the shortening was not a high priority so sims were not done.
Surface roughness improvemen
Ran study on file with cycle 2 masses not quite fully done and apogee went from 29413ft to 31347ft changing from regular paint (2.36mil) to smooth paint (0.787mil). No noticeable impact on stability.
More work done in cycle 2.0/2.1/2.2
Weight increase due to larger fin area on tip swept back shape
Early on the tip swept back shape seemed really good but weight increases not being analyzed meant that a drawback was concealed
Analyzed and found roughly 2.3in^2 increase in area and plate stock is 0.277lbs/in^2 for 3/16 thick meaning adding 0.637lbs in plate stock. Because of our own added material rounded up to 1.25lbs. dropped apogee for 1a case to 28557 which is significantly worse than previous and not really an advantage over other shapes.
Four Fin vs. 3 Fin Study:
Used the comp sim and set the material of the fins to carbon fiber and figure out how much it thinks those fins weighed
This value is 1.5 lbs which seems high but going with it.
Subtract that number from the section mass and make a copy of cycle 2.2 1a-c using this new number and see that it makes sense
Make a new file with four fins and dial in stability first
Then do flutter calcs and thickness back into openrocket and check stability again and iterate.
Results:
discovered that four fins is more efficient and leads to higher apogee
Optimized shape a lot and ended up with a more swept back shape with really good flight characteristics. Calling it tail stabilizer shape as it looks like the tail stabilizers on the f35 which aren’t really just tail stabilizers but anyway.
Checked with airframe team and no major manufacturing concerns for either sweep or four fins so going with it.
Created new cycle 2.3 mass sheet and updated based on openrocket estimate of new fin size weight