Sunday, November 27, 2016

Apollo Command/Service Module 99% done

Well, all that's left is paint touch ups, add a shock cord and 'chute, and hit it with a dull coat to protect the cardstock. The nozzle should be darker than shown below and I have already repainted it.

20161126_173600

I updated the model RockSim model with accurate dimensions, actual mass and CG values, and the nozzle. It still has a phantom cone to simulate base drag. Final flight specs include, with a C11-3 loaded:
  • Margin of 1.16 (note this used the 'phantom cone' tweak to account for base drag).
  • Stable off a 42" rod.
  • 87' altitude.
  • Optimal delay of 1.42s.
If I move up to a D12-3:
  • Margin of 1.1.
  • Stable at 37".
  • 150' altitude
  • Optimal delay of 1.25s.
I don't have confidence in the RockSim results (not that I really expected to). Most obviously from these sim results, it doesn't seem like the optimum delay should be lower on a D12 than on a C11. Next, I'm not sure how the large nozzle will affect base drag. To further confuse matters, I also found that, if I remove the 'phantom cone', the margin with a D12 is still 0.82. After thinking about said funkiness, Psuccess is about 25%.