Sunday, November 27, 2016

More finless thoughts

I entered the finless Apollo Command Service Module and actually deluded myself that there was some value other than a pre-build visual description. After my previous post, I realized there is another basic flaw with my model. That is, the outer tube is modeled as a ring fin and rocksim treats it accordingly. However, with a closed bottom and the RAIS (Ram Air Intake Stabilization) effects, it is not clear if that it acts as a ring fin. RAIS is even closer to witchcraft than Dean Black's induction stabilization (aka GDS-Gas Dynamic Stabilization). While KenECoyote has had some success, there is no rules of thumb, much less equations, to relate the size of the rocket to the geometry of the RAIS intakes and 'nozzles'.

To summarize a couple of other issues with the RockSim model:

  • The effect of the bottom nozzle on base drag is unclear.
  • The sims are not giving intuitive results.
The upshot is my mindsim has totally melted down. My inclination is to find an open area and try it. There is not much point to add fins and create just another 24mm model. I also think I should go for the D12 v. the C11. Both RAIS and GDS need airflow, the more the better.