The Rocket Formerly Known as Black

Step Eight

Aerodynamics and Stabilization

Click [HERE!] for the ç RockSim 6.0 simulation.

As with all my scratch-built designs, I rely heavily on RockSim. I recently upgraded to RockSim 6.0, and this version is better than ever. It is a must for anyone who likes designing their own rockets.

Having said that, I believe that my cigar-shaped designs really tax the calculations embedded in RockSim - especially the Barrowman formulas. The curved surfaces really freak out the Barrowman predictions, but the RockSim and Cutout estimates of CP are consistent with each other, and based on experience I'm fairly comfortable with them.

I'm not comfortable with the Coeffient of Drag calculations for ç , however. RockSim estimates the Cd at less than 0.1 - and if that were true, it would glide to over 3100 feet. But having witnessed these flights before, I'm reasonably sure that RockSim calcualtions are not designed to work with a rocket like this one. I'm guessing that RockSim ignores the shell and the calculations are using only the center tube.

At any rate, I'm glad I'm not using the ejection delay estimates from the simulated flights. I'm sure I would guess wrong. Electronic ejection is a surer bet for this type of flight.

Below are two screen shots from the software AeroCFD, also available from Apogee Rocketry. It was useful in validating the Cp and assuring me that the rocket is stabile, but it appears to me that this software is just as baffled by a contoured airframe as RockSim.

TRFKAB Index

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