Expectations vs. Reality The Banshee

Flight Data Motor – J800T, 1280ns Total Impulse, 1.9 sec burn time Apogee – seconds Main – seconds Touchdown – 73.7 seconds

Other Example Altimeter Readings

Simulation vs. Reality DesignConstructedPost OP Analysis Diameter4”4” (assumed)4.25” Lift Off Weight 10.6 lbs17.7 lbs Peak Altitude5426 ft3147 ft2754 ft Velocity at Touchdown 15 ft/sec19 ft/sec29 ft/sec

Diameter Discrepancy Public Missiles Phenolic Airframe Tubing Spec – 3.962” Public Missiles Pre-Glassed Phenolic Airframe Tubing Spec – 3.995” As used – PML Phenolic Airframe Tubing w/2 layers of Giant Leap “fiberglass sock” – measured at 4.25” (after flight) Fin can also has an additional 2oz layer of fiberglass

Lift Off Weight Discrepancy Design 10.6 lbs –Weights defaulted from Rocksim –I Assumed 8z for paint and epoxy Actual 17.7 lbs –Slightly underestimated several components –Considerably underestimated paint and epoxy Fiberglassing not in original estimate, probably about 3 lbs Aprox 1 lb of epoxy + foam Easily 15 cans of primer and paint used…

Peak Altitude Discrepancy Initial Design – 5426 Feet –Lower weight –4” diameter smooth profile –Wind estimated 8-14mph –.5” motor overhang Constructed – 3147 Feet –Correct weight –4” diameter smooth profile assumed –Wind estimated 8-14mph –.5” motor overhang Post Op – 2754 feet actual, ran simulation again – result of 2817 feet –Correct weight –4.25” diameter – turbulent transition from nose cone –Actual wind – upper end (14+mph) – more weather cocking –.5” motor RESESS – CG forward – more weather cocking –Launch rod tilted 5deg into the wind (est. from photos)

Landing Velocity Discrepancy 9’ home-made parabolic cupped design –Design from Rocket Team Vatsaas ( –Assumed cD of 1.5 (from their website) –Should have brought down 18 lb rocket at 19fps –Richard Nakka’s Experimental Rocketry website has a detailed dissertation on parachutes, suggesting a more reasonable cD of.6 –A cD of.6 on an 18 lb rocket results in 29fps, which matches my result