For RockSim accuracy it all depends on how accurate your measurements of the rocket and ambient conditions are! You can easily get to within 5%, or possibly better. I am reffering to altitude measurements I made with an Adept A1 altimeter; speed measurements should be just as accurate.
I have bracketed the RockSim predicted altitude of a low power model rocket with three or more flights in succession. The motors were selected to have the same weight as the engine file that RockSim uses to within +/- 0.05 grams. I used temperature, humidity and pressure measurements I made at the launch site; lattitude and elevation were obtained from the Terra server at:
https://terraserver.microsoft.com/
Wind speed and variability I got from the Weather Channel
https://www.weather.com/.
The rocket itself was measured three times in all dimmensions with a vernier calipers, and the average value of all three measurements was programmed into RockSim. The rockets weight was determined immediately before each launch and was adjusted to that used for the simulation to within +/- 0.05 gram (just added or removed a little wadding), and the CG was also kept constant to within 1mm.
I also have an angle finder built into my launch pad, and measure the distance from the bottom of the launch rod to the bottom of the lowest launch lug as the launch guide length.
I can get the landings to better than about 10%. I have actually given public demonstrations where I pushed the button and had the rocket either land back on the pad or in my waiting hands!
Of course everyone wants to know how I did that and I explain to them I spend a few hours programming all this flight data into RockSim to calculate the exact launch angle that would put the rocket right where I wanted it.
Bruce S. Levison, NAR #69055
