Open Rocket Sims - Unrealistic Altitudes

[Bill_Schmanski]

Hello. I am new to OpenRocket. I have run sims for a handful of rockets and they all come in with apogees 2-3x higher than the sims I run on ThrustCurve.

Here is the plot for my 4" LOC goblin flying an AT H219W. The rocket is pretty heavy: 1668g without the motor (my configuration is stock kit + wood nose cone bulk plate, EggTimer Apogee, small screamer, Jolly Logic Chute release. The time to apogee is considerably longer than expected, the apogee is unreasonably high, and the velocity decay seems mild: like there is not enough drag being modeled. I can't figure it out. Any assistance would be appreciated.





File is attached.

 

[Neutronium95]

You unchecked the "Use International Standard Atmosphere" in the simulation settings. When you do that, it will often times set the air pressure to a near vacuum, and lead to unreasonably high simulations. When I turn that setting back on, the apogee changes to about 1470 feet, with around an 8 second delay.


Your simulation settings:



Corrected settings:


Comparison of the simulations, original settings on top, corrected on the bottom:

 

[neil_w]

Covered here: https://openrocket.info/tutorials/sim-results.html

 

[Bill_Schmanski]

Very well, sir. I unchecked the STP box because my launch site is typically way warmer than standard. Perhaps I neglected to adjust the pressure.

Thank you for taking the time and the point back to the tutorial. I will study up.

 

[SiboVG]

I see you're still using OpenRocket version 15.03 @Bill_Schmanski. I advise you to download and install our latest version: https://openrocket.info/downloads.html?vers=23.09. The bug where the pressure goes to near vacuum after unchecking the ISA checkbox is fixed in OR 23.09.