I've been working with Openrocket for the past couple weeks. I like the ease of use and flexibility of this program - and I REALLY like the fact that all of the equations behind it, are documented. It is 6-degree-of-freedom so it attempts to account for canted fins, spin, effects of wind and wind turbulence. It does not have tube-fins or other "offset geometry", but does have tools for staging, clustering etc. It is by far the most powerful free tool I've seen.
For comparison, I analyzed a Quest Starhawk on a Quest B-6-4 using Wrasp and Openrocket (when it gets warmer, I'm planning to run some altimeter vs. simulations tests as well - note, that there are a couple of these in the Openrocket documentation already).
My Starhawk is 4FNC, 0.775"dia, 12.7" long and weighs 43g including the motor.
As built in Openrocket, the calculated weight was 40g and the cg was within 0.5" of actual. The differences are (I think) in the plastic "fincan" used on the starhawk which I attempted to simulate using a plastic "tube" in Openrocket.
In Openrocket you choose the actual RMS surface finish in mils (it provides some estimates, such as 2.3 mils is "smooth paint"). I chose "smooth paint" for this comparison. In Wrasp, you instead choose a single Cd value. In the past I've found the best comparison between my A & B motor powered rockets in Wrasp using 0.9 as a Cd so that is what I used here.
Here are the results of these two runs:
OpenRocket___Wrasp (Cd=0.9)
779 ft________796 ft_______max alt.
6.08 sec______6.4 sec______time to peak
319 ft/s_______322 ft/s_____max velocity
929 ft/s-s_____1092 ft/s-s___max accel
749 ft________755 ft________alt at chute deploy
51 ft/s________54 ft/s______vel. at chute deploy
80 ft/s________62.6 ft/s____vel. at launch rod tip
These results seem pretty darn close to each other, to me.
The effect of choosing the Cd in Wrasp is pretty important to peak alt.
For the starhawk....
Openrocket 779 ft
Wrasp (Cd=0.9) 796 ft
Wrasp (Cd=0.8) 844 ft
Wrasp (Cd=0.7) 900 ft
Of course it isn't worth much to say one analysis is close to another analysis - the proof is in how well any analysis matches the real world, but I have a "comfort level" with Wrasp after the past year of flying it against my HowHigh Altim, so it is good to see that Openrocket is giving similar results.
-Kerry