Thrust Curve vs. RockSim

[BigRiJoe]

Okay. I designed a large tube finned rocket in RockSim. I put the values in Thrust Curve and got what it considers appropriate engines. Thrust Curve gives an altitude of 730 ft with a GT-80 and RockSim, using a GT-80 as the motor, gives an altitude of 1800 ft. Any thoughts about what the two approximations have to say?

 

[markkoelsch]

Okay. I designed a large tube finned rocket in RockSim. I put the values in Thrust Curve and got what it considers appropriate engines. Thrust Curve gives an altitude of 730 ft with a GT-80 and RockSim, using a GT-80 as the motor, gives an altitude of 1800 ft. Any thoughts about what the two approximations have to say?

A tube fin is likely too complicated for Thrustcurve to sim. It is not intended to really replace Rocksim or OR. That said, you say large- please define what you mean.

 

[Buckeye]

Many things can cause the difference. You will need to post your RS file, thrust curve used, and TC inputs.

For the G80 in particular, there are 3 motor files in Thrustcurve. Two are similar, one is very different. The Motor Guide will take the average of all three when calculating. Rocksim uses just one.

 

[Bat-mite]

BTW, ThrustCurve assumes a standard 3 or 4FNC shape. All you get is weight, diameter, length, and Cd. It doesn't accommodate different types of nose cones, transitions, etc. ThrustCurve is a quick and dirty sim; however, I have found it to be pretty accurate for standard-shaped rockets.