OpenRocket 13.11.1 - Question about configurations for different motor cases

I hope that someone can help me with a question that I have about setting up different configurations to account for different motors that require different motor casings.

In other words, how do I set up two different motor configurations where the motor cases are different sizes/weights without having to materially change the design of my rocket? In other words, I want to click on the Flight Simulations tab and have both simulations available at the same time and have each simulation use the appropriate motor case weight for that simulation.

For example, I want to simulate my rocket with an AT J500G motor (RMS-38/720 motor case) and an AT J575FJ motor (RMS-38/1080 motor case). How do I configure things so that I associate the J500G with the 720 case and the J575FJ with the 1080 case so that the simulations use the "correct" motor case weight?

I tried to add both motor cases to my rocket design so that I could associate the motor to the appropriate motor case in the configurations tab, but OpenRocket still ended up using the weight for both motor cases in the CG calculation as well as the simulation calculations.

I hope that this all makes sense...

Cor

I haven't seen where it allows you to specify a case and motor independently. I always assumed that for reloadable motors it just already included the mass of the casing along with it. In that case, don't add weight for the casing(s) and let it do it for each configuration.

If you really need to specify them separately, I'm going to say you need to make a copy of your design file, setup one casing/motor combination in each and run two instances of OpenRocket at the same time to do this. But I'm not the expert, so perhaps someone else can shed more light on this. Good luck!

The total mass of the motor includes case and closures. However, it is simplified because it uses the standard case - that is it doesn't account for things like spacers or RMS adapter systems. This little bit of extra mass when using an adapter is not automatically included by OR, but in typical rockets, the additional mass is negligible.

Also, the mass-over-time and cg-over-time computations for burning motors is simplified. It assumes the mass burns uniformly over the duration and that the cg doesn't shift. Again, in normal rockets, these simplifications don't change things a whole lot.

Kevin

kruland said:

The total mass of the motor includes case and closures. However, it is simplified because it uses the standard case - that is it doesn't account for things like spacers or RMS adapter systems. This little bit of extra mass when using an adapter is not automatically included by OR, but in typical rockets, the additional mass is negligible...

Click to expand...

That explains things then... I will remove the motor case from the rocket design.

Thanks for the uber-quick responses!

Cor