OpenRocket to RockSim question

I'm a RockSim user, and I really love it. It does most everything I need/want it to do, and I find it intuitive to use. Good stuff.

That said, I've been seeing a lot of the "visualization" images folks have been posting from their OpenRocket files. I'm impressed, and I'm thinking I'd like to maybe start using OpenRocket for this reason. However, I'm perfectly happy with everything else about RockSim and don't really want to change. I certainly don't want to re-create all my existing files in the new software from scratch.

So, the question is: Can RockSim files be transferred to OpenRocket? And is it pretty easy to do?
What are the limitations/problems/hassles with doing so (assuming it can be done in the first place)?

thanks for your help,
s6

You can open rocksim files directly in openrocket- no real "conversion" needed. I don't know if anything gets lost in the process, but it doesn't look that way to me.

Since openrocket is free, go ahead and try it out with one of your files

stealth6 said:

I'm a RockSim user, and I really love it. It does most everything I need/want it to do, and I find it intuitive to use. Good stuff.

That said, I've been seeing a lot of the "visualization" images folks have been posting from their OpenRocket files. I'm impressed, and I'm thinking I'd like to maybe start using OpenRocket for this reason. However, I'm perfectly happy with everything else about RockSim and don't really want to change. I certainly don't want to re-create all my existing files in the new software from scratch.

So, the question is: Can RockSim files be transferred to OpenRocket? And is it pretty easy to do?
What are the limitations/problems/hassles with doing so (assuming it can be done in the first place)?

thanks for your help,
s6

Click to expand...

OpenRocket will open RockSim files, but when you save, some changes will not go with the file (i.e., OR will not save Simulation data in RockSim file format). However, I download all my Rocksim files from Vendors and RocketReviews then save as OR files. Easy.

Check your model carefully, have noticed some differences when changing from Rocksim to OR.

Open Rocket will tell you when you have an incompatible feature from a RockSim file. For example, OR does not do parachute spill holes, side-mounted pods, and fins attached to transitions. It will warn you when you try to open a model that has an incompatible feature, and then it will ignore said feature.

I think you'll find there are other minor conversion issues. From memory there is an issue with the way OR interprets nose cone length that is different to Rocksim. Also think I saw problems with mass overrides.

Conversion is a messy business.

The design goal of importing/exporting Rocksim files was always one of 'best effort', not exact representation. OR does not support fin tubes and external pods for example. There is also not a 1:1 mapping between supported nose cone shapes, so it's a best approximation in those cases. There are other differences in the way the two systems modeled their internal abstraction of a rocket that had to be mapped as best as they could.

As far as differences in dimensions or mass (other than those caused by unsupported shapes) then I'd be most interested in seeing examples of those so that they can be fixed. That code has been in production for several years now and I'm unaware of those discrepancies. Rocksim materials and their densities are imported from the file and analogous materials are created in OR. But that can cause some issues because in Rocksim any material can be used for a recovery device - but in OR it must be a 'Surface' material. There is also a Rocksim bug where in certain cases the recovery device material density is 0 in the file. Density has to be inferred by other means - and thus may not exactly match.

On a side note, Rocksim allows for nonsensical component representations, while OR is more strict. An example is that Rocksim files allow a body tube to have an inner diameter to be larger than the outer diameter (not sure how the UI allows that to happen). But in OR, that's strictly not allowed since it's a physical impossibility. As I recall there were other oddities and 'bugs' in the Rocksim file representation that may have resulted in slight differences.

Conversion is not as black and white as most think, nor what any of us, ideally, would like. I'm admittedly biased, but I think it's as about as good as it can be.

Cheers,
Doug

Found the model that caused me issues - attached.

First issue is with the nose cone, in Rocksim there is a base length field. This allows for a nose cone where there is a full diameter section next to the shoulder that does not taper off. This is simply ignored by OR and as a result the nose cone is actually shorter. What I would expect was that OR add on the base to the overall length which will give a reasonable approximation provided the base length is not too big and it should probably give a conversion notice for this. I think I ended up splitting the nose cone into 3 pieces to make work properly in OR (the alternative more complicated option, I suspect it would be easier to add a feature to enter the base length field in OR)

The second issue I have is the treatment of mass object, this is really pretty minor. I suspect that this may have something to do with how Rocksim treats masses internally. For a mass object the mass is not calculated instead you enter this amount directly into Rocksim. Note that in Rocksim there is no tab to override the mass of a mass object (which makes sense) it does however put a note on the screen that a mass override is in effect (which does not make sense). In OR it takes the entered weight as the object weight, but then it decides that a mass override is in effect and overrides the mass with the same amount. It does work, however it is weird and unnecessary and requires a lot of clean it up.

Third issue I had forgotten about, again this is pretty minor. When OR converted the Locator Cord, it applied a length to the cord that put it outside the rocket. Interestingly OR added this to the length of rocket, not sure if this would cause any issues with the simulations.

Unfortunately this happened to be one of my first attempts at converting to OR so I was a bit put off by this. These days I use OR all the time and rarely touch Rocksim, it gives better results I find

View attachment Loc Aura PK-1 with Retainer + TTF + LRL10 2.rkt