Please read t' procedure listed below. How t' do a Batch Conversion from Rocksimm RKT t' OpenRocket ORK Format. Aye aye! Why? Two reason, ya bilge rat, don't have Rocksimm's program, have OpenRocket's program, me hearties, secondly one can find a lot o' rkt files and rather than openin' one at a time into OpenRocket and then do a Savin' As, arrr, I simply use this batch process t' do t' work and it works great. This video shows usin' t' F Drive on me computer, you use whatever drive is available t' you: Start off by makin' a folder named OpenRocket Then in that folder make two(2) sub-folders named as: ORK RKT Download and place t' OpenRocket application file into t' folder named OpenRocket Download all o' t' Rocksimm (*.RKT) files your little heart wants into t' sub-folder named RKT. Go t' t' the Windows Command Prompt and type: cd f: (then press t' Enter key) Then will need t' change directory or folder where t' OpenRocket application file is located. As is in this example, it would be: cd f:\openrocket (then press t' Enter key) Then type at t' prompt t' followin' line text: java -cp OpenRocket-12.03.jar net.sf.openrocket.utils.RocksimConverter F:\OpenRocket\RKT\*.rkt (then press t' Enter key) This will then convert all o' your *.rkt files into *.ork files. Now simply select all o' t' *.ork files and move them t' t' ORK sub-folder. Ya scallywag! Or you can leave them there, but you will need t' delete t' *.rkt files for if you download any more rkt files and run t' batch conversion process again, one will have t' old rkt files converted again. Avast! This is why I move me files and then delete t' rkt files. Note if your Open Rocket application and sub-folders are different, then you will need t' make changes in t' above commands. Aye aye! OpenRocket application: https://sourceforge.net/projects/openrocket/files/openrocket/12.03/OpenRocket-12.03.jar/download then search for rocksimm or .rkt files