Yes, and it also depends on your motor. Double click your simulation for the data, it shpuld be under "launch guide data" on the last line: "minimum velocity for stable flight reached at:" On Mar 5, 2015 7:17 PM, "Rob Diehl" <rwdiehl@xxxxxxxxxxxxx> wrote: > Will rocksim give a ‘minimum rail length’ number when you enter all of the > rocket stats? > > > > Rob >