Not really applicable to this discussion, but one instance which is highly applicable is that you can't control two ships in KSP at once. If your lower stage needed to do a powered land which an upper stage was still accelerating into orbit, you couldn't replicate that in ksp.
.. Unless your name is Scott Manley ;-). But yes, good point about Lagrangian points [1]. I wasn't aware that KSP is only a two-body-simulation - interesting how the game can hide that with its sphere of influence implementation.
[1]http://forum.kerbalspaceprogram.com/threads/18623-Lagrange-p...
Also, my point with the logic is that when looking at the differences between physics in KSP and the real world, we are dealing with overlapping, rather than nesting sets.
First time I've seen this, thanks. You certainly have a point that feasible designs in KSP vs. real world aren't completely nested. When I was arguing about KSP being an upper limit, I didn't really think about the SSTO case - at least the stock simulation certainly doesn't hold up to be able do any kind of feasibility check for horizontally launched vehicles.
Do you have an example for that?
> edit - and for the same reason there are also things that would work in KSP that would fail in the real world.
That's what I wanted to say with 'the opposite doesn't hold true'.