Well for modern mobiles it’s technically possible on minimum settings, but I suggest to just develop a 2.5D version of the game, like with the same features but without the Z axis. Yes, I know, it would be similar to the other 2D rocket games, but his is the only solution.
KSP 1.11 in 2.5D will still have liquid, EVA, contracts and strategies, plane mechanics, more parts, overheat and drag effects (re-entry), navigation nodes, time wraps, original Easter eggs (no not Kraken), etc.. You see? Although it no longer features the Z axis, it would still have lot of the feathers 3D KSP have, and most importantly, it’s more achievable in mobile.
Definitely worth to think about, but it would take time to develop if this became true.
By the way, I did not mentioned the UI.
Everything I have just mentioned is pointless if we put the UI on the table. The screen is just too small. Let’s just say we remove the nav-ball. Action groups and staging order is options inside the pause menu. Parts (no matter VAB, SPH or EVA constructing) are forced to be placed in specific places only. Everything on the up right corner of the screen is options inside the pause menu. Overall it’s quite annoying to use. Maybe we can construct in portrait mode? Idk. It’s a lot of problems.
Graphics is not an issue. Modern phone should be able to deal with it. Except they can’t
Overall this is my opinion. What is the conclusion? KSP is achievable if we convert it to 2.5D, as long as the UI is not an issue.