Implementing 3 body solutions in the Kerbin system would destabilize any orbits. The force of gravity F = mMG/r^2. F = ma, so ma = mMG/r^2 Solve for a is easy: a = MG/r^2 Plug in the values for the Mun: a = (9.76e20)(6.67e-11)/(1.2e7)^2. The acceleration caused by the Mun is approx 4.52e-4 m/s^2!! That is a dV of 1.627m/s per hour in LKO, or ~0.07% of the total orbital speed. To compare, earth\'s moon only exerts 0.119 m/s dV per hour, or ~0.0015% of total orbital speed. Munar orbits are even more unstable because of Kerbin\'s influence. Also, that 0.07% is significant. That means your entire orbital velocity is countered every 1,430ish orbits, instead of every 66,000. I have made the KSP system for Orbiter. It confirms this problem.