Simulating human-scale physics in a solar-system-scale world needs far more than 8 decimal digits. Neptune's orbit is 12 orders of magnitude larger than your spacecraft, no wonder your floats are acting up. You're going to need at least 50-bit precision to make your simulations accurate to the millimeter.
If anything, the fact that KSP is pretty much the only game with serious float issues shows that doubles are just fine for most applications.
Simulating human-scale physics in a solar-system-scale world needs far more than 8 decimal digits. Neptune's orbit is 12 orders of magnitude larger than your spacecraft, no wonder your floats are acting up. You're going to need at least 50-bit precision to make your simulations accurate to the millimeter.
If anything, the fact that KSP is pretty much the only game with serious float issues shows that doubles are just fine for most applications.