If so, my first guess would be heat shielding. Test-retry cycles are much slower when launch windows are 2 years apart. My second guess would be sabatier machi

If so, my first guess would be heat shielding. Test-retry cycles are much slower when launch windows are 2 years apart. My second guess would be sabatier machines, which are vital for Mars and pointless on the Moon, and where I've failed to notice even a hint of progress.