@LiberalEd - my first answer to both questions is that, as I hinted at in the blog, the plan relies on the cubes being in perfect free-fall in vacuum, not affected by solar wind or vibrations in the satellites. The satellites containing the cubes get pushed slightly by the solar wind, etc., but they detect these deviations from their ideal course by comparing their position to the cubes inside, and correct for these deviations using thrusters. The cubes inside sail on untouched.