@revk @CascadeTommy - the satellite is steered around so the 2 gold cubes floating inside it do not touch the walls of the vacuum chamber. The cubes are in free fall. The satellite is *almost* in free fall - it's just very gently pushed by solar wind - so it only needs tiny thrusters to make very gentle course corrections that keep the cubes where they belong. This technology has been tested by LISA Pathfinder, and it worked.

spacenews.com/lisa-pathfinders