When Marcus and Dr Franklin are traveling to Mars their
transport is clearly firing its engines, yet when we see inside, objects are floating in zero gravity. Also, before going zero gravity, practically all items must be fastened down, so they *can't* float off, especially that suspiciously wrench like item floating in the middle. This is to prevent damage to people and to the objects themselves, when the ship starts boosting again.
After Dukhats death, when Delenn let's go of his head, you can see the tip of his headbone bend and bounce back revealing that it's a rubber material.