Protein crystals are very fragile, soft, and sensitive to environmental variations.
When the space shuttle is in orbit, the centrifugal force due to the orbit of the shuttle around the Earth balances or cancels the gravitational pull of the Earth, creating a condition referred to as microgravity. Microgravity is a balance of forces. Under microgravity conditions, gravity-driven phenomena such as convection and sedimentation are virtually eliminated. Elimination of the two can enhance protein crystallization. Because of this, the surrounding liquid in a sense protects the crystal.