Gravity
Gravity is the basis of Orbital Dynamics, which describe the Orbits of all space craft and objects.
Accleration of gravity (g) as measured at the equator
Earth - 9.81 m/s2
Moon - 1.622 m/s2
Mars - 3.69 m/s2
Phobos - 0.0084-0.0019 m/s2
Deimos - 0.0039 m/s2
Ceres - 0.27 m/s2
For long term habitation in any environment save the earth, a solution must be implemented to combat the muscle wasting and heart problems seen in the space station crews. The only current option is for astronauts to spend 1/3 or more of their day in a carnival like centrifuge that duplicates the earth like accelerations.
It follows if sailors in a small boat can get used to the constant movement of the waves, then astronauts can make this adaptation too.
In manufacturing, gravities below the moon (1.6 m/s2) pose a number of serious problems. Movement of loose materials must be done in closed containers. The digging of material becomes progressively more difficult. Movement becomes slower due to the inability to stop or stay on the ground.
