The crew of a starship is free to move about their ship without the problems of weightlessness because of a network of small generators working together to provide the proper sense of "down".
The gravity field itself is created by a controlled stream of gravitons, using the same principles as the ship's tractor beams.
Power is channeled into a hollow cylinder of anicium titanide 454, where a superconducting rotor of thoronium arkenide is suspended in a pressurized chrylon gas.
Once set into motion, the rotor generates a graviton field gentle enough to simulate the gravitational pull of a standard Class M planet.
Requiring only occasional energy, the rotor can continue to provide an attraction field for up to 4 hours after a power loss.