One of the greatest unknowns for human space exploration is the effect of lunar or Mars gravity levels on the long-term health of the human body. Given the current lack of detail in human Mars program plans, it is entirely possible that we will commit humans to a Mars mission without any data on the effect of Mars gravity on biological processes, and with minimal long-term experience from lunar exploration. While the obvious solution would be to create a rotating habitat to simulate different gravitation levels for research, the size and concomitant expense of such a system have always made it a non-starter in the program planning process. This paper discusses the concept of a "Gravity Kit" — a modular system similar to an ESPA ring that launches between a payload and the upper stage, and creates artificial gravity through rotation and the use of cables to adjust radius of rotation and rotation rate. In this way, it should be possible to create artificial gravity spacecraft across a variety of scales for investigation of gravitation biology prior to committing humans to extended missions to Mars or beyond. The Gravity Kit module provides necessary utilities which need to be located on the spin axis, including spin thrusters, power generation, communications, and docking fixtures. By using six cables in a Stewart-platform configuration attached to both the payload and the upper stage (used as a counterweight) and providing active control of cable lengths, the system will adjust for motions of the center of gravity in the payload and provide active damping for spin perturbations. Conceptual designs are presented to show the feasibility of the concept at a variety of scales, from a cubesat-based proof of concept to animal facilities to human-scale habitats.
David L. Akin (Sun,) studied this question.