Effect of damping on planar spin-up dynamics of artificial-gravity-generating tethered satellite system

The Human Exploration and Development of Space will involve prolonged exposure in humans to a microgravity environment; this can lead to significant loss of bone and muscle mass, particularly for missions requiring travel times of several months or more, such as oil a trip to Mars. One possible remedy for this situation is to use a spent booster as a "counter-weight" and tether it to the crew cabin for the purpose of spinning up the counter-weight/cabin system about its common center of mass like a dumbbell, hence generating artificial gravity for the crew during long duration missions. However, much needs to be learned about the dynamics and stability of such tethered systems before they can become flight possibilities. The investigation of spin-up dynamics, along with other aspects of tethered systems, is the focus of the Tethered Artificial Gravity (TAG) satellite project, which will be discussed in this paper. After the 70-kg, TAG satellite is delivered into orbit, the payload will automatically separate into two equal halves and 2000 meters of tether will be deployed. After the deployment process is complete, a spin-up experiment will commence. This will be accomplished by reeling onto a take-up reel in the deployer a portion of the tether. As the tether is reeled back in, a rapid increase in the rotational motion in the system will occur; due to the presence of gravity-gradient torques, however, angular momentum will not be conserved, so equations of motion must be generated and integrated numerically to determine the behavior of the system. In particular, the effect of tether elasticity, initial angular position and damping on the spin-up dynamics must be considered; the preliminary results of such an investigation will be presented in this paper. 0