Deployment dynamics of space tether systems

The purpose of this research is to model and understand the deployment dynamics of space systems with long and short tethers. This research is divided into two parts; in the first part, a model for short and medium length tether systems is developed and simulated by solving equations of motion. A detailed parametric study is conducted after identifying important parameters affecting the deployment and studying the effect of each parameter on the deployment performance. Certain tools are developed to assist mission planners in predicting the deployment performance of a space tether system for a given set of parameters. The second part of the research is motivated by Space Elevator (SE) dynamics. SE is a futuristic and highly challenging technology based on the idea of connecting Earth and Space by an approximately 100, 000 km long tether. The tether used for the SE would be deployed from Geostationary Orbit (GEO). With this motivation, the short tether analysis from the previous section is extended to the analysis of long tethers. A model for long tether deployment is developed and governing equations of motions are formulated. Critical parameters are identified and problems involved in SE deployment are investigated. Tether mass is initially included in the model, but it is found that the mass of the tether has very little effect on the overall qualitative dynamics of the system. Hence, for further analysis, a massless tether model is adopted. Upon simulating the system, it is found that long tethers can be highly unstable during deployment and can crash onto the Earth. However, a considerable fraction of the tether can be deployed successfully without any external control mechanism before the instability manifests itself. Hence, alternate SE designs with shorter tether deployment requirements may be a possibility.