Design of High-Tension Elastically Deforming Space Tether Deployer

Abstract

Several future applications for space tethers such as tethered artificial gravity, space hooks and the space elevator, feature high-tension tether deployment of fail-safe tethers. This paper presents the design of a deployer for high-tension flat space tethers that should further strengthen the case for future high-tension space tether applications. The presented tether deployer features two sets of linearly activated pinching plates, which are elastically hinged on cross-flexures. The elastically deforming design avoids the use of bearings and gearboxes. The fixation of the (flat) tether between flat pinching plates avoids bending of the tether, which occurs in a design using friction wheels. The bending of the tether around a friction wheel lowers the allowable tension in the tether, which is avoided in the presented design. The use of elastic hinges in space is growing, but usually the forces that occur are quite small. In the case of the presented tether deployer, the forces are extremely large, which is possible because the width of the tether is about one meter. The plate flexures are as wide as the tether, allowing very large forces. The width of the plate flexures also makes the mechanism very rigid, which is important when the force in the tether is large. The tether deployer design presented in this paper is performed for the case of MARS-g, a low Earth orbit artificial gravity test facility. The tension in the tether can be as high as 400 kN while the resulting tether deployer mechanism weighs only about 500 kilogram for low speed deployment. The design can be adapted for high speed deployment simply by adding a more powerful motor; the tension in the tether will remain the same, only more power is required. The design is therefore easily adaptable for other uses such as space hooks or the space elevator.