Development of High Strength Bolt Fastening System for Satellite Structures

Abstract

A high strength bolt fastening system for satellite structures has been developed. This fastening system enables high frictional strength by adopting titanium bolts with high strength and low torque-coefficient, as well as shims with high friction coefficient. Low torque-coefficient of the titanium bolts is achieved by PTFE (Polytetrafluoroethylene) solid-film lubricant, which is coated on the bolts. High friction coefficient of the shim is achieved by surface roughening by etching. To verify the design of the fastening system, long-term preload test, torque-coefficient test and vibration loosening test (Junker's test) were conducted and successfully completed. In addition, the fastening system was applied to a development model of satellite structure and was verified by mechanical environmental tests (static load test, system vibration test and thermal vacuum test). The observation showed no evidence of slip or alignment deviation. Thus, a conventional reamer-bolted-fastening system can be replaced with the developed high strength bolt fastening system that saves manufacturing period of satellites and furthermore enables the satellites to be competitive in terms of cost, delivery and performance.