Design and Validation Testing of Titanium Spacesuit Bearings

In the past two years, significant progress has been made in the development of titanium spacesuit bearings. While titanium is a popular aerospace alloy due to its high strength to weight ratio, concerns over flammability and low resistance to wear have kept it from being used in life-supporting flight hardware. Flammability testing conducted in 2014 showed that when titanium bearings were operating in an environment pressurized with pure oxygen, ignition was not a risk, but heavy wear was possible. This discovery promoted research towards wear-resistant designs; starting in 2015 with contact pressure wear testing (ICES-2016-60) and continuing from 2016 through 2018 with advanced analysis and optimized design efforts (ICES-2017-242). This three year bearing development effort will culminate in 2018 when the optimized designs are validated through cycle testing and delivered to NASA for integration with Z-series spacesuits. This paper will focus on the specific changes to spacesuit bearing geometry which permit the use of Titanium in these life-supporting roles. The use of stainless steel bearings in spacesuits has helped increase mobility where the pressurized suit fabric can prove restrictive to the astronaut’s motions. The bearings also serve as attachment points for restraint lines which enhance suit structure and help reduce fabric tension. The localized attachment points for these restraint lines can cause uneven loading of the bearing races, making predicting internal bearing stresses difficult. The first phase of development for titanium spacesuit bearings used cycle testing to determine contact stress limits appropriate for planetary exploration demands. The second phase developed a method to predict the stresses present in bearings using FEA and physical measurement. These techniques have resulted in brand-new bearing designs intended specifically for titanium. Reporting the specific design enhancements and resulting performance of the new bearings will show the economy and safety available through the use of titanium.