For years, subjects completing planetary suit testing have made qualitative comments that the pressure garment system (PGS) they are using will partially offload itself while pressurized. This is due to the Lower Torso Assembly (LTA) acting as a pressure column or spring that partially offloads the suit, especially while standing. The purpose of this effort was to improve upon the shoulder force sensing system that was developed in 2017. The new system was designed to have smaller force sensors on the shoulder strap weaving at the lower back and a custom strain gage sensor located at the front torso area of the HUT to reduce subject discomforts and to be wireless to reduce the complexity of transmitting data outside of the spacesuit. By using instrumented shoulder straps and shoulder strap brackets to measure the load, several subjects were taken through a series of movements, in both pressurized and unpressurized configurations and with multiple shoulder strap settings using the Exploration Extravehicular Mobility Unit (xEMU) government reference design spacesuit. Due to the small subject sample size and a 3D anthropometric comparison between the HUT and subjects was not done, statistical analysis was not performed on the data set. The results from this testing will be used to validate the software and hardware and will provide insights to inform the community about the benefit of the pressurized volume suit design, develop a better understanding of the expected loads carried by the subject in flight planetary applications, and help to inform the shoulder strap setting impacts to 1-G testing.
Davis et al. (Sun,) studied this question.