Outer Boot Sole System
The Apollo Spacesuit Boots which were used in 16 Extravehicular Activities (EVAs) have performed well over the course of 6 landing missions, but several opportunities for enhancement were identified throughout the course of the program. NASA recently initiated the development of the eXploration Extravehicular Mobility Unit (xEMU), which includes a new space suit boot configuration intended to advance its performance beyond the Apollo configuration to enable a more robust lunar exploration for the Artemis Program. Performance enhancements, needed to support the xEMU�s, include improving crew stability and ergonomic flexibility while offering thermally protection as astronauts explore Permanently Shaded Regions (PSRs) which may reach 40�K. A novel Space Boot Sole System (SBSS) was developed to address xEMU boot requirements. It consists of an inner boot worn by the crew to comfortably conform to the foot, an outer boot sole which provides thermal isolation and desired flexural characteristics, as well as a coupling mechanism which firmly interfaces the two boots so that they act as a single unit. The SBSS is intended to be integrated into the boot assembly as it is developed. A set of prototypes were fabricated and tested with human subjects in a biomechanics lab at the University of Massachusetts Amherst to verify that the desired mobility and tactility were obtained. The outer boot sole couples with an innovative spring system made of low-thermal-conductivity materials and thermal- isolation techniques to keep the inner boot surface above the authorized 55� F touch temperature, while still maintaining the overall flexibility needed to support the frequent and lengthy EVAs. This combined system of methodology keeps the astronauts� feet within 1.5 inches of the terrain so as to maintain ease of grounded walking stability. Although it was developed for integration into an xEMU boot, the technology may be adapted to other exploration configurations.