High-Purity, Defined-Envelope Pressure Bladder

The NASA Portable Life Support System (PLSS) for the Exploration Extravehicular Mobility Unit (xEMU) incorporates a Feedwater Supply Assembly (FSA) to store consumable cooling water. The FSA must accept a total of 12 lbs. of pure water prior to each Extra-Vehicular Activity (EVA), then supply this water to the cooling loop at ambient suit pressure during the EVA, functioning reliably for 700 cycles over 15 years of service. To meet these requirements, NASA has specified multiple ultra-pure fluoropolymer bladders captured in restraints providing overpressure tolerance to 38 psi. The assembly must also conform to a defined geometric envelope. Designs to date present challenges for two primary reasons. First, typical constructions involving a lay-flat bladder captured within a sewn textile restraint do not use space efficiently enough to store the required volume within the available space. Second, wrinkles that form as the bladders inflate cause the fluoropolymer membrane to tear. Other challenges include robust mounting to a rigid structure and visual access for inspection. RAPA Technologies has developed a novel defined envelope pressure bladder that meets all specifications for the FSA. The design combines the benefits of a flexible bladder with the strength and convenience of a rigid tank, providing an ultra-pure, ambient-pressure reservoir with high cycle life and pressure tolerance, high volumetric efficiency within the available envelope, near-zero dead volume, optical transparency for visual inspection, simplified mounting, and low mass, along with an integrated volume sensor. In Phase I we demonstrated the performance, overpressure resistance, and cycle life of this novel bladder system. In Phase II, we will develop and deliver multiple full-scale qualification FSA units tailored for use in the NASA xEMU. The xEMU incorporates a Feedwater Supply Assembly (FSA) to store consumable cooling water. It must supply the cooling loop with 12 lbs. of water at ambient pressure during each EVA and function for 15 years of service. NASA has specified multiple fluoropolymer bladders captured in restraints providing pressure tolerance to 38 psi. All FSA designs to date have faced challenges. Typical constructions involving a lay-flat bladder captured within a textile restraint do not use space efficiently enough to store the required volume, and wrinkles that form as the bladders inflate cause the bladder membrane to tear. Other challenges include robust mounting and visual access. Our defined envelope pressure bladder will meet all specifications for the FSA. It combines the benefits of a flexible bladder with the strength of a rigid tank, providing an ambient-pressure reservoir that is: Ultra-pure Pressure tolerant and high cycle life Volumetrically efficient Near-zero dead volume Transparent for visual inspection Robustly mounted Low mass Incorporates an integrated volume sensor The technical objectives for our Phase II effort will be: Develop a high-level design for an FSA assembly integrated with the xEMU PLSS. Refine material selections, fabrication processes, and detailed design features. Fabricate two full-scale prototypes suitable for integration in PLSS ground testing. Conduct performance and dynamic load testing of the FSA component. Compile design documentation and a preliminary manufacturing plan. Our deliverables will include: Six quarterly progress, one interim, and one final report. Two sub-scale prototypes early in the first year. Two full-scale prototypes at the end of the project.
Benefits: Our defined envelope bladder system will meet all requirements for the FSA, a critical component of the NASA xEMU. It will also make a natural choice for many other fluid handling applications in space, and can be used to store water, process chemicals, and waste streams. As NASA pursues manned missions to the Moon, lunar orbit, and Mars, the need for bladders that are reliable and stable for years-long missions will continue to grow. The recent expansion in human space activity by private industry will lead to diverse applications on vehicles, suits, and rovers. We believe that our unique design may also find use in specialized industrial, medical, and military settings for applications such as drone aircraft fuel tanks, chemical transport, medical sample storage, and hydration bladders.