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The Extravehicular Mobility Units (EMUs) onboard the International Space Station (ISS) experienced a failure due to cooling water contamination from biomass and corrosion byproducts forming solids around the EMU pump rotor. The coolant had no biocide and a low pH which induced biofilm growth and corrosion precipitates, respectively. NASA JSC was tasked with building hardware to clean the ionic, organic, and particulate load from the EMU coolant loop before and after Extravehicular Activity (EVAs). Based on a return sample of the EMU coolant loop, the chemical load was well understood, but there was not sufficient volume of the returned sample to analyze particulates. Through work with EMU specialists, chemists, (EVA) Mission Operations Directorate (MOD) representation, safety and mission assurance, astronaut crew, and team engineers, requirements were developed for the EMU Water Processing hardware (sometimes referred to as the Airlock Coolant Loop Recovery [A/L CLR] system).

Following the Colombia accident, the Extravehicular Mobility Units (EMU) onboard ISS were unused for several months. Upon startup, the units experienced a failure in the coolant system. This failure resulted in the loss of Extravehicular Activity (EVA) capability from the US segment of ISS. With limited on-orbit evidence, a team of chemists, engineers, metallurgists, and microbiologists were able to identify the cause of the failure and develop recovery hardware and procedures. As a result of this work, the ISS crew regained the capability to perform EVAs from the US segment of the ISS Figure 1.

An ISS internal Quick Disconnect (QD) coupling failure during proto-flight vibration testing of ISS regenerative Environmental Control and Life Support (ECLS) hardware raised issues concerning the performance of the male QD housing seal design. The existing QD acceptance screening process does not address performance of redundant housing seals and therefore failure tolerance cannot be assured for hardware currently in service. The possibility of performance issues has large implications when considering that currently there are 399 similar units on orbit and approximately 1100 units on the ground integrated into flight hardware. Testing, analysis, and development of a plan to address this issue both for existing hardware and future hardware has been completed to assure system safety is not adversely affected.

The Carbon Dioxide Removal Assembly (CDRA) is an essential part of the International Space Station (ISS) Environmental Control and Life Support (ECLS) system. The CDRA provides carbon dioxide (CO2) removal from the ISS on-orbit modules. Currently, the CDRA is the secondary removal system on the ISS, with the primary system being the Russian Vozdukh. The CDRA encountered some operational problems since being launched to orbit on Flight 5A in February 2001. While on-orbit, several hardware modifications and maintenance activities have been necessary to restore the CDRA to nominal capability. This paper describes the troubleshooting activities and briefly explains the failures, the operational workarounds, and the on-orbit hardware repairs performed to return the CDRA to operational status.

High pressure oxygen onboard the ISS provides support for Extra Vehicular Activities (EVA) and contingency metabolic support for the crew. This high pressure O2 is brought to the ISS by the Space Shuttle and is transferred using the Oxygen Recharge Compressor Assembly (ORCA). There are several drivers that must be considered in managing the available high pressure O2 on the ISS. The amount of O2 the Shuttle can fly up is driven by manifest mass limitations, launch slips, and on orbit Shuttle power requirements. The amount of O2 that is used from the ISS high pressure gas tanks (HPGT) is driven by the number of Shuttle docked and undocked EVAs, the type of EVA prebreath protocol that is used and contingency use of O2 for metabolic support. Also, the use of the ORCA must be managed to optimize its life on orbit and assure that it will be available to transfer the planned amount of O2 from the Shuttle.

The Orion Crew and Service Modules are often compared to the Apollo Command and Service Modules due to their similarity in basic mission objective: both were dedicated to getting a crew to lunar orbit and safely returning them to Earth. Both spacecraft rely on the environmental control, life support and active thermal control systems (ECLS/ATCS) for the basic functions of providing and maintaining a breathable atmosphere, supplying adequate amount of potable water and maintaining the crew and avionics equipment within certified thermal limits. This assessment will evaluate the driving requirements for both programs and highlight similarities and differences. Further, a short comparison of the two system architectures will be examined including a side by side assessment of some selected system's hardware mass.