46th International Conference on Environmental Systems ICES-2016-406 10-14 July 2016, Vienna, Austria International Space Station (ISS) Environmental Control and Life Support (ECLS) System Overview of Events: 2015-2016 Gregory J. Gentry 1 The Boeing Company, Houston, Texas November 2, 2015 marked the completion of the 15 th year of continuous human presence in space on board the International Space Station (ISS). After 44 expedition crews, over 115 assembly & utilization flights, over 180 combined Shuttle/Station, US & Russian Extra-Vehicular Activities (EVAs), the post-Assembly Complete ISS continues to fly and the engineering teams continue to learn from operating its systems, particularly the life support equipment. Problems with initial launch, assembly and activation of ISS elements have given way to more long term system operating trends. New issues have emerged, some with gestation periods measured in years. Major events and challenges for each U.S. ECLS subsystem occurring during the last year are summarily discussed in this paper, along with look aheads for what might be coming in the future for each U.S. ECLS subsystem. Nomenclature AC = Assembly Complete NORS = Nitrogen/Oxygen Resupply System ACS = Atmosphere Control & Supply OGA = Oxygen Generation Assembly AIK = Airlock Installation Kit OGS = Oxygen Generation System AR = Atmosphere Revitalization ORU = Orbital Replaceable Unit ARFTA = Advanced Resupply Filter Tank Assembly PDMS = polydimethylsiloxane ASV = Air Selector Valve PFE = Portable Fire Extinguisher BIT = Built-In Test PGT = Pirani Gauge Transducer CCAA = Common Cabin Air Assembly PIO = Provisioned Item Order CCT = Cold Cathode Transducer PMM = Permanent Multipurpose Module CWC = Contingency Water Collection PPT = Positive Pressure Transducer CDRA = Carbon Dioxide Removal Assembly RFTA = Resupply Filter Tank Assembly CHX = Condensing Heat Exchanger RTA = Resupply Tank Assembly DAB = Desiccant Adsorbent Bed R&R = Remove & Replace DMCPS = Decamethylcyclopentasiloxane SBA = Sorbent Bed Assembly ECLS = Environmental Control and Life Support SpX = SpaceX ECLSS = Environmental Control and Life Support Systems EVA = Extra-Vehicular Activity STS = Space Transportation System FOD = Foreign Object Damage TCCS = TraceContaminantControlSubassembl FDS = Fire Detection and Suppression THC = Temperature & Humidity Control FW = Firmware TOC = Total Organic Carbon HEPA = High Efficiency Particle Air TT&E = Test, Teardown & Evaluation HP = High Pressure TUBSS = Temporary Urine Bag Storage System HPGT = High Pressure Gas Tank UPA = Urine Processor Assembly HTCO = High Temperature Catalytic Oxidation USOS = United States Operational Segment HTV = H2 Transfer Vehicle UWMS = Universal Waste Management System ISS = International Space Station WM = Waste Management LiOH = Lithium Hydroxide WPA = Water Processor Assembly LP = Low Pressure WRS = Water Recovery Subsystem MCA = major Constituent Analyzer WRM = Water Recovery & Management MPLM = Multi-Purpose Logistics Module W&HC = Waste & Hygiene Compartment MSFC = Marshall Space Flight Center 1. Introduction he International Space Station (ISS) program achieved “Assembly Complete” (AC) in 2010, with the TEnvironmental Control and Life Support (ECLS) system supporting ISS crews and visiting Shuttle and Soyuz 1 Associate Technical Fellow & ISS ECLS Technical Lead, Boeing 3700 Bay Area Boulevard, Houston TX 77058 crews since assembly began in 1998. Shuttle retired in 2011 with completion of the last mission to the International Space Station, designated STS-137/ULF-7. Through AC, new pressurized elements including Node 3 & the Permanent Multi-purpose Module (PMM) formerly known as the Multi-Purpose Logistics Module (MPLM) have been added to the ISS, making up a total of 16 pressurized elements. ECLS activity has focused on maintaining the ISS systems currently onboard while acquiring on-orbit operational knowledge in microgravity. A. ISS ECLS OVERVIEW The ISS on-orbit ECLS system is comprised of 6 subsystems, including Atmosphere Control and Supply (ACS), Temperature and Humidity Control (THC), Fire Detection and Suppression (FDS), Atmosphere Revitalization (AR), Water Recovery and Management (WRM), and Vacuum System (VS). The following sections briefly summarize each subsystem and its function within the ISS pressurized elements. 1. Atmosphere Control and Supply (ACS) The ACS subsystem provides cabin atmosphere pressure control, overpressure relief, pressure equalization, rapid depressurization detection and response, nitrogen and oxygen distribution, and nitrogen and oxygen high pressure tank recharge from Shuttle resources. 2. Temperature and Humidity Control (THC) The THC subsystem provides airborne heat removal, air temperature control and monitoring, intra-module and inter- module ventilation, humidity removal, and airborne particulate/bacteria removal. The U.S. Lab THC provides active cooling for Node 1 and the MPLM when docked to the ISS. 3. Fire Detection and Suppression (FDS) The FDS subsystem includes smoke detection, fire isolation, fire extinguishment, and fire recovery. 4. Atmosphere Revitalization (AR) The AR subsystem revitalizes the habitable atmosphere by removing carbon dioxide, potentially hazardous volatile trace contaminants generated by inadvertent spills, crew metabolic processes, and equipment off-gassing such that cabin contaminants levels are maintained within limits. Additionally, the ISS habitable environment is monitored for atmosphere major constituents O 2, N 2, and CO 2, as well as H 2, CH 4, and H 20. In the United States On-orbit Segment (USOS), the Sample Distribution System (SDS) carries sample cabin air through lines from the various modules to the Major Constituent Analyzer mass spectrometer. 5. Water Recovery and Management (WRM) The WRM subsystem supplies potable water, hygiene water, and water for payloads, as well as collects humidity condensate. The WRM also provides excess wastewater venting; condensate storage; and potable, waste, and fuel cell water distribution. The WRM subsystem was expanded significantly prior to Shuttle retirement with the addition of the Regenerative ECLS Racks known as WRS 1, WRS 2 & OGS, which include the Urine Processor Assembly (UPA), the Water Processor Assembly (WPA) and the Oxygen Generator Assembly (OGA). WRM includes Waste Management (WM) which, for ISS, is the Waste & Hygiene Compartment (W&HC), a USOS bathroom that collects solid waste and collects, treats and transports liquid waste to the Urine Processor Assembly (UPA) for water recovery. 6. Vacuum System (VS) The VS supplies the U.S. Lab module payload rack locations with access to space vacuum. The VS consists of two separate subsystems: the Vacuum Exhaust System (VES) and the Vacuum Resource System (VRS). Connected to all thirteen payload rack locations, the VES can vent payload gases overboard. The VRS provides high-quality vacuum to nine of the thirteen payload rack locations for user access. 2 International Conference on Environmental Systems 2. SUMMARY DISCUSSION OF MAJOR SUBSYSTEM EVENTS IN UNITED STATES ON-ORBIT SEGMENT BY FUNCTION A. Atmosphere Control and Supply 1. NORS AIK Installation and 1 st gas transfer since Shuttle retirement Five High Pressure Gas Tank (HPGT) ORUs are mounted to the Quest Airlock exterior (3 oxygen & 2 nitrogen). To deal with the retirement of the Shuttle Orbiter fleet that resulted in the loss of its gaseous oxygen and nitrogen resupply to the ISS HPGTs, the high pressure (41,369 kPa (6,000 PSI)) Nitrogen/Oxygen Recharge System (NORS) was developed. Delivery of the Airlock Installation Kit (AIK) to ISS occurred on Orb-2 in July 2014, and the device was installed in the Quest Airlock Equipment Lock on November 18, 2015 to enable gas recharge of Figure 1 NORS AIK Installed in Quest the Airlock HPGTs via AIK installed Resupply Tanks Assemblies Airlock (RTAs). Two issues that occurred during AIK installation were: (1) A small N2 connection leak at a Gamah fitting due to difficult access to the connection and inability to R&R the Gamah seal, and (2) the Fluid Fitting Torque Device (FFTD) got stuck on the fitting that was leaking and could not be removed. The leak was determined to be low enough to not need repair (on the order of ~3 Kg (~ 6 lbs.) N2/year and the FFTD was abandoned in place. The crew may be asked to attempt retrieval later but a spare FFTD was launched on OA-6 in April 2016. (See Figure 1 for the AIK installed in the U.S. Airlock Quest .) The first NORS oxygen and nitrogen RTAs were flown to ISS together on HTV-5 on August 19, 2015 loaded with 38.2 kg (84 lbs.) & 28.6 kg (63 lbs.) mass of stored gas respectively. After delivery of the RTAs to ISS and installation of the AIK in the airlock, the crew installed the oxygen NORS tank onto the AIK on January 19, 2016 and accomplished the first gas transfer to a HPGT on ISS since Shuttle retirement. Once the High Pressure (HP) oxygen tanks pressure was increased from 11,721 kPa (1700 psia) to 13,789 kPa (2000 psia) in a pressure equalization process that took approximately 6 hours, the configuration was changed to transfer gas to the Low Pressure (LP) oxygen tank, resulting in a pressure increase from 689 kPa (100 psia) to 2,757 kPa (400 psia). 21.95 kg (48.3 lbs.) of oxygen was transferred to the HP tanks and 11.55 kg (25.4 lbs.) of oxygen was transferred to the LP tank with 4.7 kg (10.3 lbs.) residual oxygen still in the NORS oxygen tank. (See Figure 2 for HP & LP HPGT pressure increases resulting from the first NORS oxygen transfers.) When the nitrogen