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Inter-Module Ventilation Changes to the International Space Station Vehicle to Support the Bigelow Expandable Activity Module

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Inter-Module Ventilation Changes to the International Space Station Vehicle to Support the Bigelow Expandable Activity Module 48th International Conference on Environmental Systems ICES-2018-214 8-12 July 2018, Albuquerque, New Mexico Inter-Module Ventilation Changes to the International Space Station Vehicle to Support the Bigelow Expandable Activity Module 1 Kevin M. Braman0F The Boeing Company, Houston, Texas The Bigelow Expandable Activity Module (BEAM) was berthed to the International Space Station (ISS) as part of a two year study on the feasibility of expandable volumes for habitability. The BEAM is not outfitted with heaters for thermal control of the wall surfaces. To ensure that the module remains above the station dew point Environmental Control and Life Support System (ECLSS) Inter-module Ventilation (IMV) must be maintained between the Node 3 volume and the BEAM. This paper will describe the details, challenges, and modifications to the ECLSS on ISS and their interaction with BEAM. Nomenclature: CDRA = Carbon Dioxide Removal Assembly cfm = Cubic Feet per Minute ECLSS = Environmental Control and Life Support System ESA = European Space Agency FOD = Foreign Object Debris FIT = Failure Investigation Team HEPA = High Efficiency Particulate Air IMV = Inter Module Ventilation ISS = International Space Station JEM = Japanese Experiment Module MER = Mission Evaluation Room NPRV = Negative Pressure Relief Valve RMO = Remote Manual Override THC = Temperature and Humidity Control USOS = United States On-Orbit Segment I. Introduction An agreement between the National Aeronautics and Space Administration (NASA) and Bigelow Aerospace allowed for the berthing of an expandable module to the ISS. This paper describes the modifications to the ISS ventilation system that were required for the proper operation of the BEAM once installed. The paper does not cover the specifics of the inflation of the BEAM. 1 Environmental Control and Life Support System Engineer, The Boeing Company, [email protected] ICES-2018-214 II. Overview of System The USOS comprises seven main modules: Node 1, Node 2, Node 3, Airlock, US Lab, Columbus, and JEM. The modules mix atmosphere through fan-driven IMV with paths through both ducting and open hatchways. The ISS Program determined that the BEAM would be installed at the Aft berthing port of the Node 3 module (as shown schematically in Figure 1), which had been unused since Node 3 arrived to the ISS in 2010. The Aft ventilation is designed for an IMV Fan to push air into an attached module from the Aft-Port side of the bulkhead. The return air would travel either through an open hatch or through the Aft-Starboard bulkhead IMV ducting that is routed to the HEPA Plenum in the deck midbay of Node 3 and is subsequently filtered before returning to the Node 3 volume. The Node 3 Cabin Fan that provides ventilation for the Node 3 Module and pulls air through the HEPA Plenum does not provide a negative pressure head for the air returning from the Node 3 Aft-Starboard IMV ducting (i.e., from the BEAM). Figure 1 Node 3 to BEAM IMV Functional Schematic The concept of operations for the BEAM, unlike most modules on the ISS, is to remain with the hatch closed when the crew is not actively performing operations in the BEAM. One of the main reasons for this operational decision is because the BEAM hatch is designed to be a cover plate held in place by four bolts nominally, and when opened the hatch is a free-floating part. Thus, to close the BEAM hatch during an emergency would require significantly more time than the standard ISS hatch (which rides on a wheel-and-track system and closes quickly). Consequently, BEAM ventilation is generally provided through the IMV ducting for both supply and return air. For thermal control, ISS modules have shell-heaters that prevent the wall temperatures from dropping below the dew point of the Station atmosphere, thereby precluding condensation on the shell. The design of the BEAM did not allow for wall-heaters, and therefore the thermal control is dependent on the air flow over the interior surfaces. Due to this constraint, the air flow provides a critical function for the BEAM, as discussed later in this paper. III. Integration of IMV Valves 2 International Conference on Environmental Systems ICES-2018-214 When Node 3 was being prepared for flight, the Aft hatch was outfitted with IMV Valves designed and built by Carleton Technologies Inc. During ground testing it was discovered that the Carleton Valves did not properly communicate with ISS computers. All previous modules had been outfitted with Honeywell built IMV valves and did not have similar communication issues. Since there were no plans to have a berthed module or visiting vehicle at Node 3 Aft at the time of launch, the decision was made to replace the IMV valves with Negative Pressure Relief Valves (NPRV) for the Aft Port and Starboard bulkhead feed-through connections. Following the discovery of communication issues with the Carleton IMV Valves an investigation was performed and it was discovered that a change to the valve electronic board would correct the issue. Modification kits were created for the fleet of ten Carleton (now known as Cobham) IMV Valves that corrected the issue and allowed for the valves to be used on-orbit. Two Cobham IMV Valves were outfitted with a modification kit, each for use at the Node 3 Aft location. When the IMV Valve needs to be operated manually, this is done using a Remote Manual Override (RMO). The initial build of the Node 3 module included RMO (Figure 2) installation for the Aft Port and Starboard locations. When the IMV Valves were discovered to be faulty and removed, they were disconnected from their associated RMOs, and the RMOs remained installed. Therefore, when the IMV Valves were flown to the Station there were already RMOs installed and available to be connected to the IMV Valves. Figure 2 Honeywell IMV Valve and RMO Package Installation of the IMV Valves was completed once the BEAM arrived, and the valves were checked for both commanded closing and opening along with manual operation with the RMO. One 3 International Conference on Environmental Systems ICES-2018-214 issue was discovered during the installation of the Aft Starboard IMV Valve: the flexible coupler was missing, which was expected to be installed to the ducting that meets up with the valve. Since IMV air flow with the hatch closed is a critical function for the BEAM Module, the ground team and the crew had to produce a makeshift coupler. The following section describes in detail the issue and the subsequent solution that the crew implemented. IV. Aft Starboard IMV Coupler When it was discovered that the flexible coupler intended to make the connection between the Node 3 ducting and the newly installed IMV Valve was missing, a quick solution was required. There are spare flexible couplers aboard the ISS, but all of the couplers are for round-to-round connections that are aligned axially. The Node 3 Aft Starboard IMV ducting ends in an oblong shape, and the center of the duct is offset from the center of the circular IMV opening, thereby creating the need for a unique coupler design. During ground outfitting it was realized that the coupler initially designed and installed in Node 3 was found to be approximately 1 inch short, so it was removed. There was a non- conformance written and the as-delivered drawing was updated to reflect the absence of the coupler. Since there were no plans at the time of Node 3 delivery to support a module or vehicle at Node 3 Aft, much like the IMV Valve, there was no need for the coupler so the module was flown without a coupler. The ground team immediately investigated possible solutions so that IMV could be activated as soon as BEAM was ready for ingress. Following a Failure Investigation Team (FIT) meeting in the Mission Evaluation Room (MER) it was determined that a Kynar bag (a durable plastic material) could be used with the existing band clamps (intended to hold the flexible coupler in place),using kapton tape for additional stability. The crew was instructed to cut the bottom of a Kynar bag open and use the bag to complete the connection between the IMV valve and the ducting, as shown in Figure 3. Since this connection is not directly upstream from an IMV or Cabin Fan, the risk of a pressure differential causing a collapse of the coupler is greatly reduced and the coupler is expected to maintain a good IMV flow path. The crew has been asked to inspect the Kynar bag whenever they ingress the BEAM, and since the installation of the bag in May 2016, it has maintained its integrity. As of December, 2017, Thales Alenia Space Italia (TASI) was working towards launching a replacement coupler because the ISS Program has 4 International Conference on Environmental Systems ICES-2018-214 decided to keep the BEAM integrated with ISS and to use it for storage space. Since the mission length is now open-ended, a more permanent coupler is desired. Figure 3 Kynar Bag Installed as IMV Sleeve Node 3 Aft Stbd V. IMV Fan Each inactive IMV Fan on the ISS requires a periodic maintenance of operating for at least two hours every five years of being on-orbit, in order to maintain an even distribution of grease lubricant around the bearings. The fan installed at Node 3 Aft Port had never been operated since Node 3 arrived to the station in 2010, so in 2015 a Mission Action Request (chit) was written to operate the fan. Prior to operation, the crew had to remove the beta-cloth cover from the end of the ducting (that the beta-cloth was in place to prevent foreign objects from inadvertently entering the ducting) so the cloth would not get blown off to an unknown location behind the panels.
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