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The International Space Station (ISS) underwent a dramatic buildup in life support equipment since the delivery and activation of the U.S. Laboratory module in February 2001, followed by the Joint Airlock in July 2001. Since Laboratory activation, several Environmental Control and Life Support (ECLS) equipment failures have occurred. This paper addresses these failures, occurring through February 2002, and, where known, the root causes, with particular emphasis on probable micro-gravity causes are highlighted. Impact to overall ISS operations and proposed or accomplished fixes also are discussed.

The International Space Station (ISS) United States Laboratory module has been under test for approximately two years in the Space Station Processing Facility (SSPF) at NASA Kennedy Space Center (KSC) preparing for launch. Preparation activities for closing out the Environmental Control and Life Support (ECLS) system have included Closed Hatch testing to verify the capability of the life support equipment to support the crew, final manufacturing steps, and the close-out process itself. These activities were accomplished by an integrated Boeing and NASA team, located at the Johnson Space Center (Houston, Texas), Marshall Space Flight Center (Huntsville, Alabama) and Kennedy Space Center, Florida. On December 13, the Laboratory module hatches were sealed prior to loading into the Shuttle Orbiter payload bay for launch on February 7, 2001.

As part of the International Space Station (ISS) Trace Contaminant Control Subassembly (TCCS) development, a performance test has been conducted to provide reference data for flight verification analyses. This test, which used the U.S. Habitation Module (U.S. Hab) TCCS as the test article, was designed to add to the existing database on TCCS performance. Included in this database are results obtained during ISS development testing; testing of functionally similar TCCS prototype units; and bench scale testing of activated charcoal, oxidation catalyst, and granular lithium hydroxide (LiOH). The present database has served as the basis for the development and validation of a computerized TCCS process simulation model. This model serves as the primary means for verifying the ISS TCCS performance. In order to mitigate risk associated with this verification approach, the U.S.

The International Space Station (ISS) Thermal Control System (TCS) can be categorized into three major subsystems: Passive Thermal Control System (PTCS), External Active Thermal Control System (EATCS), and Internal Active Thermal Control System (IATCS). Each of these segments of TCS is highly automated and as such is very dependent on the on-board software for monitoring and control of the various functions. For the PTCS, software is used to monitor temperature sensor data and command heaters on and off. The active thermal systems contain a large number and a large variety of equipment that is highly dependent on software control. This paper explores the important role that software plays in the operation of the ISS TCS and the need for the hardware and software development to be well integrated. A brief overview is provided of the design and architecture of the three major thermal control subsystems and the related thermal control software.

Space Station Freedom (SSF) will be required to vent water during non-quiescent periods. During Man Tended Configuration (MTC), before the Environmental Control and Life Support System (ECLSS) water loop is closed, humidity condensate will be periodically vented. At Permanently Manned Configuration (PMC), water will be vented on contingency if there is excess water on SSF. The thrust due to venting must be minimized to be considered non-propulsive. Also, ice formation and clogging of the vent nozzle must be avoided. Many aspects of the Space Shuttle water vent design were utilized in development of the preliminary SSF water vent design presented in this paper. Design modifications which improved the shuttle vent as well as those necessary for SSF are discussed. The exterior vent location, direction and environment on SSF are unique compared to previous space water vent designs. From data collected in the vent tests and analyses, a finalized SSF water vent design will be developed.

The Space Station Freedom (SSF) Active Thermal Control System (ATCS) “collects, transports, and rejects waste heat from the pressurized elements.” The US Laboratory (USL) ATCS is independent of other SSF elements, and supports all subsystem and payload cooling requirements within the US Laboratory including redundant cooling of life and station critical loads. The thermal transport capability of the USL internal ATCS is sized to accommodate 28.6 kW of waste heat which includes electrical power (25kW), DDCU electrical conversion losses (2.2 kW), DDCU fixed losses (0.2 kW), and crew metabolic loads (1.2 kW). Active control of the coolant flowrate is required to manage the heat rejection capability of the Thermal Control System (TCS). The ATCS accomplishes these functions through pumped, single phase water thermal transport loops which collect waste heat via coldplates and heat exchangers and transport that heat to heat exchangers external to the module.

This paper contains a partial review of the requirements and design of the Environmental Control and Life Support System (ECLSS) for Space Station Freedom (SSF); a review of G189A ECLSS computer models developed for different SSF configurations; and some significant computed results from these models showing transient dew point responses during maximum and minimum dew point conditions on board SSF. SSF operational requirements which pertain to dew point have two major thrusts: 1) Quantification of high and low moisture contents allowable in the atmosphere; i.e., dew point within the range of 40°F to 60°F, and relative humidity within the range of 25% to 70%. 2) Prohibition of condensation on any interior surfaces (such as the interior pressure shell wall, or cool air/water lines) (1).* Detailed computational results presented in the paper pertain primarily to the verification of compliance with the first of the two items mentioned above.

A fundamental of the Space Station Freedom Program (SSFP) is cooperation of International Partners in the development of an on-orbit laboratory facility. The United States, Japan, and Europe will each provide a laboratory of their own design that can be used by all of the participants. The common unit within each module for experimentation is the the International Standard Payload Rack (ISPR). While the rack must provide sufficient flexibility to be useful to the scientific user, it must also provide standardized interfaces for installation and functionality within each partner's laboratory. This paper will focus on the development of the ISPR and its interface and system requirements.

The Space Station Freedom (SSF) Environmental Control and Life Support System (ECLSS) Atmosphere Revitalization (AR) subsystem conditions the cabin atmosphere to provide a safe habitable environment for the 4-person astronaut crew. The first phase of the ECLSS development testing, namely the AR POST, focuses on the SSF Man Tended Capability (MTC) configuration. The scheduled 34-day integrated AR POST was conducted by Boeing at Marshall Space Flight Center (MSFC) Building 4755, Huntsville, Alabama and completed March 21, 1992. A test timeline is presented in Figure 1. This test was the first time the three baselined ECLSS Man Tended Capability (MTC) AR assemblies were integrated and operated in a closed door chamber in which the internal atmosphere was monitored. This paper details the initial results of the Integrated AR POST. Future considerations for the Integrated Single String POST are also discussed.