Refine Your Search

Search Results

Viewing 1 to 14 of 14
Journal Article

Status of the International Space Station (ISS) Trace Contaminant Control System

2009-07-12
2009-01-2353
A habitable atmosphere is a fundamental requirement for human spaceflight. To meet this requirement, the cabin atmosphere must be constantly scrubbed to maintain human life and system functionality. The primary system for atmospheric scrubbing of the US on-orbit segment (USOS) of the International Space Station (ISS) is the Trace Contaminant Control System (TCCS). As part of the Environmental Control and Life Support Systems' (ECLSS) atmosphere revitalization rack in the US Lab, the TCCS operates continuously, scrubbing trace contaminants generated primarily by two sources: the metabolic off-gassing of crew members and the off-gassing of equipment in the ISS. It has been online for approximately 95% of the time since activated in February 2001. The TCCS is comprised of a charcoal bed, a catalytic oxidizer, and a lithium hydroxide post-sorbent bed, all of which are designed to be replaced on-orbit when necessary.
Journal Article

Root Cause Assessment of Pressure Drop Rise of a Packed Bed of Lithium Hydroxide in the International Space Station Trace Contaminant Control System

2009-07-12
2009-01-2433
The trace contaminant control system (TCCS) located in the International Space Station's (ISS) U.S. laboratory module employs physical adsorption, thermal catalytic oxidation, and chemical adsorption to remove trace chemical contamination produced by equipment offgassing and anthropogenic sources from the cabin atmosphere. The chemical adsorption stage, consisting of a packed bed of granular lithium hydroxide (LiOH), is located after the thermal catalytic oxidation stage and is designed to remove acid gas byproducts that may be formed in the upstream oxidation stage. While in service on board the ISS, the LiOH bed exhibited a change in flow resistance that leading to flow control difficulties in the TCCS. Post flight evaluation revealed LiOH granule size attrition among other changes. An experimental program was employed to investigate mechanisms hypothesized to contribute to the change in the packed bed's flow resistance.
Technical Paper

Strategies to Mitigate Ammonia Release on the International Space Station

2007-07-09
2007-01-3186
The management of off-nominal situations on-board the International Space Station (ISS) is crucial to its continuous operation. Off-nominal situations can arise from virtually any aspect of ISS operations. One situation of particular concern is the inadvertent release of a chemical into the ISS atmosphere. In sufficient quantities, a chemical release can render the ISS uninhabitable regardless of the chemical's toxicity as a result of its effect on the hardware used to maintain the environment. This is certainly true with system chemicals which are integral components to the function and purpose of the system. Safeguards, such as design for minimum risk, multiple containment, hazard assessments, rigorous safety reviews, and others, are in place to minimize the probability of a chemical release to the ISS environment thereby allowing the benefits of system chemicals to outweigh the risks associated with them. The thermal control system is an example of such a system.
Technical Paper

Cabin Air Quality on Board Mir and the International Space Station - A Comparison

2007-07-09
2007-01-3219
The maintenance of the cabin atmosphere aboard spacecraft is critical not only to its habitability but also to its function. Ideally, air quality can be maintained by striking a proper balance between the generation and removal of contaminants. Both very dynamic processes, the balance between generation and removal can be difficult to maintain and control because the state of the cabin atmosphere is in constant evolution responding to different perturbations. Typically, maintaining a clean cabin environment on board crewed spacecraft and space habitats is a central function of the environmental control and life support (ECLS) system. While active air quality control equipment is deployed on board every vehicle to remove carbon dioxide, water vapor, and trace chemical components from the cabin atmosphere, perturbations associated with logistics, vehicle construction and maintenance, and ECLS system configuration influence the resulting cabin atmospheric quality.
Technical Paper

An Environmental Impact Assessment of Perfluorocarbon Thermal Working Fluid Use on Board Crewed Spacecraft

2006-07-17
2006-01-2218
The design and operation of crewed spacecraft requires identifying and evaluating chemical compounds that may present reactivity and compatibility risks with the environmental control and life support (ECLS) system. Such risks must be understood so that appropriate design and operational controls, including specifying containment levels, can be instituted or an appropriate substitute material selected. Operational experience acquired during the International Space Station (ISS) program has found that understanding ECLS system and environmental impact presented by thermal control system working fluids is imperative to safely operating any crewed space exploration vehicle. Perfluorocarbon fluids are used as working fluids in thermal control fluid loops on board the ISS. Also, payload hardware developers have identified perfluorocarbon fluids as preferred thermal control working fluids.
Technical Paper

Replacement for Internal Active Thermal Control System Fluid Sample Bag Material

2005-07-11
2005-01-3078
The International Space Station (ISS) Internal Active Thermal Control System (IATCS) uses a water based heat transport fluid with specific chemical parameters and additives for corrosion and microbial control. The fluid and hardware have experienced anomalies since activation of the United States Laboratory (USL), including chemical and possibly, microbial corrosion. The required sampling of the fluid has the crewmembers removing samples via an in-line sampling tool to perform real-time trace ammonia contamination tests using color change strips, and filling a 150 ml bag from each loop for the ground laboratory analyses. The former activity requires stable storage of the strips, and for the latter activity, it is highly desirable to return the ground sample as stable as possible. This paper describes the process for materials selection, test methods/set-up, results, and final recommendation for a replacement outer bag.
Technical Paper

Resistively-Heated Microlith-Based Adsorber for Carbon Dioxide and Trace Contaminant Removal

2005-07-11
2005-01-2866
An integrated sorber-based Trace Contaminant Control System (TCCS) and Carbon Dioxide Removal Assembly (CDRA) prototype was designed, fabricated and tested. It corresponds to a 1-person load. Performance over several adsorption/regeneration cycles was examined. Vacuum regenerations at effective time/ temperature conditions, and estimated power requirements were experimentally verified for the combined CO2/trace contaminant removal prototype. The current paper details the design and performance of this prototype during initial testing at CO2 and trace contaminant concentrations in the existing CDRA, downstream of the drier. Additional long-term performance characterization is planned at NASA. Potential system design options permitting associated weight, volume savings and logistic benefits, especially as relevant for long-duration space flight, are reviewed.
Technical Paper

Performance Characterization of a Prototype Ultra-Short Channel Monolith Catalytic Reactor for Air Quality Control Applications

2005-07-11
2005-01-2868
Contaminated air and process gases, whether in a crewed spacecraft cabin atmosphere, the working volume of a microgravity science or ground-based laboratory experiment facility, or the exhaust from an automobile, are pervasive problems that ultimately effect human health, performance, and well-being. The need for highly-effective, economical decontamination processes spans a wide range of terrestrial and space flight applications. Adsorption processes are used widely for process gas decontamination. Most industrial packed bed adsorption processes use activated carbon because it is cheap and highly effective. Once saturated, however, the adsorbent is a concentrated source of contaminants. Industrial applications either dump or regenerate the activated carbon. Regeneration may be accomplished in-situ or at an off-site location. In either case, concentrated contaminated waste streams must be handled appropriately to minimize environmental impact.
Technical Paper

International Space Station Internal Thermal Control System Lab Module Simulator Build-Up and Validation

2003-07-07
2003-01-2519
As part of the Sustaining Engineering program for the International Space Station (ISS), a ground simulator of the Internal Thermal Control System (ITCS) in the Lab Module was designed and built at the Marshall Space Flight Center (MSFC). To predict ITCS performance and address flight issues, this facility is operationally and functionally similar to the flight system and flight-like components were used when available. Flight software algorithms, implemented using the LabVIEW® programming language, were used for monitoring performance and controlling operation. Validation testing of the low temperature loop was completed prior to activation of the Lab module in 2001. Assembly of the moderate temperature loop was completed in 2002 and it was validated in 2003. Even before complete validation the facility was used to address flight issues, successfully demonstrating the ability to add silver biocide and to adjust the pH of the coolant.
Technical Paper

International Space Station Internal Thermal Control System Cold Plate/Fluid-Stability Test - Two Year Update

2003-07-07
2003-01-2518
Operation of the Internal Thermal Control System (ITCS) Cold Plate/Fluid-Stability Test Facility commenced on September 5, 2000. The facility was intended to provide advance indication of potential problems on board the International Space Station (ISS) and was designed: To be materially similar to the flight ITCS. To allow for monitoring during operation. To run continuously for three years. During the first two years of operation the conditions of the coolant and components were remarkably stable. During this same period of time, the conditions of the ISS ITCS significantly diverged from the desired state. Due to this divergence, the test facility has not been providing information useful for predicting the flight ITCS condition. Results of the first two years are compared with flight conditions over the same time period, showing the similarities and divergences.
Technical Paper

Selection of an Alternate Biocide for the International Space Station Internal Active Thermal Control System Coolant Loops

2003-07-07
2003-01-2568
The International Space Station (ISS) IATCS (Internal Active Thermal Control System) includes two internal coolant loops that use an aqueous based coolant for heat transfer. A silver salt biocide was used initially as an additive in the coolant formulation to control the growth and proliferation of microorganisms in the coolant loops. Ground-based and in-flight testing has demonstrated that the silver salt is rapidly depleted and not effective as a long-term biocide. Efforts are now underway to select an alternate biocide for the IATCS coolant loop with greatly improved performance. An extensive evaluation of biocides was conducted to select several candidates for test trials.
Technical Paper

Octafluoropropane Concentration Dynamics On Board the International Space Station

2003-07-07
2003-01-2651
Since activating the International Space Station's (ISS) Service Module in November 2000, archival air quality samples have shown highly variable concentrations of octafluoropropane in the cabin. This variability has been directly linked to leakage from air conditioning systems on board the Service Module, Zvezda. While octafluoropropane is not highly toxic, it presents a significant challenge to the trace contaminant control systems. A discussion of octafluoropropane concentration dynamics is presented and the ability of on board trace contaminant control systems to effectively remove octafluoropropane from the cabin atmosphere is assessed. Consideration is given to operational and logistics issues that may arise from octafluoropropane and other halocarbon challenges to the contamination control systems as well as the potential for effecting cabin air quality.
Technical Paper

Cabin Air Quality Dynamics On Board the International Space Station

2003-07-07
2003-01-2650
Spacecraft cabin air quality is influenced by a variety of factors. Beyond normal equipment offgassing and crew metabolic loads, the vehicle's operational configuration contributes significantly to overall air quality. Leaks from system equipment and payload facilities, operational status of the atmospheric scrubbing systems, and the introduction of new equipment and modules to the vehicle all influence air quality. The dynamics associated with changes in the International Space Station's (ISS ) configuration since the launch of the U.S. Segment's laboratory module, Destiny, is summarized. Key classes of trace chemical contaminants that are important to crew health and equipment performance are emphasized. The temporary effects associated with attaching each multi-purpose logistics module (MPLM) to the ISS and influence of in-flight air quality on the post-flight ground processing of the MPLM are explored.
Technical Paper

Integrated Orbiter/International Space Station Air Quality Analysis for Post-Mission 2A.1 Risk Mitigation

2000-07-10
2000-01-2250
Crewmember ingress of the International Space Station (ISS) before that time accorded by the original ISS assembly sequence, and thus before the ISS capability to adequately control the levels of temperature, humidity, and carbon dioxide, poses significant impacts to ISS Environmental Control and Life Support (ECLS). Among the most significant considerations necessitated by early ingress are those associated with the capability of the Shuttle Transportation System (STS) Orbiter to control the aforementioned levels, the capability of the ISS to deliver the conditioned air among the ISS elements, and the definition and distribution of crewmember metabolic heat, carbon dioxide, and water vapor. Even under the assumption that all Orbiter and ISS elements would be operating as designed, condensation control and crewmember comfort were paramount issues preceding each of the ISS Missions 2A and 2A.1.
X