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Technical Paper

Air Circulation and Carbon Dioxide Concentration Study of International Space Station Node 2 with Attached Modules

Crew health is dependent on the concentration of carbon dioxide in the atmosphere breathed. Often, models used for concentration have used the assumption that each module of the space station is well mixed, i.e. that the CO2 concentration is constant throughout the module. In this paper, Computational Fluid Dynamics (CFD) modeling is used to assess and validate the accuracy of that assumption. The concentration of carbon dioxide as calculated by CFD was compared to the concentration as calculated by a lumped parameter model. The assumption that the module is well mixed allows the use of relatively simple models, which can be developed and run quickly in order to support decisions for on-orbit analysis. CFD models generate more detailed information, such as CO2 gradients within the modules and airflow and mixing characteristics. However, CFD models, particularly transient models, take longer to develop and use.
Technical Paper

Analysis and Predicted Temperature Control of Crew Quarters added to Node 2 of the International Space Station

Currently scheduled to be delivered to the International Space Station (ISS) in 2009, Crew Quarters (CQs) will be installed in the Node 2 Module. The CQs provide crewmembers with private space, a place to sleep, and minimal storage. Analysis is to be performed to determine if the United States Operational Segment (USOS) Node 2 can maintain temperature between 47°C and 62°C (65°F and 80°F) [units are CCGS with U.S unit in parenthesis] within the CQ. The analysis will concentrate on the nominal hot environmental case. Environmental heat is due to solar heating of the external shell of the ISS. Configurations including both three and four CQs are examined, as well as multiple configurations of the Low Temperature Loop (LTL) that flows through the Node 2 Common Cabin Air Assembly (CCAA). This paper describes the analysis performed to determine if Node 2 will be able to maintain cabin temperature between 47°C and 62°C (65°F and 85°F).
Technical Paper

Analysis of Air Ventilation and Crew Comfort for the International Space Station Cupola

The objectives of this investigation are to verify the ventilation and temperature characteristics of the Cupola and to ensure the adequacy of crew comfort and safety when the Robotic Workstation (RWS) is present. Requirements indicate that an effective air velocity in the Cupola cabin must be maintained within the range of 15 to 40 feet per minute. Based on the results obtained in this study, the performance of the Cupola ventilation system while the RWS is not operating is close to meeting the requirement. However, when the Robotic Workstation is in operation, most of the air velocity in the Cupola is too high due to the elevated flowrate caused by the RWS fans. A low velocity region is present near the crewmember as a result of the vortex created by the RWS flow. In addition to examining the ventilation of the Cupola, crew comfort and safety is evaluated by examining the air temperature and the airflow around the crewman.
Technical Paper

CFD Investigation on the Air Ventilation Characteristics in the U.S. Airlock: International Space Station Flight 7A Configuration

The objectives of this investigation were to verify the air ventilation characteristics of the U. S. Airlock and to ensure the adequacy of inter-module ventilation (IMV) of the International Space Station (ISS) Flight 7A configuration. There are three operating modes for the air ventilation in the U. S. Airlock: (1) Open Hatch configuration, (2) Closed Hatch configuration and (3) Housekeeping mode. In this study, computational fluid dynamics (CFD) models with the geometrical details representing each mode of the Airlock's operation was built. Proper airflow boundary conditions that represent the operation of the Airlock's Common Cabin Air Assembly (CCAA) and the inter-module ventilation were imposed for the subsequent CFD simulations. Based on the results obtained in this study, the performance of the Airlock ventilation system is marginally acceptable at CCAA fan running at 3600 rpm for both Open Hatch and Closed Hatch operations.
Technical Paper

CFD Simulation on the Airflow and CO2 Transport in the U.S Lab: International Space Station Flight 5A Configuration

The U. S. Laboratory (USL) module was added to the International Space Station (ISS) in Flight 5A, which would boost the Environmental Control & Life Support System (ECLSS) functional capabilities of the ISS. In the USL cabin aisle way, the air circulation is provided by a Temperature & Humidity Control (THC) system. To provide adequate ventilation under various open/close combinations of the rack panels, it would be very challenging by conducting many tests prior to the launch of Flight 5A. Computational fluid dynamics (CFD) simulation technology is utilized to investigate the airflow in the U.S. Lab for various operating scenarios. A CFD model, which includes the supply diffusers, the return registers, the ventilation of the temporary crew quarter, the gap between the outer pressure shell and all the racks, is modeled. The ventilation performance for the cabin aisle way and air behind panels is addressed.
Technical Paper

CFD Studies on the ECLSS Airflow and CO2 Accumulation of the International Space Station

During a recent International Space Station (ISS) flight (Flight 2A.1), an improper ventilation event might have occurred and resulted in stuffy air, as reported by the crew. Even though no air samples were analyzed, the accumulation of metabolic CO2 in the ISS was suspected as the cause of the crew sickness. With no possibility of conducting an on-orbit test of this kind, it was decided to utilize Computational Fluid Dynamics (CFD) analysis to investigate this problem. Based on the Flight 2A.1 and 2A.2a configurations, a CFD model of the air distribution system was built to characterize airflow between the ISS elements. This model consists of Inter-module Ventilation (IMV) covering the Functional Cargo Block (FGB), two Pressurized Mating Adapters (PMA-1 and PMA-2), the Node-1, and portions of the Orbiter volume.
Journal Article

CFD Study of Ventilation and Carbon Dioxide Transport for ISS Node 2 and Attached Modules

The objective of this study is to evaluate ventilation efficiency regarding to the International Space Station (ISS) cabin ventilation during the ISS assembly mission 1J. The focus is on carbon dioxide spatial/temporal variations within the Node 2 and attached modules. An integrated model for CO2 transport analysis that combines 3D CFD modeling with the lumped parameter approach has been implemented. CO2 scrubbing from the air by means of two ISS removal systems is taken into account. It has been established that the ventilation scheme with an ISS Node 2 bypass duct reduces short-circuiting effects and provides less CO2 gradients when the Space Shuttle Orbiter is docked to the ISS. This configuration results in reduced CO2 level within the ISS cabin.
Technical Paper

Characteristics and Performance of the Japanese Experimental Module (JEM) Air Ventilation

The Japanese Experimental Module (JEM) Pressurized Module (PM) is a facility where astronauts conduct experiments or control the total JEM facility. Inside the PM, the air composition, temperature and humidity are controlled so as to be comfortable for astronauts' activity all the time. The verification of the on-orbit performance of the functions constituting a manned space system is one of the critical points. Computational Fluid Dynamics (CFD) simulation technology is utilized to characterize and investigate the airflow in the JEM for various operating conditions. The development of a successful CFD model for International Space Station (ISS) operation is useful because there are always off-nominal and other contingency operations, which might occur and could be analyzed using an existing CFD model. This paper also presents the cabin ventilation test data obtained from the JEM flight module.
Technical Paper

Integrated Computational Fluid Dynamics Carbon Dioxide Concentration Study for the International Space Station

This paper reports results of Computational Fluid Dynamics (CFD) analysis of carbon dioxide (CO2) gradient variations in twelve ISS modules. Computations were performed using two 3D integrated models: one from the U.S. Laboratory to the forward end, and the other from the U.S. Laboratory to the aft end of the ISS. Operation of the CO2 removal systems and CO2 generation among six International Space Station (ISS) crewmembers' metabolic processes were included in the model. For several crew location scenarios, a detailed analysis of the CO2 gradients and time evolution in zones potentially occupied by astronauts is presented. In general, the paper gives an extended example of the application of CFD analysis to complex problems related to the quality of the cabin air.
Technical Paper

Integrated Humidity and Carbon Dioxide Analysis For International Space Station Using SINDA/FLUINT

The air interchange performance between the modules is an important factor in the atmosphere revitalization system of International Space Station (ISS) to maintain a habitable environment for the crew during on-orbit activities. A SINDA/FLUINT model of the integrated ISS air quality control system was constructed in support of pre and in-flight predictions of cabin air temperature and humidity, and CO2 partial pressure. This model calculates masses and partial pressure for the major gas constituents, such as O2, N2, CO2, and H2O. This model also simulates the effect of crew activities and their location in the station. The elements are linked together in terms of air interchange in the models via Inter-module ventilation (IMV). The air in each volume is assumed to be perfectly mixed. Latent loads and IMV air are assumed to be immediately and uniformly distributed throughout the cabin air volume of each element.
Technical Paper

Investigation of Airflow and Accumulation of Carbon Dioxide in the Service Module Crew Quarters

Accumulation and re-breathing of CO2 in expired air has been investigated as a possible indication for crew discomfort onboard the International Space Station (ISS) Service Module crew quarters. In addition, inadequate airflow contributes to increasing temperature that also leads to crew discomfort. The objective of this study is to evaluate possible medical hazards that can occur when a crewmember is sleeping in the crew quarter of the ISS Service without proper ventilation. This paper investigates a projected increase in CO2 in the enclosure under a no ventilation scenario. A Computational Fluid Dynamics (CFD) model of the crew quarters and of a human body are built to investigate the ventilation profile and the CO2 concentration inside the volume of the crew quarters. Respiratory characteristics of a typical 180-pound crewmember are simulated. The results for the distribution and concentration of expired air at different time intervals and at different locations are presented.
Technical Paper

Numerical Prediction and Evaluation of Space Station Intermodule Ventilation and Air Distribution Performance

This paper presents the basic test data obtained from tests of a cabin air distribution system in a simulated Space Station Man-Tended Capability (MTC) configuration and correlations of some of this data with the results from analytical modeling of the test setup flow conditions. The MTC configuration simulated in the test setup includes: Lab-A, the Node, the Cupola, and the Pressurized Module Adaptor (PMA). The test data and analytical data presented are confined to those for the Lab module. The cabin air distribution system controls the flow of air in the open space of a Space Station module. In order to meet crew comfort criteria the local velocities for this cabin air are required to be distributed within a specified range with upper and lower limits.
Technical Paper

The Effect of Gravity Induced Buoyancy on Velocity Measurement in 1-g Environment

The effects of testing cabin ventilation in gravity to meet a requirement for ventilation on orbit were analyzed. Buoyancy is due to the combined presence of a density gradient within the fluid and a body force that is proportional to the fluid density. Since gravity cannot be removed, the test must be conducted with air at as near to constant density as practical in order to remove buoyancy effects. The effects of gravity induced buoyancy force on the velocity field was analyzed by the Richardson number. Computational Fluid Dynamics (CFD) analysis was performed to verify the theoretical methods. The velocity data for a 1-g and a no gravity case were compared. The ratio between local velocity and free stream velocity, u/U∞ were analyzed for the dimensionless parameter, η (= y ✓ U∞/νx). There is a relatively sharp rise in the profile near the wall and an overshoot of the velocity beyond its free stream value.