Browsing by Author "Rundle, Tessa"
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Item Characterization of Carbon Dioxide Removal using Ionic Liquids in Novel Geometries(47th International Conference on Environmental Systems, 2017-07-16) Arquilla, Katya; Rundle, Tessa; Phillips, Daniel; Lampe, Alexander; Shaffer, Brett; Lima, Anthony; Fritz, Trevor; Denton, Jacob; Dixon, Jordan; Holquist, Jordan; Lotto, Michael; Nabity, JamesThe Cabin Atmosphere Revitalization through Ionic Liquids (CARIL) project is part of NASA's Exploration Systems and Habitation Academic Innovation Challenge program to provide enabling technologies for future long-duration space missions. Current atmosphere revitalization technologies require frequent maintenance and spare parts – these are not manageable issues for technologies used on missions travelling to Mars and beyond. As the possibility for resupply decreases with long-duration missions, regenerable technologies become increasingly important. CARIL is focused on the characterization of the removal of carbon dioxide (CO2) from the cabin atmosphere using two different absorption bed configurations: a 3-D printed capillary-driven contactor and a hollow-fiber contactor. A flat plate contactor will be used as an experimental control, and all designs will use the ionic liquid (IL) 1-butyl-3-methylimidazolium acetate. ILs were chosen due to their low vapor pressure and selectivity between CO2 and oxygen, making them a viable option for absorbing CO2 in micro-gravity. The focus of this research is to characterize the absorption of CO2 using specific contactor materials and geometries to provide a broad range of data to analyze and inform the future development of supported ionic liquid membranes.Item Compact Oxygen Heat Exchanger for the Exploration Portable Life Support System(2020 International Conference on Environmental Systems, 2020-07-31) Izenson, Michael; Servi, Amelia; Stokes, Sheldon; Rundle, TessaThe ventilation loop in NASA’s Exploration Portable Life Support System (xPLSS) includes a compact heat exchanger that cools the ventilation gas before it enters the suit helmet. This heat exchanger must provide efficient gas cooling with low pressure losses in a very compact package. It must operate across a wide range of suit pressures and be built from materials that are compatible with oxygen and the thermal control loop. Finally, the heat exchanger must serve as a pressure drop element that can be used to measure the ventilation flow rate with high accuracy. We have developed an innovative heat exchanger that meets these requirements. The miniature shell-and-tube heat exchanger uses a core built from an array of Inconel microtubes. The microtubes provide a very high surface area and high heat transfer coefficients for efficient gas cooling with minimal pressure losses in the ventilation and thermal control loops. We have designed and built several generations of the heat exchanger and measured their heat transfer and pressure drop performance in an extensive series of tests that simulate operation in the xPLSS ventilation loop. We have found that the compact heat exchanger meets all xPLSS requirements for heat transfer and pressure loss. The heat exchanger is designed for close integration with a high-accuracy flow meter, and produces a highly linear flow vs. pressure drop characteristic that is suitable for high-accuracy flow measurement. Two units have been delivered to NASA in 2019 and three additional development, verification, and test (DVT) units are scheduled for delivery in 2020. This paper will describe the design, manufacturing, and performance of the DVT heat exchangers.Item Development of an Oxygen Heat Exchanger and Flow Meter for the Exploration Portable Life Support System(50th International Conference on Environmental Systems, 7/12/2021) Izenson, Michael; Servi, Amelia; Stokes, Sheldon; Beach, Theodore; Rundle, Tessa; Hinckley, DavidThe ventilation loop in NASA�s Exploration Portable Life Support System (xPLSS) includes a compact heat exchanger that cools the ventilation gas before it enters the suit helmet. In addition to cooling the ventilation gas, the heat exchanger also serves as a pressure drop element for measuring the flow rate of ventilation gas. We have developed an innovative heat exchanger that meets the challenging requirements for service in the xPLSS. The miniature shell-and-tube heat exchanger is built from all oxygen-safe materials around a core comprising an array of Inconel microtubes. The microtubes provide a very high surface area and high heat transfer coefficients for efficient gas cooling with minimal pressure losses. The microtube design also provides a highly linear flow vs pressure drop characteristic that enables accurate measurement of gas flow. The first design validation test (DVT) heat exchanger is installed and undergoing integrated system testing in the first xPLSS prototype. This paper reports on the status of the heat exchanger development program and reviews some of the key lessons learned from the development and testing effort: (1) Maintaining stability of test conditions for a small heat exchanger across wide range of pressures and flow rates; (2) Measurement of pressure losses in a component designed for a compact, highly integrated system; (3) Challenges obtaining flight-qualified electronics for the flow sensor. The techniques that were developed to measure performance and qualify the current set of DVT heat exchangers will be used to support flight qualification tests for future units.Item Excess Water in Astronaut Helmet During EVA on ISS: Mitigations with Flight Demonstrations(2023 International Conference on Environmental Systems, 2023-07-16) Weislogel, Mark; Krishcko, Oleg; Torres, Logan; Campbell, Colin; Dum, Paul; Graf, John; Rundle, TessaFollowing a second crew report of excess water inexplicably accumulating in the helmet during EVA-80 on March 23, 2022, NASA initiated an aggressive effort to identify, mitigate, and/or eliminate all sources of the potentially life-threatening water. Our narration highlights demonstrations of microgravity flow expectations using terrestrial scale models, mitigations to dangerous water migration within the helmet, low-g two-phase flow separations for the flow entering the helmet, and an investigation of the nature of liquid carry-over from the EMU condensing heat exchanger source. Fast-to-flight demonstrations of each aspect of the work are carried out during hands-on crew interaction with flight scale hardware on ISS during the 2022-2023 timeframe. The results of the tests are described with a focus on the rarely observed, and thus rarely studied, large length scale air-driven wall-bound droplet and rivulet two-phase flows in microgravity. The success of the mitigations and directions for continued work is discussed in summary.Item High-Accuracy Oxygen Flow Meter for the Exploration Portable Life Support System(2020 International Conference on Environmental Systems, 2020-07-31) Izenson, Michael; Servi, Amelia; Stokes, Sheldon; Beach, Theodore; Kirkconnell, Carl; Huynh, Leon; Rundle, Tessa; Lee, Steven"The xEMU’s portable life support system (xPLSS) requires a high accuracy instrument to measure the rate of oxygen flow in the ventilation system. The sensor must produce accurate readings across a wide range of flow conditions while consuming very little volume or power and introducing very little pressure loss to the ventilation loop. We have developed an innovative flow sensor built around a commercial, off-the-shelf MEMS flow-sensing chip that is designed for oxygen service. We have developed a custom flow sensor housing to channel gas flow over the MEMS sensing elements and custom electronics to control the sensor and generate signals compatible with xEMU requirements. The flow sensor operates in parallel with the ventilation loop heat exchanger, so introduces no additional pressure loss to the ventilation system. The unit meets size and shape requirements for service in the xPLSS and is replaceable in space if necessary. Data from separate-effects tests and tests of the integrated xPLSS heat exchanger / flow meter system show that the flow meter achieves high accuracy requirements across the range of specified operating conditions. We built and tested a proof-of-feasibility prototype in mid-2019, followed by a “rapid turn” demonstration sensor that meets form, fit and function requirements in late 2019. Fully-qualified DVT units are scheduled for delivery in mid-2020."Item Space Suit Portable Life Support System Thermal Control Valve Ball Design(2023 International Conference on Environmental Systems, 2023-07-16) Ogilvie, Ryan; Miller, Sean; Rundle, TessaA Thermal Control Valve (TCV) has been in development for the Exploration Extravehicular Mobility Unit Portable Life Support System (xEMU PLSS). The xEMU PLSS TCV controls flow going to the liquid cooling and ventilation garment that the crew member wears during extra-vehicular activity to expel waste heat. A previous TCV version with a linear actuator and diverter valve has been tested to attempt to control the flow accurately. The previous valve has a non-linear flow response relative to valve position and has struggled to meet the setpoints desired for precise thermal control. While many diverter valve design variations have been attempted, all previous designs have had difficulty meeting set points. Additionally, high precision machining is required to create a metal-on-metal seal which has its own drawbacks and does not always meet requirements for internal leakage. This metal seal also requires stalling a linear actuator to load the seal in compression or tension which has caused sticking failures when stalled. A new approach and design for a TCV has been developed which uses a rotational ball to control flow and has demonstrated a much more precise and linear flow control. The design functions like a two-way ball valve with two Teflon seats that cradle and compress the ball for sealing. The ball outlet has a unique geometric design to create a set-able orifice like hole which is more predictable at controlling flow. Additionally, the Teflon seat performs much better for preventing internal leakage than the metal seal and prevents sticking by having a large range in which it is sealed without having to stall the actuator. This paper will review a new proposed xEMU PLSS TCV ball design and compare it with previous iterations of the design.Item Ventilation Heat Exchanger/Flow Meter for xPLSS(2023 International Conference on Environmental Systems, 2023) Izenson, Michael; Niblick, Adam; Stokes, Sheldon; Rundle, TessaThe flow meter / heat exchanger (FMHX) in the ventilation loop of the exploration EMU cools the ventilation gas and measures the ventilation flow rate. The heat exchanger transfers heat from the ventilation gas to the thermal control loop via a miniature shell-and-tube heat exchanger. The flow meters calculate the flow rate of gas through the ventilation loop based on the pressure drop across the heat exchanger core. Creare has delivered four design validation test (DVT) heat exchangers and five DVT flow meters to NASA JSC to support development of the exploration portable life support system (xPLSS). This paper describes the design and performance of the DVT units. The heat exchangers are designed to cool the ventilation gas to a specified temperature with low pressure losses under the most challenging operating conditions. The measured performance of the DVT heat exchangers agrees well with design models and meets all performance requirements. The flow meters use a MEMS thermal flow sensor to produce a signal that is proportional to a small bypass flow around the heat exchanger core. They are designed to achieve high measurement accuracy across the full range of xPLSS operating conditions. We calibrated the flow meters in a special-purpose flow facility that simulates operation in the xPLSS ventilation loop. Calibration testing shows that DVT flow meters produce digital output for vent loop mass flow that meets NASA’s accuracy requirements across the range of xPLSS operating conditions. This paper reviews the design of the heat exchangers and flow meters and presents data from the final flow meter calibration testing, heat exchanger performance validation, and initial ground testing in NASA’s xPLSS.