Gregory Quinn

The Development of the Vapor Phase Catalytic Ammonia Removal (VPCAR) Engineering Development Unit

This paper presents the results of a program to develop the next generation Vapor Phase Catalytic Ammonia Removal (VPCAR) system. VPCAR is a spacecraft water recycling system designed by NASA and constructed by Water Reuse Technology Inc. The technology has been identified by NASA to be the next generation water recycling system [1]. It is designed specifically for a Mars transit vehicle mission. This paper provides a description of the process and an evaluation of the performance of the new system. The equivalent system mass (ESM) is calculated and compared to the existing state-of-the art. A description of the contracting mechanism used to construct the new system is also provided.

Phase Change Material Trade Study: A Comparison Between Wax and Water for Manned Spacecraft

Phase change material heat sinks have been recognized as an important tool in optimizing thermal control systems for space exploration vehicles and habitats that must deal with widely varying thermal loads and environments. In order to better focus technology investment in this arena, NASA has supported a trade study with the objective of identifying where the best potential pay-off can be found among identified aqueous and paraffin wax phase change materials and phase change material heat sink design approaches. The study used a representative exploration mission with well understood parameters to support the trade. Additional sensitivity studies were performed to ensure the applicability of study results across varying systems and destinations. Results from the study indicate that a water ice PCM heat sink has the potential to decrease the equivalent system mass of the mission s vehicle through a combination of a smaller heat sink and a slight 5% increase in radiator size or the addition of a lightweight heat pump. An evaluation of existing and emerging PCM heat sink technologies indicates that further significant mass savings should be achievable through continued development of those technologies. The largest mass savings may be realized by managing the location of the liquid and the solid in the heat sink to eliminate the melting and freezing pressure of wax and water, respectively, while also accommodating the high structural loads expected on future manned launch vehicles.

Performance Testing of the Vapor Phase Catalytic Ammonia Removal Engineering Development Unit

This paper describes the results of acceptance testing of the Vapor Phase Catalytic Ammonia Removal (VPCAR) technology. The VPCAR technology is currently being developed by NASA as a Mars transit vehicle water recycling system. NASA has recently completed a grant to develop a next generation VPCAR system. This grant was peer reviewed and funded through the Advanced Life Support (ALS) National Research Announcement (NRA). The grant funded a contract with Water Reuse Technology Inc. to construct an engineering development unit. This contract concluded with the shipment of the final deliverable to NASA on 8/31/03. The objective of the acceptance testing was to characterize the performance of this new system. This paper presents the results of mass power, and volume measurements for the delivered system. In addition, product water purity analysis for a Mars transit mission and a planetary base wastewater ersatz are provided. Acoustic noise levels, interface specifications and system reliability results are also discussed. An assessment of the readiness of the technology for human testing and recommendations for future improvements are provided.

Results of VPCAR Pilot Scale and System Level Tests for the Selective Oxidation of Ammonia to Nitrogen and Water

The cost of delivering the payloads to space increases dramatically with distance and therefore missions to deep space place a strong emphasis on reducing launch weight and eliminating resupply requirements. The Vapor Phase Catalytic Ammonia Removal (VPCAR) system, which is being developed for water purification, is an example of this focus because it has no resupply requirements. A key step in the VPCAR system is the catalytic oxidation of ammonia and volatile hydrocarbons to benign compounds such as carbon dioxide, water, and nitrogen. Currently, platinum-based commercial oxidation catalysts are being used for these reactions. However, conventional platinum catalysts can convert ammonia (NH3) to NO and NO2 (collectively referred to as NOX), which are more hazardous than ammonia.

A Multi-Environment Thermal Control System With Freeze-Tolerant Radiator

Future space exploration missions require advanced thermal control systems (TCS) to dissipate heat from spacecraft, rovers, or habitats operating in environments that can vary from extremely hot to extremely cold. A lightweight, reliable TCS is being developed to effectively control cabin and equipment temperatures under widely varying heat loads and ambient temperatures. The system uses freeze-tolerant radiators, which eliminate the need for a secondary circulation loop or heat pipe systems. Each radiator has a self-regulating variable thermal conductance to its ambient environment. The TCS uses a nontoxic, water-based working fluid that is compatible with existing lightweight aluminum heat exchangers. The TCS is lightweight, compact, and requires very little pumping power. The critical characteristics of the core enabling technologies were demonstrated. Functional testing with condenser tubes demonstrated the key operating characteristics required for a reliable, freeze-tolerant TCS, namely (1) self-regulating thermal conductance with short transient responses to varying thermal loads, (2) repeatable performance through freeze-thaw cycles, and (3) fast start-up from a fully frozen state. Preliminary coolant tests demonstrated that the corrosion inhibitor in the water-based coolant can reduce the corrosion rate on aluminum by an order of magnitude. Performance comparison with state-of-the-art designs shows significant mass and power saving benefits of this technology.

Testing of the Multi-Fluid Evaporator Engineering Development Unit

Hamilton Sundstrand is under contract with the NASA Johnson Space Center to develop a scalable, evaporative heat rejection system called the Multi-Fluid Evaporator (MFE). It is being designed to support the Orion Crew Module and to support future Constellation missions. The MFE would be used from Earth sea level conditions to the vacuum of space. The current Shuttle configuration utilizes an ammonia boiler and flash evaporator system to achieve cooling at all altitudes. The MFE system combines both functions into a single compact package with significant weight reduction and improved freeze-up protection. The heat exchanger core is designed so that radial flow of the evaporant provides increasing surface area to keep the back pressure low. The multiple layer construction of the core allows for efficient scale up to the desired heat rejection rate. The full scale MFE prototype will be constructed with four core sections that, combined with a novel control scheme, manage the risk of freezing the heat exchanger cores. A sub-scale MFE engineering development unit (EDU) has been built, and is identical to one of the four sections of a full scale prototype. The EDU has completed testing at Hamilton Sundstrand. The overall test objective was to determine the thermal performance of the EDU. The first set of tests simulated how each of the four sections of the prototype would perform by varying the chamber pressure, evaporant flow rate, coolant flow rate and coolant temperature. A second set of tests was conducted with an outlet steam header in place to verify that the outlet steam orifices prevent freeze-up in the core while also allowing the desired thermal turn-down ratio. This paper discusses the EDU tests and results.

Assessment of the Multi‐Fluid Evaporator Technology

Hamilton Sundstrand has developed a scalable evaporative heat rejection system called the Multi‐Fluid Evaporator (MFE). It was designed to support the Orion Crew Module and to support future Constellation missions. The MFE would be used as a heat sink from Earth sea level conditions to the vacuum of space. The current shuttle configuration utilizes an ammonia boiler and water based flash evaporator system to achieve cooling at all altitudes. This system combines both functions into a single compact package with improved freeze‐up protection. The heat exchanger core is designed so that radial flow of the evaporant provides increasing surface area to keep the back pressure low. The multiple layer construction of the core allows for efficient scale up to the desired heat rejection rate. A full‐scale system uses multiple core sections that, combined with a novel control scheme, manage the risk of freezing the heat exchanger cores. A single‐core MFE engineering development unit (EDU) was built in 2006, followe...