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Technical Paper

The General Purpose Work Station, A Spacious Microgravity Workbench

The General Purpose Work Station (GPWS) is a laboratory multi-use facility, as demonstrated during the Spacelab Life Sciences 1 (SLS-1) flight. The unit provided particulate containment under varying conditions, served as an effective work space for manipulating live animals, e.g., rats, served as a containment facility for fixatives, and was proposed for use to conduct in-flight maintenance during connector pin repair. The cabinet has a front door large enough to allow installation of a full-size microscope in-flight and is outfitted with a side window to allow delivery of items into the cabinet without exposure to the spacelab atmosphere. Additional support subsystems include inside cabinet mounting, surgical glove fine manipulations capability, and alternating or direct current power supply for experiment equipment, as will be demonstrated during Spacelab J.
Technical Paper

Development Status of a Low-Power CO2 Removal and Compression System for Closed-Loop Air Revitalization

The “low power-CO2 removal (LPCOR) system” is an advanced air revitalization system that is under development at NASA Ames Research Center. The LPCOR utilizes the fundamental design features of the ‘four bed molecular sieve’ (4BMS) CO2 removal technology of the International Space Station (ISS). LPCOR improves power efficiency by replacing the desiccant beds of the 4BMS with a membrane dryer and a state-of-the-art, structured adsorbent device that collectively require 25% of the thermal energy required by the 4BMS desiccant beds for regeneration. Compared to the 4BMS technology, it has the added functionality to deliver pure, compressed CO2 for oxygen recovery. The CO2 removal and recovery functions are performed in a two-stage adsorption compressor. CO2 is removed from the cabin air and partially compressed in the first stage. The second stage performs further compression and delivers the compressed CO2 to a reduction unit such as a Sabatier reactor for oxygen recovery.
Technical Paper

Fluid Dynamics Assessment of the VPCAR Water Recovery System in Partial and Microgravity

The Vapor Phase Catalytic Ammonia Removal (VPCAR) system is being developed to recycle water for future NASA Exploration Missions. Testing was recently conducted on NASA's C-9B Reduced Gravity Aircraft to determine the microgravity performance of a key component of the VPCAR water recovery system. Six flights were conducted to evaluate the fluid dynamics of the Wiped-Film Rotating Disk (WFRD) distillation component of the VPCAR system in microgravity, focusing on the water delivery method. The experiments utilized a simplified system to study the process of forming a thin film on a disk similar to that in the evaporator section of VPCAR. Fluid issues are present with the current configuration, and the initial alternative configurations were only partial successful in microgravity operation. The underlying causes of these issues are understood, and new alternatives are being designed to rectify the problems.
Technical Paper

Integrated Systems Testing of Spacecraft

How much integrated system level test should be performed on a spacecraft before it is launched? Although sometimes system test is minimized, experience shows that systems level testing should be thorough and complete. Reducing subsystem testing is a less dangerous way to save cost, since it risks finding problems later in system test, while cutting systems test risks finding them even later on orbit. Human-rated spacecraft test planning is informal, subjective, and inconsistent, and its extent is often determined by the decision maker's risk tolerance, decision-making style, and long-term or short-term view. Decisions on what to test should be guided by an overall mission cost-benefit analysis, similar to the risk analysis used to guide development efforts.
Technical Paper

Compaction and Drying in a Low-Volume, Deployable Commode

We present a device for collecting and storing feces in microgravity that is user-friendly yet suitable for spacecraft in which cabin volume and mass are constrained. On Apollo missions, the commode function was served using disposable plastic bags, which proved time-consuming and caused odor problems. On Skylab, the space shuttle, and the International Space Station, toilets have used airflow beneath a seat to control odors and collect feces. We propose to incorporate airflow into a system of self-compacting, self-drying collection and stowage bags, providing the benefits of previous commodes while minimizing mass and volume. Each collection bag consists of an inner layer of hydrophobic membrane that is permeable to air but not liquid or solid waste, an outer layer of impermeable plastic, and a collapsible spacer separating the inner and outer layers. Filled bags are connected to space vacuum, compacting and drying their contents.
Technical Paper

Development Status of the VPCAR Water Processor Assembly

The purification of waste water is a critical element of any long-duration space mission. The Vapor Phase Catalytic Ammonia Removal (VPCAR) system offers the promise of a technology requiring low quantities of expendable material that is suitable for exploration missions. NASA has funded an effort to produce an engineering development unit specifically targeted for integration into the NASA Johnson Space Center's Integrated Human Exploration Mission Simulation Facility (INTEGRITY) formally known in part as the Bioregenerative Planetary Life Support Test Complex (Bio-Plex) and the Advanced Water Recovery System Development Facility. The system includes a Wiped-Film Rotating-Disk (WFRD) evaporator redesigned with micro-gravity operation enhancements, which evaporates wastewater and produces water vapor with only volatile components as contaminants. Volatile contaminants, including organics and ammonia, are oxidized in a catalytic reactor while they are in the vapor phase.
Technical Paper

Lyophilization for Water Recovery II, Model Validation

This paper presents results of research on a solid waste dryer, based of the process of lyophilization, which recovers water and stabilizes solid waste. A lyophilizer has been developed and tested that uses thermoelectric heat pumps (TECs) to recycle heat during drying. The properties of TECs facilitate direct measurement of heat flow rates, and heat flow data are used to evaluate a heat and mass transfer model of the thermoelectric lyophilizer. Data are consistent with the theoretical model in most respects. Practical problems such as insulation and vacuum maintenance are minor in this system. However, the model’s assumption of a uniformly retreating ice layer during drying is valid only for the first 30% of water removed. Beyond this point, a shrinking core or lens model is more appropriate. Heat transfer to the shrinking core surrounded by dried material is slow.
Technical Paper

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.
Journal Article

Development and Design of a Low Temperature Solid Waste Oxidation and Water Recovery System

In February 2004 NASA released “The Vision for Space Exploration.” The goals outlined in this document include extending the human presence in the solar system, culminating in the exploration of Mars. A key requirement for this effort is to identify a safe and effective method to process waste. Methods currently under consideration include incineration, microbial oxidation, pyrolysis, drying, and compaction. Although each has advantages, no single method has yet been developed that is safe, recovers valuable resources including oxygen and water, and has low energy and space requirements. Thus, the objective of this work is to develop a low temperature oxidation process to convert waste cleanly and rapidly to carbon dioxide and water. Previously, TDA Research, Inc. demonstrated the potential of a low temperature dry oxidation process using ozone in a small laboratory reactor.