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Technical Paper

Tubular Membrane Evaporator Development for the Plss

1996-07-01
961486
Current NASA space suits use porous metal plate sublimators to reject the metabolic heat generated by the astronaut into space vacuum during EVA. Relying on tubular membranes instead of the flat plate of the sublimator, a proposed alternate unit has the potential to be smaller and lighter. This work outlines the operation of the proposed tubular membrane evaporator and the evaluation of possible membrane materials for the unit.
Technical Paper

Novel Regenerable Incinerator Exhaust Purification and Trace Contaminant Control System Utilizing Humidity Swings

1998-07-13
981760
This paper offers a concept for a regenerable, low-power system for purifying exhaust from a solid waste processor. The innovations in the concept include the use of a closed-loop regeneration cycle for the adsorber, which prevents contaminants from reaching the breathable air before they are destroyed, and the use of a humidity-swing desorption cycle, which uses less power than a thermal desorption cycle and requires no venting of air and water to space vacuum or planetary atmosphere. The process would also serve well as a trace contaminant control system for the air in the closed environment. A systems-level design is presented that shows how both the exhaust and air purification tasks could be performed by one processor. Data measured with a fixed-bed apparatus demonstrate the effects of the humidity swing on regeneration of the adsorbent.
Technical Paper

Evaluation of Commercial Off-the-Shelf Ammonia Sorbents and Carbon Monoxide Oxidation Catalysts

2008-06-29
2008-01-2097
Designers of future space vehicles envision simplifying the Atmosphere Revitalization (AR) system by combining the functions of trace contaminant (TC) control and carbon dioxide removal into one swing-bed system. Flow rates and bed sizes of the TC and CO2 systems have historically been very different. There is uncertainty about the ability of trace contaminant sorbents to adsorb adequately in a high-flow or short bed length configurations, and to desorb adequately during short vacuum exposures. This paper describes preliminary results of a comparative experimental investigation into adsorbents for trace contaminant control. Ammonia sorbents and low temperature catalysts for CO oxidation are the foci. The data will be useful to designers of AR systems for Constellation. Plans for extended and repeated vacuum exposure of ammonia sorbents are also presented.
Technical Paper

Compaction and Drying in a Low-Volume, Deployable Commode

2007-07-09
2007-01-3264
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

Lyophilization for Water Recovery II, Model Validation

2004-07-19
2004-01-2377
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.
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