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Technical Paper

VOC Removal by Novel Regenerable Silica-Titania Sorbent and Photocatalytic Technology

Silica-titania composites (STC), a novel sorbent and photocatalytic technology developed at the University of Florida in Gainesville, Florida have been evaluated for removal of volatile organic compounds (VOCs) from aircraft cabin air. Currently, activated carbon filters are used, but must be replaced frequently due to their limited adsorption capacity. These filters must be disposed of and cannot be regenerated and reused. The STC technology is a significant improvement upon the current control technology because of its high adsorption capacity and the ability to regenerate via photocatalytic oxidation (PCO). When the STC sorbent is irradiated with UV, adsorbed VOCs are mineralized to CO2 and H2O and the material is regenerated and ready for reuse multiple times.
Technical Paper

Transgenic Plant Biomonitors: Stress Gene Biocompatibility Evaluation of the Plant Growth Facility for PGIM-01

The initial task in the preparation for Flight Experiment PGIM-01 (Plant Growth in Microgravity - 01) was the optimization of the plant nutrient system within the environment of the Plant Growth Facility (PGF – a Space Shuttle middeck locker plant growth unit). PGIM-01 entailed using the Transgenic Arabidopsis Gene Expression System (TAGES) to monitor effects of spaceflight-associated stress on gene expression. TAGES plants are genetically engineered arabidopsis plants designed with a sensitive reporter gene system that responds to a variety of environmental stresses. However, transgene expression can also be influenced by background environmental conditions. Thus, minimizing sources of background stress on the plants was crucial to ensure optimal growth and a high scientific return.
Technical Paper

TiO2 Coated Activated Carbon: A Regenerative Technology for Water Recovery

Two widespread practices in water treatment are, removal of pollutants via adsorption onto activated carbon, and, oxidation of pollutants using a photocatalyst slurry and ultraviolet radiation. The ultimate goal of this research is to combine the adsorptive properties of carbon and the oxidative properties of titanium dioxide (TiO2), and construct a photocatalytically regenerative carbon filter for 100% water recovery. The premise is that the activated carbon, coated with TiO2, will capture the compounds through traditional filtration and adsorption. Once the carbon becomes exhausted, it can be regenerated in-situ by turning on the UV lamps thereby activating the photocatalyst.
Journal Article

The Semantic Web and Space Operations

In this paper, we introduce the use of ontologies to implement the information developed and organized by resource planning tools into standard project management documents covering integrated cost, resource modeling and analysis, and visualization. The basic upper ontology used for NASA Space Operations is explained and the results obtained are discussed. This ontology-centered approach is looking for tighter connections between software, hardware, and systems engineering.
Technical Paper

Synthesis and Evaluation of Activated Carbon Composite Photocatalysts for Surface Enhanced Raman Scattering: Photocatalytic Layer Coating

Finding a manner to effectively filter water to the purest standards is an ongoing battle for various sectors of science. We present a set of experiments that will report the preparation of the photocatalytic component of our composite particle via sol-gel coatings with titanium n-butoxide with subsequent heat treatment at 500°C for three hours in Argon. Our ultimate goal is to create a particle with regenerative capabilities along with a surface enhanced Raman scattering effect. Characterization techniques were performed using SEM-EDS, and XRD.
Technical Paper

Subscale Testbed for Characterizing Regenerable Adsorbents used in Air Revitalization of Spacecraft Atmospheres

A sub-scale testbed for characterizing the dynamic performance of regenerable adsorbents for filtering trace contaminants (TCs) from cabin atmospheres was built and tested. Regenerable adsorbents employed in pressure-swing adsorption (PSA) systems operate in a dynamic environment, where they undergo repeated loading / regeneration cycles. Adsorbents have a given chemical specificity for non-methane TCs depending on their composition, and on the humidity and temperature at which they operate. However, their ability to filter TCs is also affected by contact time, cycle time, regeneration vacuum quality and thermal conditioning.
Technical Paper

Space-based SEBAC-II Solid Waste Management Technology for Commercial Application to Beet Sugar Industry

This paper describes an opportunity for commercial application of NASA space-based technology. Specifically, it describes application of the University of Florida's patented space-based SEBAC-II solid waste management technology to the US beet sugar industry. The project is entitled “Conversion of Biomass into Energy and Compost through Sequential Batch Anaerobic Composting”, and is being funded by the Xcel Energy Renewable Development Fund. It will be carried out by a team of researchers from the University of Florida in partnership with American Crystal Sugar Company (ACSC) of Moorhead, MN, and Minnesota Technology Inc. (MTI) in Minneapolis, MN. American Crystal Sugar generates 400 tons of sugar beet tailings daily. These tailings are a waste by-product of the raw sugar beet receiving, handling and washing operations. Currently, the company pays to have this material hauled away at the rate of 16 truckloads per day.
Technical Paper

Reliability Models for Dependent Elements Using a Method of Correlations

This paper was motivated by an interest in finding a way to determine the reliability of a system of interacting components in which the interaction effects can be specified by a set of parameters. Models are developed in which the basic assumption is that component interaction generate a linear statistical correlations among the conditions of groups of components. Formulas are then developed for the joint reliability of series and parallel systems in which the effects on system reliability are represented by these correlations.
Technical Paper

Recirculating Plug Flow Reactor

In this study, a model is developed in which a portion of the reacting flow in a plug flow reactor is recirculated back onto the inlet flow. In addressing the inherent non-uniformities in the primary zone of a combustor, the Recirculating Plug Flow Reactor should provide a superior method of correlating combustor performance over previous methods. This model was found to be governed by two parameters: the recirculation time required to complete the circuit and the ratio of the recirculated flow to the inlet flow. For a sufficiently large recirculation time, the characteristic reaction rate varied with this ratio. For a sufficiently small recirculation time, a distinct flame stability limit was observed.
Technical Paper

Post-Treatment of Anaerobically Digested Solid Waste in Long Term Space Missions

Post-treatment of anaerobically digested residue produced during long term space missions was investigated. Solid waste was anaerobically digested by employing the SEBAC system. One of the goals of post-treatment step is to convert ammonia in the residue to nitrates via biological nitrification processes. It was found that anaerobically digested residue contained nitrifying microorganisms which could be activated by aeration. Without supplying any external nitrifying inoculum, nitrification was initiated within 2 days by continuously blowing air at 15 ml/min. The maximum rate was 0.78 mg /g dry weight /day. However, denitrification process occurred soon after nitrification and ∼ 50% of nitrate was denitrified. A modified system in which aeration was carried out by holding air within the reactor at a pressure of ∼ 10 psi yielded a higher initial specific nitrification rate of 1.7 mg/g dry weight/day. Moreover, nitrification was initiated within a day.
Technical Paper

Performance of a Magnetically Agitated Photocatalytic Reactor for Oxidation of Ersatz AES Condensate

A magnetically agitated photocatalytic reactor (MAPR) has been developed and tested as a post-processor in the past using phenol and reactive red dye to simulate these waste components, yet these components ignore factors that may hinder a photocatalytic post processor including competitive adsorption of various organic compounds and their oxidation byproducts and the demonstrated detrimental effect of inorganic compounds such as ammonium bicarbonate on photocatalytic oxidation. To assess these effects, this work looks at photocatalytic oxidation of air evaporation subsystem (AES) ersatz water while modifying the photocatalyst mass, magnetic field current and frequency to find the optimal conditions. Additionally, the magnetic photocatalyst has been characterized to observe the assembled structures formed when exposed to the magnetic field array in the MAPR and the crystallinity of the titanium dioxide coating.
Technical Paper

Monitoring and Control for Artificial Climate Design

The monitoring and control of an artificial climate is necessitated by the Mars Dome Project (MDP) [ref 1]. MDP is designed to grow plants in an enclosed structure under reduced pressure. This system includes a dome enclosure, an environmental control system, a plant growth system, a data logging system, and an external vacuum vessel [ref 2]. Each of these systems is integrated by the use of a solid-state control device located inside the base of the Atmospheric Tower Management System (ATMS). Details of the controller follow a short summary of the major components of the MDP.
Technical Paper

Modeling and Design of Piezoelectric Actuators for Fluid Flow Control

A theoretical and experimental investigation into the modeling and design of piezoelectric flap actuators is described. The motivation for this study is to develop design tools for piezoelectric actuators in active flow control systems. In line with this goal, structural dynamic models of varying complexity must first be assessed. Theoretical modeling of the flaps is carried out using finite element analysis. For comparison, a companion experimental parametric study is executed in which ten otherwise identical piezo flaps with varying piezo patch sizes are fabricated in the Dynamics and Controls Laboratory at the University of Florida. The flaps are characterized using a laser displacement sensor and a scanning laser vibrometer to obtain the frequency response functions between the input voltage signal and the tip displacement and velocity of the flaps.
Technical Paper

Mission Planning for UAV Sensing Tasks in Close Proximity Environments

Unmanned aerial vehicles (UAVs) stand to play a significant role in future sensing and information gathering missions. The scope of these mission scenarios is expanding to include those missions for which the sensor and carrier vehicle will be in close proximity to the surrounding environment, such as in urban operations. Several unique problems related to guidance, navigation and control are introduced that separate these tasks from the existing paradigm for information gathering missions at standoff range. This paper examines the challenges related to autonomous sensor planning missions in these close proximity environments and discusses solution strategies to achieve maximal sensing effectiveness. Specifically, results from vision-based navigation research are discussed and the concept of a geometric sensing effectiveness criterion is introduced and subsequently utilized for motion planning.
Technical Paper

Low Pressure Greenhouse Concepts for Mars: Atmospheric Composition

The main principles of artificial atmospheric design for a Martian Greenhouse (MG) are described based on: 1. Cost-effective approach to MG realization; 2. Using in situ resources (e.g. CO2, O2, water); 3. Controlled greenhouse gas exchange by using independent pump in and pump out technologies. We show by mathematical modeling and numerical estimates based on reasonable assumptions that this approach for Martian deployable greenhouse (DG) implementation could be viable. A scenario of MG realization (in terms of plant biomass/photosynthesis, atmospheric composition, and time) is developed. A list is given of technologies (natural water collection, MG inflation, oxygen collection and storage, etc.) that are used in the design. The conclusions we reached are: 1. Initial stocks of oxygen and water probably would be required to initiate plant germination and growth; 2. Active control of MG ventilation could provide proper atmospheric composition for each period of plant growth; 3.
Technical Paper

High Speed Machining of Helicopter Gearcases

High speed machining of aluminum and magnesium helicopter gearcases was experimentally demonstrated to be five times more productive than contemporary conventional commercial practice for suitable operations. Appropriate techniques and performance characteristics are discussed for face milling, endmilling and planetary milling operations. Potential problem areas, such as surface characteristics and machine tool performance requirements are discussed.
Technical Paper

Effects of High Productivity Machining on Ti-6Al-4V Surface Topography

Surface defects were demonstrated to result from high productivity machining (HPM) as well as conventional machining of a titanium alloy Ti-6Al-4V, with HPM causing the larger sized defects. These defects could act as initiation sites for fatigue cracks showing that machining would affect fatigue strength and life of the part produced. A finishing pass appears to remove the defects. Better understanding is needed of the relationships between machining, surfaces, and strength.
Technical Paper

Effect of Photocatalyst Type on Oxidation of Ersatz Water Using a Photocatalytic Reactor with Slurry Separation

Previous work demonstrated that the Photo-Cat® developed by Purifics is capable of reducing the total organic carbon (TOC) concentration of 51 mg/L to below 0.5 ppm using Degussa P25 titanium dioxide (TiO2) as a photocatalyst. The work also showed that ammonium bicarbonate had a detrimental effect on the rate of photocatalytic oxidation, but did not prevent the system from reaching the potable water specification. Nanometer sized Degussa P25 is very popular and quite frequently used as a benchmark of performance in literature, but it may not be the most effective for oxidizing all waste streams. It is critical that each component of the water recovery system be optimized for power consumption and the effectiveness of the photocatalyst plays an important role in accomplishing this.
Technical Paper

Effect of Catalyst Support on the Photocatalytic Destruction of VOCs in a Packed-Bed Reactor

The removal of volatile organic compounds (VOCs) from the air aboard spacecrafts is necessary to maintain the health of crewmembers. The use of photocatalysis has proven effective for the removal of VOCs. A majority of studies have focused on thin films, which have a low adsorption capacity for contaminants and intermediate oxidation byproducts. Thus, this study investigates the use of adsorbent materials impregnated or coated with titania to: (1) provide a system that can remove VOCs for a period of time in the absence of UV irradiation to reduce power requirements and/or offer contaminant removal in the event of lamp failure and (2) improve the photocatalytic oxidation efficiency by concentrating VOCs and intermediate oxidation byproducts near the surface of the photocatalyst. Two adsorbent materials (porous silica gel and BioNuchar120 activated carbon) and glass beads were tested as catalyst supports for the destruction of a target VOC, in this case methanol (Co = 50 ppmv).