Momentum Space Analysis for Mixed Skew Angle Arrays

This report explores non-redundant constant-speed single-gimballed control moment gyroscope mechanics for spacecraft maneuvers. A 3/4 control moment gyroscope pyramid design was examined. This report focuses on maximum available momentum for mixed skew angle configurations. A method to maximize off-axis momentum is developed

A Miniaturized Green End-Burning Hybrid Propulsion System for CubeSats

Conventional hybrid rocket motors with thrust levels greater than 5 N rely on forced convection within the boundary layer as the primary heat-transfer mechanism for fuel vaporization. For hybrid rockets with thrust levels less than 5 N, oxidizer mass flow levels are sufficiently small that the rate of convective heat transfer is significantly reduced, and radiative heat transfer dominates the fuel vaporization mechanism. Radiative heating is a potential concern when implementing traditional hybrid rocket core burn fuel grain designs for systems with low thrust levels adequate for small satellites and CubeSats. Radiative heating causes the system to be fuel rich leading to inefficient combustion and nozzle clogging. This paper presents a novel idea of using this radiative heating phenomenon in the design of a hybrid propulsion system suitable for CubeSats and small satellites. This paper presents the test results of two fuel grain designs, the first being an end burning design and the second a “sandwich” fuel grain design. ABS, PVC, Nylon-12 and acrylic known as PMMA were used as fuel and gaseous oxygen (GOX) was used as the oxidizer during this testing campaign. These propellants provide several advantages including: benign handling properties, simplified plumbing, and greater burn efficiency over traditional monopropellant hydrazine

Reproduction and Dispersal of Biological Soil Crust Organisms

Biological soil crusts (BSCs) consist of a diverse and highly integrated community of organisms that effectively colonize and collectively stabilize soil surfaces. BSCs vary in terms of soil chemistry and texture as well as the environmental parameters that combine to support unique combinations of organisms—including cyanobacteria dominated, lichen-dominated, and bryophyte-dominated crusts. The list of organismal groups that make up BSC communities in various and unique combinations include—free living, lichenized, and mycorrhizal fungi, chemoheterotrophic bacteria, cyanobacteria, diazotrophic bacteria and archaea, eukaryotic algae, and bryophytes. The various BSC organismal groups demonstrate several common characteristics including—desiccation and extreme temperature tolerance, production of various soil binding chemistries, a near exclusive dependency on asexual reproduction, a pattern of aerial dispersal over impressive distances, and a universal vulnerability to a wide range of human-related perturbations. With this publication, we provide literature-based insights as to how each organismal group contributes to the formation and maintenance of the structural and functional attributes of BSCs, how they reproduce, and how they are dispersed. We also emphasize the importance of effective application of molecular and microenvironment sampling and assessment tools in order to provide cogent and essential answers that will allow scientists and land managers to better understand and manage the biodiversity and functional relationships of soil crust communities

A Miniaturized Hydrogen Peroxide/ABS Based Hybrid Propulsion Systems for CubeSats

The Space Dynamics Lab is developing a prototype green hybrid prototype propulsion system for SmallSats. The system is based on Utah State\u27s patented High Performance Green Hybrid Propulsion (HPGHP) technology. HPGHP leverages unique dielectric breakdown properties of 3D-printed acrylonitrile butadiene styrene (ABS), allowing re-start, stop, and re-ignition. HPGHP works most reliably using gaseous oxygen (GOX) as the oxidizer, but has experienced ignition reliability and latency issues when replaced by high test hydrogen peroxide (HTP). This deficiency results from HTP\u27s high decomposition energy barrier. Tests show that noble metal catalysts like platinum on alumina are effective at decomposing 90% HTP in monopropellant form, but the decomposition releases insufficient energy to reliably ignite a hybrid rocket. This study reports on a non-catalytic, thermal-ignition method for hybrid rockets. Combustion is initiated using a gaseous oxygen pre-lead, with HTP being introduced to the hot combustion chamber once full GOX-ignition occurs. Residual energy from the GOX/ABS combustion thermally decomposes the HTP flow, with the freed-oxygen allowing full HTP-hybrid combustion. Design options and test results are presented for prototype systems at 0.5, 1.0, and 5 N thrust levels using 90% HTP with acrylonitrile butadiene styrene (ABS) and polymethylmethacrylate (PMMA) as fuels

Escher: A Web Application for Building, Sharing, and Embedding Data-Rich Visualizations of Biological Pathways

Escher is a web application for visualizing data on biological pathways. Three key features make Escher a uniquely effective tool for pathway visualization. First, users can rapidly design new pathway maps. Escher provides pathway suggestions based on user data and genome-scale models, so users can draw pathways in a semi-automated way. Second, users can visualize data related to genes or proteins on the associated reactions and pathways, using rules that define which enzymes catalyze each reaction. Thus, users can identify trends in common genomic data types (e.g. RNA-Seq, proteomics, ChIP)--in conjunction with metabolite- and reaction-oriented data types (e.g. metabolomics, fluxomics). Third, Escher harnesses the strengths of web technologies (SVG, D3, developer tools) so that visualizations can be rapidly adapted, extended, shared, and embedded. This paper provides examples of each of these features and explains how the development approach used for Escher can be used to guide the development of future visualization tools

Optical and electrochemical effects of H₂ and O₂ bubbles at upward-facing Si photoelectrodes

The effects of the size, contact-angle, and coverage of gas bubbles on solar fuels devices were characterized at cm-scale, upward-facing planar and microwire-array Si photoelectrodes in stagnant electrolytes. Experimental measurements were supported by ray-tracing simulations of surface attached gas bubble films. A dilute, redox-active tracer allowed for the quantification of the mass-transport effects of bubble coverage during photoanodic O₂ (g) evolution at upward-facing photoanodes in 1.0 M KOH(aq.). Measurements of the gas coverage at upward-facing p-Si photocathodes in 0.50 M H₂SO₄ (aq.) allowed for the nucleation rate and contact angle of H₂ (g) bubbles to be evaluated for systems having various surface free energies. Under simulated solar illumination, the rapid departure of small O₂ (g) bubbles produced stable photocurrents at upward-facing oxygen-evolving Si photoanodes and yielded increased mass-transport velocities relative to a stagnant electrolyte, indicating that bubbles can provide a net benefit to the photoelectrochemical performance of an upward-facing photoanode in solar fuels devices

Spontaneous Formation of >90% Optically Transmissive, Electrochemically Active CoP Films for Photoelectrochemical Hydrogen Evolution

Earth-abundant catalysts for the hydrogen-evolution reaction require increased mass loadings, relative to Pt films, to achieve comparable activity and stability in acidic electrolytes. We report herein that spontaneous nanostructuring of opaque, electrodeposited CoP films, 40–120 nm in thickness, leads to transparent electrocatalyst films that exhibit up to 90% optical transmission in the visible spectrum. The photocurrent density under simulated sunlight at a representative n+p-Si(100)/CoP photocathode increases by 200% after exposure to 0.50 M H₂SO₄ (aq) and remains stable for 12 h of continuous operation. Atomic force microscopy and scanning electron microscopy of the film before and after exposure to 0.50 M H₂SO₄ (aq) validate an optical model for transparent CoP films as probed with spectroscopic ellipsometry