Constricted high enthalpy arc heater design and performance data, including calculations for a 10 MW design First interim technical report

Performance prediction and design analysis of constricted coaxial-flow arc air heaters for materials testing and atmospheric entry simulatio

2009 program of studies : nonlinear waves

The fiftieth year of the program was dedicated to Nonlinear Waves, a topic with many applications in geophysical fluid dynamics. The principal lectures were given jointly by Roger Grimshaw and Harvey Segur and between them they covered material drawn from fundamental theory, fluid experiments, asymptotics, and reaching all the way to detailed applications. These lectures set the scene for the rest of the summer, with subsequent daily lectures by staff and visitors on a wide range of topics in GFD. It was a challenge for the fellows and lecturers to provide a consistent set of lecture notes for such a wide-ranging lecture course, but not least due to the valiant efforts of Pascale Garaud, who coordinated the write-up and proof-read all the notes, we are very pleased with the final outcome contained in these pages. This year’s group of eleven international GFD fellows was as diverse as one could get in terms of gender, origin, and race, but all were unified in their desire to apply their fundamental knowledge of fluid dynamics to challenging problems in the real world. Their projects covered a huge range of physical topics and at the end of the summer each student presented his or her work in a one-hour lecture. As always, these projects are the heart of the research and education aspects of our summer study.Funding was provided by the National Science Foundation through Grant No. OCE-0824636 and the Office of Naval Research under Contract No. N00014-09-10844

Current State of the Electrodynamic Dust Shield for Mitigation

The Electrodynamic Dust Shield (EDS) has been developed as a means to lift, transport and remove dust from surfaces for over 18 years in the Electrostatics and Surface Physics Laboratory at NASA Kennedy Space Center. Resent advances in the technology have allowed large-scale EDSs to be fabricated using roll-to-roll techniques for quick efficient processing. The aim of the current research is to demonstrate the 3-dimensional (3-D) version of the EDS and its applicability to various surfaces of interest throughout the Artemis program that require dust mitigation. The conventional two dimensional (2-D) EDS has been comprised of interdigitated electrodes across a surface of alternating polarity to setup non-uniform electric fields in the location of interest for which the particles need to be removed. The 2-D system can be designed to accommodate various phases. For example, the two phase EDS is comprised of two electrodes 180 out of phase, while the 3-phase EDS is 120 out of phase with the adjacent leg. 4-phase EDS configurations are also possible but for each square wave a high voltage signal is applied to each leg

Application of Glow Discharge Plasma to Alter Surface Properties of Materials

Some polymer materials that are considered important for spaceport operations are rendered noncompliant when subjected to the Kennedy Space Center (KSC) Standard electrostatic testing. These materials operate in stringent environmental conditions, such as high humidity. Treating materials that fail electrostatic testing and altering their surface properties so that they become compliant would result in considerable cost savings. Significant improvement in electrostatic dissipation of Saf-T-Vu PVC after treatment with air Atmospheric Plasma Glow Discharge (APGD) was observed and the material now passed the KSC electrostatic test. The O:C ratio on the surface, as monitored by X-ray Photoelectron Spectroscopy, increased from 0.165 tO 0.275 indicating enhanced oxidation, and surface contact angle measurements decreased from 107.5 to 72.6 showing increased hydrophilicity that accounted for the increased conductivity. Monitoring of the aging showed that the materials hydrophobic recovery resulted in it failing the electrostatic test 30 hours after treatment. This was probably due to the out-diffusion of the added Zn, Ba, and Cd salt stabilizers detected on the surface and/or diffusion of low molecular weight oligomers. On going work includes improving the long term hydrophilicity by optimizing the APGD process with different gas mixtures. Treatment of other spaceport materials is also presented

ESD Challenges for NASA Astronauts in Upcoming Missions

Electrostatic charging of insulators is well known to pose potential threats to electronic systems under terrestrial systems. We were asked to evaluate potential hazards associated with replacement of an electronics board in the vacuum of space during the upcoming Hubble Service Repair mission in September 2008. A device called a "tribot" was built to simulate triboelectric charging of several insulators that are capable of contact charging against astronaut's gloves and suit materials. Materials were evaluated as the extent of not only the magnitude of electric fields generated by the frictional action, but also any resulting discharge which would be a source of EMI. Experimental results are quite surprising and unexpected when compared with tests performed under ambient conditions under dry and humid air

Electrostatic Characterization of Lunar Dust Simulants

Lunar dust can jeopardize exploration activities due to its ability to cling to most surfaces. In this paper, we report on our measurements of the electrostatic properties of the lunar soil simulants. Methods have been developed to measure the volume resistivity, dielectric constant, chargeability, and charge decay of lunar soil. While the first two parameters have been measured in the past [Olhoeft 1974], the last two have never been measured directly on the lunar regolith or on any of the Apollo samples. Measurements of the electrical properties of the lunar samples are being performed in an attempt to answer important problems that must be solved for the development of an effective dust mitigation technology, namely, how much charge can accumulate on the dust and how long does the charge remain on surfaces. The measurements will help develop coatings that are compatible with the intrinsic electrostatic properties of the lunar regolith

WOODSTOCC: Extracting Latent Parallelism from a DNA Sequence Aligner on a GPU

An exponential increase in the speed of DNA sequencing over the past decade has driven demand for fast, space-efficient algorithms to process the resultant data. The first step in processing is alignment of many short DNA sequences, or reads, against a large reference sequence. This work presents WOODSTOCC, an implementation of short-read alignment designed for Graphics Processing Unit (GPU) architectures. WOODSTOCC translates a novel CPU implementation of gapped short-read alignment, which has guaranteed optimal and complete results, to the GPU. Our implementation combines an irregular trie search with dynamic programming to expose regularly structured parallelism. We first describe this implementation, then discuss its port to the GPU. WOODSTOCC’s GPU port exploits three generally useful techniques for extracting regular parallelism from irregular computations: dynamic thread mapping with a worklist, kernel stage decoupling, and kernel slicing. We discuss the performance impact of these techniques and suggest further opportunities for improvement

Solid Freeform Fabrication of Ceramic Parts from Filler Loaded Preceramic Polymers

Manufacturing of ceramic parts was achieved by selective laser treatment of a preceramic polymer (polysiloxane) loaded with ceramic filler powder (alumina). Thin layers of polymer/filler powder mixture were sequentially cured with a CO2-laser (λ=10.6 µm) thereby generating the geometrical shape of the part. Subsequently, the cured thermoset part was annealed in nitrogen atmosphere at 600 to 1000 °C to convert the compact into a Si-OC/Al2O3 micro-composite material. Dimensional changes upon pyrolysis (∆l/l0 ≈ 3 %) can be controlled by adjusting the polymer-to-filler ratio and the heat treatment conditions. The new process is called Selective Laser Curing (SLC).Financial support of Fonds der Chemischen Industrie and Deutsche Forschungsgemeinschaft is gratefully acknowledged.Mechanical Engineerin