Nuclear Engine System Simulation (NESS). Volume 1: Program user's guide

A Nuclear Thermal Propulsion (NTP) engine system design analysis tool is required to support current and future Space Exploration Initiative (SEI) propulsion and vehicle design studies. Currently available NTP engine design models are those developed during the NERVA program in the 1960's and early 1970's and are highly unique to that design or are modifications of current liquid propulsion system design models. To date, NTP engine-based liquid design models lack integrated design of key NTP engine design features in the areas of reactor, shielding, multi-propellant capability, and multi-redundant pump feed fuel systems. Additionally, since the SEI effort is in the initial development stage, a robust, verified NTP analysis design tool could be of great use to the community. This effort developed an NTP engine system design analysis program (tool), known as the Nuclear Engine System Simulation (NESS) program, to support ongoing and future engine system and stage design study efforts. In this effort, Science Applications International Corporation's (SAIC) NTP version of the Expanded Liquid Engine Simulation (ELES) program was modified extensively to include Westinghouse Electric Corporation's near-term solid-core reactor design model. The ELES program has extensive capability to conduct preliminary system design analysis of liquid rocket systems and vehicles. The program is modular in nature and is versatile in terms of modeling state-of-the-art component and system options as discussed. The Westinghouse reactor design model, which was integrated in the NESS program, is based on the near-term solid-core ENABLER NTP reactor design concept. This program is now capable of accurately modeling (characterizing) a complete near-term solid-core NTP engine system in great detail, for a number of design options, in an efficient manner. The following discussion summarizes the overall analysis methodology, key assumptions, and capabilities associated with the NESS presents an example problem, and compares the results to related NTP engine system designs. Initial installation instructions and program disks are in Volume 2 of the NESS Program User's Guide

Nuclear Engine System Simulation (NESS) version 2.0

The topics are presented in viewgraph form and include the following; nuclear thermal propulsion (NTP) engine system analysis program development; nuclear thermal propulsion engine analysis capability requirements; team resources used to support NESS development; expanded liquid engine simulations (ELES) computer model; ELES verification examples; NESS program development evolution; past NTP ELES analysis code modifications and verifications; general NTP engine system features modeled by NESS; representative NTP expander, gas generator, and bleed engine system cycles modeled by NESS; NESS program overview; NESS program flow logic; enabler (NERVA type) nuclear thermal rocket engine; prismatic fuel elements and supports; reactor fuel and support element parameters; reactor parameters as a function of thrust level; internal shield sizing; and reactor thermal model

Steady States of a Nonequilibrium Lattice Gas

We present a Monte Carlo study of a lattice gas driven out of equilibrium by a local hopping bias. Sites can be empty or occupied by one of two types of particles, which are distinguished by their response to the hopping bias. All particles interact via excluded volume and a nearest-neighbor attractive force. The main result is a phase diagram with three phases: a homogeneous phase, and two distinct ordered phases. Continuous boundaries separate the homogeneous phase from the ordered phases, and a first-order line separates the two ordered phases. The three lines merge in a nonequilibrium bicritical point.Comment: 14 pages, 24 figure

Compaction and Chemical Grouting for Drain Tunnels in Phoenix

Ground runs during ml.m.ng of the Papago Freeway Drain Tunnels posed significant potential risk to utilities, street pavement, and buildings located above and adjacent to one of the three tunnel alignments. Ground response to the larger ground runs resulted in open chimneys and settlement of the ground surface of up to several feet. Modifications to the tunneling machine included addition of poling plates and breasting boards. Further modification to the tunneling method included use of compaction grouting in conjunction with mining for the entire length of one tunnel alignment, and use of chemical grouting to prestabilize the ground surrounding the tunnel opening in areas of high risk utilities and in areas where subsurface conditions suggested that running ground would be encountered during mining. This paper presents a summary of the ground behavior with and without the compaction and chemical grouting and describes the grouting methods

NASA aviation safety reporting system

The origins and development of the NASA Aviation Safety Reporting System (ASRS) are briefly reviewed. The results of the first quarter's activity are summarized and discussed. Examples are given of bulletins describing potential air safety hazards, and the disposition of these bulletins. During the first quarter of operation, the ASRS received 1464 reports; 1407 provided data relevant to air safety. All reports are being processed for entry into the ASRS data base. During the reporting period, 130 alert bulletins describing possible problems in the aviation system were generated and disseminated. Responses were received from FAA and others regarding 108 of the alert bulletins. Action was being taken with respect to 70 of the 108 responses received. Further studies are planned of a number of areas, including human factors problems related to automation of the ground and airborne portions of the national aviation system

X-Ray Standing Wave Studies of Ad-Dimers on Si(001)

X-ray standing waves generated by dynamical Bragg diffraction were used as an element-specific structural probe for investigating Ga and Sb adsorption on Si(001). Using the (004) and (022) reflections, we precisely measured Ga and Sb ad-dimer bond lengths and ad-dimer heights above the bulk-extrapolated Si(001) surface. The room temperature [001] thermal vibration amplitudes of Ga and Sb adatoms on Si(00l) were also directly determined by combining the fundamental (004) and high-order harmonic (008) X-ray standing wave measurements. These high-resolution measurements reveal important quantitative structural information regarding the dimerized surface structures, and provide a stringent test for structural models proposed by various theoretical calculations. In this paper, we also give an over-view of the X-ray standing wave technique and its application in investigating surface structure and dynamics

Whole Genome Phylogenetic Tree Reconstruction Using Colored de Bruijn Graphs

We present kleuren, a novel assembly-free method to reconstruct phylogenetic trees using the Colored de Bruijn Graph. kleuren works by constructing the Colored de Bruijn Graph and then traversing it, finding bubble structures in the graph that provide phylogenetic signal. The bubbles are then aligned and concatenated to form a supermatrix, from which a phylogenetic tree is inferred. We introduce the algorithms that kleuren uses to accomplish this task, and show its performance on reconstructing the phylogenetic tree of 12 Drosophila species. kleuren reconstructed the established phylogenetic tree accurately, and is a viable tool for phylogenetic tree reconstruction using whole genome sequences. Software package available at: https://github.com/Colelyman/kleurenComment: 6 pages, 3 figures, accepted at BIBE 2017. Minor modifications to the text due to reviewer feedback and fixed typo