Noise prediction technology for CTOL aircraft

The application of a new aircraft noise prediction program to CTOL noise prediction is outlined. Noise prediction is based on semiempirical methods for each of the propulsive system noise sources, such as the fan, the combustor, the turbine, and jet mixing, with noise-critical parameter values derived from the thermodynamic cycle of the engine. Comparisons of measured and predicted noise levels for existing CTOL aircraft indicate an acceptable level of accuracy

Predicted airframe noise levels

Calculated values of airframe noise levels corresponding to FAA noise certification conditions for six aircraft are presented. The aircraft are: DC-9-30; Boeing 727-200; A300-B2 Airbus; Lockheed L-1011; DC-10-10; and Boeing 747-200B. The prediction methodology employed is described and discussed

On the determination of near body orbits using mass concentration models

Mathematical model for near-body orbit calculation using mass concentration, perturbation theory, nonlinear equations, geopotentials, and least squares metho

Control integration concept for hypersonic cruise-turn maneuvers

Piloting difficulties associated with conducting aircraft maneuvers in hypersonic flight are caused in part by the nonintuitive nature of the aircraft response and the stringent constraints anticipated on allowable angle of attack and dynamic pressure variations. An approach is documented that provides precise, coordinated maneuver control during excursions from a hypersonic cruise flight path and the necessary flight condition constraints. The approach is to achieve specified guidance commands by resolving altitude and cross range errors into a load factor and bank angle command by using a coordinate transformation that acts as an interface between outer and inner loop flight controls. This interface, referred to as a 'resolver', applies constraints on angle of attack and dynamic pressure perturbations while prioritizing altitude regulation over cross range. An unpiloted test simulation, in which the resolver was used to drive inner loop flight controls, produced time histories of responses to guidance commands and atmospheric disturbances at Mach numbers of 6, 10, 15, and 20. Angle of attack and throttle perturbation constraints, combined with high speed flight effects and the desire to maintain constant dynamic pressure, significantly impact the maneuver envelope for a hypersonic vehicle

Preliminary noise tradeoff study of a Mach 2.7 cruise aircraft

NASA computer codes in the areas of preliminary sizing and enroute performance, takeoff and landing performance, aircraft noise prediction, and economics were used in a preliminary noise tradeoff study for a Mach 2.7 design supersonic cruise concept. Aerodynamic configuration data were based on wind-tunnel model tests and related analyses. Aircraft structural characteristics and weight were based on advanced structural design methodologies, assuming conventional titanium technology. The most advanced noise prediction techniques available were used, and aircraft operating costs were estimated using accepted industry methods. The 4-engines cycles included in the study were based on assumed 1985 technology levels. Propulsion data was provided by aircraft manufacturers. Additional empirical data is needed to define both noise reduction features and other operating characteristics of all engine cycles under study. Data on VCE design parameters, coannular nozzle inverted flow noise reduction and advanced mechanical suppressors are urgently needed to reduce the present uncertainties in studies of this type

Review of the Geology and Hydrology of the Eagle Flat Area, Hudspeth County, Texas

On February 27, 1991, the Texas Low-Level Radioactive Waste Disposal Authority requested that the Bureau of Economic Geology perform a preliminary review of the geology and hydrology of the Eagle Flat area in eastern Hudspeth County, Texas. The purpose of this review was to briefly summarize what is known about the geology and hydrology of the area from a survey of the published literature, to conduct a field reconnaissance of the area, and to comment on factors that the Authority may want to consider in its general assessment of the suitability of the area as a host for a repository for low-level radioactive wastes. Recent maps of land ownership indicate that the State does not own any sections in the main Eagle Flat area, although the State does retain an interest in the mineral rights on some sections. To minimize upstream drainage, avoid drainage basins that flow to the Rio Grande, and maximize the potential for thick basin-fill deposits, the portion of Eagle Flat that lies southeast of the road to Grayton Lake, west of the drainage divide between Grayton Lake and Eagle Flat Draw, and between the Texas and Pacific and Southern Pacific railroad tracks, has been indicated as an area of potential interest. For the purposes of this report, this block of land is referred to as the "Eagle Flat site." The Eagle Flat site is shown on the Grayton Lake 7.5-minute quadrangle topographic map published by the U.S. Geological Survey.Bureau of Economic Geolog

Surface Casing Database Project

In 2005, the Bureau of Economic Geology expanded the surface casing database developed in 2004 for Brazos County to include three additional counties: Robertson, Madison, and Leon. All work was funded by the Texas Commission on Environmental Quality (TCEQ) under the oversight of John Estepp. Methods employed and the functionality of the database, which is designed to be accessed by the public using the Internet, are essentially the same as those of the prototype project for Brazos County. All TCEQ "Q-Logs" for the three counties were scanned and delivered to TCEQ. This letter report is a summary of a few refinements and changes from the initial project, and some recommendations for how the project may be expanded in the future. Bureau personnel are essentially the same as for the initial project, which greatly facilitated the work. The geology of the study area is mostly updip from Brazos County, and the three-county area includes a salt dome and an impact structure.Bureau of Economic Geolog

Regional Ecological Resource Assessment of the Rio Grande Riparian Corridor: A Multidisciplinary Approach to Understanding Anthropogenic Effects on Riparian Communities in Semiarid Environments

Data for this report is available at the Texas Data Repository: https://doi.org/10.18738/T8/AAB1LYRiparian ecosystems of the southwestern United States are among the most productive ecosystems of North America. The rapid decline of these ecosystems throughout the United States, including the Lower Rio Grande Valley, has made riparian conservation a focal issue. This multidisciplinary study of riparian communities along the Lower Rio Grande of Texas and Mexico had several objectives, including (1) acquiring and analyzing high-resolution, remotely sensed data from multiple sensors; (2) integrating existing and new field data and remotely sensed data into a geographic information system (GIS); (3) ascertaining whether the native vegetation communities are maintaining themselves and identifying the topographic, edaphic, and other ecological factors that perpetuate these communities; (4) interpreting spatial variations in riparian habitats, including comparisons of the north and south banks of the Rio Grande; (5) analyzing temporal changes at specific locations; and (6) developing a foundation for future analysis of riparian floodplain communities by linking local and remotely sensed regional data using GIS. Analysis and classification of riparian vegetation in the Lower Rio Grande Valley using remote sensing data supported by field surveys confirmed what other researchers have qualitatively suggested, that riparian vegetation has been greatly diminished since the early 1900s. Digital analysis of historical maps and aerial photographs of woodland distribution in Cameron County as part of this study revealed that in the mid-1930s there were ~81,887 ha of woodlands in Cameron County. By the early to mid-1980s, only 7,337 ha of woodlands in this original area remained, indicating a loss of ~91% of this resource. This quantitative assessment of woodland loss helps confirm the earlier qualitative estimates of up to 95% loss.Bureau of Economic Geolog

Drafting and Use of Opinion Letters of Counsel

This article outlines the kinds of opinions which counsel may render to a non-client via letter, the functions of such opinions in a transaction, and the preparation of opinion letters in view of the possibility of counsel\u27s liability thereon to a non-client party. Material for the article was obtained in part from interviews with a number of individuals familiar with transactions commonly involving opinion letters and more particularly transactions wherein opinion letters are transmitted to non-clients for their reliance

A methodology for selective removal of orbital debris

Earth-orbiting objects, large enough to be tracked, were surveyed for possible systematic debris removal. Based upon the statistical collision studies of others, it was determined that objects in orbits approximately 1000 km above the Earth's surface are at greatest collisional risk. Russian C-1B boosters were identified as the most important target of opportunity for debris removal. Currently, more than 100 in tact boosters are orbiting the Earth with apogees between 950 km and 1050 km. Using data provided by Energia USA, specific information on the C-1B booster, in terms of rendezvous and capture strategies, was discussed