Theoretical analysis of aerodynamic characteristics of two helicopter rotor airfoils

An analytical study was conducted to predict the aerodynamic characteristics of two helicopter rotor airfoils. Documentation of the predictive process covers the development of empirical factors used in conjunction with computer programs for airfoil analysis. Tables of lift, drag, and pitching-moment coefficient for each airfoil were prepared for two dimensional, steady flow conditions at Mach numbers from 0.3 to 0.9 and Reynolds numbers of 7,700,000 to 23,000,000, respectively

Effect of aluminum substitution on the reflectance spectra of hematite

Hematite and aluminous hematite were synthesized and the diffuse reflectance spectra were recorded for the region between 0.35 and 1.20 microns. Results show that the near-IR based minimum for the aluminous hematite is shifted longward by about 0.02 microns and is much more shallow. Also, the aluminous specimen is considerably more reflective shortward of approximately 0.55 microns where the ferritic specimen is strongly absorbing. This is noteworthy since the visible slope and the red shoulder are often used in the construction of false color and band ratio images

Assessment of Variable-cycle Engines for Mach 2.7 Supersonic Transports

Three proposed SCAR propulsion systems in terms of aircraft range for a fixed payload and take-off gross weight with a design cruise Mach number 2.7 are evaluated. The effects of various noise and operational restraints are determined and sensitivities to some of the more important performance variables are presented for the most probable design noise and operational restraint case. Critical areas requiring new or improved technology for each cycle are delineated

Intensities of backscatter Mössbauer spectra

The intensities of γ‐ray and x‐ray backscatter Mössbauer spectra of ^(57)Fe nuclei in different matrix materials were studied theoretically and experimentally. A previous analysis by J. J. Bara [Phys. Status Solidi A 58, 349 (1980] showed that negative peak intensities occur in backscatter γ‐ray spectra when the ^(57)Fe nuclei are in a matrix of light elements. We report a confirmation of this work and offer a simple explanation of the phenomenon. The present paper extends Bara’s analysis to the case of conversion x‐ray spectra; expressions for the intensity of conversion x‐ray spectra as a function of absorber thickness and absorber material parameters are presented. We show that negative peak intensities are expected in conversion x‐ray spectra when the ^(57)Fe nuclei are in a matrix of heavy elements

The design of an Fe-12Mn-O.2Ti alloy steel for low temperature use

An investigation was made to improve the low temperature mechanical properties of Fe-8 approximately 12% Mn-O 2Ti alloy steels. A two-phase(alpha + gamma) tempering in combination with cold working or hot working was identified as an effective treatment. A potential application as a Ni-free cryogenic steel was shown for this alloy. It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated martensitic structure and absence of epsilon phase. A significant reduction of the ductile-brittle transition temperature was obtained in this alloy. The nature and origin of brittle fracture in Fe-Mn alloys were also investigated. Two embrittling regions were found in a cooling curve of an Fe-12Mn-O 2Ti steel which was shown to be responsible for intergranular fracture. Auger electron spectroscopy identified no segregation during solution-annealing treatment. Avoiding the embrittling zones by controlled cooling led to a high cryogenic toughness in a solution-annealed condition

A review of the NASA V-G/VGH general aviation program

The V-G and VGH data collected from a wide variety of general aviation airplanes since the inception of the NASA V-G/VGH General Aviation Program in 1962 are presented. These data were analyzed to obtain information on the gust and maneuver loads, on the operating practices, and on the effects of different types of operations on these parameters

The Chaos of Katrina: A Nonlinear Analysis of Federal Logistics Support during Hurricane Katrina Relief Operations

This thesis presents a case study of federal logistics support during Hurricane Katrina disaster relief operations. Data from federal contracts covering the first 10 weeks of Katrina are used to measure federal logistics activity. The study investigates whether chaos theory, part of complexity science, can extract information from Katrina contracting data to help managers make better logistics decisions during disaster relief operations. The study uses three analytical techniques: embedding, fitting the data to a logistic equation, and plotting the limit-cycle. Embedding and fitting a logistic equation to the data were used to test for deterministic chaos. The logistic equation and two versions of the limit-cycle model developed by Priesmeyer, Baik, and Cole were also tested as potential management tools. The study found that deterministic chaos was present during the first week of disaster relief, but that results for subsequent weeks were inconclusive, possibly due to internal changes to the relief dynamics. The thesis concludes that initial conditions and early actions will have a significant affect on disaster relief outcomes. Furthermore, many events that appear to be uncontrollable and random may actually be controllable. Therefore, managers play a critical role in preparing for and providing guidance in the early stages of disaster relief

Conceptual study of an advanced supersonic technology transport (AST-107) for transpacific range using low-bypass-ratio turbofan engines

An advanced supersonic technology configuration concept designated the AST-107, using a low bypass ratio turbofan engine, is described and analyzed. The aircraft had provisions for 273 passengers arranged five abreast. The cruise Mach number was 2.62. The mission range for the AST-107 was 8.48 Mm (4576 n.mi.) and an average lift drag ratio of 9.15 during cruise was achieved. The available lateral control was not sufficient for the required 15.4 m/s (30 kt) crosswind landing condition, and a crosswind landing gear or a significant reduction in dihedral effect would be necessary to meet this requirement. The lowest computed noise levels, including a mechanical suppressor noise reduction of 3 EPNdB at the flyover and sideline monitoring stations, were 110.3 EPNdB (sideline noise), 113.1 EPNdB (centerline noise) and 110.5 EPNdB (approach noise)

A simplified analysis of propulsion installation losses for computerized aircraft design

A simplified method is presented for computing the installation losses of aircraft gas turbine propulsion systems. The method has been programmed for use in computer aided conceptual aircraft design studies that cover a broad range of Mach numbers and altitudes. The items computed are: inlet size, pressure recovery, additive drag, subsonic spillage drag, bleed and bypass drags, auxiliary air systems drag, boundary-layer diverter drag, nozzle boattail drag, and the interference drag on the region adjacent to multiple nozzle installations. The methods for computing each of these installation effects are described and computer codes for the calculation of these effects are furnished. The results of these methods are compared with selected data for the F-5A and other aircraft. The computer program can be used with uninstalled engine performance information which is currently supplied by a cycle analysis program. The program, including comments, is about 600 FORTRAN statements long, and uses both theoretical and empirical techniques