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This work presents an approach for the structural optimization of 2D and 3D aerospace truss structures. The main goal is to reduce the volume (or weight) of the structure while satisfying constraints such as compliance, member stresses, local or global buckling, for one or more load cases. Starting from an initial ground structure built from an optimal connectivity between all points, the best topology is determined, using a Sequential Linear Programming (SLP) algorithm. The design variables are the cross sectional areas of the bars, to be chosen within a specified range (maximum and minimum possible values). Studies of this nature have great importance in the task of developing lighter structures, without jeopardizing its functionality.

Paragon Space Development Corporation is developing a single-loop, non-toxic, active pumped thermal control design for robust, reliable operation near stagnation regimes as experienced in low power/cold environments. This research uses a safe fluid named Galden® HT170, manufactured by Solvay Solexis that has lower temperature stalling characteristics over typical space-based radiator fluids such as propylene glycol/water (PGW). A test bed and stagnation test article were designed, built and then modeled using Thermal Desktop® software to explore tube stagnation using Galden. Tube stagnation was sequentially controlled in each tube in a predictable manner, while collecting data to validate models. The data compared well to the modeling results. Fluid-compatibility results also showed no degradation to the fluid or to the aluminum tubing and weld materials and structures

Current NASA space suits use porous metal plate sublimators to reject the metabolic heat generated by the astronaut into space vacuum during EVA. Relying on tubular membranes instead of the flat plate of the sublimator, a proposed alternate unit has the potential to be smaller and lighter. This work outlines the operation of the proposed tubular membrane evaporator and the evaluation of possible membrane materials for the unit.

The current status of III-V semiconductor diode lasers emitting between 1 -5 μm wavelengths to be used as light sources for absorption spectroscopy is reviewed. The emission wavelength of the laser is chosen to coincide with the primary absorption line of a molecule or one of its many overtones. The lasers, with a single longitudinal mode emission, are wavelength tuned over several angstroms by modulating the drive current of the device. This sweeping of the wavelength leads to the nomenclature tunable diode laser or TDL. Single mode distributed feedback (DFB) strained layer InGaAs(P) lasers grown on InP substrates with emission wavelengths from 1.2 to 2.06 μm have been developed at JPL, and several devices will be used for planetary atmospheric studies for the first time.

The purpose of this paper is to discuss the status of refractory metal thermocouples and recent efforts toward solving the problems associated with thermoelements, insulators, and sheathing in high temperature applications. Because of the continuing research in this field and the rapid advance of the state of the art, the author cautions that all concerned with specific applications should maintain contact with these programs so that variables associated with their problems may be considered in prescribing proper use of these elements.

It is typical in aircraft engine design to explore new configurations in a constant effort to achieve greater efficiency with respect to various considerations. An integral component of this process requires a complete and robust simulation of rotor dynamics. Tuning the design with results of rotor dynamics simulations can be made possible with a tool that has adequate modeling techniques to capture the physics associated with engine behavior under various operating conditions accurately.

Composite materials have time and again proven to be highly useful, especially in the aerospace industry with the increasing need for light-weight materials albeit with high stiffness to strength ratios. The Ceramic Particle Reinforced Composites can be effectively utilized in tuning the natural frequencies of components by varying the volume fractions up to 40% with the help of Representative Volume Element (RVE) / Unit Cell Models as explained in Reference [1]. The aim of this paper is to tune the natural frequencies of a typical blade used in a gas turbine engine by modifying the material properties without changing the design profile significantly. The design profiles of blades are arrived at after a lot of engineering iterations from aerodynamics stability point of view and are also finalized based on meeting key performance parameters.

A study was undertaken to improve the prediction of heat transfer coefficients on the suction surface of turbine blades. The study specifically investigated the effects of coupling turbulent Prandtl number models with boundary layer transition models. A two-dimensional boundary layer code, STAN5, was selected and the turbulence model modified by incorporating several turbulent Prandtl number and boundary layer transition models found in the literature. Results indicated that subtle effects were attributable to the modified turbulence model. However, desired improvements were not obtained in the heat transfer coefficient predictions. It appears that boundary layer transition models predicting natural transition are not appropriate for use in a turbine blade flow field.

Operating components found in today's high performance aircraft and industrial gas turbines are subject to the most demanding conditions and hostile operating environments imaginable. As such, sophisticated part designs and advanced materials are being utilized to overcome the stringent demands encountered in these engines. Most distressed parts include blades, vanes, shrouds, frames, combustors, etc. These are generally constructed of high strength, heat resistant nickel or cobalt base alloys. Their costs are high, often in the tens of thousands of dollars. When damage occurs, usually thermal fatigue cracking, the part is no longer serviceable and must be repaired or worse - retired and replaced. Weld repair, though satisfactory, has inherent problems. This paper discusses activated diffusion brazing as a viable repair procedure for crack healing.

This paper describes the technical approach and development of methodologies used to conduct design trade studies from a Life Cycle Cost standpoint. A discussion of computer program capability is followed by a general discussion of several engine design trade studies. The potential for influencing engine design using a Life Cycle Cost methodology is emphasized.

Aircraft turbine engine development is requiring more and more spool data to be recorded during testing. This data, which normally consists of thermocouple and strain gage type signals, demands so many channels of quality transmission as to preclude bulky and costly telemetry devices. Miniature slip ring capsule assemblies, originally developed for inertial navigation equipment, have been adapted and used in turbine applications at speeds in excess of 30,000 revolutions per minute. These slip ring and brush contacts are characterized by low resistance variation or other electrical interference. The principal adaptation required to achieve these life times is the provision of an adequate coolant/lubricant supply.

An analysis was conducted on a total of 106,000 turbojet and turbofan engines procured by the United States Air Force to ascertain if an aircraft turbine engine's cost can be effectively correlated to its technical performance. Results indicate that such technical parameters are not valid and other factors such as military situation, economic conditions, and procurement situation should be investigated.

Delivery of high quality fuels to commercial turbine engine aircraft may become more critical for supersonic transport operation. This paper presents high temperature stability test results on current aviation turbine fuel samples taken from refineries and airports throughout the world. Transportation methods involve combinations of tanker, barge, multiproduct pipeline, and truck movements. Data show that, through the application of proper handling techniques, fuels can be transported from refinery to aircraft, through complex distribution systems, with no significant loss in thermal stability. Data also indicate that current aviation turbine fuels are well above the minimum thermal stability specification limits for present subsonic jet aircraft.

Impacts of mission-related requirements on design of the J402-CA-400 missile propulsion turbojet engine are reviewed. Small-engine cost scaling rationale is presented in relation to engine thrust and functional requirements. The application of current casting technology toward achieving low cost is reviewed.

Some of the trends in gas turbine technology are traced with two central themes. Materials and process technology is seen to be the major contributor to past advancements and often fails to receive the credit which is due. And, second, projections are made of the major future technology steps which will continue the historic fast pace of advancement in aircraft propulsion.

Analytical predictions and laboratory measurements were made for the relative total temperature experienced at the tip diameter of a radial-inflow turbine used in an air turbine starter (ATS). The predictions showed that at freerun conditions the blade tip temperature would be significantly higher than the turbine inlet temperature. Tests to confirm this prediction were performed on an ATS modified to accept an optical pyrometer. The pyrometer was focused on the suction side of the blade at the tip radius. Blade temperature measurements conducted at the maximum attainable speed of the ATS verified the prediction to be within the error of the pyrometer measuring system.

The search for clean, compact, cost effective energy sources isn't new. In fact it is as old as humanity. Over the past decade AlliedSignal has focused its attention developing TurboGenerator™ Power Systems that can be used in industrial, automotive and aerospace applications, AlliedSignal's creation was inspired by meshing its best aerospace technology with its high-volume manufacturing capability. The TurboGenerator™ Power System was first developed as an electric power and water heating cogeneration system for the US Gas Research Institute. The technology next found its way into an under armor APU installed in US army tanks including being tested on the US Army's main battle tank, the M1A1. From there, the technology was applied to hybrid electric vehicles in the US with the Department of Energy and Ford and in France with Renault and Peugeot.

Many advantages can be realized by utilization of direct bleed air from the engine exhaust-driven turbosupercharger for pressurization of the cabin on buisness and utility aircraft powered with piston engines. Combining cabin supercharging and engine supercharging from the same compressor included as part of the engine package provides compactness and simplicity which leads to low cost and light weight.