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NASA NTRS2004

Assurance Technology Challenges of Advanced Space Systems

The initiative to explore space and extend a human presence across our solar system to revisit the moon and Mars post enormous technological challenges to the nation's space agency and aerospace industry. Key areas of technology development needs to enable the endeavor include advanced materials, structures and mechanisms; micro/nano sensors and detectors; power generation, storage and management; advanced thermal and cryogenic control; guidance, navigation and control; command and data handling; advanced propulsion; advanced communication; on-board processing; advanced information technology systems; modular and reconfigurable systems; precision formation flying; solar sails; distributed observing systems; space robotics; and etc. Quality assurance concerns such as functional performance, structural integrity, radiation tolerance, health monitoring, diagnosis, maintenance, calibration, and initialization can affect the performance of systems and subsystems. It is thus imperative to employ innovative nondestructive evaluation methodologies to ensure quality and integrity of advanced space systems. Advancements in integrated multi-functional sensor systems, autonomous inspection approaches, distributed embedded sensors, roaming inspectors, and shape adaptive sensors are sought. Concepts in computational models for signal processing and data interpretation to establish quantitative characterization and event determination are also of interest. Prospective evaluation technologies include ultrasonics, laser ultrasonics, optics and fiber optics, shearography, video optics and metrology, thermography, electromagnetics, acoustic emission, x-ray, data management, biomimetics, and nano-scale sensing approaches for structural health monitoring.

Chern, E. James↗

NASA NTRS2004

NASA's Aeronautics Vision

Six long-term technology focus areas are: 1. Environmentally Friendly, Clean Burning Engines. Focus: Develop innovative technologies to enable intelligent turbine engines that significantly reduce harmful emissions while maintaining high performance and increasing reliability. 2. New Aircraft Energy Sources and Management. Focus: Discover new energy sources and intelligent management techniques directed towards zero emissions and enable new vehicle concepts for public mobility and new science missions. 3. Quiet Aircraft for Community Friendly Service. Focus: Develop and integrate noise reduction technology to enable unrestricted air transportation service to all communities. 4. Aerodynamic Performance for Fuel Efficiency. Focus: Improve aerodynamic efficiency,structures and materials technologies, and design tools and methodologies to reduce fuel burn and minimize environmental impact and enable new vehicle concepts and capabilities for public mobility and new science missions. 5. Aircraft Weight Reduction and Community Access. Focus: Develop ultralight smart materials and structures, aerodynamic concepts, and lightweight subsystems to increase vehicle efficiency, leading to high altitude long endurance vehicles, planetary aircraft, advanced vertical and short takeoff and landing vehicles and beyond. 6. Smart Aircraft and Autonomous Control. Focus: Enable aircraft to fly with reduced or no human intervention, to optimize flight over multiple regimes, and to provide maintenance on demand towards the goal of a feeling, seeing, sensing, sentient air vehicle.

Tenney, Darrel R.↗

NASA NTRS2004

New Outboard Motor Firing on All Pistons

Seven years ago, NASA was in the planning stages of producing an aluminum alloy with higher strength and resistance at elevated temperatures for aerospace applications. At that time, a major automobile manufacturer happened to approach NASA for solutions to lowering engine emissions and the costs associated with developing aluminum engine pistons. The Space Agency realized the answers to the manufacturer's problems could lie within the proposed alloy. Jonathan Lee, a structural materials engineer at Marshall Space Flight Center s Materials, Processes, and Manufacturing Department, and PoShou Chen, a scientist with Huntsville, Alabama-based Morgan Research Corporation, partook in the development project as the inventors. The resulting NASA High-Strength Aluminum Alloy, or "MSFC-398," was capable of casting metal components at both high volume and low cost, making it extremely attractive for commercial application, not just in automotives, but in a variety of other industries, as well. NASA patented the technology and introduced it for public licensing in 2001.

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NASA NTRS2004

High-Solids Polyimide Precursor Solutions

The invention is a highly concentrated stable solution of polymide precursors (monometers) having a solids content ranging from about 80 to 98 percent by weight in lower aliphatic alcohols i.e. methyl and/or ethylalcohol. the concentrated polyimide precursos solution comparisons effective amounts of at least one aromatic diamine, at least one aromatic dianhydride, and a monofunctional endcap including monoamines, monoanhydrides and lower alkyl esters of said monoanhydrides. These concentrated polyimide precursor solutions are particularly useful for the preparation of fibrous prepregs and composites for use in structural materials for military and civil applications.

Chun-Hua Chuang↗

NASA NTRS2005

Lifing of Engine Components

The successful development of advanced aerospace engines depends greatly on the capabilities of high performance materials and structures. Advanced materials, such as nickel based single crystal alloys, metal foam, advanced copper alloys, and ceramics matrix composites, have been engineered to provide higher engine temperature and stress capabilities. Thermal barrier coatings have been developed to improve component durability and fuel efficiency, by reducing the substrate hot wall metal temperature and protecting against oxidation and blanching. However, these coatings are prone to oxidation and delamination failures. In order to implement the use of these materials in advanced engines, it is necessary to understand and model the evolution of damage of the metal substrate as well as the coating under actual engine conditions. The models and the understanding of material behavior are utilized in the development of a life prediction methodology for hot section components. The research activities were focused on determining the stress and strain fields in an engine environment under combined thermo-mechanical loads to develop life prediction methodologies consistent with the observed damage formation of the coating and the substrates.

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NASA NTRS1996

Microalloying Improves the Low-Cycle Fatigue Behavior of Powder-Extruded NiAl

There is considerable interest in developing new structural materials in which high use temperatures and strength, coupled with low density, are the minimum requirements. The goal for these new materials is to provide operation well beyond the working range of conventional superalloys. Of the many intermetallics under consideration, NiAl is one of the few systems that has emerged as a promising candidate for further development. This is because of a number of property advantages--including low density, high melting temperature, high thermal conductivity, and excellent environmental resistance. However, binary NiAl lacks strength and creep resistance at elevated temperatures. Also, its poor high-temperature strength results in worse-than-predicted low-cycle fatigue (LCF) lives at low strain ranges at 727 C (1341 F) because of accelerated creep damage mechanisms that result in significant intergranular cracking. One approach for improving these properties involves microalloying NiAl with either Zr or N. As an integral part of this alloy-development program at the NASA Lewis Research Center, the low-cycle fatigue behavior of Zr- and N-doped nickel aluminides produced by extrusion of prealloyed powders was investigated and compared with similarly processed binary NiAl.

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NASA NTRS1996

High-Temperature Extensometry and PdCr Temperature-Compensated Wire Resistance Strain Gages Compared

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NASA NTRS1999

MoSi2-Base Structural Composite Passed Engine Test

The intermetallic compound molybdenum disilicide (MoSi2) is an attractive high-temperature structural material for advanced engine applications. It has excellent oxidation resistance, a high melting point, relatively low density, and high thermal conductivity; and it is easily machined. Past research at the NASA Lewis Research Center has resulted in the development of a hybrid composite consisting of a MoSi2 matrix reinforced with silicon nitride (Si3N4) particulate and silicon carbide (SiC) fibers. This composite has demonstrated attractive strength, toughness, thermal fatigue, and oxidation resistance, including resistance to "pest" oxidation. These properties attracted the interest of the Office of Naval Research and Pratt & Whitney, and a joint NASA/Navy/Pratt & Whitney effort was developed to continue to mature the MoSi2 composite technology. A turbine blade outer air seal, which was part of the Integrated High Performance Turbine Engine Technology (IHPTET) program, was chosen as a first component on which to focus.

Nathal, Michael V.↗

NASA NTRS1997

High-Temperature Extensometry and PdCr Temperature-Compensated Wire Resistance Strain Gages Compared

A detailed experimental evaluation is underway at the NASA Lewis Research Center to compare and contrast the performance of the PdCr/Pt dual-element temperature-compensated wire resistance strain gage with that of conventional high-temperature extensometry. The advanced PdCr gage, developed by researchers at Lewis, exhibits desirable properties and a relatively small and repeatable apparent strain to 800 C. This gage represents a significant advance in technology because existing commercial resistance strain gages are not reliable for quasi-static strain measurements above approx. 400 C. Various thermal and mechanical loading spectra are being applied by a high-temperature thermomechanical uniaxial testing system to evaluate the two strain-measurement systems. This is being done not only to compare and contrast the two strain sensors, but also to investigate the applicability of the PdCr strain gage to the coupon-level specimen testing environment typically employed when the high-temperature mechanical behavior of structural materials is characterized. Strain measurement capabilities to 800 C are being investigated with a nickel-base superalloy, Inconel 100 (IN 100), substrate material and application to TMC's is being examined with the model system, SCS-6/Ti-15-3. Furthermore, two gage application techniques are being investigated in the comparison study: namely, flame-sprayed and spot welding. The apparent strain responses of both the weldable and flame-sprayed PdCr wire strain gages were found to be cyclically repeatable on both IN 100 and SCS-6/Ti-15-3 [0]_8. In general, each gage exhibited some uniqueness with respect to apparent strain behavior. Gages mounted on the IN 100 specimens tended to show a repeatable apparent strain within the first few cycles, because the thermal response of IN 100 was stable. This was not the case, however, for the TMC specimens, which typically required several thermal cycles to stabilize the thermal strain response. Thus, progressive changes in the apparent strain behavior were corroborated by the extensometer, which unlike the mounted gage can distinguish quantitative changes in the material's thermal strain response. One specimen was instrumented with both a fixed and floating gage. From the difference in output of these two gages, the thermal expansion strains were calculated. These data, which are given in the figure, show excellent agreement with the values measured by the high-temperature extensometry.

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NASA NTRS1999

Single-Crystal NiAl-X Alloys Tested for Hot Corrosion

Single-crystal nickel aluminide (NiAl) has been investigated extensively throughout the last several years as a potential structural material in aero-gas turbine engines. The attractive features of NiAl in comparison to Ni-base superalloys include a higher melting point, lower density, higher thermal conductivity, and excellent oxidation resistance. However, NiAl suffers from a lack of ductility and fracture toughness at low temperatures and a low creep strength at high temperatures. Alloying additions of hafnium (Hf), gallium (Ga), titanium (Ti), and chromium (Cr) have each shown some benefit to the mechanical properties over that of the binary alloy. However, the collective effect of these alloying additions on the environmental resistance of NiAl-X was unclear. Hence, the present study was undertaken to examine the hot corrosion behavior of these alloys. A companion study examined the cyclic oxidation resistance of these alloys. Several single-crystal NiAl-X alloys (where X is Hf, Ti, Cr, or Ga) underwent hot corrosion testing in a Mach 0.3 burner rig at the NASA Lewis Research Center. Samples were tested for up to 300 1-hr cycles at a temperature of 900 C. It was found that increasing the Ti content from 1 to 5 at.% degraded the hot corrosion behavior. This decline in the behavior was reflected in high weight gains and large corrosion mound formation during testing (see the figures). However, the addition of 1 to 2 at.% Cr to alloys containing 4 to 5 at.% Ti appeared to greatly reduce the susceptibility of these alloys to hot corrosion attack and negated the deleterious effect of the increased Ti addition.

Nesbitt, James A.↗

NASA NTRS2004

Third-Generation TiAl Alloy Tested: Exhibits Promising Properties for Rotating Components

The Revolutionary Turbine Accelerator/Turbine-Based Combined Cycle (RTA/TBCC) Program for the next-generation launch vehicle has targeted gamma titanium aluminide as a potential compressor and structural material. Because of the high compressor inlet and exit temperatures, the TBCC engine requires higher temperature materials than conventional Ti alloys, and because of its stringent thrust-to-weight requirements, the engine requires low-density material to be utilized wherever possible. Third-generation gamma alloys offer higher temperature capability along with low density and high stiffness. A high-temperature, high-strength *-TiAl alloy with a high Nb-content (Gamma MET PX1) was selected for evaluation. The microstructure and mechanical properties of Gamma Met PX (GMPX) in both the as-extruded and a lamellar heat-treated condition and the influence of the microstructure on the tensile, creep, and fatigue properties were investigated in-house.

Draper, Susan L.↗

NASA NTRS2000

Time-Dependent Reversible-Irreversible Deformation Threshold Determined Explicitly by Experimental Technique

Structural materials for the design of advanced aeropropulsion components are usually subject to loading under elevated temperatures, where a material's viscosity (resistance to flow) is greatly reduced in comparison to its viscosity under low-temperature conditions. As a result, the propensity for the material to exhibit time-dependent deformation is significantly enhanced, even when loading is limited to a quasi-linear stress-strain regime as an effort to avoid permanent (irreversible) nonlinear deformation. An understanding and assessment of such time-dependent effects in the context of combined reversible and irreversible deformation is critical to the development of constitutive models that can accurately predict the general hereditary behavior of material deformation. To this end, researchers at the NASA Glenn Research Center at Lewis Field developed a unique experimental technique that identifies the existence of and explicitly determines a threshold stress k, below which the time-dependent material deformation is wholly reversible, and above which irreversible deformation is incurred. This technique is unique in the sense that it allows, for the first time, an objective, explicit, experimental measurement of k. The underlying concept for the experiment is based on the assumption that the material s time-dependent reversible response is invariable, even in the presence of irreversible deformation.

Castelli, Michael G.↗

NASA NTRS2001

Thermodynamics of Volatile Silicon Hydroxides Studied

Silicon-based ceramics are promising candidate structural materials for heat engines. The long-term stability of these materials to environmental degradation is dependent on the formation and retention of a protective SiO2 layer. It is well known that SiO2 forms stable volatile hydroxides in the presence of water vapor at elevated temperatures. Combustion conditions, which characteristically are at high velocities, contain significant water vapor pressures, and high temperatures tend to promote continuous formation of these hydroxides with resulting material degradation. For the degradation of silicon-based ceramics to be predicted, accurate thermodynamic data on the formation of silicon hydroxides are needed.

Copland, Evan H.↗

NASA NTRS2001

High-Frequency Focused Water-Coupled Ultrasound Used for Three-Dimensional Surface Depression Profiling

To interface with other solids, many surfaces are engineered via methods such as plating, coating, and machining to produce a functional surface ensuring successful end products. In addition, subsurface properties such as hardness, residual stress, deformation, chemical composition, and microstructure are often linked to surface characteristics. Surface topography, therefore, contains the signatures of the surface and possibly links to volumetric properties, and as a result serves as a vital link between surface design, manufacturing, and performance. Hence, surface topography can be used to diagnose, monitor, and control fabrication methods. At the NASA Glenn Research Center, the measurement of surface topography is important in developing high-temperature structural materials and for profiling the surface changes of materials during microgravity combustion experiments. A prior study demonstrated that focused air-coupled ultrasound at 1 MHz could profile surfaces with a 25-m depth resolution and a 400-m lateral resolution over a 1.4-mm depth range. In this work, we address the question of whether higher frequency focused water-coupled ultrasound can improve on these specifications. To this end, we employed 10- and 25-MHz focused ultrasonic transducers in the water-coupled mode. The surface profile results seen in this investigation for 25-MHz water-coupled ultrasound, in comparison to those for 1-MHz air-coupled ultrasound, represent an 8 times improvement in depth resolution (3 vs. 25 m seen in practice), an improvement of at least 2 times in lateral resolution (180 vs. 400 m calculated and observed in practice), and an improvement in vertical depth range of 4 times (calculated).

Roth, Don J.↗

NASA NTRS2006

Active Solid State Dosimetry for Lunar EVA

The primary threat to astronauts from space radiation is high-energy charged particles, such as electrons, protons, alpha and heavier particles, originating from galactic cosmic radiation (GCR), solar particle events (SPEs) and trapped radiation belts in Earth orbit. There is also the added threat of secondary neutrons generated as the space radiation interacts with atmosphere, soil and structural materials.[1] For Lunar exploration missions, the habitats and transfer vehicles are expected to provide shielding from standard background radiation. Unfortunately, the Lunar Extravehicular Activity (EVA) suit is not expected to afford such shielding. Astronauts need to be aware of potentially hazardous conditions in their immediate area on EVA before a health and hardware risk arises. These conditions would include fluctuations of the local radiation field due to changes in the space radiation field and unknown variations in the local surface composition. Should undue exposure occur, knowledge of the dynamic intensity conditions during the exposure will allow more precise diagnostic assessment of the potential health risk to the exposed individual.[2]

Wrbanek, John D.↗

NASA NTRS2003

Integrated design and optimization of microelectronic devices

A genetic algorithm is used for design of infrared filters and in the understanding of the material structure of a resonant tunneling diode.

quantum device heterostructure transports↗

NASA NTRS2006

A Practical Approach to Starting Fission Surface Power Development

The Prometheus Power and Propulsion Program has been reformulated to address NASA needs relative to lunar and Mars exploration. Emphasis has switched from the Jupiter Icy Moons Orbiter (JIMO) flight system development to more generalized technology development addressing Fission Surface Power (FSP) and Nuclear Thermal Propulsion (NTP). Current NASA budget priorities and the deferred mission need date for nuclear systems prohibit a fully funded reactor Flight Development Program. However, a modestly funded Advanced Technology Program can and should be conducted to reduce the risk and cost of future flight systems. A potential roadmap for FSP technology development leading to possible flight applications could include three elements: 1) Conceptual Design Studies, 2) Advanced Component Technology, and 3) Non-Nuclear System Testing. The Conceptual Design Studies would expand on recent NASA and DOE analyses while increasing the depth of study in areas of greatest uncertainty such as reactor integration and human-rated shielding. The Advanced Component Technology element would address the major technology risks through development and testing of reactor fuels, structural materials, primary loop components, shielding, power conversion, heat rejection, and power management and distribution (PMAD). The Non-Nuclear System Testing would provide a modular, technology testbed to investigate and resolve system integration issues.

Mason, Lee S.↗

NASA NTRS1979

An Energy Saver Called NECAP

One of the most comprehensive and most effective programs is NECAP, an acronym for NASA Energy Cost Analysis Program. Developed by Langley Research Center, NECAP operates according to heating/cooling calculation procedures formulated by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE). The program enables examination of a multitude of influences on heat flow into and out of buildings. For example, NECAP considers traditional weather patterns for a given locale and predicts the effects on a particular building design of sun, rain, wind, even shadows from other buildings. It takes into account the mass of structural materials, insulating values, the type of equipment the building will house, equipment operating schedules, heat by people and machinery, heat loss or gain through windows and other openings and a variety of additional details. NECAP ascertains how much energy the building should require ideally, aids selection of the most economical and most efficient energy systems and suggests design and operational measures for reducing the building's energy needs. Most importantly, NECAP determines cost effectiveness- whether an energy-saving measure will pay back its installation cost through monetary savings in energy bills. thrown off

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