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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1939

The Pack Method for Compressive Tests of Thin Specimens of Materials Used in Thin-Wall Structures

The strength of modern lightweight thin-wall structures is generally limited by the strength of the compression members. An adequate design of these members requires a knowledge of the compressive stress-strain graph of the thin-wall material. The "pack" method was developed at the National Bureau of Standards with the support of the National Advisory Committee for Aeronautics to make possible a determination of compressive stress-strain graphs for such material. In the pack test an odd number of specimens are assembled into a relatively stable pack, like a "pack of cards." Additional lateral stability is obtained from lateral supports between the external sheet faces of the pack and outside reactions. The tests seems adequate for many problems in structural research.

Aitchison, C S↗
NASA NTRS1985

Derivation and test of elevated temperature thermal-stress-free fastener concept

Future aerospace vehicles must withstand high temperatures and be able to function over a wide temperature range. New composite materials are being developed for use in designing high-temperature lightweight structures. Due to the difference between coefficients of thermal expansion for the new composite materials and conventional high-temperature metallic fasteners, innovative joining techniques are needed to produce tight joints at all temperatures without excessive thermal stresses. A thermal-stress-free fastening technique is presented that can be used to provide structurally tight joints at all temperatures even when the fastener and joined materials have different coefficients of thermal expansion. The derivation of thermal-stress-free fasteners and joint shapes is presented for a wide variety of fastener materials and materials being joined together. Approximations to the thermal-stress-free shapes that result in joints with low-thermal-stresses and that simplify the fastener/joint shape are discussed. The low-thermal-stress fastener concept is verified by thermal and shear tests in joints using oxide-dispersion-strengthened alloy fasteners in carbon-carbon material. The test results show no evidence of thermal stress damage for temperatures up to 2000 F and the resulting joints carried shear loads at room temperature typical of those for conventional joints.

Sawyer, J. W.↗
NASA NTRS2019

Ablators - From Apollo to Future Missions to Moon, Mars and Beyond

Apollo was designed to carry astronauts safely back from the Moon at return speeds exceeding 11 km/s and requireddevelopment of a new ablative thermal protection system (TPS) to protect the capsule from entry heating. Mercuryand Gemini, that preceded Apollo, were focused on Earth orbiting system demonstration and lessons learned fromthem were used in Apollo. The ablative material and associated system development for Lunar return conditionsrequired considerable ground and flight testing. Mars Viking Lander missions required a new lighter weight ablatoras entry heating was benign compared to Apollo. Pioneer-Venus and Galileo Probe missions required a new and morecapable ablator than Apollo. After two decades, Mars Pathfinder followed by Mars Exploration Rover missions,smaller than Viking but more demanding, were able to use Viking ablative TPS. At the same time, advances in manufacturing and materials technology led to development of innovative lightweight ablators. These new ablators enabled Stardust and Genesis Sample Return Missions. Around the turn of this century, NASA decided on a scaled-upversion of the Apollo capsule for human exploration of Moon and Mars and the ablative heat shield to protect the CrewExploration Vehicle ended up being the Apollo ablative TPS. The Artemis 1 mission is currently fitted with tiledsystem, different than Orion EFT-1 but with the Apollo ablative material as a result of lessons learned. NASA iscurrently planning on sample return missions from Mars, and this will require robust ablative TPS that can providehigher reliability than any other past mission. There are still unexplored high scientific value destinations in the solarsystem. In situ exploration of Uranus, Neptune, Saturn and sample return missions with return speed much higher thanStardust will require ablators capable of withstanding extreme entry that are also efficient. New ablative TPS havebeen developed in anticipation of these future missions. This paper is intended to tell the story of these ablators,illustrated through examples. We see the use of flight proven ablators was sometimes a risky proposition and newablators perceived to be higher risk have proved otherwise. The history of ablators illustrates the challenges eachmission had to address, either through the use of flight proven or new ablative TPS, to be successful.

Venkatapathy, Ethiraj↗
NASA NTRSDate not supplied

Structures and Materials Research at NASA Langley Research Center

NASA explores the unknown in air and space, innovates for the benefit of humanity, and inspires the world through discovery. The Structures and Materials discipline at NASA Langley Research Center supports this mission through advanced materials and manufacturing approaches applied to innovative structural concepts. We start with synthesizing novel material systems and applying tools and methods to predict and validate their static, dynamic, durability and damage tolerance behavior. We mature materials from test tube to test flight by developing manufacturing techniques that enable the advancement of aerospace structures from concept to reality. We develop advanced measurement techniques for health management and nondestructive evaluation. We draw on our structures and materials core capabilities to enable safe, reliable lightweight aerospace structures for application in all environments. You will find the results of our work in the assembly of large structures in space and on other planets, vehicles that carry crew into space, vehicles that operate at high speeds and in extreme environments, and technology for passenger and crew safety in commercial aviation. This presentation will provide an overview of Langley Research Center’s role within the agency, then focus on how current Structures and Materials research areas support a variety of NASA missions in space operations, exploration, and aeronautics.

Structures↗
NASA NTRS2004

Lightweight, Rack-Mountable Composite Cold Plate/Shelves

Rack-mountable composite-material structural components that would serve as both shelves and cold plates for removing heat from electronic or other equipment mounted on the shelves have been proposed as lightweight alternatives to all-metal cold plate/shelves now in use. A proposed cold plate/shelf would include a highly thermally conductive face sheet containing oriented graphite fibers bonded to an aluminum honeycomb core, plus an extruded stainless-steel substructure containing optimized flow passages for a cooling fluid, and an inlet and outlet that could be connected to standard manifold sections. To maximize heat-transfer efficiency, the extruded stainless-steel substructure would be connected directly to the face sheet. On the basis of a tentative design, the proposed composite cold plate/shelf would weigh about 38 percent less than does an all-aluminum cold plate in use or planned for use in some spacecraft and possibly aircraft. Although weight is a primary consideration, the tentative design offers the additional benefit of reduction of thickness to half that of the all-aluminum version.

Hurlbert, Kathryn M.↗
NASA NTRS1991

An overview of the LeRC CSTI thermal management program

This report presents an integrated multielement project effort, currently being carried out at NASA LeRC, for the development of space heat rejection subsystems, with special emphasis on lightweight radiators, in support of SEI power system technology, and in particular the SP-100 program. Principal project elements include both contracted and in-house efforts. Included in the first category are two contracts aimed at the development of advanced radiator concepts, and demonstration of a flexible fabric heat pipe radiator concept. In-house work is designed to guide and support the overall program by system integration studies, heat pipe testing and analytical code development, radiator surface morphology alteration for emissivity enhancement, and composite materials research focused on the development of lightweight high conductivity fins.

Juhasz, Albert J.↗
NASA NTRS1991

An overview of the Lewis Research Center CSTI thermal management program

An integrated multi-element project effort, currently being carried out at NASA LeRC, for the development of space heat rejection subsystems, with special emphasis on lightweight radiators, in support of SEI power system technology, and in particular the SP-100 program, is reported. Principal project elements include both contracted and in-house efforts. Included in the first category are two contracts aimed at the development of advanced radiator concepts, and demonstration of a flexible fabric heat pipe radiator concept. In-house work is designed to guide and support the overall program by system integration studies, heat pipe testing and analytical code development, radiator surface morphology alteration for emissivity enhancement, and composite materials research focused on the development of lightweight high conductivity fins.

Juhasz, Albert J.↗
NASA NTRS2009

Improved Joining of Metal Components to Composite Structures

Systems requirements for complex spacecraft drive design requirements that lead to structures, components, and/or enclosures of a multi-material and multifunctional design. The varying physical properties of aluminum, tungsten, Invar, or other high-grade aerospace metals when utilized in conjunction with lightweight composites multiply system level solutions. These multi-material designs are largely dependent upon effective joining techAn improved method of joining metal components to matrix/fiber composite material structures has been invented. The method is particularly applicable to equipping such thin-wall polymer-matrix composite (PMC) structures as tanks with flanges, ceramic matrix composite (CMC) liners for high heat engine nozzles, and other metallic-to-composite attachments. The method is oriented toward new architectures and distributing mechanical loads as widely as possible in the vicinities of attachment locations to prevent excessive concentrations of stresses that could give rise to delaminations, debonds, leaks, and other failures. The method in its most basic form can be summarized as follows: A metal component is to be joined to a designated attachment area on a composite-material structure. In preparation for joining, the metal component is fabricated to include multiple studs projecting from the aforementioned face. Also in preparation for joining, holes just wide enough to accept the studs are molded into, drilled, or otherwise formed in the corresponding locations in the designated attachment area of the uncured ("wet') composite structure. The metal component is brought together with the uncured composite structure so that the studs become firmly seated in the holes, thereby causing the composite material to become intertwined with the metal component in the joining area. Alternately, it is proposed to utilize other mechanical attachment schemes whereby the uncured composite and metallic parts are joined with "z-direction" fasteners. The resulting "wet" assembly is then subjected to the composite-curing heat treatment, becoming a unitary structure. It should be noted that this new art will require different techniques for CMC s versus PMC's, but the final architecture and companion curing philosophy is the same. For instance, a chemical vapor infiltration (CVI) fabrication technique may require special integration of the pre-form and

Semmes, Edmund↗
NASA NTRS2006

Rapid Fabrication of Lightweight SiC Optics using Reactive Atom Plasma (RAP) Processing

Reactive Atom Plasma (RAP) processing is a non-contact, plasma-based processing technology that can be used to generate damage-free optical surfaces. We have developed tools and processes using RAP that allow us to shape extremely lightweight mirror Surfaces made from extremely hard-to-machine materials (e.g. SiC). We will describe our latest results using RAP in combination with other technologies to produce finished lightweight SiC mirrors and also discuss applications for RAP in the rapid fabrication of mirror segments for reflective and grazing incidence telescopes.

Fiske, Peter S.↗
NASA NTRS2007

Polymer-Layered Silicate Nanocomposites for Cryotank Applications

Previous composite cryotank designs have relied on the use of conventional composite materials to reduce microcracking and permeability. However, revolutionary advances in nanotechnology derived materials may enable the production of ultra-lightweight cryotanks with significantly enhanced durability and damage tolerance, as well as reduced propellant permeability. Layered silicate nanocomposites are especially attractive in cryogenic storage tanks based on results that have been reported for epoxy nanocomposite systems. These materials often exhibit an order of magnitude reduction in gas permeability when compared to the base resin. In addition, polymer-silicate nanocomposites have been shown to yield improved dimensional stability, strength, and toughness. The enhancement in material performance of these systems occurs without property trade-offs which are often observed in conventionally filled polymer composites. Research efforts at NASA Glenn Research Center have led to the development of epoxy-clay nanocomposites with 70% lower hydrogen permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. The pronounced reduction observed with the tank may be due to flow induced alignment of the clay layers during processing. Additionally, the nanocomposites showed CTE reductions of up to 30%, as well as a 100% increase in toughness.

Miller, Sandi G.↗
NASA NTRS2004

Vibration Characteristics Determined for Stainless Steel Sandwich Panels With a Metal Foam Core for Lightweight Fan Blade Design

The goal of this project at the NASA Glenn Research Center is to provide fan materials that are safer, weigh less, and cost less than the currently used titanium alloy or polymer matrix composite fans. The proposed material system is a sandwich fan construction made up of thin solid face sheets and a lightweight metal foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by the foam layer. The resulting structure has a high stiffness and lighter weight in comparison to the solid facesheet material alone. The face sheets carry the applied in-plane and bending loads (ref. 1). The metal foam core must resist the transverse shear and transverse normal loads, as well as keep the facings supported and working as a single unit. Metal foams have ranges of mechanical properties, such as light weight, impact resistance, and vibration suppression (ref. 2), which makes them more suitable for use in lightweight fan structures. Metal foams have been available for decades (refs. 3 and 4), but the difficulties in the original processes and high costs have prevented their widespread use. However, advances in production techniques and cost reduction have created a new interest in this class of materials (ref. 5). The material chosen for the face sheet and the metal foam for this study was the aerospace-grade stainless steel 17-4PH. This steel was chosen because of its attractive mechanical properties and the ease with which it can be made through the powder metallurgy process (ref. 6). The advantages of a metal foam core, in comparison to a typical honeycomb core, are material isotropy and the ease of forming complex geometries, such as fan blades. A section of a 17-4PH sandwich structure is shown in the following photograph. Part of process of designing any blade is to determine the natural frequencies of the particular blade shape. A designer needs to predict the resonance frequencies of a new blade design to properly identify a useful operating range. Operating a blade at or near the resonance frequencies leads to high-cycle fatigue, which ultimately limits the blade's durability and life. So the aim of this study is to determine the variation of the resonance frequencies for an idealized sandwich blade as a function of its face-sheet thickness, core thickness, and foam density. The finite element method is used to determine the natural frequencies for an idealized rectangular sandwich blade. The proven Lanczos method (ref. 7) is used in the study to extract the natural frequency.

Ghosn, Louis J.↗
NASA NTRS2000

Radiation exposure for human Mars exploration

One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human space flight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle events was of great concern. A new challenge appears in deep-space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays since the missions are of long duration, and accumulated exposures can be high. Because cancer induction rates increase behind low to moderate thicknesses of aluminum shielding, according to available biological data on mammalian exposures to galactic cosmic ray-like ions, aluminum shield requirements for a Mars mission may be prohibitively expensive in terms of mission launch costs. Alternative materials for vehicle construction are under investigation to provide lightweight habitat structures with enhanced shielding properties. In the present paper, updated estimates for astronaut exposures on a Mars mission are presented and shielding properties of alternative materials are compared with aluminum.

NASA Center LaRC↗
NASA NTRS1992

Development of a material processing plant for lunar soil

Currently there is considerable interest in developing in-situ materials processing plants for both the Moon and Mars. Two of the most important aspects of developing such a materials processing plant is the overall system design and the integration of the different technologies into a reliable, lightweight, and cost-effective unit. The concept of an autonomous materials processing plant that is capable of producing useful substances from lunar regolith was developed. In order for such a materials processing plant to be considered as a viable option, it must be totally self-contained, able to operate autonomously, cost effective, light weight, and fault tolerant. In order to assess the impact of different technologies on the overall systems design and integration, a one-half scale model was constructed that is capable of scooping up (or digging) lunar soil, transferring the soil to a solar furnace, heating the soil in the furnace to liberate the gasses, and transferring the spent soil to a 'tile' processing center. All aspects of the control system are handled by a 386 class PC via D/A, A/D, and DSP (Digital Signal Processor) control cards.

Goettsch, Ulix↗
NASA NTRS2000

How Will We Keep Warm on the Red Planet?

Among the many challenges that the Mars environment poses for EVA (extravehicular activity) space suit designers, development of an appropriate thermal insulation is one of the most important. The latest in thermal insulation technologies that could be applied or modified for planetary exploration have been reviewed. These include porous and hollow structures, phase change materials, soluble gas elements, as well as vacuum enclosures and fibrous materials. Using current technology, none of these structures offers all of the features needed for Mars exploration, namely lightweight, low bulk, high flexibility, and low thermal insulation. Nonwoven fibrous materials are still the prime design candidates because they are more flexible than other structures while having good resiliency. They are usually safe to use. They are also available in many types of materials, fiber shapes, as well as fabric densities and constructions. However, a recent study conducted at the NASA Johnson Space Center shows clearly that these structures alone are not sufficient to provide effective thermal insulation in the harsh Mars environment. A more promising solution is being developed using aerogel fillers in the nonwoven structures.

Orndoff, Evelyne↗
NASA NTRS2017

Strain Monitoring of Flexible Structures

One of the biggest challenges facing NASA's deep space exploration goals is structural mass. A long duration transit vehicle on a journey to Mars, for example, requires a large internal volume for cargo, supplies and crew support. As with all space structures, a large pressure vessel is not enough. The vehicle also requires thermal, micro-meteoroid, and radiation protection, a navigation and control system, a propulsion system, and a power system, etc. As vehicles get larger, their associated systems also get larger and more complex. These vehicles require larger lift capacities and force the mission to become extremely costly. In order to build large volume habitable vehicles, with only minimal increases in launch volume and mass, NASA is developing lightweight structures. Lightweight structures are made from non-metallic materials including graphite composites and high strength fabrics and could provide similar or better structural capability than metals, but with significant launch volume and mass savings. Fabric structures specifically, have been worked by NASA off and on since its inception, but most notably in the 1990's with the TransHAB program. These TransHAB developed structures use a layered material approach to form a pressure vessel with integrated thermal and micro-meteoroid and orbital debris (MMOD) protection. The flexible fabrics allow the vessel to be packed in a small volume during launch and expand into a much larger volume once in orbit. NASA and Bigelow Aerospace recently installed the first human-rated inflatable module on the International Space Station (ISS), known as the Bigelow Expandable Activity Module (BEAM) in May of 2016. The module provides a similar internal volume to that of an Orbital ATK Cygnus cargo vehicle, but with a 77% launch volume savings. As lightweight structures are developed, testing methods are vital to understanding their behavior and validating analytical models. Common techniques can be applied to fabric materials, such as tensile testing, fatigue testing, and shear testing, but common measurement techniques cannot be used on fabric. Measuring strain in a material and during a test is a critical parameter for an engineer to monitor the structure during the test and correlate to an analytical model. The ability to measure strain in fabric structures is a challenge for NASA. Foil strain gauges, for example, are commonplace on metallic structures testing, but are extremely difficult to interface with a fabric substrate. New strain measuring techniques need to be developed for use with fabric structures. This paper investigates options for measuring strain in fabric structures for both ground testing and in-space structural health monitoring. It evaluates current commercially available options and outlines development work underway to build custom measurement solutions for NASA's fabric structures.

Litteken, Douglas A.↗
NASA NTRS2000

Nonlinearity and Strain-Rate Dependence in the Deformation Response of Polymer Matrix Composites Modeled

There has been no accurate procedure for modeling the high-speed impact of composite materials, but such an analytical capability will be required in designing reliable lightweight engine-containment systems. The majority of the models in use assume a linear elastic material response that does not vary with strain rate. However, for containment systems, polymer matrix composites incorporating ductile polymers are likely to be used. For such a material, the deformation response is likely to be nonlinear and to vary with strain rate. An analytical model has been developed at the NASA Glenn Research Center at Lewis Field that incorporates both of these features. A set of constitutive equations that was originally developed to analyze the viscoplastic deformation of metals (Ramaswamy-Stouffer equations) was modified to simulate the nonlinear, rate-dependent deformation of polymers. Specifically, the effects of hydrostatic stresses on the inelastic response, which can be significant in polymers, were accounted for by a modification of the definition of the effective stress. The constitutive equations were then incorporated into a composite micromechanics model based on the mechanics of materials theory. This theory predicts the deformation response of a composite material from the properties and behavior of the individual constituents. In this manner, the nonlinear, rate-dependent deformation response of a polymer matrix composite can be predicted.

Goldberg, Robert K.↗
NASA NTRS2016

Tribological Studies of Dynamic Thermal Seal Materials

Thermal seals are required on high-speed vehicles in many dynamic applications such as variable inlets in propulsion systems and control surfaces. These seals, often referred to as dynamic thermal seals, must not only mitigate inboard heat transfer, but must also exhibit sufficient durability when scrubbed against mating surfaces. For high-temperature high-speed vehicle applications, the mating surfaces are often made from thermal protection system (TPS) materials, which are typically rougher and more abrasive than TPS materials used at lower temperatures. The high-temperature TPS materials used can include non-ablative (e.g., lightweight porous oxides, ceramic matrix composites) andor ablative systems (e.g., phenolic systems). Due to the increased need for durable high-temperature dynamic seals, researchers working with the NASA Glenn Research Center embarked on an effort to (a) characterize the tribological performance of state-of-the-art thermal seal materials against a variety of TPS materials and (b) develop approaches for improved wear resistance. Tests were conducted using a recently upgraded high-temperature tribometer to assess wear resistance for a variety of tribopairs under multiple conditions. This data will begin to frame the challenges of using these materials and eventually permit an improved ability to design and implement these critical TPS components.

thermal protection↗