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At least 811 records · Page 45

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NASA NTRS2014

Thermal Testing of Planetary Probe TPS in Extreme Entry Environments

High temperature testing of thermal protection system (TPS) materials is a critical aspect of heat-shield materials development, as it determines the suitability and performance envelope of the materials. The present talk provides an overview of recent updates to NASAs IHF and AEDCs H3 high temperature arcjet test facilities that to enable higher heat flux (5000-8000 Wcm2) and high pressure (5-14 atm) testing of TPS. Some recent thermal tests of fully dense carbon phenolic will be discussed in this paper. These new facility upgrades will help improve the TRL level of novel TPS materials and will help qualifycertify heritage TPS material candidates for future missions that are expected to encounter extreme entry conditions, such as entry into Venus or Saturn.

Gasch, M.↗

NASA NTRS2014

Thermal Testing of Thermal Protection System (TPS) Materials

High temperature testing of thermal protection system (TPS) materials is a critical aspect of heat-shield materials development, as it determines the suitability and performance envelope of the materials. The present talk provides an overview of different high temperature test facilities that are available for conducting thermal tests for TPS materials. The facilities include arcjet testing, solar tower testing facilities and laser test facility. The facilities are selected based on the requirements and objectives of the tests and each have their benefits and limitations. The paper also describes the process of determining the test environments based on mission profiles and requirements. Some of the recent thermal tests of TPS materials are discussed in this paper. These tests have helped improve the TRL (Technology Readiness Level) level of novel TPS materials and make them viable TPS material candidates for future missions.

Thermal Protection Materials↗

NASA NTRSDate not supplied

Wire-break Ignition Testing of Materials for Spacesuit Fire Hazard Control

The input design constraints applied to the extravehicular activity (EVA) spacesuit pose a significant challenge for mitigation of fire hazards. To minimize fatigue and increase comfort of the crewmember operating the suit, the suit pressure is lowered below sea level conditions with typical EVA suit designs operating with 4.3 psia (29.7 kPa). With the lowered operating pressures and the use of closed-loop life support, the suit requires elevated concentrations of oxygen, typically >95%. At these oxygen concentrations, nearly the entirety of the suit internal materials are flammable. This leaves one remaining possible control leg of the fire triangle: ignition sources. Since the Gemini and Apollo programs, this has been a risk that has undergone constant reassessment, with a focus on improved mitigation. After the Apollo I fire, an arc ignition method was developed and used to quantify ignition thresholds for in-suit materials resulting in a current limit for powered in-suit devices applied to all subsequent suit designs. After the discovery of a frayed spacesuit biomed cable on STS-113 during the Shuttle Program, the previous arcing method was repeated with additional methods developed to extend the testing further. One of those methods was wire-break ignition testing, in which the current in a single strand of wire was progressively increased, preheating the material in proximity with a resultant break and the application of a reasonably repeatable arc to ignite the material, all while exposed in the selected environment. This method was used to test a suite of spacesuit materials providing relative performance with respect to ignition with this configuration for application of energy. This paper discusses extension of the current data set to address recent material additions, lowering of energy test levels for quantification of materials too low to measure in previous testing, as well as future plans to improve this method.

Colin Campbell↗

NASA NTRS1993

Nonlinear optical thin films

A focused approach to development and evaluation of organic polymer films for use in optoelectronics is presented. The issues and challenges that are addressed include: (1) material synthesis, purification, and the tailoring of the material properties; (2) deposition of uniform thin films by a variety of methods; (3) characterization of material physical properties (thermal, electrical, optical, and electro-optical); and (4) device fabrication and testing. Photonic materials, devices, and systems were identified as critical technology areas by the Department of Commerce and the Department of Defense. This approach offers strong integration of basic material issues through engineering applications by the development of materials that can be exploited as the active unit in a variety of polymeric thin film devices. Improved materials were developed with unprecedented purity and stability. The absorptive properties can be tailored and controlled to provide significant improvement in propagation losses and nonlinear performance. Furthermore, the materials were incorporated into polymers that are highly compatible with fabrication and patterning processes for integrated optical devices and circuits. By simultaneously addressing the issues of materials development and characterization, keeping device design and fabrication in mind, many obstacles were overcome for implementation of these polymeric materials and devices into systems. We intend to considerably improve the upper use temperature, poling stability, and compatibility with silicon based devices. The principal device application that was targeted is a linear electro-optic modulation etalon. Organic polymers need to be properly designed and coupled with existing integrated circuit technology to create new photonic devices for optical communication, image processing, other laser applications such as harmonic generation, and eventually optical computing. The progression from microscopic sample to a suitable film-forming material in a working device is a complex, multifaceted endeavor. It requires close attention to maintaining the optical properties of the electro-optic active portion of the polymer while manipulating the polymer structure to obtain the desired secondary polymer properties.

Leslie, Thomas M.↗

NASA NTRS2018

A Reliability Comparison of Classical and Stochastic Thickness Margin Approaches to Address Material Property Uncertainties for the Orion Heat Shield

The Orion Thermal Protection System (TPS) margin process uses a root-sum-square approach with branches addressing trajectory, aerothermodynamics, and material response uncertainties in ablator thickness design. The material response branch applies a bondline temperature reduction between the Avcoat ablator and EA9394 adhesive by 60 C (108 F) from its peak allowed value of 260 C (500 F). This process is known as the Bond Line Temperature Material Margin (BTMM) and is intended to cover material property and performance uncertainties. The value of 60 C (108 F) is a constant, applied at any spacecraft body location and for any trajectory. By varying only material properties in a random (monte carlo) manner, the perl-based script mcCHAR is used to investigate the confidence interval provided by the BTMM. In particular, this study will look at various locations on the Orion heat shield forebody for a guided and an abort (ballistic) trajectory.

margins↗

NASA NTRS2018

A Reliability Comparison of Classical and Stochastic Thickness Margin Approaches to Address Material Property Uncertainties for the Orion Heat Shield

The Orion Thermal Protection System (TPS) margin process uses a root-sum-square approach with branches addressing trajectory, aerothermodynamics, and material response uncertainties in ablator thickness design. The material response branch applies a bond line temperature reduction between the Avcoat ablator and EA9394 adhesive by 60 C (108 F) from its peak allowed value of 260 C (500 F). This process is known as the Bond Line Temperature Material Margin (BTMM) and is intended to cover material property and performance uncertainties. The value of 60 C (108 F) is a constant, applied at any spacecraft body location and for any trajectory. By varying only material properties in a random (monte carlo) manner, the perl-based script mcCHAR is used to investigate the confidence interval provided by the BTMM. In particular, this study will look at various locations on the Orion heat shield forebody for a guided and an abort (ballistic) trajectory.

FIAT↗

NASA NTRS1999

Materials Science Experiments on the International Space Station

The Performance Goal for NASA's Microgravity Materials Science Program reads "Use microgravity to establish and improve quantitative and predictive relationships between the structure, processing and properties of materials." The advent of the International Space Station will open up a new era in Materials Science Research including the ability to perform long term and frequent experiments in microgravity. As indicated the objective is to gain a greater understanding of issues of materials science in an environment in which the force of gravity can be effectively switched off. Thus gravity related issues of convection, buoyancy and hydrostatic forces can be reduced and the science behind the structure/processing/properties relationship can more easily be understood. The specific areas of research covered within the program are (1) the study of Nucleation and Metastable States, (2) Prediction and Control of Microstructure (including pattern formation and morphological stability), (3) Phase Separation and Interfacial Stability, (4) Transport Phenomena (including process modeling and thermophysical properties measurement), and (5) Crystal Growth, and Defect Generation and Control. All classes of materials, including metals and alloys, glasses and ceramics, polymers, electronic materials (including organic and inorganic single crystals), aerogels and nanostructures, are included in these areas. The principal experimental equipment available to the materials scientist on the International Space Station (ISS) will be the Materials Science Research Facility (MSRF). Each of these systems will be accommodated in a single ISS rack, which can operate autonomously, will accommodate telescience operations, and will provide real time data to the ground. Eventual plans call for three MSRF racks, the first of which will be shared with the European Space Agency (ESA). Under international agreements, ESA and other partners will provide some of the equipment, while NASA covers launch and integration costs. The MSRF facilities will include modular components, which can be exchanged to provide inserts specifically matched to the engineering requirements of the particular Principal Investigator. To defray costs and avoid duplication of engineering effort NASA is also pursuing the possibility of using facilities provided by international partners. By this means it is anticipated that all of the types of research outlined in the previous paragraph can be done on the ISS.

Gillies, Donald C.↗

NASA NTRSDate not supplied

Voxel Based Three-Dimensional Topology Optimization of Heat Exchanger Fins

Increasing interest in novel aircraft propulsion systems and potential for unwanted heat generation, or capture and reuse of waste heat, may require increasingly lightweight and high performing heat exchangers. Advances in manufacturing technologies have shown potential to create complex designs, but design tools need more flexibility. This study utilizes genetic algorithm-driven topology optimization to develop high performance heat exchanger fins for critical applications such as aerospace. The solid domain is generated using voxel representation where a voxel value of 1 indicates the solid domain and a voxel value of 0 refers to the fluid domain. The use of voxel representation somewhat matches the digitization of a model that is required to fabricate using additive manufacturing, and also allows for a highly unconstrained geometry. To test the topology optimization approach, a three-dimensional(3D)baseline offset strip fin geometry in steady laminar flow(Reynolds number = 215)with conjugate heat transfer(simultaneous solution of solid and fluid temperature fields)is optimized. New designs are generated using the genetic algorithm (GA) and sent to evaluation by the CFD software OpenFOAM; then the GA sorts and selects the reproduction pool for the following generation. This process is repeated for 60 generations. The study also investigates the effect off in material on the performance of the GA and the resulting designs. The results show that the optimal designs have overall performance improvement of 18% relative to the baseline. Additionally, a fin constructed of a lower conductivity material (such as an Inconel super alloy that might be necessary for waste heat recovery applications)results in lower overall performance improvement (11%)and optimal designs with higher pressure drop relative to their baseline, and relative to optimal designs produced using higher conductivity materials.

3D Optimization↗

NASA NTRS2005

Performance of a Light-Weight Ablative Thermal Protection Material for the Stardust Mission Sample Return Capsule

New tests and analyses are reported that were carried out to resolve testing uncertainties in the original development and qualification of a lightweight ablative material used for the Stardust spacecraft forebody heat shield. These additional arcjet tests and analyses confirmed the ablative and thermal performance of low density Phenolic Impregnated Carbon Ablator (PICA) material used for the Stardust design. Testing was done under conditions that simulate the peak convective heating conditions (1200 W/cm2 and 0.5 atm) expected during Earth entry of the Stardust Sample Return Capsule. Test data and predictions from an ablative material response computer code for the in-depth temperatures were compared to guide iterative adjustment of material thermophysical properties used in the code so that the measured and predicted temperatures agreed. The PICA recession rates and maximum internal temperatures were satisfactorily predicted by the computer code with the revised properties. Predicted recession rates were also in acceptable agreement with measured rates for heating conditions 37% greater than the nominal peak heating rate of 1200 W/sq cm. The measured in-depth temperature response data show consistent temperature rise deviations that may be caused by an undocumented endothermic process within the PICA material that is not accurately modeled by the computer code. Predictions of the Stardust heat shield performance based on the present evaluation provide evidence that the maximum adhesive bondline temperature will be much lower than the maximum allowable of 250 C and an earlier design prediction. The re-evaluation also suggests that even with a 25 percent increase in peak heating rates, the total recession of the heat shield would be a small fraction of the as-designed thickness. These results give confidence in the Stardust heat shield design and confirm the potential of PICA material for use in new planetary probe and sample return applications.

Covington, M. A.↗

NASA NTRS1993

An overview of the Evaluation of Oxygen Interaction with Materials-third phase (EOIM-3) experiment: Space Shuttle Mission 46

The interaction of the atomic oxygen (AO) component of the low earth orbit (LEO) environment with spacecraft materials has been the subject of several flight experiments over the past 11 years. The effect of AO interactions with materials has been shown to be significant for long-lived spacecraft such as Space Station Freedom and has resulted in materials changes for externally exposed surfaces. The data obtained from previous flight experiments, augmented by limited ground-based evaluation, have been used to evaluate hardware performance and select materials. Questions pertaining to the accuracy of this data base remain, resulting from the use of long-term ambient density models to estimate the O-atom fluxes and fluences needed to calculate materials reactivity in short-term flight experiments. The EOIM-3 flight experiment was designed to produce benchmark AO reactivity data and was carried out during STS-46. Ambient density measurements were made with a quadrupole mass spectrometer which was calibrated for AO measurements in a unique ground-based test facility. The combination of these data with the predictions of ambient density models allows an assessment of the accuracy of measured reaction rates on a wide variety of materials, many of which had never been tested in LEO before. The mass spectrometer is also used to obtain a better definition of the local neutral and plasma environments resulting from interaction of the ambient atmosphere with various spacecraft surfaces. In addition, the EOIM-3 experiment was designed to produce information on the effects of temperature, mechanical stress, and solar exposure on the AO reactivity of a wide range of materials. An overview of the EOIM-3 methods and results are presented.

Leger, Lubert J.↗

NASA NTRS1996

Novel Composites for Wing and Fuselage Applications: Novel Wing Design Concepts - Task 1

Design trade studies were conducted to arrive at advanced wing designs that integrated new material forms with innovative structural concepts and cost-effective fabrication methods. A representative spar was selected for design, fabrication, and test to validate the predicted performance. Textile processes, such as knitting, weaving and stitching, were used to produce fiber preforms that were later fabricated into composite span through epoxy Resin Transfer Molding (RTM), Resin Film Infusion (RFI), and consolidation of commingled thermoplastic and graphite tows. The target design ultimate strain level for these innovative structural design concepts was 6000 mu in. per in. The spars were subjected to four-point beam bending to validate their structural performance. The various material form /processing combination Y-spars were rated for their structural efficiency and acquisition cost. The acquisition cost elements were material, tooling, and labor.

Suarez, J. A.↗

NASA NTRSDate not supplied

Developments on Reusable TPS Materials Based Upon Shuttle Tile

The insulating tiles used on the Space Shuttler Orbiter, principally AETB (Alumina Enhanced Thermal Barrier), have been seen by new vehicle developers in the aerospace industry as a fast-track approach for fielding a reusable thermal protection system (TPS) given the extensive use by both the Orbiter program and the current Orion vehicle. NASA has, and is, supporting the industry through technology transfer and commercial crew and payloads programs. However, the reusable TPS community is rapidly encountering challenges rooted in Orbiter’s and Orion’s dependence on legacy material and processes. With the aim of alleviating these issues, improving availability of reusable TPS, and strengthening the nation’s space economy, ongoing efforts at NASA Ames have focused on understanding process-property relationships in AETB as well as novel materials and technologies for reusable TPS. The first portion of this talk will address the effects of raw materials and processing conditions on the properties of AETB-8, including the raw materials used, mixing and casting parameters, and thermal history. Understanding these relationships, and how they extend to aerothermal performance, is instrumental in alleviating supply chain constraints and improving manufacturability. The implications of these finding on development of novel TPS materials and systems will be discussed. AETB will likely continue to fill a niche of relatively high performance with associated costs. There exists, therefore, a gap in developed reusable TPS for a lower cost, moderate performing material system. The later portion of this talk will touch on current development efforts at Ames focusing on reduced cost and ease of integration, which are being pursued in addition to AETB and higher performing systems. In addition to summarizing these efforts, an outlook for these projects and collaborations will be given.

Peter Edward Marshall↗

NASA NTRSDate not supplied

Developments on Reusable TPS Materials Based Upon Shuttle Tile

Thermal Protection Systems↗

NASA NTRSDate not supplied

3D Woven Mid-Density Carbon Phenolic (3MDCP) Thermal Protection System Development

3-Dimensionally Woven, Mid-Density, Carbon Phenolic (3MDCP) Thermal Protection System (TPS) material is derived from the dual layer 3D woven Heatshield for Extreme Entry Environment Technology (HEEET) material. The baseline 3MDCP design is a single piece thermal protection system that avoids the manufacturing and certification challenges associated with a tiled configuration. 3MDCP is targeted for very aggressive entry environments such as high-speed sample return missions to Earth and missions to Saturn, Venus and the ice giants. A 3MDCP heatshield begins as a flat woven preform that is formed to a given heatshield shape and then infused with phenolic resin. NASA Ames, in collaboration with TEAM Inc. (weaving) and Fiber Materials Inc. (both Spirit AeroSystems Companies) have been developing and demonstrating the manufacturing processes to fabricate a 3MDCP heatshield at a diameter of 1.25 meters. The process of forming the flat woven preform into the final heatshield shape, a sphere-cone geometry, involves local movement of the yarns in the weave. This results in a single piece heatshield with continuous fibers, albeit with property variations between different regions on the heatshield. This presentation will provide a high-level status of 3MDCP development. This will include an overview of the manufacturing processes, with an emphasis on the impact of forming on fiber orientation, material properties and performance. The presentation will layout the plan for testing to assess the impact of forming on properties and review preliminary data comparing properties of flat to formed materials.

Thermal Protection System↗

NASA NTRS2017

Arc Jet Test and Analysis of Asbestos Free Solid Rocket Motor Nozzle Dome Ablative Materials

Asbestos free solid motor internal insulation samples were recently tested at the MSFC Hyperthermal Arc Jet Facility. Objectives of the test were to gather data for solid rocket motor analog characterization of ablative and in-depth thermal performance of rubber materials subject to high enthalpy/pressure flow conditions. Tests were conducted over a range of convective heat fluxes for both inert and chemically reactive sub-sonic free stream gas flow. Active instrumentation included use of total calorimeters, in-depth thermocouples, and a surface pyrometer for in-situ surface temperature measurement. Post-test sample forensics involved determination of eroded depth, charred depth, total sample weight loss, and documentation of the general condition of the eroded profile. A complete Charring Material Ablator (CMA) style aero thermal analysis was conducted for the test matrix and results compared to the measured data. In general, comparisons were possible for a number of the cases and the results show a limited predictive ability to model accurately both the ablative response and the in-depth temperature profiles. Lessons learned and modeling recommendations are made regarding future testing and modeling improvements that will increase understanding of the basic chemistry/physics associated with the complicated material ablation process of rubber materials.

Clayton, J. Louie↗

NASA NTRS2017

Simulated Space Environmental Effects on Thin Film Solar Array Components

The Lightweight Integrated Solar Array and Transceiver (LISA-T) experiment consists of thin-film, low mass, low volume solar panels. Given the variety of thin solar cells and cover materials and the lack of environmental protection afforded by typical thick coverglasses, a series of tests were conducted in Marshall Space Flight Center's Space Environmental Effects Facility to evaluate the performance of these materials. Candidate thin polymeric films and nitinol wires used for deployment were also exposed. Simulated space environment exposures were selected based on SSP 30425 rev. B, "Space Station Program Natural Environment Definition for Design" or AIAA Standard S-111A-2014, "Qualification and Quality Requirements for Space Solar Cells." One set of candidate materials were exposed to 5 eV atomic oxygen and concurrent vacuum ultraviolet (VUV) radiation for low Earth orbit simulation. A second set of materials were exposed to 1 MeV electrons. A third set of samples were exposed to 50, 500, and 750 keV energy protons, and a fourth set were exposed to >2,000 hours of ultraviolet radiation. A final set was rapidly thermal cycled between -50 and +120 C. This test series provides data on enhanced power generation, particularly for small satellites with reduced mass and volume resources. Performance versus mass and cost per Watt is discussed.

Finckenor, Miria↗

NASA NTRS2017

Simulated Space Environmental Effects on Thin Film Solar Array Components

The Lightweight Integrated Solar Array and Transceiver (LISA-T) experiment consists of thin-film, low mass, low volume solar panels. Given the variety of thin solar cells and cover materials and the lack of environmental protection typically afforded by thick coverglasses, a series of tests were conducted in Marshall Space Flight Center's Space Environmental Effects Facility to evaluate the performance of these materials. Candidate thin polymeric films and nitinol wires used for deployment were also exposed. Simulated space environment exposures were selected based on SSP 30425 rev. B, "Space Station Program Natural Environment Definition for Design" or AIAA Standard S-111A-2014, "Qualification and Quality Requirements for Space Solar Cells." One set of candidate materials were exposed to 5 eV atomic oxygen and concurrent vacuum ultraviolet (VUV) radiation for low Earth orbit simulation. A second set of materials were exposed to 1 MeV electrons. A third set of samples were exposed to 50, 100, 500, and 700 keV energy protons, and a fourth set were exposed to >2,000 hours of near ultraviolet (NUV) radiation. A final set was rapidly thermal cycled between -55 and +125 C. This test series provides data on enhanced power generation, particularly for small satellites with reduced mass and volume resources. Performance versus mass and cost per Watt is discussed.

Finckenor, Miria↗

NASA NTRS2017

Simulated Space Environmental Effects on Thin Film Solar Array Components

The Lightweight Integrated Solar Array and Transceiver (LISA-T) experiment consists of thin-film, low mass, low volume solar panels. Given the variety of thin solar cells and cover materials and the lack of environmental protection typically afforded by thick coverglasses, a series of tests were conducted in Marshall Space Flight Center's Space Environmental Effects Facility to evaluate the performance of these materials. Candidate thin polymeric films and nitinol wires used for deployment were also exposed. Simulated space environment exposures were selected based on SSP 30425 rev. B, "Space Station Program Natural Environment Definition for Design" or AIAA Standard S-111A-2014, "Qualification and Quality Requirements for Space Solar Cells." One set of candidate materials were exposed to 5 eV atomic oxygen and concurrent vacuum ultraviolet (VUV) radiation for low Earth orbit simulation. A second set of materials were exposed to 1 MeV electrons. A third set of samples were exposed to 50, 100, 500, and 700 keV energy protons, and a fourth set were exposed to >2,000 hours of near ultraviolet (NUV) radiation. A final set was rapidly thermal cycled between -55 and +125degC. This test series provides data on enhanced power generation, particularly for small satellites with reduced mass and volume resources. Performance versus mass and cost per Watt is discussed.

Finckenor, Miria↗