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NASA NTRS2017

Micrometeoroid and Orbital Debris Risk Assessment With Bumper 3

The Bumper 3 computer code is the primary tool used by NASA for micrometeoroid and orbital debris (MMOD) risk analysis. Bumper 3 (and its predecessors) have been used to analyze a variety of manned and unmanned spacecraft. The code uses NASA's latest micrometeoroid (MEM-R2) and orbital debris (ORDEM 3.0) environment definition models and is updated frequently with ballistic limit equations that describe the hypervelocity impact performance of spacecraft materials. The Bumper 3 program uses these inputs along with a finite element representation of spacecraft geometry to provide a deterministic calculation of the expected number of failures. The Bumper 3 software is configuration controlled by the NASA/JSC Hypervelocity Impact Technology (HVIT) Group. This paper will demonstrate MMOD risk assessment techniques with Bumper 3 used by NASA's HVIT Group. The Permanent Multipurpose Module (PMM) was added to the International Space Station in 2011. A Bumper 3 MMOD risk assessment of this module will show techniques used to create the input model and assign the property IDs. The methodology used to optimize the MMOD shielding for minimum mass while still meeting structural penetration requirements will also be demonstrated.

Hyde, J.↗

NASA NTRS2016

ASTM Committee C28: International Standards for Properties and Performance of Advanced Ceramics, Three Decades of High-quality, Technically-rigorous Normalization

Physical and mechanical properties and performance of advanced ceramics and glasses are difficult to measure correctly without the proper techniques. For over three decades, ASTM Committee C28 on Advanced Ceramics, has developed high quality, rigorous, full-consensus standards (e.g., test methods, practices, guides, terminology) to measure properties and performance of monolithic and composite ceramics that may be applied to glasses in some cases. These standards testing particulars for many mechanical, physical, thermal, properties and performance of these materials. As a result these standards provide accurate, reliable, repeatable and complete data. Within Committee C28 users, producers, researchers, designers, academicians, etc. have written, continually updated, and validated through round-robin test programs, nearly 50 standards since the Committees founding in 1986. This paper provides a retrospective review of the 30 years of ASTM Committee C28 including a graphical pictogram listing of C28 standards along with examples of the tangible benefits of advanced ceramics standards to demonstrate their practical applications.

properties↗

NASA NTRS2018

Mars Sample Return: Grand Challenge for EDL

A year ago, I gave a talk in anticipation of a Mars Sample Return effort at the 9th Ablation Workshop. Since then a lot has happened. "April of this year, after a year of study phase, NASA and ESA (European Space Agency) signed a Statement of Intent (SOI) to jointly develop a Mars Sample Return plan to be submitted to their respective authorities by the end of 2019. This signing is historic, as it signals the desire, the readiness, and the willingness to work together to execute this inspiring mission, we all have the opportunity to tackle this grand challenge. We have the scientific and engineering maturity to identify the critical technologies ready to be applied, and with discipline this campaign can be executed affordably," Jim Watzin, Mars Program Executive, NASA. NASA Centers with JPL (Jet Propulsion Laboratory) leading the charge is in the midst of a pre-formulation phase for executing a Mars Sample Return before the end of next decade. The proposed talk builds on the previous year talk. In light of the agreement between NASA and ESA, NASA has assumed the responsibilities for developing the earth entry vehicle (EEV) that will fly along with a European Spacecraft and return with the sample from Mars. EEV will be deployed for entry into earth. The EEV design, development, testing and certification have to result in a highly reliable sample return system. The entire architecture has to be demonstrated to meet the planetary protection requirement. NASA is considering two distinctly different earth entry vehicle architectures and with each choice, many different ablative TPS (Thermal Protective Shield) candidates. As a result of the NASA-ESA ongoing studies, some of the key entry conditions and design requirements are better understood today and more are being scoped out. The heat-shield ablative TPS choice need to be done with a good understanding as it plays a very significant role in determining the robustness of the EEV. Knowledge about how materials and system perform, and how the features could become flaws and how flaws lead to failure, etc. need to be clearly understood and the knowledge then need to be used to down select the TPS. This proposed talk will provide greater insight into the progress being made and the challenges that need to be tackled.

Mars Sample Return: Grand Challenge for EDL↗

NASA NTRS2017

Environmental Testbed Development to Evaluate Power Distribution Materials in Electrified Aircraft (EA)

NASA is pursuing the development of electrified propulsion (EP) technologies to improve air transportation in terms of efficiency, affordability, and sustainability. The power requirements are expected to reach 20 megawatts for large EP commercial airliners. A key challenge is transmission and distribution of the high voltage (20 kilovolts) needed for some EP systems. This is a challenge because the risk of electrical failure in aircraft at high altitude (low pressure) due to corona discharge and other forms of partial discharge increases significantly when voltages exceed 327 V. Corona discharge is a form of partial discharge in which gaseous molecules are ionized by strong electric fields. Corona discharge leads to aging in power transmission lines. Aging is a leading cause of electrical failure in electrical insulation materials. In particular, aging from electrical, vibrational, and thermal stresses decrease the performance life of insulation materials. There are currently no test standards or equipment that can effectively age materials under high altitude, voltage and frequency conditions. This poster proposes a design for a test system including an environmental chamber that can simulate the environment of future EP systems for material and component aging tests.

Materials Test chamber Design↗

NASA NTRS2018

Orion EM-2 TPS Radiometer & Spectrometer

Radiometers and Spectrometers embedded as flight instrumentation in a spacecraft's thermal protection system (TPS) can generate data on shock layer radiation to a spacecraft's surface for high-speed trajectories such as lunar return. Robust and accurate flight measurements of shock layer radiation can validate models and inform TPS selection and sizing, to reduce risk and TPS launch mass. Contamination from soot deposition and ablation products in the boundary layer condensing on a cold sapphire radiometer window or blocking open ports interferes with measurements. This poster describes characterization of the optical properties and performance of relevant materials, components, and contaminated windows, as well as investigation of contamination control strategies for the optics.

Ablation↗

NASA NTRSDate not supplied

Progressive Damage Failure Analysis of a Multi-Stringer Post-Buckled Panel

Validation of a progressive damage finite element analysis model using the CompDam material model was performed on a large multi-stringer panel subjected to compressive loading. The panel had a Teflon insert embedded between the skin panel and stiffener to cause an ultimate failure mode of stiffener separation. The compressive loading of the panel caused the skin between the stiffeners to locally buckle before any damage began to occur. The post-buckled behavior of the panel was the driving mechanism to the onset of damage and the damage growth that led to skin-stiffener separation. An integrated global-local modeling approach was used to validate several aspects the overall behavior of the panel from start to failure. The global region captured the pre-buckled stiffness of the test panel within 10% and the buckling load of the skin panel at the critical location within 2%. The skin’s five half-wave buckled mode shape was accurately predicted by the model. The integrated local model captured the load corresponding to the onset of damage within 5% of the average test data. Comparisons are made for key aspects of the damage morphology, such as a growth pattern that included a significant matrix split in the first ply of the skin and a migration of the delamination from the skin-stiffener interface to the skin’sply1-ply2 interface. The ultimate failure mode was shown to be an unstable growth of delamination damage under the stiffeners which led to a peak load of the analysis that was approximately 5% above the average peak load of the testing. The validated global-local modeling approach used on the multi-stringer post-buckled panel with a Teflon insert used a methodology and lessons learned using smaller specimens applied to a subcomponent that captured several aspects of a modern aircraft design.

Jason Action↗

NASA NTRSDate not supplied

Automatic Dependent Surveillance-Broadcast (ADS-B) In-Trail Procedures (ITP)

Aircraft in oceanic and remote non-radar airspace frequently fly for extended periods of time in the same direction, at the same time, along similar flight paths as other aircraft. Since there is no radar surveillance, controllers use procedural separation to ensure that aircraft remain separated. Procedural separation distances are typically larger than radar separation distances and as a result aircraft operating in oceanic airspace are sometimes held at non-optimal flight levels due to conflicting traffic at intervening flight levels. Automatic Dependent Surveillance-Broadcast (ADS-B) In-Trail Procedures (ITP) were developed to enable flight level change maneuvers that would otherwise not be possible with current procedural separation standards. Aircraft operators choosing to equip with an ADS-B transceiver and an appropriate onboard decision support system would be able to take advantage of these procedures when operating in proximity to aircraft equipped with a suitable ADS-B transmitter (“ADS-B Out”). The ability to perform in-trail maneuvers to achieve more time at optimum altitudes could result in more efficient and predictable flight profiles thereby saving fuel and in some cases allowing operators to make beneficial operational decisions. NASA first began developing ADS-B ITP in 2003 as a result of a desire to develop methodologies, concepts, and procedures to reduce separation requirements for future air transportation systems using airborne ADS-B. The objectives were to provide insight into the details necessary to reduce separation requirements for the future and to develop applications that could provide incentives for operators to voluntarily equip with transformational technologies. From 2003 to 2008, NASA conducted research that supported the development of ITP including batch simulations, human-in-the-loop experiments and avionics and separation standards development. This research showed enough maturity and benefit that in 2008, the FAA Surveillance and Broadcast Services (SBS) program adopted ADS-B ITP as one of their three key, near-term applications to make use of ADS-B-In. The FAA developed an agreement with NASA to transition the technology and established an FAA project for the purpose of performing an operational trial of ADS-B ITP in revenue service in the summer of 2011. The objectives of the project are to a) validate the operational performance and economic benefits of ITP; and b) develop and validate ADS-B ITP Minimum Operational Performance Specifications (MOPS) material. As a part of this project, the FAA established agreements with United Airlines and Honeywell. The agreements include the work necessary for the development, certification and installation of onboard systems for twelve United Airlines 747-400s. ITP system development is nearly complete and certification activities are underway. The FAA project has also been working with Oakland Oceanic Control Center (ZOA) and the FAA’s Oceanic and Offshore Operations Office to develop controller procedures and safety analyses that are required to support the flight trial. The FAA has also been working on the development of an ITP Operational Specification that should be approved this April. The presentation will cover some of the key aspects of the development, challenges, and integration required to successfully transition ADS-B ITP from a concept in 2003 to flight trials in revenue service in 2011.

Kenneth M Jones↗

NASA NTRS1999

A New High Efficiency Segmented Thermoelectric Unicouple

To achieve high thermal-to-electric energy conversion efficiency, it is desirable to operate thermoelectric geneteor devices over large temperature gradients and also to maximize the thermoelectric performance of the materials used to build the devices.

Energy↗

NASA NTRSDate not supplied

Power Cable Mass Estimation for Electric Aircraft Propulsion

Electric aircraft propulsion relies on power transmission cables to carry energy through the vehicle's electrical power train. The mass of these cables is an important consideration in overall aircraft weight, and hence cable design methods that can offer lower weight cables offer a significant opportunity.This paper compares three strategies for cable design: selection of cables from off-the-shelf options, design based on steady-state thermal limits, and design based on transient thermal limits. The thermal models consider both conductor diameter and insulation thickness, as well as a comparison between multiple conductor materials. The thermal analysis evaluates the transfer of waste heat from the conductor to the insulation and from the insulation to the air via convection. Optimizations to minimize cable mass by changing conductor radius and material properties were performed using all three modeling approaches and the results show that both custom sized cables using both steady-state and transient based model offer potential mass savings.

Electrical↗

NASA NTRSDate not supplied

Progressive Damage Failure Analysis of Post-Buckled Composite Single-Stringer Panel with Teflon Inserts

The high strength-to-weight and stiffness-to-weight ratio materials, such as laminated composites, are advantageous for modern aircraft. Laminated composites with initial flaws are susceptible to delamination under buckling loads. PDA tools help enhance the industry’s understanding of the mechanisms for damage initiation and growth in composite structures while assisting in the design, analysis, and sustainment methods of these composite structures. The global-local modeling approach for the single-stringer post-buckled panel was evaluated through this effort, using Teflon inserts to simulate the defect of damage during manufacturing. This understanding is essential for designing the post-buckled structure, reducing weight while predicting damage initiation location, and addressing a potential design review for future aircraft repairs. In this work, the initial damage was captured with Teflon inserts as the starting configuration; and any reference to the damage initiation refers to any damage beyond the “initial unbonded region.” The effort aims to develop, evaluate, and enhance methods to predict damage initiation and progression and the failure of post-buckled hat-stiffened panels using multiple Abaqus FEA Virtual Crack Closure Technique (VCCT) definitions. Validation of the PDA using the VCCT material model was performed on a large single-stringer panel subjected to compressive loading. The compressive loading of the panel caused the skin to buckle before any damage began to occur locally. In addition, comparisons are made for critical aspects of the damage morphology, such as a growth pattern that included delamination from the skin-stiffener interface to the skin and ply interfaces. When compared against the experimental data produced through the NASA Advanced Composites Project (ACP), the present model captured damage migration from one surface to another, and model validations were within 4% of the experimental data.

PDA↗

NASA NTRSDate not supplied

Ground Testing of the MISSE-16 Materials

The harsh space environment imposes very stringent requirements upon spacecraft materials, especially those located on exterior surfaces of space objects in low Earth orbit (LEO). As humankind moves from space exploration to space commercialization, these materials may have to last for 15–20 years without considerable degradation of their optical, electrical, mechanical, and thermal properties. Operational requirements dictate that these materials continue to function according to expectations. Hence, we must understand the effects of the space environment on materials currently in use as well as on untested materials. For the years, the Materials International Space Station Experiment Flight Facility (MISSE-FF) have flown many different materials to investigate the effect of LEO space weather exposure on the performance and durability of materials and devices. The MISSE-16 scientific team members plan to launch fifteen different novel and well-characterized spacecraft-relevant materials to the LEO environment for a duration of six months during the MISSE-16 mission. Changes in spectral reflectivity will be measured throughout the mission as the samples are exposed to the space environment. The same chemical damage the produces changes in optical reflectance also causes changes in numerous other physical properties such as electrical conductivity, mechanical strength, and chemical reactivity. Correlation of the changes in each of these properties as a function of radiation type, flux, and fluence allows various material properties to be inferred from one experimentally tractable measurement: color change. Flying identical test fixtures on the ram, zenith, and wake positions of the MISSE-FF, collecting spectrally resolved images of the materials, and concomitantly measuring the ambient space environment allows deconvolution of the material effects which occur as a result of exposure to neutral atomic oxygen (AO), unfiltered solar ultraviolet (UV) radiation, and electrons. The flight experiment will function as a ground truth reference for our team’s ongoing laboratory-based space weather-material interactions experiments. Comparison of the MISSE-16 data with extensive testing of “flight-duplicate” samples under simulated space weather conditions will enable development of chemical models for prediction of material degradation. This paper discusses preliminary results from the ground test campaign including measurements of UV/VIS/IR reflectance spectra, bidirectional reflectance distribution function (BRDF), surface potential decay, and surface morphology under electron and AO exposure.

Elena A. Plis↗

NASA NTRSDate not supplied

Multiscale Analysis of Thermo-Mechanical Behavior of Boron Nitride-Reinforced Epoxy Nanocomposites

The effect of size, shape, morphology, and arrangement of micro constituents of Boron Nitrite (BN) nanoplatelet/epoxy composites on their properties were investigated using a multi scale approach that includes Molecular Dynamics (MD) and micromechanics. The thermo-mechanical properties of the composites were evaluated using molecular theory and the analysis showed that the elastic constants of BN/epoxy composites were not severely affected by temperature. Also, the micromechanical analysis of Generalized Method of Cells (GMC) was utilized at higher length scale to evaluate elastic properties of the composites, for different geometries and arrangements of micro constituents. The predicted results of the analysis showed that the size, aspect ratios, morphology, and the arrangements of inclusions in BN/epoxy nanocomposites all have remarkable effect on the mechanical performances of the material systems.

nanocomposites↗

NASA NTRSDate not supplied

A Partitioned - Task Parallel Implementation of the NASA Multiscale Analysis Tool for High Performance Computing

The NASA Multiscale Analysis Tool (NASMAT) is a platform for multiscale modeling of composites which can perform analysis of materials with any arbitrary number of length scales. The platform supports modularity, scalability, and interoperability using recursive procedures and data structures. A Macro solver driven parallelization scheme often limits the capability of NASMAT to scale as it has access to limited memory and number of cores (often one core/thread) and often forces to implement macro solver specific changes to the platform. In this work, a partitioned task-parallel approach is adopted, where the parallelization strategy adopted for NASMAT is independent of the macro solver and the computational resources are managed independently. The programming architecture takes into account the hierarchy of multiple scales (task-dependence) and the heterogeneous nature (dynamic load balancing) of computation through implementation of a hierarchy-informed task parallel model. The partitioned nature of the framework further extends the “plug and play” capability of NASMAT. preCICE, an open-source library for coupling multiphysics solver in a partitioned manner, is adopted to integrate NASMAT with an external macro solver by implementing a NASMAT adapter for preCICE. Speedup and scalability of the framework is studied for micromechanical models of varying size.

task-parallel↗

NASA NTRSDate not supplied

Refractory Carbides for Hydrogen Erosion Resistance in Carbon Tubes for Nuclear Thermal Propulsion

As crewed travel becomes more common to the Moon and beyond, space nuclear propulsion-based craft offer reduced travel times and double the specific impulse compared to conventional chemical rockets. The nuclear core and its integral hydrogen propellant channels will require advanced refractory carbide coatings over a carbon/carbon substrate for hydrogen resistance. Using ab initio and other computational techniques, we studied select (Zr/Ta/Nb)C mixed carbide systems for erosion resistance and hydrogen diffusion using realistic levels of carbon vacancies and experimentally obtainable stoichiometries. Various contributions to the formation and hydrogen erosion free energies were calculated, including configurational, electronic, and vibrational terms. Our calculations indicate that ZrC is less likely to lose carbon than NbC or TaC, providing an explanation for heritage NERVA data on ZrC and NbC mass loss performance. Additionally, binary mixtures show compositions that are more stable than their end-member counterparts. Hydrogen diffusion in stoichiometric ZrC was found to be slightly higher than previously theorized, with the caveat that hydrogen saturation of carbon vacancies will hinder further hydrogen diffusion through the bulk, while hydrogen diffusion in ZrNbC is slightly enhanced over ZrC. And finally, we show that as carbon is depleted, the deformation mechanism of ZrC changes from brittle to ductile. Though many questions still remain as to the bulk performance of these materials, these trends and results are important in terms of materials selection efforts for hydrogen-resistant coatings on carbon/carbon substrates.

William C Tucker↗

NASA NTRSDate not supplied

Refractory Carbides for Hydrogen Erosion Resistance in Carbon Tubes for Nuclear Thermal Propulsion

As crewed travel becomes more common to the Moon and beyond, space nuclear propulsion-based craft offer reduced travel times and double the specific impulse compared to conventional chemical rockets. The nuclear core and its integral hydrogen propellant channels will require advanced refractory carbide coatings over a carbon/carbon substrate for hydrogen resistance. Using \textit{ab initio} and other computational techniques, we studied select (Zr/Ta/Nb)C mixed carbide systems for erosion resistance and hydrogen diffusion using realistic levels of carbon vacancies and experimentally obtainable stoichiometries. Various contributions to the formation and hydrogen erosion free energies were calculated, including configurational, electronic, and vibrational terms. Our calculations indicate that ZrC is less likely to lose carbon than NbC or TaC, providing an explanation for heritage NERVA data on ZrC and NbC mass loss performance. Additionally, binary mixtures show compositions that are more stable than their end-member counterparts. Hydrogen diffusion in stoichiometric ZrC was found to be slightly higher than previously theorized, with the caveat that hydrogen saturation of carbon vacancies will hinder further hydrogen diffusion through the bulk, while hydrogen diffusion in ZrNbC is slightly enhanced over ZrC. And finally, we show that as carbon is depleted, the deformation mechanism of ZrC changes from brittle to ductile. Though many questions still remain as to the bulk performance of these materials, these trends and results are important in terms of materials selection efforts for hydrogen-resistant coatings on carbon/carbon substrates.

William C. Tucker↗

NASA NTRSDate not supplied

Refractory Carbides for Hydrogen Erosion Resistance in Carbon Tubes for Nuclear Thermal Propulsion

William C Tucker↗

NASA NTRS2023

Experimental Investigation of Block-TPS Fence/Gap Roughness Effects on Transition Onset and Turbulent Heating at Mach 6

An experimental investigation of boundary-layer transition and convective surface heating on wind tunnel models that simulated aeroshells comprised of multiple blocks of thermal protection system (TPS) material has been performed. Two representative entry vehicle geometries, a sphere-cone aeroshell and a sphere-cone aeroshell, were considered. Multiple cast ceramic models of each geometry were fabricated with varying fence heights or gap depths to represent gap fillers that either protrude above, or are recessed below, the TPS blocks due to differential ablation during reentry. Wind tunnel testing was performed at Mach 6 over a range of Reynolds numbers sufficient to produce laminar, transitional, and turbulent flow. Convective surface heating and boundary-layer transition onset data were obtained using global phosphor thermography. The experimental heating data are presented herein, as are comparisons to laminar and turbulent smooth-wall heat transfer distributions from computational flow field simulations.

Aerothermodynamics↗

NASA NTRS2024

Metal Extraction from Trash via Trash-to-Gas Processing for Use in 3D Printing

This work synergized state-of-the-art trash-to-gas (TtG) and in-space manufacturing (ISM) technologies to successfully extract metals from astronaut waste items for use in 3D printing. This was accomplished by isolating pure aluminum (Al 1235) from astronaut multilayer food packaging via TtG processing, cleaning the extracted aluminum, and preparing it for compatibility with the bound metal deposition (BMD) 3D printing process. A suite of material analyses was performed on the extracted aluminum product to fully characterize the key properties linked to effective additive manufacturing, including particle size distribution, oxygen content quantitation, and elemental composition. Metal extraction from Lunar and Martian regolith has become a significant area of interest for the in-situ resource utilization (ISRU) community to produce metallic equipment for various mission scenarios. However, the extraction of metals from astronaut waste streams has yet to be investigated. This project demonstrated an end-to-end waste metallic reuse process which may garner considerable metal production that would otherwise be disposed of.

Ray Pitts↗