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At least 307 records · Page 17

Evaluation of Spacecraft Shielding Effectiveness for Radiation Protection

The potential for serious health risks from solar particle events (SPE) and galactic cosmic rays (GCR) is a critical issue in the NASA strategic plan for the Human Exploration and Development of Space (HEDS). The excess cost to protect against the GCR and SPE due to current uncertainties in radiation transmission properties and cancer biology could be exceedingly large based on the excess launch costs to shield against uncertainties. The development of advanced shielding concepts is an important risk mitigation area with the potential to significantly reduce risk below conventional mission designs. A key issue in spacecraft material selection is the understanding of nuclear reactions on the transmission properties of materials. High-energy nuclear particles undergo nuclear reactions in passing through materials and tissue altering their composition and producing new radiation types. Spacecraft and planetary habitat designers can utilize radiation transport codes to identify optimal materials for lowering exposures and to optimize spacecraft design to reduce astronaut exposures. To reach these objectives will require providing design engineers with accurate data bases and computationally efficient software for describing the transmission properties of space radiation in materials. Our program will reduce the uncertainty in the transmission properties of space radiation by improving the theoretical description of nuclear reactions and radiation transport, and provide accurate physical descriptions of the track structure of microscopic energy deposition.

Cucinotta, Francis A.↗

Space Environments and Spacecraft Effects Concept: Transitioning Research to Operations and Applications

The National Aeronautics and Space Administration (NASA) is embarking on a course to expand human presence beyond Low Earth Orbit (LEO) while expanding its mission to explore the solar system. Destinations such as Near Earth Asteroids (NEA), Mars and its moons, and the outer planets are but a few of the mission targets. NASA has established numerous organizations specializing in specific space environments disciplines that will serve to enable these missions. To complement these existing discipline organizations, a concept is presented focusing on the development of a space environment and spacecraft effects organization. This includes space climate, space weather, natural and induced space environments, and effects on spacecraft materials and systems. This space environment and spacecraft effects organization would be comprised of Technical Working Groups (TWG) focusing on, for example: a) Charged Particles (CP), b) Space Environmental Effects (SEE), and c) Interplanetary and Extraterrestrial Environments (IEE). These technical working groups will generate products and provide knowledge supporting four functional areas: design environments, environment effects, operational support, and programmatic support. The four functional areas align with phases in the program mission lifecycle and are briefly described below. Design environments are used primarily in the mission concept and design phases of a program. Environment effects focuses on the material, component, sub-system and system-level selection and the testing to verify design and operational performance. Operational support provides products based on real time or near real time space weather observations to mission operators to aid in real time and near-term decision-making. The programmatic support function maintains an interface with the numerous programs within NASA and other federal agencies to ensure that communications are well established and the needs of the programs are being met. The programmatic support function also includes working in coordination with the program in anomaly resolution and generation of lesson learned documentation. The goal of this space environment and spacecraft effects organization is to develop decision-making tools and engineering products to support the mission phases of mission concept through operations by focusing on transitioning research to application. Products generated by this space environments and spacecraft effects organization are suitable for use in anomaly investigations. This paper will describe the organizational structure for this space environments and spacecraft effects organization, and outline the scope of conceptual TWG's and their relationship to the functional areas.

Edwards, D. L.↗

Space Materials Handbook, 3rd ed.

This edition is the result of an extensive revision and reworking of the second edition of the Space Materials Handbook along with the incorporation of entirely new subject matter coverage and new materials data. All of the most significant material, phenomena, properties, and principles covered in the original Handbook are presented and expanded in this revised and updated version. However, treatment of theoretical aspects has been condensed in order that more emphasis could be placed on the extensive new materials knowledge and data obtained from the design and successful launching of a wide variety of space systems. The handbook is organized into four parts, namely: space environment, effect of space environment on materials, materials in space, and biological interaction with spacecraft materials. Information on mechanical, physical, and chemical properties and characteristics is given for a wide variety of metallic and nonmetallic materials. The effects of natural and induced environments on materials are appraised. Materials categories include coverage of thermal control materials, optical materials, adhesives, organic structural materials, inorganic structural materials, electronic components and materials, materials for sealing applications, and lubrication materials. In addition, a comprehensive multiple citation index is incorporated which gives ready access to information on specific subject areas with regard to their locations within the Handbook.

John B Rittenhouse↗

Performance of thermal control tape in the protection of composite materials

The selection of materials for construction of long duration mission spacecraft has presented many challenges to the aerospace design community. After nearly six years in low earth orbit, NASA's Long duration Exposure Facility (LDEF), retrieved in January of 1990, has provided valuable information on both the nature of the space environment as well as the effects of the space environment on potential spacecraft materials. Composites, long a favorite of the design community because of a high strength-to-weight ratio, were flown in various configurations on LDEF in order to evaluate the effects of radiation, atomic oxygen, vacuum, micrometeoroid debris, and thermal variation on their performance. Fiberglass composite samples covered with an aluminum thermal control tape were flown as part of the flight experiment A0171, the Solar Array Materials Passive LDEF Experiment (SAMPLE). Visual observations and test results indicate that the thermal control tape suffered little degradation from the space exposure and proved to be a reliable source of protection from atomic oxygen erosion and UV radiation for the underlying composite material.

Kamenetzky, Rachel R.↗

Evaluation of Cyclo Olefin Polymer as Sabot Material for High-Density Projectiles

Assuring the integrity of spacecraft and its occupants are a priority in the field of space exploration. Micrometeoroids and orbital debris are one of the primary threats that affect spacecraft materials due to the high kinetic energies involved with hypervelocity impacts. Improvement of projectile launching capabilities prompts the investigation of adequate materials for the manufacturing of sabots able to carry high-density projectiles without catastrophic failure. Polycarbonate has been the chosen material by the Hypervelocity Team at White Sands Test Facility for sabots on the 0.50 caliber launcher; however, there is a material constraint when the projectile becomes significantly dense and the inertial stresses surpass the yield strength of the sabot material. This research proposes a new polymer material for manufacturing sabots, known as cyclo olefin polymer (COP) with the purpose of successfully shooting the intended high-density projectiles. In this investigation, both polycarbonate and COP were analyzed using tensile and impact testing to observe the differences in their mechanical properties. The experimental details along with the detailed characterization of the materials are presented.

Tarango, Estebanne↗

Embrittlement of MISSE 5 Polymers After 13 Months of Space Exposure

Understanding space environment induced degradation of spacecraft materials is essential when designing durable and stable spacecraft components. As a result of space radiation, debris impacts, atomic oxygen interaction, and thermal cycling, the outer surfaces of space materials degrade when exposed to low Earth orbit (LEO). The objective of this study was to measure the embrittlement of 37 thin film polymers after LEO space exposure. The polymers were flown aboard the International Space Station and exposed to the LEO space environment as part of the Materials International Space Station Experiment 5 (MISSE 5). The samples were flown in a nadir-facing position for 13 months and were exposed to thermal cycling along with low doses of atomic oxygen, direct solar radiation and omnidirectional charged particle radiation. The samples were analyzed for space-induced embrittlement using a bend-test procedure in which the strain necessary to induce surface cracking was determined. Bend-testing was conducted using successively smaller mandrels to apply a surface strain to samples placed on a semi-suspended pliable platform. A pristine sample was also tested for each flight sample. Eighteen of the 37 flight samples experienced some degree of surface cracking during bend-testing, while none of the pristine samples experienced any degree of cracking. The results indicate that 49 percent of the MISSE 5 thin film polymers became embrittled in the space environment even though they were exposed to low doses (approx.2.75 krad (Si) dose through 127 mm Kapton) of ionizing radiation.

Guo, Aobo↗

Nickel Accounting for the Psyche Spacecraft

(16) Psyche is a metallic asteroid located in the asteroid belt between Mars and Jupiter. The composition of Psyche is unknown, but the scientific community believes it is composed primarily of iron, nickel, and silicates. The Psyche mission will be the first space mission to study this asteroid in close proximity, and as such, determining the elemental composition of the asteroid is one of the primary objectives of this mission. The spacecraft measures this elemental composition using the Gamma Ray Spectrometer (GRS), which detects cosmic-ray induced gamma rays from Psyche’s surface. In addition to gamma rays from Psyche, the GRS will also detect background gamma rays from spacecraft material nearby the GRS. Because Ni is such a key element for achieving the mission science objectives, a special effort has been made to minimize background gamma rays from Ni, thus maximizing sensitivity to the Ni gamma rays from Psyche. The Psyche mission approached this potential Ni background issue with two methods, locating the GRS away from the spacecraft/source of Ni and setting a threshold requirement against the total Ni mass of the spacecraft. Verifying that the total amount of Ni on the spacecraft is within this threshold is thus a key part of ensuring the GRS can meet its science objectives. Ni alloys are commonly used on spacecraft, but the mass and location of elemental Ni is not typically accounted for. Ni can be found in many materials all over the spacecraft – in fasteners, optical assemblies, magnetic shields, electromagnetic interference (EMI) tape, under gold plating, in connectors, and so on. The task proved further challenging because of the distributed nature of the build of this spacecraft and the use of vendors external to JPL. While the analysis was atypical and source information difficult to cull, the approach described in this paper used tools and data available to the project in some form to achieve this goal. For Psyche, current analysis shows there is margin in meeting the Ni mass requirement. This paper explains the systematic approach used to accurately and precisely record Ni content on the Psyche spacecraft. While this approach was defined for Ni on the Psyche mission, it can be used for any future project with the need to accurately estimate the total mass of a single element or material on a spacecraft.

Cullinan, Joe↗

Nickel Accounting for the Psyche Spacecraft

(16) Psyche is a metallic asteroid located in the asteroid belt between Mars and Jupiter. The composition of Psyche is unknown, but the scientific community believes it is composed primarily of iron, nickel, and silicates. The Psyche mission will be the first space mission to study this asteroid in close proximity, and as such, determining the elemental composition of the asteroid is one of the primary objectives of this mission. The spacecraft measures this elemental composition using the Gamma Ray Spectrometer (GRS), which detects cosmic-ray induced gamma rays from Psyche’s surface. In addition to gamma rays from Psyche, the GRS will also detect background gamma rays from spacecraft material nearby the GRS. Because Ni is such a key element for achieving the mission science objectives, a special effort has been made to minimize background gamma rays from Ni, thus maximizing sensitivity to the Ni gamma rays from Psyche. The Psyche mission approached this potential Ni background issue with two methods, locating the GRS away from the spacecraft/source of Ni and setting a threshold requirement against the total Ni mass of the spacecraft. Verifying that the total amount of Ni on the spacecraft is within this threshold is thus a key part of ensuring the GRS can meet its science objectives. Ni alloys are commonly used on spacecraft, but the mass and location of elemental Ni is not typically accounted for. Ni can be found in many materials all over the spacecraft – in fasteners, optical assemblies, magnetic shields, electromagnetic interference (EMI) tape, under gold plating, in connectors, and so on. The task proved further challenging because of the distributed nature of the build of this spacecraft and the use of vendors external to JPL. While the analysis was atypical and source information difficult to cull, the approach described in this paper used tools and data available to the project in some form to achieve this goal. For Psyche, current analysis shows there is margin in meeting the Ni mass requirement. This paper explains the systematic approach used to accurately and precisely record Ni content on the Psyche spacecraft. While this approach was defined for Ni on the Psyche mission, it can be used for any future project with the need to accurately estimate the total mass of a single element or material on a spacecraft.

Cullinan, Joe↗

Science Data Report for the Optical Properties Monitor (OPM) Experiment

Long term stability of spacecraft materials when exposed to the space environment continues to be a major area of investigation. The natural and induced environment surrounding a spacecraft can decrease material performance and limit useful lifetimes. The Optical Properties Monitor (OPM) experiment provided the capability to perform the important flight testing of materials and was flown on the Russian Mir Station to study the long term effects of the natural and induced space environment on materials. The core of the OPM in-flight analysis was three independent optical instruments. These instruments included an integrating sphere spectral reflectometer, a vacuum ultraviolet spectrometer, and a Total Integrated Scatter instrument. The OPM also monitored selected components of the environment including molecular contamination. The OPM was exposed on the exterior of the Mir Docking Module for approximately 8-1/2 months. This report describes the OPM experiment, a brief background of its development, program organization, experiment description, mission overview including space environment definition, performance overview, materials data including flight and ground data, in-depth post flight analysis including ground analysis measurements and a summary discussion of the findings and results.

Wilkes, Donald R.↗

Materials International Space Station Experiment-9 (MISSE-9) Polymers and Composites Experiment

Spacecraft in low Earth orbit (LEO) are subjected to harsh environmental conditions, including radiation (cosmic rays, ultraviolet, x-ray, and charged particle radiation), micrometeoroids and orbital debris, temperature extremes, thermal cycling, and atomic oxygen (AO). These environmental exposures can result in erosion, embrittlement and optical property degradation, threatening spacecraft performance and durability. To increase our understanding of effects such as AO erosion and radiation induced embrittlement of spacecraft materials, NASA Glenn has developed a series of experiments flown as part of the Materials International Space Station Experiment (MISSE) missions on the exterior of the International Space Station (ISS). These experiments have provided critical LEO space environment durability data such as AO erosion data for many materials and mechanical properties changes after long term space exposure. In continuing these studies, a new experiment called the Polymers and Composites Experiment has been selected for flight on the MISSE-Flight Facility (MISSE-FF). The Polymers and Composites Experiment will be flown as part of the MISSE-9 mission, the inaugural mission of MISSE-FF manifested on SpaceX-14. This experiment includes 138 samples being flown in ram, wake or zenith orientations for space environmental durability assessment. The primary objective is to determine the LEO AO erosion yield, Ey (the volume loss per incident oxygen atom (cm3/atom)), of polymers, composites, and coated samples, as a function of solar irradiation and AO fluence. In addition, epoxy samples with varying levels of ZnO powder are included to study the effect of filler quantity on AO erosion. An AO Scattering Chamber is included to help improve the understanding of AO scattering mechanisms for improved AO undercutting modeling. Indium tin oxide (ITO) coated samples are included to validate the durability of ITO conductive coatings in LEO. Tensile samples of Teflon fluorinated ethylene propylene (FEP) of varying thicknesses and back-surface coatings will be flown in wake and zenith orientations to study radiation embrittlement versus thickness, and the effect of heating on FEP embrittlement. Finally, shape memory composite and cosmic ray shielding samples will be flown for LEO durability assessment. This paper presents an overview of the MISSE-9 Polymers and Composites Experiment.

Embrittlement↗

Novel Material for Future Spacecrafts

Outside earth's protective magnetosphere crew members and sensitive equipment need to be protected against two primary radiation sources, namely Galactic Cosmic Rays (GCR) and Solar Energetic Particles (SEP). For planetary missions, this combination of radiation particles could result in doses that are higher than the allowable level currently permitted for low-earth orbit manned missions. This SBIR project aims to develop a multifunctional and lightweight composite material that not only provides sufficient radiation shielding but also provides sufficient structural integrity to be considered as a spacecraft material. This presentation will discuss the deep space radiation problem and the material based solutions being proposed by BAE SYS scientists to overcome this problem. The presentation will focus on the initiative taken by BAE SYS scientists to proactively engage and team with experts at NASA, small business, and other federal laboratories to develop and test a dual phase composite material. The presentation will also highlight the potential benefits to our customer, NASA and also to BAE SYS.

Sen, Subbayu↗

Long Duration Exposure Facility M0003-5 recent results on polymeric films

The M0003-5 polymeric film specimens orbited on the LDEF M0003 Space Environment Effects on Spacecraft Materials were a part of a Wright Laboratories Materials Directorate larger thermal control materials experiment. They were selected from new materials which emerged from development programs during the 1978-1982 time frame. Included were materials described in the technical literature which were being considered or had been applied to satellites. Materials that had been exposed on previous satellite materials experiments were also included to provide data correlation with earlier space flight experiments. The objective was to determine the effects of the LDEF environment on the physical and optical properties of polymeric thin film thermal control materials, the interaction of the LDEF environment with silvered spacecraft surfaces, and the performance of low outgassing adhesives. Sixteen combinations of various polymeric films, metallized and unmetallized, adhesively bonded and unbonded films were orbited on LDEF in the M0003-5 experiment. The films were exposed in two separate locations on the vehicle. One set was exposed on the direct leading edge of the satellite. The other set was exposed on the direct trailing edge of the vehicle. The purpose of the experiment was to understand the changes in the properties of materials before and after exposure to the space environment and to compare the changes with predictions based on laboratory experiments. The basic approach was to measure the optical and physical properties of materials before and after long-term exposure to a low earth orbital environment comprised of UV, VUV, electrons, protons, atomic oxygen, thermal cycling, vacuum, debris and micrometeoroids. Due to the unanticipated extended orbital flight of LDEF, the polymeric film materials were exposed for a full five years and ten months to the space environment.

Hurley, Charles J.↗

Insitu Calibration of Quartz Crystal Microbalances

Computer models that predict the rate at which molecular contamination will deposit on optical surfaces typically use outgassing source terms, measured with quartz crystal microbalances, as a basis for the prediction. The American Society of Testing and Materials, Standard Test Method for Contamination Outgassing Characteristics of Spacecraft Materials (Method E-1559), is probably the best know technique used by the aerospace community to measure the outgassing rates or source terms of materials. A simple method for the insitu calibration of quartz crystal microbalances, based on the heat of enthalphy of Adipic Acid, has been developed and demonstrated by the Marshall Space Flight Center, Environmental Effects Group. The calibration has been demonstrated over a sample temperature range of 25 to 66 degrees Celsius and deposition rates of 7 x 10 (exp -11) grams/cm(sup 2)-s and greater, for several measurement system configurations. This calibration technique is fully compatible with the American Society for Testing and Materials, Method E-1559, as well as other methodology. The calibration requires no modification of outgassing facilities employing an effusion cell and does not degrade the performance or function of typical vacuum systems.

Albyn, Keith↗

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.↗

Assessment of probability of detection of delaminations in fiber-reinforced composites

Delamination is one of the critical defects in composite materials and structures. An ultrasonic C-scan imaging technique which maps out the acoustic impedance mismatched areas with respect to the sample coordinates, is particularly well suited for detecting and characterizing delaminations in composites. To properly interpret the results, it is necessary to correlate the indications with the detection limits and probability of detection (POD) of the ultrasonic C-scan imaging technique. The baseline information on the assessment of POD of delaminations in composite materials and structures is very beneficial to the evaluation of spacecraft materials. In this study, we review the principle of POD, describe the laboratory set-up and procedure, and present the experimental results as well as assessment of POD of delaminations in fiber reinforced composite panels using ultrasonic C-scan techniques.

Chern, E. J.↗