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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Evaluation of Coatings for the Electrodynamic Dust Shield Application on Thermal Radiators

Dust acts as a blackbody, becoming hot if left in direct sunlight. This is a problem for thermal radiators where the main function is to radiate heat away from an object. If dust lands on the thermal radiator, the unit will less effectively reject heat, and it will overheat. This can lead to electrical or system failure. The current state-of-the-art in active dust mitigation is the Electrodynamic Dust Shield (EDS) which uses an electric field generated by alternating high positive and negative voltages (low current) to eject the charged dust off surfaces. An EDS made from copper coated Kapton is an ideal candidate to be bonded to a thermal radiator and coated with a low solar absorptance, high heat-emitter coating. This work compares the dust removal of copper-Kapton EDSs covered with different thermal radiator coatings in air and vacuum environments. The coatings include AZ-93 paint, Thermal Bright, and Solar White, a coating developed by the Applied Physics Lab (APL) at NASA Kennedy Space Center (KSC). The resistance and the thickness of the various coatings impact how well it works as an insulative layer for the EDS. Preliminary results indicate that Solar White may have better properties for dust removal and thermal rejection than the other coatings.

Krystal L Acosta↗
NASA NTRSDate not supplied

Evaluation of Coatings for the Electrodynamic Dust Shield Application on Thermal Radiators

Space dust acts as a blackbody, becoming hot if left in direct sunlight. This is a problem for thermal radiators used in space missions, where the main function is to radiate heat away from an object. If dust lands on the thermal radiator, the unit will less effectively reject heat, and it will overheat, leading to electrical or system failure. The current state-of-the-art in active dust mitigation is the Electrodynamic Dust Shield (EDS) which uses an electric field generated by alternating high positive and negative voltages (low current) to eject the charged dust off surfaces. An EDS made from copper coated Kapton is an ideal candidate to be bonded to a thermal radiator and coated with a low solar absorptance, high heat-emitter coating. This work compares the dust removal of copper-Kapton EDSs covered with different thermal radiator coatings in air and vacuum environments. The coatings include AZ-93 paint, Thermal Bright, and Solar White, a coating developed by the Applied Physics Lab (APL) at NASA Kennedy Space Center (KSC). The resistance and the thickness of the various coatings impact how well it works as an insulative layer for the EDS. Preliminary results indicate that Solar White may have better properties for dust removal and thermal rejection than the other coatings.

Krystal L. Acosta↗
DOE OSTI2021

mystic : software for autonomous discovery and design under uncertainty

Throughout the diverse range of science and engineering applications, there is a growing desire to develop computational methods that can reliably predict the behavior of complex systems. Specifically, there is a strategic need for tools that can robustly forecast the behavior of complex physical systems, where data may be high-dimensional, noisy, or sparse, and models of the system may be time-dependent or include uncertainty. We use mystic to build tools that leverage statistical learning, physics-informed learning, and active learning in the efficient generation of reliably predictive surrogates for complex physical systems. mystic is a robust, proven, open-source optimization and uncertainty quantification toolkit with over a decade of use in the design and optimization of neutron instrumentation, solar-powered drones, and gasguns, and in iterative tuning of models for Raman spectroscopy and elastoplastic materials strength. Recent developments have focused on automated learning of statistically robust surrogates under uncertainty, with applications in materials in extreme environments, nanostructures, materials simulations and strength models, and the failure of shielding under particle radiation. In 2020, McKerns demonstrated active learning of optimally robust surrogates with respect to new simulated data for molecular dynamics simulations of materials mixing in warm dense matter, and is currently applying active learning to the automated steering of particle accelerator beams and the optimal design and control of quantum optical sensor instrumentation.

42 ENGINEERING↗
NASA NTRS1998

Status and Design Concepts for the Hydrogen On-Orbit Storage and Supply Experiment

This paper studies concepts for the Hydrogen On-Orbit Storage and Supply Experiment (HOSS). HOSS is a space flight experiment whose objectives are: Show stable gas supply for storage and direct gain solar-thermal thruster designs; and evaluate and compare low-g performance of active and passive pressure control via a thermodynamic vent system (TVS) suitable for solar-thermal upper stages. This paper shows that the necessary experimental equipment for HOSS can be accommodated in a small hydrogen dewar of 36 to 80 liter. Thermal designs for these dewars which meet the on-orbit storage requirements can be achieved. Furthermore ground hold insulation and shielding concepts are achieved which enable storing initially subcooled liquid hydrogen in these small dewars without venting in excess of 144 hours.

Chato, David J.↗
NASA NTRS2016

Radiation-Induced Backgrounds in Astronomical Instruments: Considerations for Geosynchronous Orbit and Implications for the Design of the WFIRST Wide-Field Instrument

Geosynchronous orbits are appealing for solar or astrophysical observatories because they permit continuous data downlink at high rates. The radiation environment in these orbits presents unique challenges, however. This paper describes both the characteristics of the radiation environment in geosynchronous orbit and the mechanisms by which this radiation generates backgrounds in photon detectors. Shielding considerations are described, and a preliminary shielding design for the proposed Wide-Field InfraRed Survey Telescope observatory is presented as a reference for future space telescope concept studies that consider a geosynchronous orbit.

Kruk, Jeffrey W.↗
NASA NTRS1979

Silicon Web Process Development

Silicon dendritic web, ribbon form of silicon and capable of fabrication into solar cells with greater than 15% AMl conversion efficiency, was produced from the melt without die shaping. Improvements were made both in the width of the web ribbons grown and in the techniques to replenish the liquid silicon as it is transformed to web. Through means of improved thermal shielding stress was reduced sufficiently so that web crystals nearly 4.5 cm wide were grown. The development of two subsystems, a silicon feeder and a melt level sensor, necessary to achieve an operational melt replenishment system, is described. A gas flow management technique is discussed and a laser reflection method to sense and control the melt level as silicon is replenished is examined.

Duncan, C. S.↗
NASA NTRS1995

LDEF contributions to cosmic ray and radiation environments research

LDEF-1 carried three experiments which are producing significant advances in our knowledge of ultra heavy and anomalous cosmic rays, solar flare particles, and heavy nuclei in the trapped belts. Nine other experiments made measurements on the radiation environments or performed dosmetric monitoring. Data from those experiments, and from measurements of induced radioactivity in LDEF components have significantly improved our knowledge of LEO radiation environment. Measurements at various locations shielding depths of radiation absorbed dose, linear energy transfer spectra, proton, neutron and heavy ion fluences, and induced radioactivity have been made, and many of these results have been compared to models. This has allowed the assessment of accuracy, and the potential for improvement, of the models. Serendipitous results from the radiation measurements include the discovery of atmospheric Be-7 plated on the front surface of LDEF, which has motivated a series of new investigations. A sample of measurements and modeling results will be presented, as well as the status of archiving the measurements and models.

Parnell, Thomas A.↗
NASA NTRS2000

Insights Developed Into the Damage Mechanism of Teflon FEP Thermal Control Material on the Hubble Space Telescope

Metalized Teflon FEP (DuPont; fluorinated ethylene propylene) thermal control material on the Hubble Space Telescope (HST) has been found to degrade in the space environment. Teflon FEP thermal control blankets retrieved during the first servicing mission were found to be embrittled on solar-facing surfaces and to contain microscopic cracks (the FEP surface is exposed to the space environment). During the second servicing mission, astronauts noticed that the FEP outer layer of the multilayer insulation blanketing covering the telescope was cracked in many locations. Large cracks were observed on the light shield, forward shell, and equipment bays. A tightly curled piece of cracked FEP from the light shield was retrieved during the second mission. This piece was severely embrittled, as witnessed by ground testing. A Failure Review Board was organized by NASA Goddard Space Flight Center to determine the mechanism causing the multilayer insulation degradation. This board included members of the Electro-Physics Branch of the NASA Glenn Research Center at Lewis Field. Density measurements of the retrieved materials obtained under the review board's investigations indicated that FEP from the first servicing mission was essentially unchanged from pristine FEP but that the second servicing mission FEP had increased in density in comparison to pristine FEP (ref. 1). The results were consistent with crystallinity measurements taken using x-ray diffraction and with results from solid-state nuclear magnetic resonance tests (see the table and ref. 1). Because the second servicing mission FEP was embrittled and its density and crystallinity had increased in comparison to pristine FEP, board researchers expected that the first servicing mission FEP, which was also embrittled, would also have increased in crystallinity and density, but it did not. Because the retrieved second servicing mission material curled while in space, it experienced a higher temperature extreme during thermal cycling (estimated at 200 C) than the first servicing mission material (estimated at 50 C). Therefore, Glenn initiated and conducted an investigation of the effects of heating pristine FEP and FEP that had been exposed on the Hubble Space Telescope. Samples of pristine and first and second servicing mission FEP were heated to 200 C and evaluated for changes in density and morphology. We hoped that the results would help explain why FEP degrades in the Hubble Space Telescope space environment.

deGroh, Kim K.↗
NASA NTRS2015

Comparison and Validation of FLUKA and HZETRN as Tools for Investigating the Secondary Neutron Production in Large Space Vehicles

NASA's exploration goals are focused on deep space travel and Mars surface operations. To accomplish these goals, large structures will be necessary to transport crew and logistics in the initial stages, and NASA will need to keep the crew and the vehicle safe during transport and any surface activities. One of the major challenges of deep space travel is the space radiation environment and its impacts on the crew, the electronics, and the vehicle materials. The primary radiation from the sun (solar particle events) and from outside the solar system (galactic cosmic rays) interact with materials of the vehicle. These interactions lead to some of the primary radiation being absorbed, being modified, or producing secondary radiation (primarily neutrons). With all vehicles, the high energy primary radiation is of most concern. However, with larger vehicles that have large shielding masses, there is more opportunity for secondary radiation production, and this secondary radiation can be significant enough to cause concern. When considering surface operations, there is also a secondary radiation source from the surface of the planet, known as albedo, with neutrons being one of the most significant species. Given new vehicle designs for deep space and Mars missions, the secondary radiation environment and the implications of that environment is currently not well understood. Thus, several studies are necessary to fill the knowledge gaps of this secondary radiation environment. In this paper, we put forth the initial steps to increasing our understanding of neutron production from large vehicles by comparing the neutron production resulting from our radiation transport codes and providing a preliminary validation of our results against flight data. This paper will review the details of these results and discuss the finer points of the analysis.

Rojdev, Kristina↗
NASA NTRS1976

The magnetic moment of Venus - Venera-4 measurements reinterpreted

Venera-4 magnetic-field measurements made during that spacecraft's descent through the atmosphere of Venus are reexamined using three models for the interaction of the solar-wind with the planet. The first model assumes the existence of just the interplanetary and planetary magnetic fields; the second admits the presence of a magnetosheath and a current layer, but assumes that the magnetosheath field is spatially uniform between the planet and the bow shock; the third assumes shielding of the planetary field from the magnetosheath field by a current layer. All three models are found to yield a strong altitude dependence for the magnitude of the planetary field, suggesting that the intrinsic magnetic dipole moment of Venus may exceed that of both Mars and Mercury. It is concluded that a Venusian surface field of 30 gammas is a plausible interpretation of the Venera-4 measurements.-

Russell, C. T.↗
NASA NTRS1979

The hard X-ray burst spectrometer on the solar maximum mission

The primary scientific objective of the spectrometer is to provide a greater understanding of the role of energetic electrons in solar flares. This will be achieved by observations of high energy X-rays in the energy range from 20 to 200 keV with time resolution of 0.128s on a continuous basis and as short as 1 ms for limited intervals. The X-ray detector is an actively shielded CsI(Na) crystal with a thickness of 0.635 cm and a sensitive area of 71 sq cm. In the first year after launch, it is expected that approximately 1000 flares above the sensitivity threshold of 0.2 photons/(sq cm s) lasting for one second, will be detected.

Orwig, L. E.↗
NASA NTRS1996

Effects of orbit progression on the radiation exposures from solar proton fluxes in low Earth orbit under geomagnetic storm conditions

The present study examines the effects of orbit progression on the exposures within a Space Station Freedom module in a 51.6-degree inclined orbit at 450 km. The storm evolution is modeled after the November 1960 event, and the solar proton flux evolution is taken from the August 1972 solar proton event. The effects of a strong magnetic shock, such as was observed during the October 1989 event, is also modeled. The statistics on hourly average storm fields for the last forty years reveal that the largest geomagnetic storms geomagnetic storms approach a Dst value of -500 nanotesla at the storm peak. Similarly, one of the largest satellite-measured proton flux (greater than 10 MeV) for space exposures is the event of August 1972. The effects of orbit progression (advance of the line of nodes) is examined for the above conditions to study the variation of exposures under differing times of occurrence of the solar proton peak intensity, attainment of geomagnetic storm maximum, and the location of the line of nodes of the last geomagnetically protected orbit. The impact of the inherent inhomogeneity of the space station module is examined as a limiting factor on exposure with regard to the need of additional parasitic shielding.

Nealy, J. E.↗
NASA NTRS2005

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↗
NASA NTRS2011

Space Radiation Effects on Human Cells: Modeling DNA Breakage, DNA Damage Foci Distribution, Chromosomal Aberrations and Tissue Effects

Future long-tem space travel will face challenges from radiation concerns as the space environment poses health risk to humans in space from radiations with high biological efficiency and adverse post-flight long-term effects. Solar particles events may dramatically affect the crew performance, while Galactic Cosmic Rays will induce a chronic exposure to high-linear-energy-transfer (LET) particles. These types of radiation, not present on the ground level, can increase the probability of a fatal cancer later in astronaut life. No feasible shielding is possible from radiation in space, especially for the heavy ion component, as suggested solutions will require a dramatic increase in the mass of the mission. Our research group focuses on fundamental research and strategic analysis leading to better shielding design and to better understanding of the biological mechanisms of radiation damage. We present our recent effort to model DNA damage and tissue damage using computational models based on the physics of heavy ion radiation, DNA structure and DNA damage and repair in human cells. Our particular area of expertise include the clustered DNA damage from high-LET radiation, the visualization of DSBs (DNA double strand breaks) via DNA damage foci, image analysis and the statistics of the foci for different experimental situations, chromosomal aberration formation through DSB misrepair, the kinetics of DSB repair leading to a model-derived spectrum of chromosomal aberrations, and, finally, the simulation of human tissue and the pattern of apoptotic cell damage. This compendium of theoretical and experimental data sheds light on the complex nature of radiation interacting with human DNA, cells and tissues, which can lead to mutagenesis and carcinogenesis later in human life after the space mission.

Ponomarev, A. L.↗
NASA NTRS2015

Electrodynamic Dust Shield for Lunar/ISS Experiment Project

The Electrostatics and Surface Physics Laboratory at Kennedy Space Center is developing a dust mitigation experiment and testing it on the lunar surface and on the International Space Station (ISS). The Electrodynamic Dust Shield (EDS) clears dust off surfaces and prevents accumulation by using a pattern of electrodes to generate a non-uniform electric field over the surface being protected. The EDS experiment will repel dust off materials such as painted Kapton and glass to demonstrate applications for thermal radiators, camera lenses, solar panels, and other hardware and equipment.

Zeitlin, Nancy↗
NASA NTRS1982

Gamma-ray and optical observations of the 1979 November 8 solar flare

The solar flare on 1979 November 8 11h 21m 28s UT was observed by the Tel Aviv telescope of the Big Bear Solar Observatory and the High Resolution Gamma-Ray Spectrometer on the High Energy Astronomy Observatory HEAO 3. Photographs in alpha hydrogen show the development of the flare and a subsequent Moreton wave. Although the flare was not detected with the high spectral resolution germanium detectors, the HEAO C-1 CsI shield detected a statistically significant signal above 80 keV, from 420 to 585 keV, and above 3.8 MeV. The temporal structure of microwave, optical, X-ray, and gamma-ray emission is consistent to within about 1 s with a simultaneous flare response at all energies. There is no evidence for either second-stage acceleration of charged particles (Bai and Ramaty, 1979) or a delay between gamma-ray and X-ray continuum emission due to energy-dependent electron energy loss times (Bai and Ramaty).

Riegler, G. R.↗
NASA NTRS1995

Evaluation of adhesive materials used on the Long Duration Exposure Facility

The adhesive and adhesive-like materials flown on LDEF included epoxies and silicones (including lap shear specimens), conformal coatings, potting compounds, and several tapes and transfer films. With the exception of the lap shear specimens, these materials were used in the fabrication and assembly of the experiments such as bonding thermal control surfaces to other hardware and holding individual specimens in place, similar to applications on other spacecraft. Typically, the adhesives were not exposed to solar radiation or atomic oxygen. Only one adhesive system was used in a structural application. This report documents all results of the Materials and Systems SIG investigation into the effect of long term low Earth orbit (LEO) exposure of these materials. Results of this investigation show that if the material was shielded from exposure to LDEF's external environment, the 69 month exposure to LEO had, in most cases, minimal effect on the material.

Dursch, H. W.↗