Sheila Bailey, NASA Lewis Research Center
J. Robert Fowler, Federal Data Corp
Aloysius Hepp, NASA Lewis Research Center
Theo Keith, Ohio Aerospace Inst
Joseph Prahl, Case Western Reserve Univ
- Elsevier Science Ltd.
- NASA Headquarters
- NASA Lewis Research Center
1998 Fall Exhibitor
Proceedings published as Volume 551
of the Materials Research Society
Symposium Proceedings Series.
* Invited paper
Ftj: MATERIALS IN SPACE: SCIENCE, TECHNOLOGY, AND EXPLORATION
Sunday, November 29, 1:00-5:00 p.m.
Three aspects (science, technology, and exploration) of materials in space will be presented in this wide-ranging tutorial. The first topic is a presentation on experience with and research on materials degradation in low-earth orbit. Results of recent flight experiments as well as laboratory research will be presented. This is an issue for a number of payloads such as satellites and the Hubble Space Telescope, and it will be a critical concern for operation of the International Space Station. The second topic will address the technology of space photovoltaics. While this has always been an important source of power for near-Earth space payloads, the proposed launch of communication constellations and solar power for planetary missions will heighten interest in this critical technology. A review of recent advances and fundamentals will be included, as well as a discussion of the future of space photovoltaics. Finally, materials issues for recent and future Mars exploration will be addressed. The presentation will include a short summary of the environment on Mars. The findings of materials experiments on the recent Mars Pathfinder missions will also be described. Finally, specifics of near-term missions and a more general presentation on future missions to Mars will be given. Instructors:
Dennis J. Flood
, NASA Lewis Research Center Bruce A. Banks
, NASA Lewis Research Center
Geoffrey A. Landis
, NASA Lewis Research Center
8:30 AM *JJ1.1
SESSION JJ1: PLENARY SESSION - KEY ISSUES FOR MATERIALS SCIENCE AND SPACE EXPLORATION
Chair: Theo G. Keith
Monday Morning, November 30, 1998
Berkeley A/B (S)
NASA¹S MICROGRAVITY MATERIALS SCIENCE PROGRAM: OPPORTUNITIES FOR FLIGHT EXPERIMENTS AND GROUND BASED RESEARCH. Michael J. Wargo , Enterprise Scientist for Materials Science, Microgravity Research Division, NASA Headquarters, Washington, DC.
NASA¹s Microgravity Materials Science Program has a rich history of supporting a broad range of research in academia, industry, and government. Pioneering work was done on Skylab and the Apollo-Soyuz Test Project. We moved to an era of exploration and discovery during the early years of the Shuttle program where microgravity was recognized as a new tool to help understand many of the important problems in materials science. Since 1992 there has been an average of one shuttle flight every year dedicated to microgravity research. With this increased access to long duration, high quality microgravity conditions has come more reliable flight hardware with better performance and telescience capabilities that allow the researcher to control the experiment from the ground.
The next step is the International Space Station. With more power and more time, researchers will finally have the opportunity to conduct experiments in a manner similar to how they conduct them in their own laboratories; there will be enough time and other resources for reproducibility runs and for a comprehensive investigation of the phenomena of interest. The next experiment need not wait for two years or more to be run. In addition we have instituted a program that provides access to the microgravity environment of the shuttle and space station within three years using a Glovebox Facility to execute simple, low power scientific investigations and technology demonstrations.
A NASA Research Announcement (NRA) for Microgravity Materials Science will be released this fall soliciting flight experiments and ground based research. Grants for ground based research are typically supported for up to four years at an average level of approximately $100k/yr. Experiments selected for flight definition are supported at approximately $175k/yr.
9:00 AM *JJ1.2
MATERIALS FOR SHIELDING ASTRONAUTS FROM THE HAZARDS OF SPACE RADIATIONS. J. W. Wilson , NASA Langley Research Center, Hampton, VA; F. A. Cucinotta, NASA Johnson Space Center, Houston, TX; J. Miller, DOE Lawrence Berkeley National Laboratory, Berkeley, CA; J. L. Shinn, S. A. Thibeault, and R. C. Singleterry, NASA Langley Research Center, Hampton, VA.
One major obstacle to human space exploration is the possible limitations imposed by the adverse health effects of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar particle events (SPE) were of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated exposures can be high. Because cancer induction rates increase behind low to rather large thicknesses of aluminum shielding according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Preliminary studies indicate that materials with high hydrogen content and low atomic number constituents are most efficient in protecting the astronauts. This occurs for two reasons: the hydrogen is efficient in breaking up the heavy GCR ions into smaller less damaging fragments and the light constituents produce few secondary radiations (especially few biologically damaging neutrons). An overview of the materials related issues and their impact on human space exploration will be given.
9:30 AM JJ1.3
SENSITIVITY OF EXPERIMENTAL MEASUREMENTS TO G-JITTER AND THEIR SIGNIFICANCE TO ISS FACILITY DEVELOPMENT. Rodney A. Herring , Bjarni Tryggvason*
Microgravity Sciences Program, Canadian Space Agency, St. Hubert, PQ, CANADA; *
Canadian Astronaut Program, Canadian Space Agency, St. Hubert, PQ, CANADA.
There is a need to know the quality of microgravity necessary for taking good measurements of fundamental material properties and enabling some types of materials processing. Experiments sensitive to g-jitter have been performed using Mir and the Space Shuttle as the reference microgravity condition. These experiments had their platform either isolated, non-isolated or had induced g-pulses performed using the Microgravity-vibration Isolation Mount (MIM). The Mir experiments involved 1) measurements of intrinsic metal diffusion, 2) measurements of Soret coefficients and the Ostwald ripening phenomenon and, 3) processing of semiconductor materials and glasses. The Space Shuttle measurements were taken on the STS-85 flight and involved 1) the generation of resonance patterns experiments, 2) wave maker experiments, 3) bubble motion experiments, 4) liquid diffusion experiments and, 5) Brownian motion of small particles. More recent measurements include the growth of protein crystals on/off MIM which were returned from Mir on STS-89. While the results of these experiments are still being analyzed, several of these indicate a clearly observable difference between isolated and non-isolated conditions. These results are significant since they predict significantly greater sensitivity to g-jitter than the current ISS vibratory specification for ARIS isolated racks. They are contentious in that they contradict the results of many analytic and numerical studies conducted over the years to predict the g-jitter sensitivity. There is a need to continue taking these measurements in order to know the quality of gravity necessary to make good measurements of fundamental material properties and enable some types of materials processing. should be noted that if the acceleration environment on Mir and the Space Shuttle are not good enough for experimental measurements then those measurements taken on platforms which just meet the ISS requirements or are non-isolated will also not be good enough. If the results seen thus far are accurate predictors of the sensitivity for experiments planned for the ISS then the various experimental facilities being developed for the ISS and not mounted in an ARIS will need to incorporate provision for isolation systems. These results have raised interest and concerns of facility developers in Canada, Europe and Japan. While any decision to incorporate isolation systems as integral components of facilities implies additional costs, it will be far more cost effective to do this as part of the facility development, rather than to try to fix facilities once they are on orbit in the ISS.
10:15 AM JJ1.4
THERMOPHYSICAL PROPERTIES OF FLUIDS MEASURED UNDER MICROGRAVITY CONDITIONS. H.J. Fecht , Faculty of Engineering, University of Ulm, Ulm, GERMANY.
The analysis of nucleation and growth processes relies mostly on circular arguments since basic thermophysical properties necessary, such as the density, emissivity, thermal conductivity (diffusivity), diffusion coefficients, surface tension, viscosity, interfacial crystal / liquid tension, Gibbs free energy (enthalpy of crystallization, specific heat), etc. are generally unknown and therefore often deduced from insufficient linear interpolations from the elements. The paucity of thermophysical property data for commercial materials as well as research materials is mostly a result of the experimental difficulties arising from the unwanted convection and reactions of melts with containers at high temperatures. On the other hand, the knowledge of these properties is essential for the numerical modeling of industrial solidification processes where the solid / liquid phase transformation plays a crucial role at low levels of undercooling (crystal growth) and at high levels of undercooling (glass formation). An overview will be given on the results of thermophysical property measurements during several different space flights using containerless during the IML-2 mission, MIR 94, MIR 95, MSL-1 mission, parabolic flights as well as drop tube processing. Furthermore, a perspective on a future measurement program of thermophysical properties supported by the European Space Agency will be given. In this regard, the International Space Station is considered as the ideal laboratory for high precision measurements of thermophysical properties of fluids which help to improve manufacturing processes for a number of key industries. The financial support by the Deutsche Agentur für Raumfahrtangelegenheiten (DARA) and the European Space Agency (ESA) is gratefully acknowledged.
10:30 AM *JJ1.5
MATERIALS DEGRADATION IN LOW EARTH ORBIT. Bruce A. Banks , NASA Lewis Research Center, Cleveland, OH.
Spacecraft materials subjected to the effects of the low Earth orbital environment can suffer degradation consequences which can easily compromise the performance and durability of a mission. Degradation effects associated with atomic oxygen, ultraviolet radiation, thermal cycling, charged particle radiation and self contamination can produce surprisingly damaging consequences rarely observed in ground laboratory use of the same materials.
Atomic oxygen exists in low Earth orbit as a result of photodissociation of diatomic oxygen in the Earth's upper atmosphere where reassociation is improbable because of the low pressure. The spacecraft orbiting the Earth ram into the atomic oxygen with impact energies sufficient to break chemical bonds causing reactions with polymers to readily occur. As a consequence, almost all hydrocarbon polymers are subjected to gradual oxidative erosion unless otherwise protected from atomic oxygen attack.
Ultraviolet radiation can cause cross-linking, chain scission, and darkening of polymers and paints on spacecraft surfaces. This can cause changes in the solar absorptance as well as embrittlement of materials which otherwise may be flexible in ground laboratory use.
Thermal cycling of materials coupled with other degradation effects can lead to synergistic degradation effects on metalized FEP Teflon thermal control insulation. Spacecraft self-contamination as a result of outgassing of materials as well as atomic oxygen interactions has led to the deposition of silicones followed by conversion to silica contaminant layers on many spacecraft materials. Such contamination issues may present durability concerns for lengthy missions such as the International Space Station. Examples of low Earth orbital environmental interaction issues and degradation effects will be presented based on the results of space shuttle experiments, the Long Duration Exposure Facility, the Hubble Space Telescope and materials retrieved from Mir.
11:00 AM *JJ1.6
SPACE SOLAR ENERGY CONVERSION TECHNOLOGY: PAST, PRESENT, AND FUTURE. Dennis J. Flood , Photovoltaic and Space Environments Branch, NASA Lewis Research Center, Cleveland, OH.
Solar cells have been the predominant power sources in space for over forty years, beginning with the launch of the first U.S. solar powered satellite in 1958. Although the solar panels were relatively easy to build and use, their low efficiency was of concern. Solar cell efficiencies on the earliest arrays were typically around 10%, and much had to be learned about the survivability of the devices in the space environment. Enormous progress has been made since 1958, both in understanding the fundamental mechanisms which determine solar cell efficiency and lifetime, and in turning that understanding into tangible cell improvements. In addition, array structural mechanisms have become much more reliable and sophisticated, and array sizes have grown from a few tens of watts to tens of kilowatts. In the past decades, hundreds of kilowatts of photovoltaic solar power have been placed in orbit on various commercial, civilian and military satellites. Small arrays have even been transported to and left behind on the surfaces of the moon and Mars. In at least one instance a photovoltaic array was in orbit for nearly two decades, and still functioned well enough to bring the satellite back to an operational state following several years of dormancy). The elements of a space photovoltaic power system will be described, the status of solar cell technologies presently in use will be reviewed, and advances in both cell and array technology which will lead to improved satellite power system performance in the future will be discussed.
11:30 AM *JJ1.7
MARS IN-SITU-PROPELLANT-PRODUCTION PRECURSOR (MIP) FLIGHT DEMONSTRATION. David Kaplan , NASA Johnson Space Center, Houston, TX.
Strategic planning for human missions of exploration to Mars has conclusively identified in-situ propellant production (ISPP) as a critical, enabling technology. NASAís Human Exploration and Development of Space (HEDS) Enterprise is preparing a program of increasingly sophisticated flight demonstrations of ISPP to be flown on upcoming robotic missions to Mars. The first such flight demonstration is the Mars ISPP Precursor (MIP), which is manifested for launch to Mars onboard the SURVEYOR Lander in April 2001. The objective of MIP is to characterize the performance of processes and hardware which are both important to ISPP concepts and which also interact directly with the Mars environment during operation. Because of uncertainties associated with the Mars environment and conditions that cannot be adequately simulated on Earth, operating this hardware at Mars is extremely important.
The MIP is comprised of five distinctive demonstrations:
1.Mars Atmospheric Acquisition and Compression;
3.Mars Thermal Environment/Radiator Characterization;
4.Mars Array Technology Experiment;
5.Dust Accumulation and Repulsion Test; and
The MIP Flight Demonstration will be the first hardware ever deployed to a planet or moon. Its successful operation will pave the way for future robotic and human missions to manufacture and rely on propellants produced using Martian resources as feedstock
1:30 PM *JJ2.1
SESSION JJ2: MARS PATHFINDER MISSION RESULTS
Chair: David Kaplan
Monday Afternoon, November 30, 1998
Berkeley A/B (S)
THE ABRASION OF ALUMINUM, PLATINUM, AND NICKEL BY MARTIAN DUST AS DETERMINED BY THE MARS PATHFINDER WHEEL ABRASION EXPERIMENT. Dale Ferguson , Mark Siebert, David Wilt, Joseph Kolecki, NASA Lewis Research Center, Cleveland, OH.
The Mars Pathfinder Wheel Abrasion Experiment (WAE) spun a specially prepared wheel with strips of aluminum, platinum, and nickel, in the Martian soil. These materials were chosen because of their differing hardnesses, their ability to stick to anodized aluminum, and their comparative chemical inertness under Earth launch and Mars landing conditions. Abrasion of those samples was detected by the change in their specular reflectances of sunlight as measured by a photovoltaic sensor mounted above the wheel. The degree of abrasion occurring on the samples will be discussed, along with comparisons to the abrasion seen in Earth-based laboratory experiments using Martian soil analogs. Conclusions will be reached about the hardness, grain size, and angularity of the Martian soil particles, and the precautions which must be undertaken to avoid abrasion on moving parts exposed to the Martian dust.
2:00 PM *JJ2.2
MATERIALS ADHERENCE EXPERIMENT ON MARS PATHFINDER. Geoffrey A. Landis and Phillip P. Jenkins.
The Materials Adherance Experiment on the Mars Pathfinder measured the degradation of the solar panel on the Sojourner rover due to dust deposition. The experiment's design, operation, and results will be presented, along with a discussion of upcoming experiments which will characterize materials properties on future missions to Mars.
2:30 PM JJ2.3
MATERIALS FOR THERMAL CONTROL FOR MARS SURFACE ROBOTIC MISSIONS. Gregory Hickey , Jet Propulsion Laboratory, Pasadena CA.
The thermal environment for Mars surace exploration provides unique challenges for materials for use in structure and thermal control. The Sojourner Mars Rover has a lightweight integrated structure/insulation that has been environmentally tested and qualified for the Pathfinder mission to Mars. The basic structure with insulation, called the Warm Electronics Box (WEB), accounts for only 10% of the total Rover mass. The WEB is a thermal isolating composite structure with co-cured thermal control surfaces and an ultralightweight hydrophobic solid silica aerogel which minimizes conduction and radiation. This design provides excellent thermal insulation at low gas pressures and meets the structural requirements for spacecraft launch loads and for a 60 g impact landing at Mars without damage to the insulation or structure. Since the Pathfinder mission, this basic design concept has been developed and improved for future Mars surface robotic missions.
3:15 PM JJ3.1
SESSION JJ3: MATERIALS AND TECHNOLOGIES FOR SPACE EXPLORATION I
Chair: J. Robert Fowler
Monday Afternoon, November 30, 1998
Berkeley A/B (S)
LARGE SCALE TELEOPERATION ON THE LUNAR SURFACE. Gregory Konesky , ATH Ventures Inc., Hampton Bays, NY.
The popular success of the Mars Pathfinder mission, especially in terms of individual access to ``live'' pictures over the internet, demonstrates substantial mass appeal of space exploration on a personal level. Teleoperation provides an inexpensive approach to remote presence, but is distance-limited due to finite signal propagation times. The proximity of the Lunar surface permits near real-time teleoperation, and through a Virtual Reality approach, presents a sense of ``being there'' without the difficulty of getting there (and back). While limited single user teleoperated Lunar Rover concepts have been proposed (Luna Corp. Inc.), an on-going and economically self supporting venture would require simultaneous teleoperation of many vehicles on a large scale. In addition, each vehicle would carry several simultaneous stereoscopic remote viewing television camera heads, whose position is controlled by the head movements of Earth bound viewers. The overall concept is similar to a small fleet of touring buses, although some smaller scout vehicles may be included,as well as a tow truck. An access fee structure for Earth bound teleoperators provides for return on investment within the first year of operation. Technical issues such as an on-going operation in the Lunar enviroment include temperature extremes, high vacuum, solar radiation, micrometeorites, abrasive nature of Lunar dust and its capacity to electrostatically attach to surfaces are discussed and their impact on vehicle design and operation. Optical data links are considered to handle bandwidth requirements of 500 simultaneous users. The economics of scale, on multiple levels, demonstrates the feasibility, of large scale teleoperation. Various base-line studies are presented.
3:30 PM *JJ3.2
A PHOTOELECTROCHEMICAL APPROACH TO SPLITTING CARBON DIOXIDE FOR A MANNED MISSION TO MARS. Clifford P. Kubiak , Brian K. Breedlove, University of California, Dept of Chemistry and Biochemistry, San Diego, CA.
A photoelectrochemical system for splitting carbon dioxide to carbon monoxide and oxygen will be discussed. The Martian atmosphere consists of 95% carbon dioxide. Splitting carbon dioxide would provide both oxygen to support life and carbon monoxide which can be used as a substitute for hydrogen fuel. The photoelectrochemical system involves a cathodic compartment where reduction of carbon dioxide to carbon monoxide occurs, and an anodic compartment where ìoxideî equivalents from the carbon dioxide/carbonate equilibrium are oxidized to oxygen. Recent studies of soluble trinuclear nickel cluster electrocatalysts for the reduction of carbon dioxide in the cathodic compartment will be presented. These catalysts are found to mediate the reduction of carbon dioxide to carbon monoxide essentially at the thermodynamic potential for this process. Recent studies on nickel-tin catalysts for carbon dioxide reduction will be presented. Evidence for the cooperative interaction of the electrophilic tin cap and nucleophilic nickel cluster core in carbon dioxide binding and activation will be described.
4:00 PM *JJ3.3
SYNTHESIS OF THIN FILM LITHIUM-ION BATTERY COMPONENTS USING THE SPRAY DECOMPOSITION APPROACH, K. Scott Weil and Prashant N. Kumta , Carnegie Mellon University, Pittsburgh, PA, Aloysius F. Hepp and Jerry Harris, NASA Lewis Research Center, Cleveland, OH.
Thin films of LiCoO2
have been synthesized using a spray decomposition technique. A lithium-cobalt solution for spray decomposition was prepared by dissolving lithium nitrate, LiNO2
, and cobalt nitrate, hexahydrate, Co(NO3
O, in reagent grade ethanol. The tin solution was prepared by dissolving tin ethylhexanoate in high purity methanol. Each solution was sprayed separately using a fine atomizing nozzle onto 1/2"
diameter nickel substrates heated to temperatures between 500-700C. Scanning electron micrographs of the thin film electrodes demonstrate that the films are 1-10 m thick, depending on the concentration of the solution, the rate and duration of spraying, and the temperature of the substrate. Preliminary electrochemical characterization of the films indicates that the LiCoO2
cathodes in general, display a relatively high open circuit voltage (OCV) of 4.10-4.25V, good specific capacity 120 mAh/g, and a decent cyclability performance, with a 16-25% decay in capacity after 50 cycles. The SnO2
films on the other hand, display an expected initial drop in capacity, with an OCV of 1.00-1.10V. However, the films exhibit an excellent capacity of 600 mAh/g, which is retained with virtually no loss after 50 cycles. Recent attempts to synthesize a lithium borosilicate thin film electrolyte using this approach appear to be successful, although the electrochemical studies on this film are currently in progress. Results of these studies and plans to extend this approach for fabrication of an all solid state thin film microbattery will be described and discussed.
4:30 PM JJ3.4
MULTILAYER COATINGS FOR INTEGRAL CYLINDRICAL SUBSTRATES FOR HARD X-RAY TELESCOPES. A. Ivan , MIT, Dept of Nuclear Engr, Cambridge, MA; R. Bruni, J. Everett, P. Gorenstein, S. Romaine, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA.
Scientific objectives for hard X-ray astronomy require the development of new, focusing telescope optics for the energy band > 10 keV. The proposed next X-ray mission, Constellation X, plans to use a hard X-ray telescope system with a sensitivity of 20-100 times over that of current non-focusing instruments. We are currently engaged in a feasibility study based on a new design for the grazing incidence X-ray optics. Our objective is the production of graded d-spacing multilayer coatings on the inner surface of cylindrical replicated substrates. Combinations of reflector and spacer materials under study for this application are: W/Si, W/C, and Ni/C. The coating process is DC magnetron sputtering. Data presented here were obtained from flat substrates mounted in a cylindrical shaped surrogate. The substrates were coated and characterized using X-ray reflectivity, AFM, and cross-sectional TEM. Additional analytical techniques (RBS, Auger analysis, residual stress measurements) were used in the optimization of thin film properties.
4:45 PM JJ3.5
MICROGRAVITY PROCESSING OF BIOPOLYMER/METAL COMPOSITES FOR NON-LINEAR OPTICAL APPLICATIONS. Debra J. Trantolo, Roslyn L. White , Joseph D. Gresser, Paul H. Fackler, Donald L. Wise, Cambridge Scientific, Inc., Belmont, MA; Donald O. Frazier, National Aeronautics and Space Administration, George C. Marshall Space Flight Center, Huntsville, AL.
One objective of our microgravity research is the development of NLO-active materials with optical clarity and mechanical strength. The target materials must not only possess reasonable NLO (i.e.; x2
) susceptibilities, but also be optically clear, thermally stable and have high impact strength. To develop this material, a x3
-active TCVA (tricyanovinyl aniline)/silver sol is processed with a x2
-active polymeric host to develop a NLO-active polymer-metal (``polymet'') composite. Crystals grown in space have been shown to be of higher quality than ``earth-grown'' crystals because more defect-free specimens are thought to be obtained in the absence of gravity-fueled convection. Defect-free organic crystals are of particular interest because they can exhibit high optical nonlinearities. However, as these are molecular crystals, they tend to be brittle and cannot be as easily fabricated into thin films as can polymer analogs. Polymers having a controlled supramolecular structure and morphology are likely even more promising candidates as NLOM. Our early work showed that by orienting biopolymers, materials with known supramolecular structure, in an electric field under microgravity conditions optical nonlinearity can be optimized. The magnitude of the NLO response (i.e., second harmonic generation, SHG) was directly related to the degree of molecular order within the film). The work now to be discussed, focuses on improving upon the NLO activity of the biopolymer system by using a metal dopant. By analogy to microgravity processing of metal/ceramic alloys (``cermets''), the resulting polymet should benefit from homogeneous orientation of the minor metal phase within the polymer phase and optimize the potential of polymeric NLOM.