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NASA NTRS1999

Undercooling, Rapid Solidification, and Relations to Processing in Low Earth Orbit (A Review of the Works of Bingbo Wei)

This is a survey of the published works of Prof. Bingbo Wei of the Department of Applied Physics at Northwestern Polytechnical University, Xian P.R. China. Transformations among solid - liquid - and vapor are fundamental to the foundations of life and culture on Earth. The development and understanding of materials has lead the evolution and advancement of the human race since antiquity. Materials and fluids research is continuing today, with us standing on the shoulders of those that have gone before us. Technological and scientific breakthroughs continue due to studies of greater and greater complexity, that include for example, research done at high pressures, in high magnetic fields, at temperatures near absolute zero, and in the low gravity environment of low Earth orbit. Of particular technological importance is the liquid to solid transformation of metals and alloys. Solidification processing is generally the most important factor in the final properties of objects made of metal; and undercooling is the fundamental driving force for all solidification. The interest and resources dedicated to the study of solidification and undercooling are great and World wide. For many years B. Wei and his coworkers have been studying undercooling and rapid solidification and have amassed a significant body of published research in this important field, contributing to the leading edge of the state-of-the-art. It is the goal of this memorandum to provide a review of the research of B. Wei et al.; publications in Chinese are included in the reference list but are not discussed. The bulk of Wei's work has been in the area of undercooling and rapid solidification [1-11, 13-16, 24-36] with papers dating back to 1989, the same year he earned his Ph.D. Below, discussions of Wei's undercooling and rapid solidification research have been grouped together mostly on the basis of alloy type, such as eutectic, intermetallic, or monotectic.

deGroh, Henry C., III↗
NASA NTRS1999

Turbomachinery Design Quality Checks to Avoid Friction Induced Structural Failure

A unique configuration of the P&W SSME Alternate Fuel Turbopump turbine disk/blade assembly, combined with a severe thermal environment, resulted in several structural anomalies that were driven by frictional contact forces. Understanding the mechanics of these problems provides new quality checks for future turbo machinery designs. During development testing in 1997 of the SSME alternate fuel turbopump at Stennis Space Center, several potentially serious problems surfaced with the turbine disk/blade assembly that had not been experienced in extensive earlier testing. Changes to the operational thermal environment were noted based on analytical prediction of modifications that affected performance and on stationary thermal measurements adjacent to the rotor assembly. A detailed structural investigation was required to reveal the mechanism of distress induced by the change. The turbine disk experienced cracking in several locations due to increased thermal gradient induced stress during start and shutdown transients. This was easily predictable using standard analysis procedures and expected once the thermal environment was characterized. What was not expected was the curling of a piston ring used for blade axial retention in the disk, indentation of the axial face of the blade attachment by a spacer separating the first and second stage blades, and most significantly, galling and cracking of the blade root attachment that could have resulted in blade release. Past experience, in gas turbine environments, set a precedent of never relying on friction for help and to evaluate it only in specific instances where it was obvious that it would degrade capability. In each of the three cases above, friction proved to be a determining factor that pushed the components into an unsatisfactory mode of operation. The higher than expected temperatures and rapid thermal transients combined with friction to move beyond past experience. The turbine disk/blade assembly configuration contributed to the potential for these problems to occur by limiting the radial deflection from thermals and centrifugal loading. The cooled solid bore configuration was chosen to improve rotordynamic stability by limiting the length of rotor overhang while still protecting the roller bearing by maintaining zero slope under the inner race. During a start transient, the rim area of the disk heats rapidly and expands axially and circumferentially and requires corresponding radial and axial growth of the disk to maintain relative positioning of the disk, blades, spacers and retainer rings. The stiffness, large thermal mass, and bore cooling flow combine to severely limit the disk rim radial growth which results in the potential for relative movement between these parts. Friction then becomes a player in the determination of component stress.

Moore, Jerry H.↗
NASA NTRS1999

Dreams, Hopes, Realities: NASA's Goddard Space Flight Center, the First Forty Years

Throughout history, the great achievements of civilizations and cultures have been recorded in lists of dates and events. But to look only at the machinery, discoveries, or milestones is to miss the value of these achievements. Each goal achieved or discovery or made represents a supreme effort on the part of individual people who came and worked together for a purpose greater than themselves. Driven by an innate curiosity of the spirit, we have built civilizations and discovered new worlds, always reaching out beyond what we knew or thought was possible. These efforts may have used ships or machinery, but the achievement was that of the humans who made those machines possible- remarkable people willing to endure discomfort, frustration, fatigue, and the risk of failure in the hope of finding out something new. This is the case with the history of the Goddard Space Flight Center. This publication traces the legacy of successes, risks, disappointments and internationally recognized triumphs of the Center's first 40 years. It is a story of technological achievement and scientific discovery; of reaching back to the dawn of time and opening up a new set of eyes on our own planet Earth. In the end, it is not a story about machinery or discoveries, but a story about ourselves. If we were able to step off our planet, and if we continue to discover new mysteries and better technology, it is because the people who work at Goddard always had a passion for exploration and the dedication to make it happen. The text that follows is a testimony to the challenges people at the Goddard Space Flight Center have faced and overcome over almost half a century. Today, we stand on the threshold of a new and equally challenging era. It will once again test our ingenuity, skills, and flexibility as we find new ways of working with our colleagues in industry, government, and academia. Doing more with less is every bit as ambitious as designing the first science instrument to study the heavens. But if we are to continue exploring our world and our universe, it is every bit as important. Robert H. Goddard once said, "The dream of yesterday is the hope of today and the reality of tomorrow." This is our heritage. Our challenge is to keep our spirit of dedication, vision, and innovative thinking alive, so we can turn today's dreams into a new century of possibility and progress. Our journeys into space are the greatest ongoing adventure the human race has ever undertaken, and everyone here has played an important role in that endeavor. This book is about everyone who has worked at the Goddard Space Flight Center.

Wallace, Lane E.↗
NASA NTRS2000

Dry Air Entrainment into Hurricane Earl

Hurricane Earl formed in the Gulf of Mexico in September 1998. It quickly was upgraded from a tropical disturbance to tropical storm status and then to a hurricane. Earl possessed hybrid (tropical and extratropical) characteristics throughout its lifetime. The system maintained and erratic track, which led to wide variability in the operational track forecasts. It eventually made landfall on the Florida panhandle on 2 September and raced northeastward. During August and September 1998, NASA conducted the third Convection and Moisture Experiment (CAMEX-3). The experiment was focused on studying hurricanes with an emphasis toward developing a better understanding of their intensification and motion. Earl provides a unique opportunity to utilize high spatial and temporal resolution data collected from the DC-8 and high altitude ER-2 NASA platforms, which flew over Earl as it made landfall. These data can also be put into broader view provided by other instruments from the Geosychronous Operational Environmental Satellites (GOES) and the Tropical Rainfall Measuring Mission (TRMM) satellites. Hurricane Earl was affected by entrainment of dry air from the northwest. Hurricane Isis was intensifying and approaching the Mexican Pacific coast with its associated outflow potentially affecting the inflow into Earl as the storm neared Florida. In addition, a longwave synoptic trough circulation was present over the eastern U.S. Either or both of these could be responsible for the dry air into the system. This paper will focus on identifying the source of the dry by using upper-level wind and moisture fields derived from the GOES 6.7 um water vapor imagery. We will attempt to relate the large-scale observations to those from the NASA aircraft. An infrared instrument onboard the ER-2 also has a similar wavelength and may be able to confirm some of the GOES findings. In addition, a microwave radiometer with 4 channels focused on measuring precipitation and its associated ice scattering was also aboard the ER-2. The microwave observations will allow the authors to relate the entrainment to precipitation changes near the flight path of the aircraft.

Guillory, Anthony R.↗
NASA NTRS1999

Entrainment of Upper Level Dry Air Into Hurricane Earl

Hurricane Earl formed in the Gulf of Mexico in September 1998. It quickly was upgraded from a tropical disturbance to tropical storm status and then to a hurricane. Earl possessed hybrid (tropical and extratropical) characteristics throughout its lifetime. The system maintained and erratic track, which led to wide variability in the operational track forecasts. It eventually made landfall on the Florida panhandle on 2 September and raced northeastward. During August and September 1998, NASA conducted the third Convection and Moisture Experiment (CAMEX-3). The experiment was focused on studying hurricanes with an emphasis toward developing a better understanding of their intensification and motion. Earl provides a unique opportunity to utilize high spatial and temporal resolution data collected from the DC-8 and high altitude ER-2 NASA platforms, which flew over Earl as it made landfall. These data can also be put into broader view provided by other instruments from the Geosynchronous Operational Environmental Satellites (GOES) and the Tropical Rainfall Measuring Mission (TRMM) satellites. Hurricane Earl was affected by entrainment of dry air from the northwest. Hurricane Isis was intensifying and approaching the Mexican Pacific coast with its associated outflow potentially affecting the inflow into Earl as the storm neared Florida. In addition, a longwave synoptic trough circulation was present over the eastern U.S. Either or both of these could be responsible for the dry air into the system. This paper will focus on identifying the source of the dry by using upper-level wind and moisture fields derived from the GOES 6.7 um water vapor imagery. We will attempt to relate the large-scale observations to those from the NASA aircraft. An infrared instrument onboard the ER-2 also has a similar wavelength and may be able to confirm some of the GOES findings. In addition, a microwave radiometer with 4 channels focused on measuring precipitation and its associated ice scattering was also aboard the ER-2. The microwave observations will allow the authors to relate the entrainment to precipitation changes near the flight path of the aircraft.

Guillory, Anthony R.↗
NASA NTRS1999

Remembering Apollo 11: The 30th Anniversary Data Archive CD-ROM

On July 20, 1969, the human race accomplished its single greatest technological achievement of all time when a human first set foot on another celestial body. Six hours after landing at 4:17 p.m. Eastern Standard Time (with less than thirty seconds of fuel remaining), Neil A. Armstrong took the "small step" into our greater future when he stepped off the Lunar Module, named Eagle, onto the surface of the Moon, from which he could look up and see Earth in the heavens as no one had done before him. He was shortly joined by Edwin "Buzz" Aldrin, and the two astronauts spent twenty-one hours on the lunar surface and returned forty-six pounds of lunar rocks. After their historic walks on the Moon, they successfully docked with Michael Collins, patiently orbiting the cold but no longer lifeless Moon alone in the Command module Columbia. This CR-ROM is intended as a collection of hard to find technical data and other interesting information about the Apollo 11 mission, as well as the apollo program in general. It includes basic overviews, such as a retrospective analysis, an annotated bibliography, and history of the lunar-orbit rendezvous concept. It also contains technical data, such as mission operations reports, press kits, and news references for all of the Apollo missions, the Apollo spacecraft, and the Saturn V launch vehicle. Rounding out this CD-ROM are extensive histories of the lunar Orbiter program (the robotic predecessor to Apollo, biographies of the Apollo astronauts and other key individuals, and interesting audio-visual materials, such as video and audio clips, photo galleries, and blueprint-like diagrams of the Apollo spacecraft.

Edgar M Cortright↗
NASA NTRS2000

Marshall Space Flight Center High Speed Turbopump Bearing Test Rig

The Marshall Space Flight Center has a unique test rig that is used to test and develop rolling element bearings used in high-speed cryogenic turbopumps. The tester is unique in that it uses liquid hydrogen as the coolant for the bearings. This test rig can simulate speeds and loads experienced in the Space Shuttle Main Engine turbopumps. With internal modifications, the tester can be used for evaluating fluid film, hydrostatic, and foil bearing designs. At the present time, the test rig is configured to run two ball bearings or a ball and roller bearing, both with a hydrostatic bearing. The rig is being used to evaluate the lifetimes of hybrid bearings with silicon nitride rolling elements and steel races.

Gibson, Howard↗
NASA NTRS1999

Altimeter Data for Operational Use in the Marine Environment

TOPEX/Poseidon has been collecting altimeter data continuously since October 1992. Altimeter data have been used to produce maps of sea surface height, geostrophic velocity, significant wave height, and wind speed. This information is of proven use to mariners as well as to the scientific community. Uses of the data include commercial and recreational vessel routing, ocean acoustics, input to geographic information systems developed for the fishing industry, identification of marine mammal habitats, fisheries management, and monitoring ocean debris. As with sea surface temperature data from the Advanced Very High Resolution Radiometer (AVHRR) in the late 1980s and early 1990s, altimeter data from TOPEX/Poseidon and ERS-1 and -2 are in the process of being introduced to the marine world for operational maritime use. It is anticipated that over the next few years companies that specialize in producing custom products for shipping agencies, fisheries and yacht race competitors will be incorporating altimeter data into their products. The data are also being incorporated into weather and climate forecasts by operational agencies both in the US and Europe. This paper will discuss these products, their uses, operational demonstrations and means of accessing the data.

Digby, Susan↗
NASA NTRS2000

Spacecraft Autonomy and Automation: A Comparative Analysis of Strategies for Cost Effective Mission Operations

The evolution of satellite operations over the last 40 years has drastically changed. October 4, 1957 (during the cold war) the Soviet Union launched the world's first spacecraft into orbit. The Sputnik satellite orbited Earth for three months and catapulted the United States into a race for dominance in space. A year after Sputnik, President Dwight Eisenhower formed the National Space and Aeronautics Administration (NASA). With a team of scientists and engineers, NASA successfully launched Explorer 1, the first US satellite to orbit Earth. During these early years, massive amounts of ground support equipment and operators were required to successfully operate spacecraft vehicles. Today, budget reductions and technological advances have forced new approaches to spacecraft operations. These approaches require increasingly complex, on board spacecraft systems, that enable autonomous operations, resulting in more cost-effective mission operations. NASA's Goddard Space Flight Center, considered world class in satellite development and operations, has developed and operated over 200 satellites during its 40 years of existence. NASA Goddard is adopting several new millennium initiatives that lower operational costs through the spacecraft autonomy and automation. This paper examines NASA's approach to spacecraft autonomy and ground system automation through a comparative analysis of satellite missions for Hubble Space Telescope-HST, Near Earth Asteroid Rendezvous-NEAR, and Solar Heliospheric Observatory-SoHO, with emphasis on cost reduction methods, risk analysis and anomalies and strategies employed for mitigating risk.

Wright, Nathaniel, Jr.↗
NASA NTRS2000

Estimating Forest Vertical Structure from Multialtitude, Fixed-Baseline Radar Interferometric and Polarimetric Data

Parameters describing the vertical structure of forests, for example tree height, height-to-base-of-live-crown, underlying topography, and leaf area density, bear on land-surface, biogeochemical, and climate modeling efforts. Single, fixed-baseline interferometric synthetic aperture radar (INSAR) normalized cross-correlations constitute two observations from which to estimate forest vertical structure parameters: Cross-correlation amplitude and phase. Multialtitude INSAR observations increase the effective number of baselines potentially enabling the estimation of a larger set of vertical-structure parameters. Polarimetry and polarimetric interferometry can further extend the observation set. This paper describes the first acquisition of multialtitude INSAR for the purpose of estimating the parameters describing a vegetated land surface. These data were collected over ponderosa pine in central Oregon near longitude and latitude -121 37 25 and 44 29 56. The JPL interferometric TOPSAR system was flown at the standard 8-km altitude, and also at 4-km and 2-km altitudes, in a race track. A reference line including the above coordinates was maintained at 35 deg for both the north-east heading and the return southwest heading, at all altitudes. In addition to the three altitudes for interferometry, one line was flown with full zero-baseline polarimetry at the 8-km altitude. A preliminary analysis of part of the data collected suggests that they are consistent with one of two physical models describing the vegetation: 1) a single-layer, randomly oriented forest volume with a very strong ground return or 2) a multilayered randomly oriented volume; a homogeneous, single-layer model with no ground return cannot account for the multialtitude correlation amplitudes. Below the inconsistency of the data with a single-layer model is followed by analysis scenarios which include either the ground or a layered structure. The ground returns suggested by this preliminary analysis seem too strong to be plausible, but parameters describing a two-layer compare reasonably well to a field-measured probability distribution of tree heights in the area.

Treuhaft, Robert N.↗
NASA NTRS2000

Transportation: The Key to Unlocking the Final Frontier

For this future generations in this new millennium, only two new frontiers remain to be explored and developed by humans: Under the oceans, seas and lakes (about 80 percent of the Earth) and The vast reaches of near and outer space. We are slowly running out of resources while this planet's population is exploding. We must establish new, highly reliable and low-cost ways to colonize under the seas and to get people permanently off "Spaceship Planet Earth". We must establish new colonies permanently in space because it is vital to the ultimate survival of the human race. Reliable and affordable space transportation for routine human travel into space and the planets is once again the key to developing this last great frontier. This talk will now focus on what NASA is now doing to initiate the process in earnest. Space transportation is the key, and once again will only meet the needs with new generations of competent, talented, and innovative mechanical engineers.

Sackheim, Robert L.↗
NASA NTRS2000

Nuclear Pulse Propulsion: Orion and Beyond

The race to the Moon dominated manned space Fight during the 1960's. and culminated in Project Apollo. which placed 12 humans on the Moon Unbeknownst to the public at that time, several U.S. Government agencies sponsored a project that could have conceivably, placed 150 people on the Moon and eventually sent crewed expeditions to Mars and the outer Planets. These feats could have possibly been accomplished during, the same period of time as Apollo. and for approximately the same cost. The project. code-named Orion. featured an extraordinary propulsion method known n as Nuclear Pulse The concept is probably as radical today as t was at the down of the space age. However its development appeared to he so promising that it was only by Political and non-technical considerations that it was not used to extend humanity reach throughout the solar system and quite possible to the stars. This paper discusses the rationale for nuclear pulse propulsion and presents a general history of the concept. focusing particularly on Project Orion. It describes some of the reexaminations being done in this area and discusses some of the new ideas that could mitigate many of the political and environmental issues associated with the concept.

Schmidt, George R.↗
NASA NTRS2001

Using Runtime Analysis to Guide Model Checking of Java Programs

This paper describes how two runtime analysis algorithms, an existing data race detection algorithm and a new deadlock detection algorithm, have been implemented to analyze Java programs. Runtime analysis is based on the idea of executing the program once. and observing the generated run to extract various kinds of information. This information can then be used to predict whether other different runs may violate some properties of interest, in addition of course to demonstrate whether the generated run itself violates such properties. These runtime analyses can be performed stand-alone to generate a set of warnings. It is furthermore demonstrated how these warnings can be used to guide a model checker, thereby reducing the search space. The described techniques have been implemented in the b e grown Java model checker called PathFinder.

Havelund, Klaus↗
NASA NTRS2001

Water Ice and Life's Roots in Space

Nearly three decades ago as Voyager 2 spacecraft raced out of the Solar System. NASA engineers turned its camera arm around (at the request of the American astronomer Carl Sagan) to take a parting snapshot of Earth. Earth's image was a single pale blue pixel, its color caused by the Rayleigh scattering of sunlight in the water of our oceans. Earth is a water planet, and this is the color of life. No matter how far we travel on our planet, no matter how high or deep, if we find liquid water, we find some form of life that manages to survive there. And yet there is a cruel irony. Water in its solid crystalline form is hostile to life. Organisms can roost in geysers, wallow in brine and gulp down acid, but they cowered from ice. The rigid ordering of water molecules in ice crystals expels impurities and tears organic tissue beyond repair. In fact, about the only good thing you can say about ice is that it gets out of the way: Its low density ensures that it floats and leaves the water dwelling creatures in peace. Recent discoveries have caused us to rethink this basic premise. New lines of evidence both observational and experimental - suggest that prebiotic organic compounds are not only comfortable in, but in fact had their origin in a peculiar form of solid water ice that is ubiquitous in interstellar space, but completely absent from Earth. Only recently have we been able to create even submicroscopic quantities of this ice in terrestrial laboratories, yet it constitutes the most abundant form of water in the universe. Interstellar ice is a far cry from the ice we are so familiar with on Earth. This interstellar ice has no crystalline structure, and despite the fact that its temperature is a scant few degrees above absolute zero (where all molecular motion ceases), it is highly reactive and can flow like water when exposed to radiation. It is in fact this ice's similarity to liquid water that allows it to participate in the creation of the very first organic compounds.

Blake, David↗
NASA NTRS1994

Biomedical Use of Aerospace Personal Cooling Garments

Personal thermoregulatory systems are required during extravehicular activity (EVA) to remove the metabolic heat generated by the suited astronaut. The Extravehicular and Protective Systems (STE) Branch of NASA Ames Research Center has developed advanced concepts or liquid cooling garments for both industrial and biomedical applications for the past 25 years. Examples of this work include: (1) liquid cooled helmets for helicopter pilots and race car drivers; (2) vests for fire and mine rescue personnel; (3) bras to increase the definition of tumors during thermography; (4) lower body garments for young women with erythomelaigia; and (5) whole body garments used by patients with multiple sclerosis (MS). The benefits of the biomedical application of artificial thermoregulation received national attention through two recent events: (1) the liquid-cooled garment technology was inducted into the United States Space Foundation's Space Technology Hall of Fame (1993); and (2) NASA has signed a joint Memorandum of Understanding with the Multiple Sclerosis Association (1994) to share this technology for use with MS patient treatment. The STE Branch is currently pursuing a program to refine thermoregulatory design in light of recent technology developments that might be applicable for use by several medical patient populations. Projects have been initiated to apply thermoregulatory technology for the treatment and/or rehabilitation of patients with spinal cord injuries, multiple sclerosis, migraine headaches, and to help prevent the loss of hair during chemotherapy.

Webbon, Bruce W.↗
NASA NTRS1995

Building a Successful Security Infrastructure: What You Want vs. What You Need vs. What You Can Afford

With the fast growing popularity of the Internet, many organizations are racing to get onto the on-ramp to the Information Superhighway. However, with frequent headlines such as 'Hackers' break in at General Electric raises questions about the Net's Security', 'Internet Security Imperiled - Hackers steal data that could threaten computers world-wide' and 'Stanford Computer system infiltrated; Security fears grow', organizations find themselves rethinking their approach to the on-ramp. Is the Internet safe? What do I need to do to protect my organization? Will hackers try to break into my systems? These are questions many organizations are asking themselves today. In order to safely travel along the Information Superhighway, organizations need a strong security framework. Developing such a framework for a computer site, whether it be just a few dozen hosts or several thousand hosts is not an easy task. The security infrastructure for a site is often developed piece-by-piece in response to security incidents which have affected that site over time. Or worse yet, no coordinated effort has been dedicated toward security. The end result is that many sites are still poorly prepared to handle the security dangers of the Internet. This paper presents guidelines for building a successful security infrastructure. The problem is addressed in a cookbook style method. First is a discussion on how to identify your assets and evaluate the threats to those assets; next are suggestions and tips for identifying the weak areas in your security armor. Armed with this information we can begin to think about what you really need for your site and what you can afford. In this stage of the process we examine the different categories of security tools and products that are available and then present some tips for deciding what is best for your site.

Crabb, Michele D.↗
NASA NTRS2001

Effect of Roller Profile on Cylindrical Roller Bearing Life Prediction: Comparison of Bearing Life Theories - Part 1

Four rolling-element bearing life theories were chosen for analysis and compared for a simple roller-race geometry model. The life theories were those of Weibull; Lundberg and Palmgren; Ioannides and Harris; and Zaretsky. The analysis without a fatigue limit of Ioannides and Harris is identical to the Lundberg and Palmgren analysis, and the Weibull analysis is similar to that of Zaretsky if the exponents are chosen to be identical. The resultant predicted life a each stress condition not only depends on the life equation used but also on the Weibull slope assumed. The least variation in predicted life with Weibull slope comes with the Zaretsky equation. Except for a Weibull slope of 1.11, at which the Weibull equation predicts the highest lives, the highest lives are predicted for the Zaretsky equation. For Weibull slopes of 1.5 and 2, both the Lundherg-Palmgren and Ioannides-Harris (where tau(sub u) = 0) equations predict lower lives than the ANSI/ABMA/ISO standard. Based upon the Hertz stresses for line contact, the accepted load-life exponent of 10/3 results in a maximum Hertz stress-life exponent equal to 6.6. This value is inconsistent with that experienced in the field. The assumption of as shear stress fatigue limit tau(sub u) results in Hertz stress-life exponents greater than are experimentally verifiable.

Poplawski, Joseph V.↗
NASA NTRS2001

Java PathExplorer: A Runtime Verification Tool

We describe recent work on designing an environment called Java PathExplorer for monitoring the execution of Java programs. This environment facilitates the testing of execution traces against high level specifications, including temporal logic formulae. In addition, it contains algorithms for detecting classical error patterns in concurrent programs, such as deadlocks and data races. An initial prototype of the tool has been applied to the executive module of the planetary Rover K9, developed at NASA Ames. In this paper we describe the background and motivation for the development of this tool, including comments on how it relates to formal methods tools as well as to traditional testing, and we then present the tool itself.

Havelund, Klaus↗