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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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New non-contact techniques of measuring electrical conductivity and surface tension are introduced.
The main objective of this task was to experimentally determine the feasibility of using a non-contact IR emission spectroscopy technique to measure the hot spot channel temperature of sub-micron GaAs metal semiconductor field effect transistor gate during operation.
Non-contact methods have been implemented in conjunction with levitation techniques to carry out the measurement of the macroscopic properties of liquids significantly cooled below their nominal melting point. Free suspension of the sample and remote methods allow the deep excursion into the metastable liquid state and the determination of its thermophysical properties. We used this approach to investigate common substances such as water, o-terphenyl, succinonitrile, as well as higher temperature melts such as molten indium, aluminum and other metals. Although these techniques have thus far involved ultrasonic, electromagnetic, and more recently electrostatic levitation, we restrict our attention to ultrasonic methods in this paper. The resulting magnitude of maximum thermal supercooling achieved have ranged between 10 and 15% of the absolute temperature of the melting point for the materials mentioned above. The physical properties measurement methods have been mostly novel approaches, and the typical accuracy achieved have not yet matched their standard equivalent techniques involving contained samples and invasive probing. They are currently being refined, however, as the levitation techniques become more widespread, and as we gain a better understanding of the physics of levitated liquid samples.
Foam loss on the External Tank (ET) during launch can be caused by a number of factors. Voids are the best understood mechanism of foam loss, although it is known that delaminations, cracks and crushed foam can also lead to liberation of foam. Shortly after the Columbia accident, work began on non-destructive evaluation of foam targeted at finding voids and delaminations. After several months of searching for candidate methods capable of inspecting ET foam, the five most promising techniques were taken through a blind test and narrowed down to two methods to develop and use for inspection of the ET. These methods were backscatter radiography and terahertz imaging. The backscatter radiography system measures a test part by detecting Compton backscattered x-ray energy generated by a collimated beam of x-rays directed at the test subject. This collimated beam is scanned across the subject, recording scatter intensity data one pixel at a time until the area of interest is covered. The resulting data can be used to generate an image similar to a radiograph. Some depth information can be gathered utilizing apertures or collimation on the detectors. The detectors are located around the collimated source, making this a single sided inspection. The void detection limit with the currently utilized system is around 0.5 inches in diameter by 0.2 inches high. The terahertz imaging system inspects a test part by utilizing a transceiver to emit a pulse focused at the aluminum skin of the ET, which reflects it back to the transceiver where it is analyzed. The transceiver is scanned across the area of interest until a measurement has been taken at every location. Amplitude, time delay and frequency content are examined to note any discontinuities which may be the result of a void or other type of defect. The pulse currently utilized is in the millimeter wave regime. The void detection limit with this system is around 0.5 inches in diameter by 0.2 inches high. With increased interest in other causes of foam loss following the flight of Discovery in July 2005, laser shearography was added to the techniques used for inspecting ET foam. The shearography method records a sheared image of a laser speckle pattern projected on a test part before And after some sort of excitation. The resultant fringe pattern allows the slope of the out of plane displacement to be measured. For crushed and delaminated foam applications, a non-contact air coupled acoustic force is used to excite the surface of the foam. Regions without defects tend to respond differently to the sound energy than do regions with defects, generating a map of the foam integrity. Foam crushed to a depth of about 0.1 inches is detectable with shearography even after it has relaxed to its original shape.
A non-contact fast erase method for erasing information stored on a magnetic or optical media. The magnetic media element includes a magnetic surface affixed to a toroidal conductor and stores information in a magnetic polarization pattern. The fast erase method includes applying an alternating current to a planar inductive element positioned near the toroidal conductor, inducing an alternating current in the toroidal conductor, and heating the magnetic surface to a temperature that exceeds the Curie-point so that information stored on the magnetic media element is permanently erased. The optical disc element stores information in a plurality of locations being defined by pits and lands in a toroidal conductive layer. The fast erase method includes similarly inducing a plurality of currents in the optical media element conductive layer and melting a predetermined portion of the conductive layer so that the information stored on the optical medium is destroyed.
The NASA John H. Glenn Research Center has developed and tested a revolutionary Radial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Radial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Radial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical applications, manufacturing equipment, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Radial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.
The NASA John H. Glenn Research Center has developed a revolutionary 32 in. diameter Levitated Ducted Fan (LDF) conceptual design. The objective of this work is to develop a viable non-contact propulsion system utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels, and mitigate many of the concerns and limitations encountered in conventional aircraft propulsors. The physical layout consists of a ducted fan drum rotor with blades attached at the outer diameter and supported by a stress tuner ring at the inner diameter. The rotor is contained within a stator. This concept exploits the unique physical dimensions and large available surface area to optimize a custom, integrated, electromagnetic system that provides both the levitation and propulsion functions. The rotor is driven by modulated electromagnetic fields between the rotor and the stator. When set in motion, the time varying magnetic fields interact with passive coils in the stator assembly to produce repulsive forces between the stator and the rotor providing magnetic suspension. LDF can provide significant improvements in aviation efficiency, reliability, and safety, and has potential application in ultra-efficient motors, computers, and space power systems.
The NASA Glenn Research Center (GRC) has been testing free-piston Stirling convertors for potential use in radioisotope power systems. These convertors tend to be in the 35 to 80 watt electric power output range. Tests at GRC have accumulated over 80,000 hours of operation. Test articles have been received from Infinia Corporation of Kennewick, WA and from Sunpower of Athens, OH. Infinia designed and built the developmental Stirling Technology Demonstration Convertors (TDC) in addition to the more advanced Test Bed and Engineering Unit convertors. GRC has eight of the TDC's under test including two that operate in a thermal vacuum environment. Sunpower designed and developed the EE- 35 and the Advanced Stirling Convertor (ASC). GRC has six of the EE-35's and is preparing for testing multiple ASC's. Free-piston Stirling convertors for radioisotope power systems make use of non-contacting operation that eliminates wear and is suited for longterm operation. Space missions with radioisotope power systems are often considered that extend from three to 14 years. One of the key capabilities of the GRC test facility is the ability to support continuous, unattended operation. Hardware, software, and procedures for preparing the test articles were developed to support these tests. These included the processing of the convertors for minimizing the contaminants in the working fluid, developing a helium charging system for filling and for gas sample analysis, and the development of new control software and a high-speed protection circuit to insure safe, round-the-clock operation. Performance data of Stirling convertors over time is required to demonstrate that a radioisotope power system is capable of providing reliable power for multi-year missions. This paper will discuss the status of Stirling convertor testing at GRC.
This paper describes a unique experimental facility designed to measure damping of materials at cryogenic temperatures for the Terrestrial Planet Finder (TPF) mission at the Jet Propulsion Laboratory. The test facility removes other sources of damping in the measurement by avoiding frictional interfaces, decoupling the test specimen from the support system, and by using a non-contacting measurement device. Damping data reported herein are obtained for materials (Aluminum, Aluminum/Terbium/Dysprosium, Titanium, Composites) vibrating in free-free bending modes with low strain levels (< 10(exp -6) ppm). The fundamental frequencies of material samples are ranged from 14 to 202 Hz. To provide the most beneficial data relevant to TPF-like precision optical space missions, the damping data are collected from room temperatures (around 293 K) to cryogenic temperatures (below 40 K) at unevenly-spaced intervals. More data points are collected over any region of interest. The test data shows a significant decrease in viscous damping at cryogenic temperatures. The cryogenic damping can be as low as 10(exp -4) %, but the amount of the damping decrease is a function of frequency and material. However, Titanium 15-3-3-3 shows a remarkable increase in damping at cryogenic temperatures. It demonstrates over one order of magnitude increase in damping in comparison to Aluminum 6061-T6. Given its other properties (e.g., good stiffness and low conductivity) this may prove itself to be a good candidate for the application on TPF. At room temperatures, the test data are correlated well with the damping predicted by the Zener theory. However, large discrepancies at cryogenic temperatures between the Zener theory and the test data are observed.
AlliedSignal aerospace company is committed to significantly improving the reliabilities of air/oil seals in their gas turbine engines. One motivation for this is that aircraft cabin air quality can be affected by the performance of mainshaft air/oil seals. In the recent past, coking related failure modes have been the focus of air/oil seal R&D at AlliedSignal. Many significant advances have been made to combat coke related failures, with some more work continuing in this area. This years R&D begins to address other commin failure modes. Among them, carbon seal "blistering" has been a chronic problem facing the sealing industry for many decades. AlliedSignal has launched an aggressive effort this year to solve this problem for our aerospace rated carbon seals in a short (one to two year) timeframe. Work also continues in developing more user-friendly tools and data for seal analysis & design. Innovations in seal cooling continue. Nominally non-contacting hydropad sealing concept is being developed for aerospace applications. Finally, proprietary work is in planning stages for development of a seal with the aggressive aim of zero oil leakage.
A device and method are provided which non-destructively detect crack length and crack geometry in thin metallic plates. A non-contacting vibration apparatus produces resonant vibrations without introducing extraneous noise. Resulting resonant vibration shifts in cracked plates are correlated to known crack length in plates with similar resonant vibration shifts. In addition, acoustic emissions of cracks at resonance frequencies are correlated to acoustic emissions from known crack geometries.
A counter-rotating machine, such as a positive displacement pump having a pair of meshed, non-contacting helical screws (10,12), subjects its rotating members to axial and radial thrust forces when used for such purposes as compression of liquid or gaseous phase fluids while transporting them through a pump cavity (11,13). Each helical screw (10,12) has a shaft (17,17') which is actively suspended at opposite ends (11a,11b) of the pump cavity by a servo-controlled magnetic bearing assembly (19) and a servo-controlled rotary drive motor (20). Both bearing assemblies and drive motors are mounted on the outside of the pump cavity (11,13). Opto-electric angular position sensors (250) provide synchronization between radial orientation of the drive motors. The bearing assemblies and drive motors conjugately provide axial stabilization and radial centering of the helical screws during volumetric compression of aspirated liquid or gaseous phase fluids.
Two laser beams derived from a laser pass through a furnace and are superposed in a laser spot to produce interference fringes having the same pitch as that of a Ronchi grating printed on a retroreflecting screen. Minute fluctuations of the laser beams caused by sound waves from leaks result in intensity fluctuations of the laser spot when the laser fringes move past the fixed grating. A telescope and photocell arrangement detects the light variations to produce an electrical signal which is amplified and filtered to detect the sound of leaks. This non-contact laser Schlieren microphone is sensitive to sounds all along the path of the beams.
Since the Space Shuttle Columbia accident, NASA has focused on improving advanced nondestructive evaluation (NDE) techniques for the Reinforced Carbon-Carbon (RCC) panels that comprise the orbiter's wing leading edge and nose cap. Various nondestructive inspection techniques have been used in the examination of the RCC, but thermography has emerged as an effective inspection alternative to more traditional methods. Thermography is a non-contact inspection method as compared to ultrasonic techniques which typically require the use of a coupling medium between the transducer and material. Like radiographic techniques, thermography can inspect large areas, but has the advantage of minimal safety concerns and the ability for single-sided measurements. Details of the analysis technique that has been developed to allow insitu inspection of a majority of shuttle RCC components is discussed. Additionally, validation testing, performed to quantify the performance of the system, will be discussed. Finally, the results of applying this technology to the Space Shuttle Discovery after its return from the STS-114 mission in July 2005 are discussed.
NASA is pursuing the development of large ultra-lightweight structures, commonly referred to as gossamer space structures. These structures have large areas and small areal densities, which complicates ground testing significantly as the ground operations interfaces and gravity loading can become cumbersome. Laser vibrometry has proven to be a critical sensing technology for validating the structural characteristics of these gossamer structures, due to its precision, range, and non-contacting nature.
A unique experimental facility has been designed to measure damping of materials at cryogenic temperatures. The test facility pays special attention to removing other sources of damping in the measurement by avoiding frictional interfaces, decoupling the test specimen from the support system, and by using a non-contacting measurement device; Damping data is obtained for materials (AI, GrEp, Be, Fused Quartz), strain amplitudes (less than 10-6 ppm), frequencies (20Hz-330Hz) and temperatures (20K-293K) relevant to future precision optical space missions. The test data shows a significant decrease in viscous damping at cryogenic temperatures and can be as low as 10-4%, but the amount of the damping decrease is a function of frequency and material. Contrary to the other materials whose damping monotonically decreased with temperature, damping of Fused Quartz increased substantially at cryo, after reaching a minimum at around l50 K. The damping is also shown to be insensitive to strain for low strain levels. At room temperatures, the test data correlates well to the analytical predictions of the Zener damping model. Discrepancies at cryogenic temperatures between the model predictions and the test data are observed.
An electronic instrument has been developed as a prototype of a portable crane-load contact sensor. Such a sensor could be helpful in an application in which the load rests on a base in a horizontal position determined by vertical alignment pins (see Figure 1). If the crane is not positioned to lift the load precisely vertically, then the load can be expected to swing once it has been lifted clear of the pins. If the load is especially heavy, large, and/or fragile, it could hurt workers and/or damage itself and nearby objects. By indicating whether the load remains in contact with the pins when it has been lifted a fraction of the length of the pins, the crane-load contact sensor helps the crane operator determine whether it is safe to lift the load clear of the pins: If there is contact, then the load is resting against the sides of the pins and, hence, it may not be safe to lift; if contact is occasionally broken, then the load is probably not resting against the pins, so it should be safe to lift. It is assumed that the load and base, or at least the pins and the surfaces of the alignment holes in the load, are electrically conductive, so the instrument can use electrical contact to indicate mechanical contact. However, DC resistance cannot be used as an indicator of contact for the following reasons: The load and the base are both electrically grounded through cables (the load is grounded through the lifting cable of the crane) to prevent discharge of static electricity. In other words, the DC resistance between the load and the pins is always low, as though they were always in direct contact. Therefore, instead of DC resistance, the instrument utilizes the AC electrical impedance between the pins and the load. The signal frequency used in the measurement is high enough (.1 MHz) that the impedance contributed by the cables and the electrical ground network of the building in which the crane and the base are situated is significantly greater than the contact impedance between the pins and the load. The instrument includes a signal generator and voltage-measuring circuitry, and is connected to the load and the base as shown in Figure 2. The output of the signal generator (typically having amplitude of the order of a volt) is applied to the load via a 50-resistor, and the voltage between the load and the pins is measured. When the load and the pins are not in contact, the impedance between them is relatively high, causing the measured voltage to exceed a threshold value. When the load and the pins are in contact, the impedance between them falls to a much lower value, causing the voltage to fall below the threshold value. The voltage-measuring circuitry turns on a red light-emitting diode (LED) to indicate the lower-voltage/ contact condition. Whenever the contact has been broken and the non-contact/higher-voltage condition has lasted for more than 2 ms, the voltage-measuring circuitry indicates this condition by blinking a green LED.
In-space joining technologies are crucial for stimulating an in-space economy and for enabling sustained space exploration by in-space manufacturing and repair of metallic structures. Compared to brazing or soldering, in-space welding (ISW) can provide highly hermetic, strong, and complex joints, potentially without introducing additional material. However, the influence of extreme temperatures, reduced pressure, and reduced gravity on ISW is not yet fully elucidated. Several efforts at NASA are investigating laser beam welding (LBW) as a joining and repair method in both thermal vacuum (TVAC) and combined vacuum & reduced gravity environments. NASA Marshall Space Flight Center (MSFC) shepherded several ISW projects in its past, including the 1973 electron beam welding on Skylab, the 1989 low-power LBW on parabolic flights, and the unflown 1990s-era In-Space Welding Experiment. Recent parabolic flights and 3 degree-of-freedom ground testing build upon this heritage. A collaboration with the Ohio State University using NASA Langley Research Center (LaRC) hardware retrofitted for LBW achieved the first high-powered laser welds under vacuum and low gravity and developed a workforce capable developing such experimental hardware. A ground testing campaign at the MSFC Flat Floor simulated fit-up and welding representative of ISW in 3 degrees of freedom to emulate microgravity effects on inertial systems. One ongoing effort is a NASA Early Career Initiative project – Lunar Assembly and Servicing by Autonomous Robotics (LASAR). Ruggedized LBW components were developed by an external partner for use in TVAC. A TVAC-rated robotic arm was procured by MSFC and used in the first known robotic laser weld where all components save the laser generator were under vacuum. NASA Johnson Space Center (JSC) is advancing supervised autonomy of ISW. NASA LaRC continues to adapt their unique snowflake joint geometry, suitable for connecting segments in trusses and other structures, to LBW. Upcoming TVAC campaigns will focus on testing extreme temperatures, proving out autonomous operations, and demonstrating weld repair. Weld inspection will occur via a non-contact nondestructive evaluation (NDE) technique – electromagnetic acoustic transduction (EMAT). Another ongoing effort based at MSFC is the DISCMAN -- DIsk-Shaped Configurable and Modular vAcuum uNit – which seeks to development a compact, modular payload that can provide a vacuum environment while in a reduced gravity condition. This payload could support multiple in-space manufacturing developmental efforts, with the first demonstration technology being LBW. Currently, the design is targeting operations in the pressurized volume of a space station, but the payload could readily be adapted to other flight platforms such as parabolic or even suborbital vehicles. LASAR elucidates the effects of temperature and vacuum on LBW while DISCMAN probes those of vacuum and gravity. Through these complementary efforts, NASA is addressing the primary challenges of ISW across the space environment while simultaneously developing and maturing technologies including robotic systems and inspection methodologies for future practical implementation on the Moon and beyond. This approach is timely, as upcoming missions requiring sustained human presence in space will depend on reliable ISW capabilities to create robust metallic joints currently unproven in the space environment and to perform repairs in situ .