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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Electronically Controlled Mechanical Seal for Aerospace Applications -- Part 1: Design, Analysis, and Steady State Tests

An electronically-controlled mechanial seal, for use as the purge gas seal in a liquid oxygen turbopump, has been designed, analyzed, and built. The thickness of the lubricating film between the faces is controlled by adjusting the coning of the carbon face. This is done by applying a voltage across a piezoelectric element to which the carbon face is bound. Steady state tests have shown that the leakage rate (and film thickness) can be adjusted over a substantial range, utilizing the available range of voltage.

Salant, Richard F.↗
NASA NTRS1995

Electronically controlled mechanical seal for aerospace applications--Part 2: Transient tests

An electronically controlled mechanical seal for use as the purge gas seal in a liquid oxygen turbopump has been fabricated and tested under transient operating conditions. The thickness of the lubricating film is controlled by adjusting the coning of the carbon face. This is accomplished by applying a voltage to a piezoelectric actuator to which the carbon face is bonded. The seal has been operated with a closed-loop control system that utilizes either the leakage rate or seal face temperature as the feedback. Both speed and pressure transients have been imposed on the seal. The transient tests have demonstrated that the seal is capable of maintaing low leakage rates while limiting face temperatures.

Wolff, Paul J.↗
NASA NTRS2009

Detecting Phase Boundaries in Hard-Sphere Suspensions

A special image-data-processing technique has been developed for use in experiments that involve observation, via optical microscopes equipped with electronic cameras, of moving boundaries between the colloidal-solid and colloidal-liquid phases of colloidal suspensions of monodisperse hard spheres. During an experiment, it is necessary to adjust the position of a microscope to keep the phase boundary within view. A boundary typically moves at a speed of the order of microns per hour. Because an experiment can last days or even weeks, it is impractical to require human intervention to keep the phase boundary in view. The present image-data-processing technique yields results within a computation time short enough to enable generation of automated-microscope-positioning commands to track the moving phase boundary

McDowell, Mark↗
NASA NTRS2012

Mars Science Laboratory Rover System Thermal Test

On November 26, 2011, NASA launched a large (900 kg) rover as part of the Mars Science Laboratory (MSL) mission to Mars. The MSL rover is scheduled to land on Mars on August 5, 2012. Prior to launch, the Rover was successfully operated in simulated mission extreme environments during a 16-day long Rover System Thermal Test (STT). This paper describes the MSL Rover STT, test planning, test execution, test results, thermal model correlation and flight predictions. The rover was tested in the JPL 25-Foot Diameter Space Simulator Facility at the Jet Propulsion Laboratory (JPL). The Rover operated in simulated Cruise (vacuum) and Mars Surface environments (8 Torr nitrogen gas) with mission extreme hot and cold boundary conditions. A Xenon lamp solar simulator was used to impose simulated solar loads on the rover during a bounding hot case and during a simulated Mars diurnal test case. All thermal hardware was exercised and performed nominally. The Rover Heat Rejection System, a liquid-phase fluid loop used to transport heat in and out of the electronics boxes inside the rover chassis, performed better than predicted. Steady state and transient data were collected to allow correlation of analytical thermal models. These thermal models were subsequently used to predict rover thermal performance for the MSL Gale Crater landing site. Models predict that critical hardware temperatures will be maintained within allowable flight limits over the entire 669 Sol surface mission.

Novak, Keith S.↗
NASA NTRS2012

Mars Science Laboratory Rover System Thermal Test

On November 26, 2011, NASA launched a large (900 kg) rover as part of the Mars Science Laboratory (MSL) mission to Mars. The MSL rover is scheduled to land on Mars on August 5, 2012. Prior to launch, the Rover was successfully operated in simulated mission extreme environments during a 16-day long Rover System Thermal Test (STT). This paper describes the MSL Rover STT, test planning, test execution, test results, thermal model correlation and flight predictions. The rover was tested in the JPL 25-Foot Diameter Space Simulator Facility at the Jet Propulsion Laboratory (JPL). The Rover operated in simulated Cruise (vacuum) and Mars Surface environments (8 Torr nitrogen gas) with mission extreme hot and cold boundary conditions. A Xenon lamp solar simulator was used to impose simulated solar loads on the rover during a bounding hot case and during a simulated Mars diurnal test case. All thermal hardware was exercised and performed nominally. The Rover Heat Rejection System, a liquid-phase fluid loop used to transport heat in and out of the electronics boxes inside the rover chassis, performed better than predicted. Steady state and transient data were collected to allow correlation of analytical thermal models. These thermal models were subsequently used to predict rover thermal performance for the MSL Gale Crater landing site. Models predict that critical hardware temperatures will be maintained within allowable flight limits over the entire 669 Sol surface mission.

Novak, Keith S.↗
NASA NTRS1990

Applications of high thermal conductivity composites to electronics and spacecraft thermal design

Recently, high thermal conductivity continuous graphite fiber reinforced metal matrix composites (MMC's) have become available that can save much weight over present methods of heat conduction. These materials have two or three times higher thermal conductivity in the fiber direction than the pure metals when compared on a thermal conductivity to weight basis. Use of these materials for heat conduction purposes can result in weight savings of from 50 to 70 percent over structural aluminum. Another significant advantage is that these materials can be used without the plumbing and testing complexities that accompany the use of liquid heat pipes. A spinoff of this research was the development of other MMC's as electronic device heat sinks. These use particulates rather than fibers and are formulated to match the coefficient of thermal expansion of electronic substrates in order to alleviate thermally induced stresses. The development of both types of these materials as viable weight saving substitutes for traditional methods of thermal control for electronics packaging and also for spacecraft thermal control applications are the subject of this report.

Sharp, G. Richard↗
NASA NTRS1995

Characterizing and testing a thermally isolating superconducting link for SAFIRE-like missions

The discovery of a new class of ceramic superconductors with transition temperatures above the boiling point of liquid nitrogen has opened the doors for several space applications. One important space application is the fabrication of an electrically conducting and thermally isolating link to replace manganin wires used in connecting IR detectors to data acquisition electronics on remote sensing platforms like SAFIRE and SIRTF. These NASA platforms designed to monitor the earth's atmosphere from space use infrared detectors which operate at liquid helium temperature (4.2K) for optimum performance. The SAFIRE mission employs hybrid dewars which combine both mechanical and cryogenic liquid cooling. The lifetime of such a mission is limited by the heat conducted through sensor array leads that connect the electronics (at approximately 80 K) to the sensors (at approximately 4 K). Currently these remoter sensing systems use manganin wires to connect the IR detectors to the data acquisition electronics. This link between a detector operating at 4 K and electronics operating at 80 K must be made of material that has high electrical conductivity and high thermal resistance. The YBCO superconductor with a transition temperature, Tc, of 93 K can achieve these conflicting requirements. A link with these characteristics will improve the thermal isolation of IR detectors and will increase the lifetime of the cryogen. The fabrication of an electrically conducting and thermally isolating link that replaces the manganin wires is an important application that will improve thermal isolation of IR detectors and will increase the lifetime of the cryogen. The link is made by screen printing superconducting lines on a low thermal conductivity ceramic substrate. Developing, modeling, and testing this high temperature superconducting link is a collaborative effort among NASA-Langley Research Center, Christopher Newport University (CNU), Clemson University and the industrial companies that have joined the Commercialization of Space Program for the purpose of developing and testing this link. CNU's effort in the development of this superconducting link included the following major efforts: (1) Development of a thermal conductivity measurement system for high temperature superconductors and ceramic materials which are potential candidates for use as substrates in this link. (2) Development of a mathematical model for the superconducting link that studies the effect of materials and geometry on the heat load and life time of missions. (3) Characterization of high Tc materials and assemblies made for space applications. Properties studied include humidity effects and aging effects on high Tc materials. This report summarizes the results of the research studies that were completed. Copies of publications detailing these findings are attached to this report.

Selim, Raouf R.↗
NASA NTRS1988

Effects of electron irradiation on high temperature superconductors and contacts to high temperature superconductors

The discovery of a new class of ceramic superconductors with transition temperatures above liquid nitrogen has opened the doors for exciting space applications. Energy storage, pointing maneuvers, magnetic shielding, and sensitive detection of electromagnetic radiation are some of the longer term possible applications. One near term application involves low electrical resistance, high thermal resistance connections between a detector operating at approximatly or equal to 4 and the electronics operating at approximatly or equal to 77 K. The new high temperature superconductors could accomplish this providing the necessary electrical connections to the ground plane while isolating the system thermally, thus prolonging the life of the mission. With such possibilities it is clearly of value to study the effects of radiation that would be experienced during a typical space mission. In this work we focused specifically on the effects of the electron radiation environment.

Caton, Randall↗
NASA NTRS1992

Electronic energy gap of molecular hydrogen from electrical conductivity measurements at high shock pressures

Electrical conductivities were measured for liquid D2 and H2 shock compressed to pressures of 10-20 GPa (100-200 kbar), molar volumes near 8 cu cm/mol, and calculated temperatures of 2900-4600 K. The semiconducting energy gap derived from the conductivities is 12 eV, in good agreement with recent quasi-particle calculations and with oscillator frequencies measured in diamond-anvil cells.

Nellis, W. J.↗
NASA NTRS1999

Identification of Gravity-Related Effects on Crystal Growth From Melts With an Immiscibility Gap

This work involves an experimental-numerical approach to study the effects of natural and Marangoni convections on solidification of single crystals from a silicate melt with a liquid-liquid immiscibility gap. Industrial use of crystals grown from silicate melts is becoming increasingly important in electronic, optical, and high temperature structural applications. Even the simplest silicate systems like Al203-SiO2 have had, and will continue to have, a significant role in the development of traditional and advanced ceramics. A unique feature of crystals grown from the silicate systems is their outstanding linear electro-optic properties. They also exhibit exceptionally high optical rotativity. As a result, these crystals are attractive materials for dielectric, optical, and microwave applications. Experimental work in our laboratory has indicated that directional solidification of a single crystal mullite appears to be preceded by liquid-liquid phase separation in the melt. Disruption of the immiscible state results in crystallization of a two phase structure. There is also evidence that mixing in the melt caused by density-driven convection can significantly affect the stability of the immiscible liquid layers and result in poly-crystalline growth. On earth, the immiscible state has only been observed for small diameter crystals grown in float zone systems where natural convection is almost negligible. Therefore, it is anticipated that growth of large single crystals from silicate melts would benefit from microgravity conditions because of the reduction of the natural convective mixing. The main objective of this research is to determine the effects of transport processes on the phase separation in the melt during growth of a single crystal while addressing the following issues: (1) When do the immiscible layers form and are they real?; (2) What are the main physical characteristics of the immiscible liquids?; and (3) How mixing by natural or Marangoni convection affects the stability of the phase separated melt.

Kassemi, M.↗
NASA NTRS1992

Secondary electron yields of solar system ices

The secondary electron yields of H2O, CO2, NH3, and CH3OH ices have been measured as a function of electron beam energy in the 2- to 30-keV energy range. The ices were produced on a liquid-nitrogen-cooled cold finger and transferred under vacuum to a SEM where the yield measurements were made. The imaging capabilities of the SEM provide a means of correlating the yield measurements with the morphology of the ices and are also used to monitor charging effects. The yields were determined by measuring the amplified current from a secondary electron detector and calibrating this current signal with the amplified current signal from samples of metals with known secondary electron yields. Each of the measured yields is found to decrease with an increase in energy in the 2- to 30-keV range. Estimates are given for the maximum secondary electron yield Y(max) of each ice and the energy at which this maximum yield occurs. Implications for the charging of solar system ice grains are discussed.

Suszcynsky, David M.↗
NASA NTRS2017

Application of Temperature-Controlled Thermal Atomization for Printing Electronics in Space

Additive Manufacturing (AM) is a technology that builds three dimensional objects by adding material layer-upon-layer throughout the fabrication process. The Electrical, Electronic and Electromechanical (EEE) parts packaging group at Marshall Space Flight Center (MSFC) is investigating how various AM and 3D printing processes can be adapted to the microgravity environment of space to enable on demand manufacturing of electronics. The current state-of-the art processes for accomplishing the task of printing electronics through non-contact, direct-write means rely heavily on the process of atomization of liquid inks into fine aerosols to be delivered ultimately to a machine's print head and through its nozzle. As a result of cumulative International Space Station (ISS) research into the behaviors of fluids in zero-gravity, our experience leads us to conclude that the direct adaptation of conventional atomization processes will likely fall short and alternative approaches will need to be explored. In this report, we investigate the development of an alternative approach to atomizing electronic materials by way of thermal atomization, to be used in place of conventional aerosol generation and delivery processes for printing electronics in space.

Wu, Chih-Hao↗
NASA NTRS1966

Liquid-metal cathode research.

Design of gravity-independent force-fed liquid-metal cathode providing unlimited cathode life in gas discharge devices and mercury electron-bombardment thrustors

GAS DISCHARGE↗
NASA NTRS1991

Rapid solidification of polymorphic transition metals induced by nanosecond laser pulses

An Nd-YAG laser giving 5 ns, 266 nm pulses was used to melt and subsequently quench thin, pure metallic films on a liquid Al/Al2O3 substrate at 10 to the 10th - 10 to the 12th K/s. Transmission electron microscopy together with electron diffraction was used to study the competitive nucleation and growth behavior of the crystals from the undercooled melt. In the case of Fe and Co, the high-temperature bcc and fcc structures were retained after laser quenching. Ti and Zr in spite of the structural similarities exhibit different preferences for nucleation from the undercooled melt. In all the metals the solid-state transformations were completely suppressed and the crystal growth was found to be limited by the collisional frequency of the atoms onto the growing interface.

Vitta, Satish↗
NASA NTRS2003

A Program to Detect and Characterize Extra-Solar Giant Planets

We initiated a significant hardware upgrade to the AFOE, to increase its efficiency for precise radial velocity studies to the level where we can continue to contribute usefully to extrasolar planet research on relatively bright stars. The AFOE, at a 1.5-m telescope, will of course not have the sensitivity of radial velocity instruments at larger telescopes, such as the HIRES on Keck or the Hectochelle on the MMT telescope (about to come on line). However, it has been possible to increase its efficiency for precise radial velocity studies by a factor of 4 to 5, which-combined with the large amount of telescope time available at the 1.5-m telescope-will permit us to do intensive follow-up observations of stars brighter than about 8 magnitude. The AFOE was originally designed primarily for asteroseismology using a ThAr reference. This provided useful wavelength stability over tens of minutes as required for asteroseismology, but we were unable to get a long-term (month-to-month) velocity precision better than about 15 m/s with that setup. Hence, we implemented an iodine cell as a wavelength reference for extrasolar planet studies. However, the optical design of the original AFOE did not completely span the wavelength range covered by the iodine absorption spectrum, and furthermore the optics suffered significant light loss through optical obscuration in the camera secondary. To remedy this, we replaced the AFOE grating with a new one that covered the entire iodine spectral range at somewhat lower spectral resolution, and replaced the camera with a transmitting lens. (The use of a lens was made possible by restricting the spectral range covered by the upgraded AFOE to only the iodine region.) These upgrades were successfully completed, and the instrument was tested for three nights in fall of 2002. The expected improvement in sensitivity by a factor of 4 to 5 was observed: that is, the same velocity precision as previously attained (of order 5 to 7 m/s) was now obtained on a stars that are about 4 to 5 times fainter. Unfortunately, just after installing the new AFOE optics, there was a catastrophic failure of the old Tektronix CCD. A careful investigation was made, and it was determined that the failure was probably due to too many thermal cyclings over the previous 8 years. The only solution was to purchase a new CCD. Internal funds of $16,000 were found for this purpose, and the new CCD (a thinned, back-illuminated Marconi 2K x 2K device with 13.5 micron pixels, and employing dual readout channels to keep the readout time as short as 20 seconds) was ordered, has now arrived, and is currently under test before 1 being installed in the AFOE liquid nitrogen dewar. At the same time, we expect to implement new CCD control electronics. This system should be better in many ways than the previous detector (including eliminating the need for UV flashing to maximize the quantum efficiency). We plan to install the detector on the telescope and begin operations again in April of this year.

Lindstrom, David↗
NASA NTRSDate not supplied

Results from the Radio Frequency Mass Gauge Technology Demonstration on the Intuitive Machines Nova-C Lunar Lander

A cryogenic propellant mass gauge known as the Radio Frequency Mass Gauge (RFMG) was integrated into the Intuitive Machines (IM) Nova-C lunar lander and provided an estimate of the liquid oxygen and liquid methane mass in the lander propellant tanks throughout the IM-1 mission, including during microgravity coast phases. An RFMG electronics controller was used to measure and record the spectrum of the RF signal reflected from an antenna sensor in each tank over the frequency range 100 to 1,300 MHz. The RF spectrum of each of the tanks is unique and is sensitive to the index of refraction of the propellants and the spatial distribution of the liquid within the tanks. Electromagnetic simulation software was used to simulate the antenna response spectra for a given tank geometry, fluid properties, and liquid–vapor configurations within the tank. Over 10,000 antenna response simulations were completed for each propellant tank prior to the IM-1 mission and represented various volumetric fill levels and fluid configurations. The simulated spectra served as a database against which measured tank spectra were compared. For analysis, a spectral matching algorithm was used to find the best match between measured and simulated spectra, and the gauged mass was calculated from the most highly correlated fluid mass simulations. RFMG measurements were recorded during tank loading on the launch pad and during translunar coast, lunar orbit insertion, low lunar orbit, powered descent to the lunar surface, and postlanding on the Moon. This paper describes the RF and fluid simulations, the RFMG measurements and analysis of spectral data, the RFMG instrument, and the gauged results throughout all phases of the IM-1 mission.

lunar lander↗