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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 307 records · Page 17
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NASA NTRS1986

The international cometary explorer mission to comet Giacobini-Zinner

The encounter, on September 11, 1985, between the International Cometary Explorer (ICE) and the comet Giacobini-Zinner, is described in detail. The primary goal of this encounter was to study the interaction between the solar wind and the comet. At the time of the encounter, the spacecraft was approximately 50 times farther from the earth than it was designed to go, making it difficult to recover data. The seven instruments on board ICE which were operational in this mission were the plasma electron, magnetometer, plasma waves, radio waves, plasma composition, low-energy cosmic ray, and energetic proton instruments. The encounter is depicted schematically, showing the times different regions were crossed. The spacecraft velocity vector, measured relative to the comet, made a 93 deg angle with respect to the plasma tail axis. The spacecraft crossed the center of the comet ion tail at approximately 1102 U.T. A cold, dense plasma was found near the center of the tail; at the very center was a temperature reading of only 13,000 K and a density of 670 electrons/cu cm. Alfven's model of comet tail formation was confirmed and it was found that water group ions are the dominant comet component. Pulses were detected which were attributed to dust particles hitting the spacecraft.

Von Rosenvinge, T. T.↗
NASA NTRS1986

The clumpy circumstellar medium around young supernova remnants

Each of the youngest supernova remnants known in the Milky Way, Cas A, Kepler's SNR, and Tycho's SNR, shows a different morphological structure caused by different conditions in the progenitor stars and their surroundings. In all three cases, however, the observed shells have a thickness of about 1/4 the radius, a sharp outer edge, and significant brightness irregularities. These features require that the circumstellar medium be highly clumped. To investigate the phenomenon, models of the expansion have been constructed using a one-dimensional spherical hydrodynamic code. As a supernova shock moves down the external density gradient of the star, material behind the shock begins to go into free expansion. Then as surrounding material is encountered a reverse shock moving back into the ejectum will be formed. Until the expansion has swept up about eight times the ejected mass when the situation can be considered as a point explosion in its surroundings, the dynamics are controlled by conditions between the shocks. The region is also where the synchrotron radio emission from relativistic electrons trapped in magnetic fields arises. Initial particles and fields are accelerated and amplified by eddy motion at the interface between the ejected and swept-up material and at the boundaries of clumps. Polarimetry shows that these SNR have a net radial orientation of their magnetic fields apparently from stretching by Rayleigh-Taylor instabilities at the contact surfaces. Without clumps the observed shell is much too narrow and steep on the inside.

Dickel, J. R.↗
NASA NTRS1990

Ulysses - An investigation of the polar regions of the heliosphere

This paper describes the Ulysses mission, a cooperative NASA/ESA mission for exploring the heliosphere within 1 to 2 AU of the sun. The nine instruments of the Ulysses spacecraft will collect information continuously, recording and compressing data for a playback through NASA's Deep Space Network. Prominent features of the Ulysses include the 1.65-m parabolic high-gain antenna pointing continuously toward earth, which will provide the earth-to-spacecraft communications link; the Radioisotope Thermoelectric Generator; and the 5.5-m radial boom which will provide an electromagnetically clean environment for certain experiments. Individual studies will include investigations of solar-wind plasma, solar-wind ion composition, cosmic dust, magnetic field, solar X-rays/cosmic gamma ray bursts, energetic-particle composition, low energy ions and electrons, cosmic rays/solar particles, radio and plasma waves, coronal plasma sounding, and gravitational waves.

Meeks, Willis G.↗
NASA NTRS1992

RF FEL for power beaming

The laser device components associated with operating a radio frequency-free electron laser (RF-FEL) for beaming power from Earth were designed and tested. Analysis of the power beaming system requirements reveals that the FEL, identified by NASA as the laser of choice, is the major subsystem requiring demonstration before proceeding further in proving the efficacy of laser power beaming. Rocketdyne has identified a series of low cost, low risk demonstrations which proceed sequentially, as follows: (1) a 1 kW proof-of-principle demonstration; (2) a 150 kW demonstration of beaming power to a satellite; and (3) a MW class demonstration of Earth to lunar surface power transmission. This sequence of events can be completed in 5.5 years at a cost of $188M, with key milestones each year.

Burke, Robert↗
NASA NTRS1992

Comparisons of peak ionosphere pressures at Mars and Venus with incident solar wind dynamic pressure

Radio occultation measurements of electron density profiles from Mariner 6 and 7, the Mariner 9 extended mission, and the U.S. Viking orbiters, together with model ion and electron temperature profiles, are used to derive thermal pressure profiles in the Mars ionosphere. The comparison of the Mars peak ionosphere pressure with the incident solar and dynamic pressure suggests that at solar maximum the Mars ionosphere, like that of Venus, should generally be sufficient to balance the incident solar wind pressure. At solar minimum, when the ionosphere is weakest and the solar wind dynamic pressure is highest, only the peak pressures at high solar zenith angles (SZAs) at Mars appear to be strong enough to balance the incident solar wind pressure. This is similar to the situation at Venus at solar minimum.

Zhang, M. H. G.↗
NASA NTRS2001

Low Power Silicon Germanium Electronics for Microwave Radiometers

Space-based radiometric observations of key hydrological parameters (e.g., soil moisture) at the spatial and temporal scales required in the post-2002 era face significant technological challenges. These measurements are based on relatively low frequency thermal microwave emission (at 1.4 GHz for soil moisture and salinity, 10 GHz and up for precipitation, and 19 and 37 GHz for snow). The long wavelengths at these frequencies coupled with the high spatial and radiometric resolutions required by the various global hydrology communities necessitate the use of very large apertures (e.g., greater than 20 m at 1.4 GHz) and highly integrated stable RF electronics on orbit. Radio-interferometric techniques such as Synthetic Thinned Array Radiometry (STAR), using silicon germanium (SiGe) low power radio frequency integrated circuits (RFIC), is one of the most promising technologies to enable very large non-rotating apertures in space. STAR instruments are composed of arrays of small antenna/receiving elements that are arranged so that the collecting area is smaller than an equivalent real aperture system, allowing very high packing densities for launch. A 20 meter aperture at L-band, for example, will require greater than 1000 of these receiving elements. SiGe RFIC's reduce power consumption enough to make an array like this possible in the power-limited environment of space flight. An overview of the state-of-the-art will be given, and current work in the area of SiGe radiometer development for soil moisture remote sensing will be discussed.

Doiron, Terence A.↗
NASA NTRS2002

The Software Element of the NASA Portable Electronic Device Radiated Emissions Investigation

NASA Langley Research Center's (LaRC) High Intensity Radiated Fields Laboratory (HIRF Lab) recently conducted a series of electromagnetic radiated emissions tests under a cooperative agreement with Delta Airlines and an interagency agreement with the FAA. The frequency spectrum environment at a commercial airport was measured on location. The environment survey provides a comprehensive picture of the complex nature of the electromagnetic environment present in those areas outside the aircraft. In addition, radiated emissions tests were conducted on portable electronic devices (PEDs) that may be brought onboard aircraft. These tests were performed in both semi-anechoic and reverberation chambers located in the HIRF Lab. The PEDs included cell phones, laptop computers, electronic toys, and family radio systems. The data generated during the tests are intended to support the research on the effect of radiated emissions from wireless devices on aircraft systems. Both tests systems relied on customized control and data reduction software to provide test and instrument control, data acquisition, a user interface, real time data reduction, and data analysis. The software executed on PC's running MS Windows 98 and 2000, and used Agilent Pro Visual Engineering Environment (VEE) development software, Common Object Model (COM) technology, and MS Excel.

Koppen, Sandra V.↗
NASA NTRS2004

Microsystem Cooler Development

A patented microsystem Stirling cooler is under development with potential application to electronics, sensors, optical and radio frequency (RF) systems, microarrays, and other microsystems. The microsystem Stirling cooler is most suited to volume-limited applications that require cooling below the ambient or sink temperature. Primary components of the planar device include: two diaphragm actuators that replace the pistons found in traditional-scale Stirling machines; and a micro-regenerator that stores and releases thermal energy to the working gas during the Stirling cycle. The use of diaphragms eliminates frictional losses and bypass leakage concerns associated with pistons, while permitting reversal of the hot and cold sides of the device during operation to allow precise temperature control. Three candidate microregenerators were custom fabricated for initial evaluation: two constructed of porous ceramic, and one made of multiple layers of nickel and photoresist in an offset grating pattern. An additional regenerator was prepared with a random stainless steel fiber matrix commonly used in existing Stirling machines for comparison to the custom fabricated regenerators. The candidate regenerators were tested in a piezoelectric-actuated test apparatus designed to simulate the Stirling refrigeration cycle. In parallel with the regenerator testing, electrostatically-driven comb-drive diaphragm actuators for the prototype device have been designed for deep reactive ion etching (DRIE) fabrication.

Moran, Matthew E.↗
NASA NTRS2006

Electro-optic Q-switch

An electro-optic Q-switch for generating sequence of laser pulses was disclosed. The Q-switch comprises a quadratic electro-optic material and is connected with an electronic unit generating a radio frequency wave with positive and negative pulses alternatively. The Q-switch is controlled by the radio frequency wave in such a way that laser pulse is generated when the radio frequency wave changes its polarity.

Zou, Yingyin↗
NASA NTRS2006

Using Quasiparticle Poisoning To Detect Photons

According to a proposal, a phenomenon associated with excitation of quasiparticles in certain superconducting quantum devices would be exploited as a means of detecting photons with exquisite sensitivity. The phenomenon could also be exploited to perform medium-resolution spectroscopy. The proposal was inspired by the observation that Coulomb blockade devices upon which some quantum logic gates are based are extremely sensitive to quasiparticles excited above the superconducting gaps in their leads. The presence of quasiparticles in the leads can be easily detected via the charge states. If quasiparticles could be generated in the leads by absorption of photons, then the devices could be used as very sensitive detectors of electromagnetic radiation over the spectral range from x-rays to submillimeter waves. The devices in question are single-Cooper-pair boxes (SCBs), which are mesoscopic superconducting devices developed for quantum computing. An SCB consists of a small superconducting island connected to a reservoir via a small tunnel junction and connected to a voltage source through a gate capacitor. An SCB is an artificial two-level quantum system, the Hamiltonian of which can be controlled by the gate voltage. One measures the expected value of the charge of the eigenvectors of this quantum system by use of a radio-frequency single-electron transistor. A plot of this expected value of charge as a function of gate voltage resembles a staircase that, in the ideal case, consists of steps of height 2 e (where e is the charge of one electron). Experiments have shown that depending on the parameters of the device, quasiparticles in the form of "broken" Cooper pairs present in the reservoir can tunnel to the island, giving rise to steps of 1 e. This effect is sometimes called "poisoning." Simulations have shown that an extremely small average number of quasiparticles can generate a 1-e periodic signal. In a device according to the proposal, this poisoning would be turned to advantage. Depending on the wavelength, an antenna or other component would be used to couple radiation into the reservoir, wherein the absorption of photons would break Cooper pairs, thereby creating quasiparticles that, in turn, would tunnel to the island, creating a 1-e signal. On the basis of conservative estimates of device parameters derived from experimental data and computational simulations that fit the data, it has been estimated that the noise equivalent power of a device according to the proposal could be as low as 6 10(exp -22) W/Hz(exp 1/2). It has also been estimated that the spectroscopic resolution (photon energy divided by increment of photon energy) of such a device in visible light would exceed 100.

Echternach, Pierre↗
NASA NTRS2010

Meeting Radiation Protection Requirements and Reducing Spacecraft Mass - A Multifunctional Materials Approach

Both crew and radio-sensitive systems, especially electronics must be protected from the effects of the space radiation environment. One method of mitigating this radiation exposure is to use passive-shielding materials. In previous vehicle designs such as the International Space Station (ISS), materials such as aluminum and polyethylene have been used as parasitic shielding to protect crew and electronics from exposure, but these designs add mass and decrease the amount of usable volume inside the vehicle. Thus, it is of interest to understand whether structural materials can also be designed to provide the radiation shielding capability needed for crew and electronics, while still providing weight savings and increased useable volume when compared against previous vehicle shielding designs. In this paper, we present calculations and analysis using the HZETRN (deterministic) and FLUKA (Monte Carlo) codes to investigate the radiation mitigation properties of these structural shielding materials, which includes graded-Z and composite materials. This work is also a follow-on to an earlier paper, that compared computational results for three radiation transport codes, HZETRN, HETC, and FLUKA, using the Feb. 1956 solar particle event (SPE) spectrum. In the following analysis, we consider the October 1989 Ground Level Enhanced (GLE) SPE as the input source term based on the Band function fitting method. Using HZETRN and FLUKA, parametric absorbed doses at the center of a hemispherical structure on the lunar surface are calculated for various thicknesses of graded-Z layups and an all-aluminum structure. HZETRN and FLUKA calculations are compared and are in reasonable (18% to 27%) agreement. Both codes are in agreement with respect to the predicted shielding material performance trends. The results from both HZETRN and FLUKA are analyzed and the radiation protection properties and potential weight savings of various materials and materials lay-ups are compared.

Atwell, William↗
NASA NTRS2010

Fisk-Gloeckler Suprathermal Proton Spectrum in the Heliosheath and the Local Interstellar Medium

Convergence of suprathermal keV-MeV proton and ion spectra approximately to the Fisk-Gloeckler (F-G) form j(E) = j(sub 0) E(sup -1.5) in Voyager land 2 heliosheath measurements is suggestive of distributed acceleration in Kolmogorov turbulence which may extend well beyond the heliopause into the local interstellar medium (LISM). Turbulence of this type is already indicated by interstellar radio scintillation measurements of electron density power spectra. Previously published extrapolations (Cooper et al., 2003, 2006) of the LISM proton spectrum from eV to GeV energies are highly consistent with the F-G power-law and further indicative of such turbulence and LISM effectiveness of the F-G cascade acceleration process. The LISM pressure computed from this spectrum well exceeds that from current estimates for the LISM magnetic field, so exchange of energy between the protons and the magnetic field would likely have a strong role in evolution of the turbulence as per the F-G theory and as long ago proposed for cosmic ray energies by Parker and others. Pressure-dependent estimates of the LISM field strength should not ignore this potentially strong and even dominant contribution from the plasma. Presence of high-beta suprathermal plasma on LISM field lines could significantly affect interactions with the heliospheric outer boundary region and might potentially account for distributed and more discrete features in ongoing measurements of energetic neutral emission from the Interstellar Boundary Explorer (IBEX) mission.

Cooper, John F.↗
NASA NTRS2011

Spectral Analyses and Radiation Exposures from Several Ground-Level Enhancement (GLE) Solar Proton Events: A Comparison of Methodologies

Several methods for analyzing the particle spectra from extremely large solar proton events, called Ground-Level Enhancements (GLEs), have been developed and utilized by the scientific community to describe the solar proton energy spectra and have been further applied to ascertain the radiation exposures to humans and radio-sensitive systems, namely electronics. In this paper 12 GLEs dating back to 1956 are discussed, and the three methods for describing the solar proton energy spectra are reviewed. The three spectral fitting methodologies are EXP [an exponential in proton rigidity (R)], WEIB [Weibull fit: an exponential in proton energy], and the Band function (BAND) [a double power law in proton rigidity]. The EXP and WEIB methods use low energy (MeV) GLE solar proton data and make extrapolations out to approx.1 GeV. On the other hand, the BAND method utilizes low- and medium-energy satellite solar proton data combined with high-energy solar proton data deduced from high-latitude neutron monitoring stations. Thus, the BAND method completely describes the entire proton energy spectrum based on actual solar proton observations out to ~10 GeV. Using the differential spectra produced from each of the 12 selected GLEs for each of the three methods, radiation exposures are presented and discussed in detail. These radiation exposures are then compared with the current 30-day and annual crew exposure limits and the radiation effects to electronics.

Atwell, William↗
NASA NTRS2012

VLBI: A Fascinating Technique for Geodesy and Astrometry

Since the 1970s Very Long Baseline Interferometry (VLBI) has proven to be a primary space-geodetic technique by determining precise coordinates on the Earth, by monitoring the variable Earth rotation and orientation with highest precision, and by deriving many other parameters of the Earth system. VLBI provides an important linkage to astronomy through, for instance, the determination of very precise coordinates of extragalactic radio sources. Additionally, it contributes to determining parameters of relativistic and cosmological models. After a short review of the history of geodetic VLBI and a summary of recent results, this paper describes future perspectives of this fascinating technique. The International VLBI Service for Geodesy and Astrometry (IVS), as a service of the International Association of Geodesy (IAG) and the International Astronomical Union (IAU), is well on its way to fully defining a next generation VLBI system, called VLBI2010. The goals of the new system are to achieve on scales up to the size of the Earth an accuracy of 1 mm in position and of 0.1 mm/year in velocity. Continuous observations shall be carried out 24 h per day 7 days per week in the future with initial results to be delivered within 24 h after taking the data. Special sessions, e.g. for monitoring the Earth rotation parameters, will provide the results in near real-time. These goals require a completely new technical and conceptual design of VLBI measurements. Based on extensive simulation studies, strategies have been developed by the IVS to significantly improve its product accuracy through the use of a network of small (approx 12 m) fast-slewing antennas. A new method for generating high precision delay measurements as well as improved methods for handling biases related to radio source structure, system electronics, and deformations of the antenna structures has been developed. Furthermore, as of January 2012, the construction of ten new VLBI2010 sites has been funded, with good prospects for one dozen more antennas, which will improve the geographical distribution of geodetic VLBI sites on Earth and provide an important step toward a global VLBI2010 network. Within this paper, the Global Geodetic Observing System (GGOS) of the IAG will also be introduced and the contribution of VLBI to GGOS will be described.

Geodesy↗
NASA NTRS2017

Elastomeric Sensing of Pressure with Liquid Metal and Wireless Inductive Coupling

This project describes resistance-based soft sensors filled with liquid metal, which permit measurements of large strains (0 percent to 110 percent), associated with small forces of less than 30 Newtons. This work also demonstrates a methodology for wireless transfer of these strain measurements without connected electrodes. These sensors allow intermittent detection of pressure on soft membranes with low force. Adapting these sensors for passive wireless pressure sensing will eliminate the need for embedded batteries, and will allow the sensors to transmit pressure data through non-conductive materials including glass and acrylic. The absence of batteries allows us to embed these sensors into materials for long-term use because the sensors only use passive analog circuit elements. We found the oxidation of the liquid metal (eutectic gallium indium) plays a role in the repeatability of the soft sensors. We investigated how the oxidation layer affected the behavior of the sensor by encapsulating materials (silicone, fluorosilicone, and PVC) with varied permeabilities to oxygen. We measured the effects of mechanical loading on the oxidation layer and the effects of wireless inductive coupling on the oxidation layer. We concluded our research by investigating the effects of embedding self-resonant circuits into polydimethylsiloxane (PDMS). Efforts to design engineered systems with soft materials are a growing field with progress in soft robotics, epidermal electronics, and wearable electronics. In the field of soft robotics, PDMS-based grippers are capable of picking up delicate objects because their form-fitting properties allow them to conform to the shape of objects more easily than conventional robotic grippers. Epidermal devices also use PDMS as a substrate to hold electronic components such as radios, sensors, and power supply circuits. Additionally, PDMS-based soft sensors can monitor human motion with liquid metal embedded within micro-channels. Passive wireless sensors have applications in structural health monitoring and medical health monitoring. Doctors can take wireless blood pressure measurements inside arteries to monitor the progression of heart disease. Glaucoma patients can use this technology to monitor the pressure in their eyes to track the progression of the disease.

Dick, Jacob↗
NASA NTRS1983

Decimetric gyrosynchrotron emission during a solar flare

A decimetric, microwave, and hard X-ray burst was observed during a solar flare in which the radio spectrum below peak flux fits an f+2 power law over more than a decade in frequency. The spectrum is interpreted to mean that the radio emission originated in a homogeneous, thermal, gyrosynchrotron source. This is the first time that gyrosynchrotron radiation has been identified at such low decimetric frequencies (900-998) MHz). The radio emission was cotemporal with the largest single hard X-ray spike burst ever reported. The spectrum of the hard X-ray burst can be well represented by a thermal bremsstrahlung function over the energy range from 30 to 463 keV at the time of maximum flux. The temporal coincidence and thermal form of both the X-ray and radio spectra suggest a common source electron distribution. The unusual low-frequency extent of the single-temperature thermal radio spectrum and its association with the hard X-ray burst imply that the source had an area approx. 10(18) sq cm a temperature approx 5x10(8) K, an electron density approx. 7.10(9) cu cm and a magnetic field of approx. 120 G. H(alpha) and 400-800 MHz evidence suggest that a loop structure of length 10,000 km existed in the flare active region which could have been the common, thermal source of the observed impulsive emissions.

Batchelor, D. A.↗