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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 433 records · Page 24
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NASA NTRS2015

Iodine Satellite

The Iodine Satellite (iSat) spacecraft will be the first CubeSat to demonstrate high change in velocity from a primary propulsion system by using Hall thruster technology and iodine as a propellant. The mission will demonstrate CubeSat maneuverability, including plane change, altitude change and change in its closest approach to Earth to ensure atmospheric reentry in less than 90 days. The mission is planned for launch in fall 2017. Hall thruster technology is a type of electric propulsion. Electric propulsion uses electricity, typically from solar panels, to accelerate the propellant. Electric propulsion can accelerate propellant to 10 times higher velocities than traditional chemical propulsion systems, which significantly increases fuel efficiency. To enable the success of the propulsion subsystem, iSat will also demonstrate power management and thermal control capabilities well beyond the current state-of-the-art for spacecraft of its size. This technology is a viable primary propulsion system that can be used on small satellites ranging from about 22 pounds (10 kilograms) to more than 1,000 pounds (450 kilograms). iSat's fuel efficiency is ten times greater and its propulsion per volume is 100 times greater than current cold-gas systems and three times better than the same system operating on xenon. iSat's iodine propulsion system consists of a 200 watt (W) Hall thruster, a cathode, a tank to store solid iodine, a power processing unit (PPU) and the feed system to supply the iodine. This propulsion system is based on a 200 W Hall thruster developed by Busek Co. Inc., which was previously flown using xenon as the propellant. Several improvements have been made to the original system to include a compact PPU, targeting greater than 80 percent reduction in mass and volume of conventional PPU designs. The cathode technology is planned to enable heaterless cathode conditioning, significantly increasing total system efficiency. The feed system has been designed to include iodine compatible control valves with internal heaters and temperature sensors to coincide with the iodine-compatible thruster. A key advantage to using iodine as a propellant is that it may be stored in the tank as an unpressurized solid on the ground and before flight operations. During operations, the tank is heated to vaporize the propellant. Iodine vapor is then routed through custom flow control valves to control mass flow to the thruster and cathode assembly. The thruster then ionizes the vapor and accelerates it via magnetic and electrostatic fields, resulting in high specific impulse, characteristic of a highly efficient propulsion system. The iSat spacecraft is a 12-unit (12U) CubeSat with dimensions of about 8 inches x 8 inches x 12 inches (20 centimeters x 20 centimeters x 30 centimeters). The spacecraft frame will be constructed from aluminum with a finish to prevent iodine-driven corrosion. The iSat spacecraft includes full three-axis control and will leverage heat generated by spacecraft components and radiators for a passive thermal control system. After the CubeSat has successfully detached from its launch vehicle, it will deploy its solar panels, correct for tip-off and maintain attitude control before ground contact. An initial check-out period of two weeks is planned for testing all subsystems. The spacecraft will charge the power system while in sunlight, using momentum wheels and magnetic torque rods to rotate the vehicle to the required attitude.

iSat↗
NASA NTRS1979

Broadband electrostatic acoustic transducer for ultrasonic measurements in liquids

A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing. The membrane functions as the ground plate of a parallel plate capacitor, the other plate being a dc biased electrode recessed approximately 10 microns from the electrically grounded membrane. An ultrasonic wave incident on the membrane varies the membrane-electrode gap spacing and generates an electrical signal proportional to the wave amplitude. The entire assembly is sealed for immersion in a liquid environment. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 15 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. The use of the ESAT as a broadband ultrasonic transducer in liquids with a predictable frequency response is promising.

Cantrell, J. H., Jr.↗
NASA NTRS1986

The electron-cyclotron maser instability as a source of plasma radiation

The generation of continuum bursts from the sun at dm and m wavelengths (in particular, type IV bursts) via the electron-cyclotron-maser instability is examined. The maser instability can be driven by an electron distribution with either a loss-cone anisotropy or a peak at large pitch angles. For omega(p)/Omega(e) much greater than 1, the maser emission is produced by electrons interacting through a harmonic (cyclotron) resonance and is electrostatic, being in the upper hybrid mode at frequencies approximately equal to omega(p). Coalescence processes are required to convert the electrostatic waves into transverse radiation which can escape from the source region. Whether the resultant spectrum is nearly a smooth continuum or has a zebra-stripe pattern (both of which occur in type IV bursts) depends on the form of the electron distribution, inhomogeneities in the density and magnetic field, and whether the maser reaches saturation. For at least the case of some type IV dm bursts with fine structure, comparison with observations seems to indicate that the electrons producing the emission are more likely to have a loss-cone distribution, and that the maser instability is not at saturation.

Winglee, R. M.↗
NASA NTRS2007

Arrays of Bundles of Carbon Nanotubes as Field Emitters

Experiments have shown that with suitable choices of critical dimensions, planar arrays of bundles of carbon nanotubes (see figure) can serve as high-current-density field emitter (cold-cathode) electron sources. Whereas some hot-cathode electron sources must be operated at supply potentials of thousands of volts, these cold-cathode sources generate comparable current densities when operated at tens of volts. Consequently, arrays of bundles of carbon nanotubes might prove useful as cold-cathode sources in miniature, lightweight electron-beam devices (e.g., nanoklystrons) soon to be developed. Prior to the experiments, all reported efforts to develop carbon-nanotube-based field-emission sources had yielded low current densities from a few hundred microamperes to a few hundred milliamperes per square centimeter. An electrostatic screening effect, in which taller nanotubes screen the shorter ones from participating in field emission, was conjectured to be what restricts the emission of electrons to such low levels. It was further conjectured that the screening effect could be reduced and thus emission levels increased by increasing the spacing between nanotubes to at least by a factor of one to two times the height of the nanotubes. While this change might increase the emission from individual nanotubes, it would decrease the number of nanotubes per unit area and thereby reduce the total possible emission current. Therefore, to maximize the area-averaged current density, it would be necessary to find an optimum combination of nanotube spacing and nanotube height. The present concept of using an array of bundles of nanotubes arises partly from the concept of optimizing the spacing and height of field emitters. It also arises partly from the idea that single nanotubes may have short lifetimes as field emitters, whereas bundles of nanotubes could afford redundancy so that the loss of a single nanotube would not significantly reduce the overall field emission.

Manohara, Harish↗
NASA NTRSDate not supplied

Insights From Routine Microbiological Monitoring of Air in Astromaterials Curation Cleanrooms

NASA maintains nine separate cleanrooms at the Johnson Space Center to curate and preserve astromaterials samples. Routine microbial monitoring of the surfaces in these cleanrooms began in 20181. Until recently, materials compatibility requirements prevented monitoring airborne biological particles in all but one of these cleanrooms. New astromaterials collections from carbon rich asteroids are more susceptible to biological degradation than previous collections. Therefore, it is important to monitor the bioburden in the air and on surfaces in these labs. Establishing a comprehensive microbial monitoring program will help inform the monitoring and curation plans for Mars sample return which will include samples that are extremely biologically sensitive. In April of 2022 we began routinely collecting air samples in seven of the nine curation cleanrooms (Meteorite ISO 7 equivalent, Lunar ISO 6 equivalent, Stardust, Hayabusa2, OSIRIS-REx ISO 5 equivalent, and Genesis ISO 4 equivalent) using a sampling device that collects airborne biological particles on an electret filter instead conventional sampler that collect cells in a liquid media or onto organic rich Petri dishes. Electret is a generic term for electrostatically charged media. The charge on these materials increases particle trapping when compared to non-charged filters of similar thickness. N95 respirators also use electret filters. This dry sample collection method allows us to meet materials requirements for all the curation labs and reduces the risk of inadvertently introducing contamination as part of our monitoring effort. This method also allows us to preserve a portion of each sample for DNA extraction and next generation sequencing. DNA sequencing helps us to characterize the portion of the cleanroom microbiome that we cannot culture. We will present the results of our first 8 months of monitoring, compare these results to particle counts in the labs and to measurements made directly onto Petri dishes when possible. We will also make recommendations for modifications to the sampling method to improve sampling efficiency and preserve diversity.

A. B. Regberg↗
NASA NTRS1996

Testing Protocol Proposal to Identify and Evaluate Candidate Materials to Substitute for Silverized Teflon in Thermal Control Applications

Electrostatic discharge (ESD) has been shown to be the primary cause of several glitches in spacecraft operations. It appears that charged particles encountered in the natural environment in certain orbits can collect on the outer surfaces of a spacecraft, building up a charge of several thousand volts. If the potential exceeds the breakdown voltage of the charged material, then an ESD will occur. ESD events involving relatively low voltages, on the order of 100 V, have been shown to damage electronic components. When ESD occurs, electronic and electrical components can be damaged, computer instructions can be garbled, and ablation of material from the spacecraft may occur; degrading both the performance of the thermal control blankets, and the cleanliness of any surfaces on which the detritus becomes deposited. There appear to be six ways to prevent or mitigate the effects of ESD: (1) Choose an orbit where charging is not a problem; (2) Carry extra electromagnetic shielding; (3) Provide redundancy in components and programming; (4) Provide for active dissipation of the charge, by generating a plasma with which to bathe susceptible surfaces; (5) Provide for passive dissipation from a plasma contactors on the susceptible surfaces; and (6) Provide thermal control blankets that do not hold a charge, i.e., that are conductive enough to bleed a charge off harmlessly. These six options are discussed in detail in Losure (1996). Of these six options, number 1 is not always practical, given other requirements of the mission; 2, 3, 4 and 5 will require that extra mass in the form of shielding, etc., be carried by the spacecraft. The most attractive option from a mass and energy point of view seems to be that of finding a material which matches the other performance characteristics of the current thermal control blankets without their tendency to build up an electrostatic charge. The goal of this paper is to describe and justify a testing program which will lead to the approval of materials of this kind.

Losure, Nancy S.↗
NASA NTRS1976

Plasma kinetic processes in a strong d.c. magnetic field

Recent results in the kinetic theory of a strongly magnetized plasma are surveyed. Emphasis is on the electrostatic guiding-center plasma in two dimensions, in both the fluid and 'charged rod' descriptions. The basic kinetic description of the plasma is in terms of the statistically-distributed Fourier coefficients associated with the velocity and 'enstrophy' (charge density) fields. It is a universal tendency in such media for enstrophy to flow to shorter wavelengths but for energy to flow to longer wavelengths. A consequence of the energy flow to longer wavelengths is the generation of long-range order in the form of macroscopic vortices. These kinds of structure have been called 'convection cells' and can be extraordinarily efficient in transporting particles transverse to a magnetic field. The tendency to vortex formation can be disrupted by collisions between particles. Modifications of the Fokker-Planck equation for a plasma produced by a strong dc magnetic field are considered in both two and three dimensions.

Montgomery, D.↗
NASA NTRS2001

Microshutter Array Development for the Multi-Object Spectrograph for the New Generation Space Telescope, and Its Ground-based Demonstrator

The 6.5-m NASA/ESA/Canada New Generation Space Telescope to be operated at the L2 Lagrangian point will require a multi-object spectrograph (MOS) operating from 1 to 5 microns. Up to 3000 targets will be selected for simultaneous spectroscopy using a programmable cryogenic (approx. 35K) aperture array, consisting of a mosaic of arrays of micromirrors or microshutters. We describe the current status of the GSFC microshutter array development. The 100 micron square shutters are opened magnetically and latched open or closed electrostatically. Selection will be by two crossed one-dimensional addressing circuits. We will demonstrate the use of a 512 x 512 unit array on a ground-based IR MOS which will cover 0.6 to 5 microns, and operate rapidly to include spectroscopy of gamma ray burst afterglows.

Woodgate, Bruce E.↗
NASA NTRS2000

Electrospraying and Electrospinning of Polymers for Biomedical Applications. Poly(Lactic-Co-Glycolic Acid) and Poly(Ethylene-Co-Vinylacetate)

Significant opportunities exist for the processing of polymers (homopolymers and blends) using electric fields. Specific attention is given here to electrospinning, but we note that electroaerosol formation and field-modulated film casting represent additional processing options. Of particular interest is the ability to generate polymer fibers of sub-micron dimensions using electrospinning, down to about 0.05 microns (50 nm), a size range that has been traditionally difficult to access. In our work, poly(lactic-co-glycolic acid), PLA/PGA, poly(lactic acid) PLA, and poly(ethylene-co-vinylacetate) (PEVA) have been deposited from solutions in methylene chloride or chloroform by electrospraying or electrospinning to afford morphologically tailored materials for tissue engineering and related applications. Low solution concentrations tend to favor electrostatic spraying ('electro-aerosolization') while higher concentrations lead to spinning on fibrous mats. Preliminary observations of muscle cell growth on PLA electrospun mats are reported.

Stitzel, Joel D.↗
NASA NTRS2019

Steady-State Solution of a Solar Wind-Generated Electron Cloud in a Lunar Crater

We formulate an analytic description of a steady-state electron cloud and affiliated surface charge, formed in the plasma wake generated as the solar wind flows horizontally over a lunar crater. The solution is complementary to the well-known self-similar plasma expansion formulation, which breaksdown at the plasma wake front and thus fails to capture a substantial region of the crater interior. The present model establishes a theoretical basis for existing simulation results, which suggest that the cavity formed below the wake front is populated mainly by electrons, resulting in a substantial negative surface charge. The electrostatic potential throughout this subwake region is determined by solving Poisson'sequation for a Maxwellian electron cloud, bounded above by the self-similar plasma expansion front and below by the electrostatically charged surface.

Rhodes, Dov J.↗
NASA NTRS2005

Potential of Organic Matrix Composites for Liquid Oxygen Tank

Composite materials are being considered for the tankage of cryogenic propellants in access to space because of potentially lower structural weights. A major hurdle for composites is an inherent concern about the safety of using flammable structural materials in contact with liquid and gaseous oxygen. A hazards analysis approach addresses a series of specific concerns that must be addressed based upon test data. Under the 2nd Generation Reusable Launch Vehicle contracts, testing was begun for a variety of organic matrix composite materials both to aid in the selection of materials and to provide needed test data to support hazards analyses. The work has continued at NASA MSFC and the NASA WSTF to provide information on the potential for using composite materials in oxygen systems. Appropriate methods for oxygen compatibility testing of structural materials and data for a range of composite materials from impact, friction, flammability and electrostatic discharge testing are presented. Remaining concerns and conclusions about composite tank structures, and recommendations for additional testing are discussed. Requirements for system specific hazards analysis are identified.

Davis, Samuel E.↗
NASA NTRS1990

Strong Langmuir turbulence generated by electron beams - Electric-field distributions and electron scattering

Strong turbulence and transit-time scattering theory are applied here to calculate the statistical distribution of intense Langmuir fields and the consequent beam scattering in plasma turbulence driven by an electron beam. The experimentally observed electric-field distributions are compared with predictions of strong-turbulence theory, concentrating on the wave levels, the Gaussian tail of the high-field distribution observed in one experiment, the arrest scale of collapse, and the fractional volume occupied by the highest fields. The Guassian form of the tail is confirmed, and the results imply that the collapse is arrested at a scale where the peak electrostatic energy density is of the same order as the thermal energy density. The theory of transit-time interactions is generalized to include relativistic particle dynamics and is applied to predict the scattering of the beam electrons in energy and angle as they pass through strong Langmuir turbulence. The results support the validity of the recently developed scaling theory of strong turbulence.

Robinson, P. A.↗
NASA NTRS1982

Mapping of electrical potential distributions with charged particle beams

Methods for measuring electrostatic potentials on and near dielectric surfaces charged to several kilovolts are studied. Secondary emission from those charged dielectrics is measured. Candidates for potential measurement include the induced charge, from which potential is calculated; the trajectory endpoints of either high or low energy particles traversing the region near the surface; trajectory impact on the surface; and creating ions at points of interest near the surface. Some of the methods require computer simulations and iterative calculation if potential maps are to be generated. Several approaches are described and compared. A method using a half-cylinder as a test chamber and low-energy probing beams is adapted for the measurement of seconary emission.

Robinson, J. W.↗
NASA NTRS1990

The coherent Cerenkov radiated power from a group of field-aligned test particles in a magnetoplasma

An expression is derived that describes the coherent Cerenkov radiated power from a group of test particles in a plasma medium moving parallel to a magnetic field. In this analysis, each particle has an arbitrary position and velocity along a field line and, as a consequence, both the spatial and temporal coherence of the radiation are considered. As an example, it is demonstrated that a monoenergetic electron beam consisting of small pulses can generate wave powers well above incoherent levels if the pulse spacing is comparable to an integer number of emission wavelengths. It is also shown that, if the beam particles have a velocity spread, Delta-V, the wave powers will decrease in time due to the reduced temporal coherence of the particle radiators, where this coherence scales as 1/Delta-V. This latter effect applies to any charged particle beam propagating in a magnetoplasma, because even an initially monoenergetic beam becomes thermalized by electrostatic wave-particle interactions reducing the radiated power.

Farrell, W. M.↗
NASA NTRS1986

Plasma waves in magnetotail flux ropes

The plasma waves associated with the magnetotail flux ropes of December 28, 1982, December 30, 1982, and March 25, 1983, originally identified by Sibeck et al. (1984) are studied. Broadband electrostatic noise was found in the sheaths and cores of all three flux ropes. The frequency range extended from about 100 Hz to the local electron plasma frequency. The electric field vector tended to be aligned either parallel or antiparallel to the local magnetic field direction throughout the complex flux rope magnetic field configuration. The March 25, 1983, flux rope also contained an intense band of whistler mode noise extending up to one half the local electron cyclotron frequency. The superthermal electrons generating the observed whistler mode noise may have had highly anisotropic pitch angle distributions.

Kennel, C. F.↗
NASA NTRS1978

Electrostatic emissions between electron gyroharmonics in the outer magnetosphere

Electrostatic emissions are often observed by spacecraft in the outer magnetosphere at frequencies between low electron gyroharmonics. The emissions include the well-known odd half-harmonic emissions as well as weaker emissions which occur near the electron plasma frequency. A scheme is constructed for classifying the emissions, and it is shown that a theoretical model which has been previously used to explain '3/2' emissions can be extended to the other classes of emissions. All of the emissions therefore appear to be generated by the same basic mechanism: an unstable electron plasma distribution consisting of cold electrons (below 100 eV) and hot loss cone electrons (about 1 keV). Each emission class is associated with a particular range of model parameters; the wide-band electric field data can thus be used to infer the density and temperature of the cold plasma component. The model predicts that gyroharmonic emissions near the plasma frequency require large cold plasma densities.

Hubbard, R. F.↗
NASA NTRS1991

Migration and generation of contaminants from launch through recovery: LDEF case history

The migration of contaminants to and between Long Duration Exposure Facility (LDEF) surfaces reveals new information relevant to all future space missions. The surface of the LDEF satellite closely paralleled over seven meters of the shuttle during one launch and one reentry. Transfer of contaminants from the shuttle bay to the payload were documented and partially quantified for both the launch and recovery separately. LDEF carried a load of volatile silicones and hydrocarbons into orbit which were then polymerized by UV radiation into tough, dark brown stains on exposed surfaces. The distribution of these stains is providing new information on deposition mechanisms that should be studied on future missions. Electrostatic effects, diffusional flow, and effects due to small surface temperature differences at the time of UV exposure are suggested. The types of functional groups present in the LDEF deposit it nearly identical to stains recovered from other spacecraft. These stains were remarkably stable in low Earth orbit even with atomic oxygen exposure if the amount of silicones present was sufficient to create a sealing layer of silicon dioxide over the dark brown stain beneath.

Crutcher, E. Russ↗