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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
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NASA NTRSDate not supplied

Computational Modeling Development of Solid-state Architecture Batteries for Enhanced Rechargeability and Safety for Electric Aircraft

All electric vertical take-off and landing vehicles (eVTOL) for urban air mobility (UAM) concepts face numerous challenging technical barriers before their introduction into the consumer marketplace. The most challenging of these technical barriers to overcome is developing an energy storage system capable of meeting the rigorous aerospace safety and performance criteria. The performance metrics for eVTOL craft are at least 2 times greater than those of electric automobiles. Furthermore, safety is essential for operation of commercial electric aerovehicles. Preliminary systems level analysis has indicated that there are five key properties which must be optimized for successful implementation of battery systems. Those five key criteria are: safety, energy density, power, packaging design and scalability. Current state-of-the-art (SOA) lithium-ion batteries meet or exceed the requirements for electric aviation in the areas of power and scalability, yet are insufficient in the key performance criteria of energy, safety and packaging design. The SABERS concept proposes a battery that meets all five key performance criteria through development of a solid-state architecture battery utilizing high energy density and power density sulfur-selenium cathode with a lithium metal anode. The combination of sulfur and selenium offers a balanced energy-to-power density ratio, which can be tailored to the specific application by altering the stoichiometric ratios of sulfur to selenium. This cathode will be developed by implementing NASA patented holey graphene technology as a highly conductive, ultra-lightweight electrode scaffold. A solid-state electrolyte will be used as a safe, non-flammable replacement to the highly flammable liquid organic electrolytes currently used in SOA lithium-ion batteries. This solid-state lithium-sulfur-selenium cell will be designed into a serial stacking configuration to enable dense packaging of the battery cells. The serial stacking configuration is termed a bipolar stack, which has the advantages of reducing overall cell weight, reducing the amount of interfaced connections for the cell, and minimizing the cooling requirements for the cell. Lastly, optimization of battery components will occur through a robust and rigorous combination of various computational modeling techniques covering multiple length scales. The expected result will be a fully solid-state battery with operational temperatures from 0 °C to 150 °C which provides the required energy density, discharge rates, and inherent safety to meet the strict aerospace performance criteria. This presentation will show initial results that demonstrate the SABERS Team has developed a composite carbon-sulfur cathode which exceeds 1100 Wh/kg at a discharge rate of 0.4C, and 804 Wh/kg at a discharge rate of 1C. Additionally, this presentation will show the SABERS Team multiscale computational modeling approach and has produced a novel particle dynamics method called Solid Electrolyte Sphere Approximation Model (SESAM). SESAM is on the 1-10 µm scale and provides electromechanical and grain interactions for predictive design guidelines for the experimental team to follow.

Urban Air Mobility (UAM) Vehicles↗
NASA NTRS1970

Survey, analysis and evaluation test on high voltage/current pulse transmission cables

A survey, analysis, and testing of available cable connector configurations were carried out in connection with transmission of high voltage/current to an exploding wire bridge. Transmission was desired at high efficiency with maximum cable flexibility, at minimum weight and size of the cable connector, with maximum cable length while maintaining applicable voltage/current pulse characteristics, and with due consideration to environmental parameters.

Dann, J. E.↗
NASA NTRS1973

Space shuttle heat pipe thermal control systems

Heat pipe (HP) thermal control systems designed for possible space shuttle applications were built and tested under this program. They are: (1) a HP augmented cold rail, (2) a HP/phase change material (PCM) modular heat sink and (3) a HP radiating panel for compartment temperature control. The HP augmented cold rail is similar to a standard two-passage fluid cold rail except that it contains an integral, centrally located HP throughout its length. The central HP core helps to increase the local power density capability by spreading concentrated heat inputs over the entire rail. The HP/PCM modular heat sink system consists of a diode HP connected in series to a standard HP that has a PCM canister attached to its mid-section. It is designed to connect a heat source to a structural heat sink during normal operation, and to automatically decouple from it and sink to the PCM whenever structural temperatures are too high. The HP radiating panel is designed to conductively couple the panel feeder HPs directly to a fluid line that serves as a source of waste heat. It is a simple strap-on type of system that requires no internal or external line modifications to distribute the heat to a large radiating area.

Alario, J.↗
NASA NTRS1975

A Theoretical Investigation of the Input Characteristics of a Rectangular Cavity-Backed Slot Antenna

Equations which represent the magnetic and electric stored energies are derived for an infinite section of rectangular waveguide and a rectangular cavity. These representations which are referred to as being physically observable are obtained by considering the difference in the volume integrals appearing in the complex Poynting theorem. It is shown that the physically observable stored energies are determined by the field components that vanish in a reference plane outside the aperture. These physically observable representations are used to compute the input admittance of a rectangular cavity-backed slot antenna in which a single propagating wave is assumed to exist in the cavity. The slot is excited by a voltage source connected across its center; a sinusoidal distribution is assumed in the slot. Input-admittance calculations are compared with measured data. In addition, input-admittance curves as a function of electrical slot length are presented for several size cavities. For the rectangular cavity backed slot antenna, the quality factor and relative bandwidth were computed independently by using these energy relationships. It is shown that the asymptotic relationship which is usually assumed to exist between the quality bandwidth and the reciprocal of relative bandwidth is equally valid for the rectangular cavity backed slot antenna.

Cockrell, C. R.↗
NASA NTRS2005

Participation in the Analysis of the Far-Infrared/Submillimeter Interferometer

We have contributed to the development of the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) by analyzing various aspects related to the tethers that connect the spacecraft of this space interferometer. We have focused our analysis on key topics as follows: (a) helping in the configuration selection; (b) computing the system eigenfrequencies as a function of baseline length; (c) developing techniques and conceptual design of devices for damping the tether oscillations; (d) carrying out numerical simulations of tethered formation to assess the effects of environmental perturbations upon the baseline length variation; (e) devising control laws for fast retargeting of the interferometer at moderate baseline lengths; (f) estimating the survivability to micrometeoroid impacts of a tether at L2; and (g) developing a conceptual design of a high-strength and survivable tether.

Lorenzini, Enrico C.↗
NASA NTRS2005

Participation in the Analysis of the Far-Infrared/Submillmeter Interferometer

We have contributed to the development of the Submillimiter Probe of the Evolution of Cosmic Structure (SPECS) by analyzing various aspects related to the tethers that connect the spacecraft of this space interferometer. We have focused our analysis on key topics as follows: (a) helping in the configuration selection; (b) computing the system eigenfrequencies as a function of baseline length; (c) developing techniques and conceptual design of devices for damping the tether oscillations; (d) carrying out numerical simulations of tethered formation to assess the effects of environmental perturbations upon the baseline length variation; (e) developing control laws for reconfiguring the baseline length; (f) devising control laws for fast retargeting of the interferometer at moderate baseline lengths; (g) estimating the survivability to micrometeoroid impacts of a tether at L2; and (h) developing a conceptual design of a high- strength and survivable tether. The work was conducted for NASA Goddard Space Flight Center under Grant NNG04GQ21G with William Danchi as technical monitor.

Lorenzini, Enrico C.↗
NASA NTRS1977

Bright X-ray arcs and the emergence of solar magnetic flux

The Skylab S-056 and S-082A experiments and ground-based magnetograms have been used to study the role of bright X-ray arcs and the emergence of solar magnetic flux in the McMath region 12476. The S-056 X-ray images show a system of one or sometimes two bright arcs within a diffuse emitting region. The arcs seem to directly connect regions of opposite magnetic polarity in the photosphere. Magnetograms suggest the possible emergence of a magnetic flux. The width of the main arc is approximately 6 arcsec when most clearly defined, and the length is approximately 30-50 arcsec. Although the arc system is observed to vary in brightness over a period exceeding 24 hours, it remains fixed in orientation. The temperature of the main arc is approximately 3 x 10 to the 6th K. It is suggested that merging magnetic fields may provide the primary energy source, perhaps accompanied by resistive heating from a force-free current.

Chapman, G. A.↗
NASA NTRS1981

Models for Jupiter's decametric arcs

Arc-shaped structures that dominate Jupiter's decametric emission are discussed in terms of a magnetic fine structure. The sequence of arcs manifest the occurence of widespread fine structures similar to the white ovals on Jupiter's visible surface. An arc concave toward increasing time occurs at the east limb passage, and an arc convex occurs at the west limb passage, which is consistent with the early source producing vertex early arcs, and the late source producing vertex late arcs. Due to the geometry of the Io plasma torus (IPT) which is arranged so that Io skims the northern surface of the IPT, for any connection between Io and Jupiter's surface that involves Alfven waves, the propagation time, the refraction and the directional defocusing of these waves must be strongly influenced by the amount of Alfven wave path length between the instantaneous position of Io and the surface of the IPT.

Warwick, J. W.↗
NASA NTRS1989

Closure of field-aligned currents carried by super-Alfvenic auroral electrons

A linear analysis is carried out to investigate how the return current is generated for the field-aligned current carried by a super-Alfvenic auroral electron beam. If the electron beam is a thin sheet with thickness less than or equal to the electron inertia length, the negative space charge of the beam is neutralized by the ion polarization current produced by the beam. The return current in this case is generated on the two outsides of the beam connected to the polarization current to form a closed current loop. This current structure can explain the thin (a few km) current sheets in the auroral arcs observed by satellites.

Nakamura, Tadas↗
NASA NTRS1992

Birefringence-balanced polarimetric optical fiber sensor for high-temperature measurements

A birefringence-balanced polarimetric multimode fiber temperature sensor is proposed and demonstrated. Two single-crystal sapphire rods are incorporated into the sensor head. They are connected end to end in such a way that the slow axis of the first rod is aligned with the fast axis of the second rod, referred to as the referencing rod. Since the lengths of the two rods are chosen to be almost the same, the original birefringence of the first rod is balanced by that of the second rod. A light-emitting diode serves as the light source. This sensor has been experimentally demonstrated for high-temperature measurements as high as 1500 C. A sensitivity of 5 C has been obtained.

Wang, Anbo↗
NASA NTRS1994

Preliminary evidence for dust in galactic halos

I use B and I photometry of distant galaxies observed through the halos of two nearby spiral galaxies, NGC 2835 and NGC 3521, to test for the existence of dust in galactic halos out to at least a radius of 60 kpc. B - I colors of background galaxies in fields centered along the nearby galaxy's major axis at a projected separation of 60 kpc are compared to the colors of background galaxies in fields centered at a projected separation of about 220 kpc. Background galaxies in the fields at smaller projected separations have average B - I colors that are 0.067 +/- 0.033 mag redder than those in the outer fields. Such a result will occur by chance less than 2.2% of the time and so is taken as preliminary evidence that galaxy halos contain more dust at galactic radii of 60 than 220 kpc. A model which assumes that the radial dust profile in galactic disks and halos is a single exponential has a corresponding scale length of 31 +/- 8 kpc. I argue on the basis of the Infrared Astronomy Satellite (IRAS) 100 micron flux maps that absorption by Galactic dust is not responsible for this result and briefly discuss connections between this result and other observations of the baryonic component of galaxy halos.

Zaritsky, Dennis↗
NASA NTRS1978

Polycrystalline or amorphous semiconductor photovoltaic device having improved collection efficiency

A body of semiconductor material having a first surface and a second surface spaced from the first surface includes a first layer along the first surface, a second layer along the second surface, a third layer between and contiguous to the first and second layers. The third layer is of a conductivity type opposite that of the first and second layers so as to form first and second P-N junctions respectively therebetween. The thickness of the third layer is at least twice the minority carrier diffusion length of the semiconductor material, so that carriers generated within the third layer have a high probability of being collected by one of the P-N junctions. The body includes means for electrically connecting the first and second P-N junctions and means for transferring the carriers collected at the first P-N junction to a portion of the first surface.

Kressel, Henry↗
NASA NTRS1976

Computer simulation of earthquakes

Two computer simulation models of earthquakes were studied for the dependence of the pattern of events on the model assumptions and input parameters. Both models represent the seismically active region by mechanical blocks which are connected to one another and to a driving plate. The blocks slide on a friction surface. In the first model elastic forces were employed and time independent friction to simulate main shock events. The size, length, and time and place of event occurrence were influenced strongly by the magnitude and degree of homogeniety in the elastic and friction parameters of the fault region. Periodically reoccurring similar events were frequently observed in simulations with near homogeneous parameters along the fault, whereas, seismic gaps were a common feature of simulations employing large variations in the fault parameters. The second model incorporated viscoelastic forces and time-dependent friction to account for aftershock sequences. The periods between aftershock events increased with time and the aftershock region was confined to that which moved in the main event.

Cohen, S. C.↗
NASA NTRS1980

Minority carrier diffusion lengths and absorption coefficients in silicon sheet material

Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.

Dumas, K. A.↗
NASA NTRS1990

The growth and development of a turbulent junction vortex system

The growth and development of a vortex system in an incompressible three-dimensional flow generated by a streamlined cylinder mounted with its axis normal to a flat surface was investigated using data from surface flow visualizations, surface pressure measurements, and mean flow measurements. The results from velocity measurements revealed the presence of a single large dominant vortex and a small vortex in the junction between the cylinder and the flat surface. This second vortex is tentatively identified as being connected with a corner separation occurring just downstream of the body at its thickest cross section. It is shown that, as the principal horseshoe vortex develops downstream, the strength of the vortex decreases, while its length scale increases.

Pierce, F. J.↗
NASA NTRS2010

Methods of Using a Magnetic Field Response Sensor Within Closed, Electrically Conductive Containers

Magnetic field response sensors are a class of sensors that are powered via oscillating magnetic fields, and when electrically active, respond with their own magnetic fields with attributes dependent upon the magnitude of the physical quantity being measured. A magnetic field response recorder powers and interrogates the magnetic sensors [see Magnetic-Field-Response Measurement- Acquisition System, NASA Tech Briefs Vol. 30, No, 6 (June 2006, page 28)]. Electrically conductive containers have low transmissivity for radio frequency (RF) energy and thus present problems for magnetic field response sensors. It is necessary in some applications to have a magnetic field response sensor s capacitor placed in these containers. Proximity to conductive surfaces alters the inductance and capacitance of the sensors. As the sensor gets closer to a conductive surface, the electric field and magnetic field energy of the sensor is reduced due to eddy currents being induced in the conductive surface. Therefore, the capacitors and inductors cannot be affixed to a conductive surface or embedded in a conductive material. It is necessary to have a fixed separation away from the conductive material. The minimum distance for separation is determined by the desired sensor response signal to noise ratio. Although the inductance is less than what it would be if it were not in proximity to the conductive surface, the inductance is fixed. As long as the inductance is fixed, all variations of the magnetic field response are due to capacitance changes. Numerous variations of inductor mounting can be utilized, such as providing a housing that provides separation from the conductive material as well as protection from impact damage. The sensor can be on the same flexible substrate with a narrow throat portion of the sensor between the inductor and the capacitor, Figure 1. The throat is of sufficient length to allow the capacitor to be appropriately placed within the container and the inductor placed outside the container. The throat is fed through the orifice in the container wall (e.g., fuel tank opening) and connects to the inductor and capacitor via electrical leads to form a closed circuit, Figure 2. Another embodiment is to have the inductor and capacitor fabricated as separate units. In this embodiment, the inductor is mounted external to the container, and the capacitor is mounted internal to the container, Figure 1. Electrical leads are fed through the orifice to connect the inductor and capacitor, Figure 2. When a container holding multiple sensors is made of a conductive material, an antenna can be placed internal to the container. An internal antenna allows all components of the sensors to reside inside the container. The antenna must be separated from the container wall s conductive surface. Additionally, the inductors must be maintained in a fixed position relative to and separated from the container

Woodward, Stanley E.↗
NASA NTRS2005

Elastic-Tether Suits for Artificial Gravity and Exercise

Body suits harnessed to systems of elastic tethers have been proposed as means of approximating the effects of normal Earth gravitation on crewmembers of spacecraft in flight to help preserve the crewmembers physical fitness. The suits could also be used on Earth to increase effective gravitational loads for purposes of athletic training. The suit according to the proposal would include numerous small tether-attachment fixtures distributed over its outer surface so as to distribute the artificial gravitational force as nearly evenly as possible over the wearer s body. Elastic tethers would be connected between these fixtures and a single attachment fixture on a main elastic tether that would be anchored to a fixture on or under a floor. This fixture might include multiple pulleys to make the effective length of the main tether great enough that normal motions of the wearer cause no more than acceptably small variations in the total artificial gravitational force. Among the problems in designing the suit would be equalizing the load in the shoulder area and keeping tethers out of the way below the knees to prevent tripping. The solution would likely include running tethers through rings on the sides. Body suits with a weight or water ballast system are also proposed for very slight spinning space-station scenarios, in which cases the proposed body suits will easily be able to provide the equivalency of a 1-G or even greater load.

Torrance, Paul↗
NASA NTRS1988

Sensitivity of supersonic combustion to combustor/flameholder design

The present test series was conducted to ascertain the effects of various scale and geometric parameters on the combustion and pressure rise limits of a direct-connect supersonic combustor employing hydrogen fuel in a Mach 2 flow and 1-atm static pressure. The injector configuration was similar to that developed by Wagner et al. (1987). Attention is given to the effects of upstream length, fuel-injection gap, and constant-area combustor length, as well as to those of equivalence ratios and stagnation temperature. It is found that, for a given scale, combustion can be strongly dependent on such geometric factors as the use of either constant-area combustion or immediate expansion.

Diskin, Glenn S.↗