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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Air turbo-ramjet engine

A jet engine designed to power a supersonic airplane throughout a range of speeds from subsonic to high supersonic includes a housing which bounds an internal passage having in succession a fixed-area inlet section, a diverging passage section, a mixing section, a combustion section, and an outlet section. A fan rotor rotates in the inlet section and includes a plurality of rotor blade members. The housing includes a main body and at least one flap which is movable between one end position in which it externally bounds a portion of the diverging passage section and another end position in which it externally delimits a diverging discharge passage connecting the diverging passage section with the exterior of the housing. The cross-sectional area of the outlet section is adjustable. The rotor is driven in rotation by a fuel/oxygen powered turbine the outlet of which communicates with the mixing section, but the driving action of the turbine is discontinued at actual supersonic velocities exceeding a predetermined supersonic velocity. The pitch of at least one element of each of the rotor blade members is adjustable.

Kepler, Charles E.↗
NASA NTRS2016

Electrostatic Discharge Testing of Carbon Composite Solar Array Panels for NASA's Planned Europa Mission to Jupiter

The next planned NASA mission to visit Jupiter is known as the Europa Mission. The objective of this mission concept is to enter orbit around Jupiter in order to conduct multiple close flybys of the icy moon Europa. After careful trade studies, the mission designers have selected solar arrays as the baseline power system for the proposed mission rather than more traditional radioisotope thermoelectric generators. In order to examine the risk of using solar arrays, a series of tests were devised to determine the response of a typical solar array coupon to energetic electrons. Test coupons were fabricated and exposed to electrons ranging from 10 keV to 100 keV, at 1 nA/cm2, while being held at both room and cryogenic temperatures and exposed to end of mission radiation levels. While under electron bombardment, electrical discharges were observed and recorded with the majority of discharges occurring with electron energies of 25 keV. The largest effects on discharge size and rate were the decrease in temperature and the reduction of dielectric material on the sample surface. These tests indicate that solar array panels could be used by the planned Europa Mission in the Jovian environment, but that electrostatic discharges could be expected on the carbon composite solar arrays.

carbon composite↗
NASA NTRS1975

Fabrication and testing of negative limited sealed nickel-cadmium cells

A number of 20 Ah and 3 Ah negative limited nickel-cadmium cells were fabricated and assembled in hermetically sealed stainless steel containers. The cells exhibit a large voltage rise signal, in excess of 250 mA, at the end of each charge period. They also exhibit lower self discharge rates than conventional sealed nickel-cadmium cells and do not require overcharge. The cells are capable of operating at charge and discharge rates up to 5C and can deliver at least 1000 cycles on a 30 minute regime at 25% DOD. A small amount of gassing occurs, but is not deemed critical or detrimental in view of the facts that, (1) operating pressures are in the range of 7 to 20 psig and (2) the cells are operated in the flooded condition so therefore contain little internal void volume. The cells were found to exhibit somewhat higher capacity loss rates during cycling than conventional sealed nickel-cadmium batteries.

Gordy, D. J.↗
NASA NTRS1978

Fabrication and testing of silver-hydrogen cells

The development and life testing of single electrode and multi electrode stacks to optimize the individual components and characterize the performance of a silver hydrogen battery system are described. A NASA-developed inorganic separator material was used as the main separator within the cells. Single electrode test cells were cycled at 75% of nominal capacity out through approximately 1,000 cycles in a number of cases where deterioration in performance was observed. This deterioration appears to be a decay in usable capacity of the silver electrode; but the exact mechanism is still unidentified. Twenty ampere-hour boilerplate test cells consisting of a stack of ten silver electrodes and twenty hydrogen electrodes were cycled also at 75% depth of discharge. The oldest stack achieved 522 stable cycles to the end of the program. Weight analysis of light-weight cells showed that 50 ampere-hour cells with improved components could be capable of as much as 40 watt hours per pound.

Klein, M. G.↗
NASA NTRS2016

Post-Launch Calibration and Testing of Space Weather Instruments on GOES-R Satellite

The Geostationary Operational Environmental Satellite - R (GOES-R) is the first of a series of satellites to be launched, with the first launch scheduled for October 2016. The three instruments - Solar Ultra Violet Imager (SUVI), Extreme ultraviolet and X-ray Irradiance Sensor (EXIS), and Space Environment In-Situ Suite (SEISS) provide the data needed as inputs for the product updates National Oceanic and Atmospheric Administration (NOAA) provides to the public. SUVI is a full-disk extreme ultraviolet imager enabling Active Region characterization, filament eruption, and flare detection. EXIS provides inputs to solar backgrounds/events impacting climate models. SEISS provides particle measurements over a wide energy-and-flux range that varies by several orders of magnitude and these data enable updates to spacecraft charge models for electrostatic discharge. EXIS and SEISS have been tested and calibrated end-to-end in ground test facilities around the United States. Due to the complexity of the SUVI design, data from component tests were used in a model to predict on-orbit performance. The ground tests and model updates provided inputs for designing the on-orbit calibration tests. A series of such tests have been planned for the Post-Launch Testing (PLT) of each of these instruments, and specific parameters have been identified that will be updated in the Ground Processing Algorithms, on-orbit parameter tables, or both. Some of SUVI and EXIS calibrations require slewing them off the Sun, while no such maneuvers are needed for SEISS. After a six-month PLT period the GOES-R is expected to be operational. The calibration details are presented in this paper.

On-orbit Calibration↗
NASA NTRS2016

Post-Launch Calibration and Testing of Space Weather Instruments on GOES-R Satellite

The Geostationary Operational Environmental Satellite - R (GOES-R) is the first of a series of satellites to be launched, with the first launch scheduled for October 2016. The three instruments Solar UltraViolet Imager (SUVI), Extreme ultraviolet and X-ray Irradiance Sensor (EXIS), and Space Environment In-Situ Suite (SEISS) provide the data needed as inputs for the product updates National Oceanic and Atmospheric Administration (NOAA) provides to the public. SUVI is a full-disk extreme ultraviolet imager enabling Active Region characterization, filament eruption, and flare detection. EXIS provides inputs to solar back-ground-sevents impacting climate models. SEISS provides particle measurements over a wide energy-and-flux range that varies by several orders of magnitude and these data enable updates to spacecraft charge models for electrostatic discharge. EXIS and SEISS have been tested and calibrated end-to-end in ground test facilities around the United States. Due to the complexity of the SUVI design, data from component tests were used in a model to predict on-orbit performance. The ground tests and model updates provided inputs for designing the on-orbit calibration tests. A series of such tests have been planned for the Post-Launch Testing (PLT) of each of these instruments, and specific parameters have been identified that will be updated in the Ground Processing Algorithms, on-orbit parameter tables, or both. Some of SUVI and EXIS calibrations require slewing them off the Sun, while no such maneuvers are needed for SEISS. After a six-month PLT period the GOES-R is expected to be operational. The calibration details are presented in this paper.

On-orbit Calibration↗
NASA NTRS1993

Impedance measurements on a spiral-wound nickel/metal hydride cell cycled in a simulated Leo orbit

A spiral-wound size C cell was cycled at 25 C in a low earth orbit (LEO) regime at 50 percent depth of discharge (DOD) with approximately five percent over-charge. The nominal capacity was 3.5 AH. The cell was cycled for 2000 cycles. Capacity checks and impedance measurements over the complete range of state of charge were made upon receipt and after 500, 1000, and 2000 cycles. The capacity of the cell was essentially unchanged until after the impedance measurements at 2000 cycles. Only small changes in the impedance parameters were observed, but there was somewhat more scatter in the data after 2000 cycles. When the cell was returned to LEO cycling after 2000 cycles, only 38 percent of the capacity could be obtained. It is believed that the cell failed because of an equipment failure at the end of the final impedance measurements which allowed an over-discharge.

Reid, Margaret A.↗
NASA NTRS1976

Probe studies in a modified penning discharge

The axial and radial floating potential distribution in a modified Penning discharge were studied at different values of the background pressure, discharge voltage, and magnetic field. An array of small disc probes arranged radially with their planes perpendicular to the magnetic field and movable along the axial direction was inserted in the plasma through one open end of the magnetic mirror system. Results show that depending on the operating conditions, the discharge can undergo different mode transitions in which the plasma can sustain different floating potentials in the radial as well as in the axial directions. Preliminary results of measurement, using RF probes in the modified Penning discharge plasma are also discussed.

Sen, C.↗
NASA NTRS1976

Probe studies in a modified Penning discharge

The axial and radial floating potential distribution in a modified Penning discharge have been studied at different values of the background pressure, discharge voltage, and magnetic field. An array of small disc probes arranged radially with their planes perpendicular to the magnetic field and movable along the axial direction was inserted in the plasma through one open end of the magnetic mirror system. Results show that depending on the operating conditions, the discharge can undergo different mode transitions in which the plasma can sustain different floating potentials in the radial as well as in the axial directions. Preliminary results of measurement, using RF probes in the modified Penning discharge plasma are also discussed.

Sen, C.↗
NASA NTRS1980

Another look at aircraft-triggered lightning

There is positive evidence that a rapidly moving aircraft charged to high potentials by triboelectric processes can trigger lightning discharges by passage through freezing precipitation. The freezing zone in a nonstormy rain cloud is shown to be an electrically volatile region because of the potent charge exchange mechanisms which are active in agitated mixtures of supercooled water droplet and ice. Several intensifying effects are suggested which can be produced by the passage of an aircraft through this precipitation, resulting in a highly-ionized wake which acts like a trailing conductor. If weak charge centers are present in the cloud, the ionized wake acts to short out the gradient field resulting in very high potentials at the aircraft. The high potentials explain the electrical activity at the aircraft described by pilots, including intense corona, sparks and radio interference terminating in a loud discharge. Lightning strikes to naval aircraft towing gunnery targets at the end of long steel cables are described, showing that the same triggering mechanism may be involved in those cases. Recommendations are made to include triggering experiments in government flight programs now in progress.

Clifford, D. W.↗
NASA NTRS1978

Development of long life lightweight nickel-cadmium cells and batteries

The paper describes the development of a high-specific energy Ni-Cd cell for a lightweight battery. After preliminary cycling tests on laboratory and commercial cells, a cell was produced that features electrochemically impregnated positive and negative electrodes, a single terminal, and increased amount of electrolyte. This cell weighed an average of 948 g and had a measured specific energy of over 50 Wh/kg at a C/2 discharge to 1.0 V. The epoxy graphite case capable of withstanding internal pressures in excess of 300 psig represents a 35% weight reduction from a lightweight 0.30 mm Ni-Cd case. A pack of these cells was cycled at 70% maximum depth of discharge beyond 10 simulated geosynchronous orbit-eclipse seasons, and high end-of-charge voltages were obtained. A prototype battery consisting of 14 such cells was fabricated and has a measured specific energy of 46 Wh/kg.

Ritterman, P. F.↗
NASA NTRSDate not supplied

Initial Motor Winding Insulation Lifetime Experimental Results for Electric Aircraft Applications

Electric and hybrid-electric aircraft require high-performance and reliable electric motors to meet aviation performance and safety requirements. One of the most common failure mechanisms in electric motors is winding insulation breakdown. In this paper, initial set of aging experiments are carried out on twisted pairs and motorette specimens. The twisted pairs are aged with multiple steady-temperature thermal aging cycles. The motorette specimens are thermally cycled by applying current to the windings. Partial discharge inception voltage is tracked and reported throughout the aging process. The end goal of this work is to develop methods and models for assessing the lifetime of motor winding insulation in electric and hybrid electric aircraft applications.

Thomas Tallerico↗
NASA NTRS1976

Mach 4 free-jet tunnel starting experiments for a hypersonic research engine model causing high blockage

Tests of a full scale hypersonic research engine (HRE) were conducted in the hypersonic tunnel facility at Mach numbers of 5, 6, and 7. Since the HRE would cause a rather high blockage (48.83 percent of the nozzle area), subscale tests were conducted in various available small wind tunnels prior to the full scale tests to study the effects of model blockage on tunnel starting. The results of the Mach 4 subscale tests which utilized a model system at 0.0952 scale which simulated the HRE in the test section of the tunnel are presented. A satisfactory tunnel starting could not be achieved by varying the free jet length or diffuser size nor by inserting the model into the test stream after tunnel starting. However, the installation of a shroud around the HRE model allowed the tunnel to start with the model preset in the tunnel at a tunnel stagnation pressure to atmospheric exit pressure ratio of 13.4. The simulation of the discharge of instrumentation cooling water and the addition of test hardware at the aft end of the HRE model did not have a significant effect on the tunnel starting.

Carson, G. T., Jr.↗
NASA NTRS2013

SparkJet Efficiency

A novel method for determining the thermal efficiency of the SparkJet is proposed. A SparkJet is attached to the end of a pendulum. The motion of the pendulum subsequent to a single spark discharge is measured using a laser displacement sensor. The measured displacement vs time is compared with the predictions of a theoretical perfect gas model to estimate the fraction of the spark discharge energy which results in heating the gas (i.e., increasing the translational-rotational temperature). The results from multiple runs for different capacitances of c = 3, 5, 10, 20, and 40 micro-F show that the thermal efficiency decreases with higher capacitive discharges.

Golbabaei-Asl, Mona↗
NASA NTRS1974

Experimental Investigation of Electron Cloud Containment in a Nonuniform Magnetic Field

Dense clouds of electrons were generated and studied in an axisymmetric, nonuniform magnetic field created by a short solenoid. The operation of the experiment was similar to that of a low-pressure (approximately 0.000001 Torr) magnetron discharge. Discharge current characteristics are presented as a function of pressure, magnetic field strength, voltage, and cathode end-plate location. The rotation of the electron cloud is determined from the frequency of diocotron waves. In the space charge saturated regime of operation, the cloud is found to rotate as a solid body with frequency close to V sub a/phi sub a where V sub a is the anode voltage and phi suba is the total magnetic flux. This result indicates that, in regions where electrons are present, the magnetic field lines are electrostatic equipotentials (E bar, B bar = 0). Equilibrium electron density distributions suggested by this conditions are integrated with respect to total ionizing power and are found consistent with measured discharge currents.

Eninger, J. E.↗
NASA NTRS1976

Impedance of silver oxide-zinc cells

Over 100 sealed AgO-Zn cells were subjected to prolonged periods of storage over a range of temperatures and storage modes including open circuit, trickle charge, and float charge. Impedances of these cells were monitored throughout, and at the end of the storage period their transient voltage characteristics were observed at the onset of discharge. Results revealed that the impedances of these cells tended to increase with storage time; the magnitude of the impedance rise was dependent primarily on temperature and to a lesser degree on storage mode. Typical values for 50 A-hr cells were usually less than 100 mohm immediately after activation and from 1 to 30 ohm after 6-10 months of storage. Transient voltages of these cells droped sharply during the first msec of discharge and then rose to a stablized value during the following few seconds. The magnitude of the initial drop and the stabilized voltage values were found to be related to impedance but not in a linear manner. The magnitude and duration of the low transient voltages may be unacceptable in some applications of these cells. The impedance variations are attributed to changes occurring at the positive electrode.

Frank, H. A.↗
NASA NTRS1978

An electro-optic, high-voltage, transient probe

A newly developed electro-optic voltage transducer is described. It is capable of measuring 30 ns rise time, floating or single-ended, 0 to 20 kV transients in a high noise environment such as a fast discharge laser or energetic switch system. The voltage transient is detected by a specially developed resistor in series with a light emitting diode. The light output (proportional to voltage) is transmitted remotely via a fiber-optic cable to a detector and recorder. Typical signals and comparison with commercial probe system signals are described.

Posta, S. J.↗