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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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Low-melting resistor connected in series with the load protects the circuit against current overloads. It protects test subjects and patients being monitored by electronic instrumentation from inadvertant overloads of current, and sensitive electronic equipment against high-voltage damage.
Optical-capacitive coupling is used for isolation of control voltages, such as the high-voltage level of a klystron control electrode that is not referenced to ground, to serve as error voltages referenced to system ground so that the magnitude and sense of correction may be transferred.
Potting techniques of high-voltage module and testing of amplitron tube and RF problems in microwave circulator
Open construction magnetic components for SERT 2 power conditioner and high-voltage transformer
Dielectric liquid for transfer of heat provides liquid flow from the condenser section to the evaporator section in conventional heat pipes. Working fluid is guided or pumped by an array of wire electrodes connected to a high-voltage source.
A dielectric breakdown study was made of several materials proposed for high-voltage (16-kV) use on solar-cell arrays at space conditions. The tests were made in an argon plasma whose electron density and temperature approximately simulated conditions at an altitude of 300 km. The maximum voltage used was 20 kV. The results indicate that the breakdown voltages of the materials tested are larger than those quoted in the literature for dielectric between two metal electrodes.
The internal structure of painted and unpainted aluminum alloy sheet samples from the TV camera shrouds were examined by high-voltage transmission electron microscopy. No clear-cut evidence of radiation damage effects was observed. Noticeable differences in microstructures between the upper visor and the sides and bottom of the lower shroud suggest different thermal histories, and the maximum temperatures due to solar heating are estimated to be between 164 and 319 C. Some correlation between microstructures and maximum estimated temperature is noted. It is felt that the apparent temperature rise due to solar heating will not affect the structural integrity of spacecraft components except possibly for very long periods of exposure. However, substantial thermal diffusion could affect interpretation of solar wind rare gas studies.
The circular piezoelectric bender laser tuner to replace conventional laser tuners when mirror diameters up to 0.50 inch are sufficient is described. The circular piezoelectric bender laser tuner offers much higher displacements per applied volt and permits laser control circuits to be fabricated using standard operational amplifiers, rather than the expensive high-voltage amplifiers required by conventional tuners. The cost of the device is more than one order of magnitude lower than conventional tuners and the device is very rugged with all mechanical resonances easily designed to be greater than 3kHz. In addition to its use as a laser frequency tuner, the circular bender tuner should find many applications in interferometers and similar devices.
Possible improvements to present aircraft electrical power systems for use in future advanced types of aircraft have been investigated. The conventional power system is examined, the characteristics of electric loads are reviewed, and various methods of power generation and distribution are appraised. It is shown that a hybrid system, with variable-frequency generation and high-voltage dc distribution, could overcome some of the limitations of the conventional system.
The design concept for the TWT amplifier converter for possible use in the Thermoelectric Outer Planet Spacecraft (TOPS) is presented. An unusual combination of semiconductors and magnetics was utilized to achieve very stable voltage regulation on a number of separate outputs to satisfy the requirements of a high-power TWT, and at the same time operate at an efficiency of better than 90% from a 30-V source. The circuitry consists of an output filter, an auxiliary Jensen oscillator driving a high-reactance transformer to provide current limiting to the heater, a variable time delay, a main Jensen oscillator driving the power transformer with a maximum step-up ratio of 120 to 1, and series transistorized post regulators to provide precise voltage adjustment and low output impedance. This paper discusses the design of the high-reactance transformer and the high step-up ratio transformer, as well as the high-voltage series regulators that are limited in range and operate at the top of the unregulated output voltage. Test data are presented, and details of current transients caused by charging the filter circuits, input current ripple, and output voltage ripples are considered.
High-voltage electron microscopy has been used to compare radiation effects in micron-size soil grains from the Luna 16 site (Mare Fecunditatis) and the four Apollo landing sites. Radiation damage by heavy solar particles is strikingly greater in the Luna 16 sample than in the other four samples. It is suggested that less movement of the soil at Mare Fecunditatis has taken place, perhaps because of its proximity to the limb and consequent lower exposure to energetic electrons in the earth's magnetospheric tail, which would cause electrostatic agitation of fine particles.
Description of the star sensor used in the spin-stabilized Uhuru satellite for the purpose of detecting and locating stellar X-ray sources. The star sensor had the capability of detecting fourth-magnitude stars to within 1 arc minute of azimuth and 2 arc minutes of elevation. This was achieved with the aid of a slightly modified 76-mm, f/0.87 Super Farron lens, an 'n' shaped reticle located in the focal plane, and an RCA CF70114F photomultiplier serving as the detection element. The star sensor is composed of three major components - a high-voltage power supply, the photomultiplier, and an amplifier.
Comparative optical and high-voltage electron petrographic analyses of igneous rocks and several types of breccias the Fra Mauro and Apennine sites of Apollo 14 and 15 are reported and interpreted. The crystalline rocks are found to differ substantially from the Apollo 11 and 12 basalts. Substructures in the Apollo 14 breccias are complex. At least two bonding mechanisms can be discerned from the electron petrographic examination: (a) 'shock sintering' due to high pressures and temperatures associated with the shock waves of meteoritic impacts; and (b) lithification by glass bonding.
Optical and high-voltage electron microscopy were used to study radiation-produced defects. There is no systematic decrease in solar flare track distributions in lunar fines even to a depth of 2.5 m. The soil gradually accumulates in thickness; stirring by impacts is usually on a small scale. The accumulation rate at Luna 16 site is far lower than at the Apollo sites; the mean track density in micron-size grains there exceeds one trillion per sq cm; more than 90% of those grains are metamict; the Luna 16 site is at high longitude where electrostatic charging and transport of soil by geomagnetic tail electrons are minimal. A large fraction of soil grains on sloping ground have been isotropically irradiated, suggesting a tumbling downhill motion.-
Description of a general case solution that synthesizes a high voltage solar array system from a switchable building block concept which makes possible system optimization for specific load requirements. A specific optimized solution is demonstrated, with performance estimates relating array area, weight, and power. Significant technology problems peculiar to a high-voltage switchable solar array design are discussed, along with special requirements anticipated during a hardware development effort.
The effect of an axial magnetic field on the breakdown voltage of a coaxial system of electrodes has been investigated by earlier workers. For low values of gas pressure times electrode spacing, the breakdown voltage is decreased by the application of the magnetic field. The electron cyclotron radius now assumes the role held by the mean free path in nonmagnetic discharges and the breakdown voltage becomes a function of the magnetic flux density. In this paper the dependence of the formative time lag as a function of the magnetic flux density is established and the feasibility of using a magnetic field for igniting high-voltage, high-current discharges is shown through theory and experiment. With a 36 microfarad capacitor bank charged to 48,000 volts, a peak current of 1.3 x 10( exp 6) amperes in a coaxial type of plasma gun was achieved with a current rise time of only 2 microseconds.
An investigation was conducted in the Cleveland altitude wind tunnel to determine the operational characteristics of an axial flow-type turbojet engine with a 4000-pound-thrust rating over a range of pressure altitudes from 5,000 to 50,OOO feet, ram pressure ratios from 1.00 to 1.86, and temperatures from 60 deg to -50 deg F. The low-flow (standard) compressor with which the engine was originally equipped was replaced by a high-flow compressor for part of the investigation. The effects of altitude and airspeed on such operating characteristics as operating range, stability of combustion, acceleration, starting, operation of fuel-control systems, and bearing cooling were investigated. With the low-flow compressor, the engine could be operated at full speed without serious burner unbalance at altitudes up to 50,000 feet. Increasing the altitude and airspeed greatly reduced the operable speed range of the engine by raising the minimum operating speed of the engine. In several runs with the high-flow compressor the maximum engine speed was limited to less than 7600 rpm by combustion blow-out, high tail-pipe temperatures, and compressor stall. Acceleration of the engine was relatively slow and the time required for acceleration increased with altitude. At maximum engine speed a sudden reduction in jet-nozzle area resulted in an immediate increase in thrust. The engine started normally and easily below 20,000 feet with each configuration. The use of a high-voltage ignition system made possible starts at a pressure altitude of 40,000 feet; but on these starts the tail-pipe temperatures were very high, a great deal of fuel burned in and behind the tail-pipe, and acceleration was very slow. Operation of the engine was similar with both fuel regulators except that the modified fuel regulator restricted the fuel flow in such a manner that the acceleration above 6000 rpm was very slow. The bearings did not cool properly at high altitudes and high engine speeds with a low-flow compressor, and bearing cooling was even poorer with a high-flow compressor.
Advanced electrified aircraft propulsion (EAP) concepts with integrated power, propulsion, and thermal systems require the development of equally sophisticated controllers to fly safe and efficient missions. Hybrid electric aircraft utilize electric machines mechanically coupled to the engine shafts to extract and insert power for a variety of purposes. Additionally, electric machines may drive propulsive fans pulling from a combination of on-board energy storage devices and engine extracted power. NASA’s investment in hybrid electric aircraft hardware-in-the-loop testing enables controls research on representative engine models using a novel emulation and scaling methodology. High-voltage, high-power electrical powertrain presents several technical risks at altitude. High-power requires high efficiency to minimize losses. Superconducting electric machines and power distribution research at NASA has identified key challenges with potential controls solutions. These risks necessitate the development of controllers robust to model uncertainty, disturbances, and fault conditions. System health management and fault detection schemes play an important role in a multi-layer controls approach that utilizes a supervisor which oversees inner loops for the highly coupled power, propulsion, and thermal systems. Such a supervisory controller enables coordinates energy transfer between engines, energy storage devices, electric machines, propulsors, and heat exchangers. Existing methods have shown an improvement in engine operability using the hybrid electric powertrain.