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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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NASA NTRS2015

High Input Voltage, Silicon Carbide Power Processing Unit Performance Demonstration

A silicon carbide brassboard power processing unit has been developed by the NASA Glenn Research Center in Cleveland, Ohio. The power processing unit operates from two sources - a nominal 300-Volt high voltage input bus and a nominal 28-Volt low voltage input bus. The design of the power processing unit includes four low voltage, low power supplies that provide power to the thruster auxiliary supplies, and two parallel 7.5 kilowatt power supplies that are capable of providing up to 15 kilowatts of total power at 300-Volts to 500-Volts to the thruster discharge supply. Additionally, the unit contains a housekeeping supply, high voltage input filter, low voltage input filter, and master control board, such that the complete brassboard unit is capable of operating a 12.5 kilowatt Hall Effect Thruster. The performance of unit was characterized under both ambient and thermal vacuum test conditions, and the results demonstrate the exceptional performance with full power efficiencies exceeding 97. With a space-qualified silicon carbide or similar high voltage, high efficiency power device, this design could evolve into a flight design for future missions that require high power electric propulsion systems.

Technology↗

NASA NTRS2003

Lightning and Other Influences On Tropical Tropospheric Ozone: Empirical Studies of Covariation

Tropical and subtropical tropospheric ozone are important radiatively active species, with particularly large effects in the upper third of the troposphere. Temporal variability of O3 has proved difficult to simulate day by day in process models. Thus, individual roles of lightning, biomass burning, and other pollution in providing precursor NO(x), radicals, and chain carriers (CO, hydrocarbons) remain unquantified by simulation, and it is theoretically reasonable that individual roles are magnified by a joint synergy. We use wavelet analysis and Burg-algorithm maximum entropy spectral analyses to describe time-scales and correlation of ozone with proxies for processes controlling its concentration. Our empirical studies link time variations apparent in several datasets: the SHADOZ (Southern Hemisphere Additional Ozonesondes) network stations (Nairobi, Fiji), and auxiliary series with power to explain ozone-determining processes, with some interpretation based on the TTO (Tropical Tropospheric Ozone) product derived from TOMS (the Total Ozone Mapping Spectrometer). The auxiliary series are The OTD/LIS(Optical Transient Detector/Lightning Imaging Sensor) measurements of the lightning NO(x) source, the OLR (Outgoing Longwave Radiation)measurement of high-topped clouds, and standard meteorological variables from the United States NCEP (National Centers for Environmental Prediction) and Data Assimilation Office analyses. Concentrating on equatorial ozone, we compare the statistical evidence on the variability of tropospheric ozone. Important variations occur on approximately two-week, two-month (Madden-Julian Oscillation) and annual scales, and relations with OLR suggest controls associated with continental clouds. Hence we are now using the Lightning Imaging Sensor data set to indicate NO(x) sources. We report initial results defining relative roles of the process mentioned affecting O3 using their covariance properties.

Chatfield, Robert B.↗

NASA NTRS2006

A Search for the X-ray Counterpart of the Unidentified Gamma-ray Source 3EG J2020+4017 (2CG078+2)

We report observations with the Chandra X-ray Observatory of a field in the gamma-Cygni supernova remnant (SNR78.2+2.1) centered on the cataloged location of the unidentified, bright gamma-ray source 3EG J2020+4017. In this search for an X-ray counterpart to the gamma-ray source, we detected 30 X-ray sources. Of these, we found 17 strong-candidate counterparts in optical (visible through near-infrared) cataloged and an additional 3 through our optical observations. Based upon colors and (for several objects) optical spectra, nearly all the optically identified objects appear to be reddened main-sequence stars: None of the X-ray sources with an optical counterpart is a plausible X-ray counterpart to 3EG J2020+4017-if that gamma-ray source is a spin-powered pulsar. Many of the 10 X-ray sources lacking optical counterparts are likely (extragalactic) active galactic nuclei, based upon the sky density of such sources. Although one of the 10 optically unidentified X-ray sources could be the gamma-ray source, there is no auxiliary evidence supporting such an identification

Weisskopf, Martin↗

NASA NTRSDate not supplied

Design of a Dynamic Radioisotope Power System Generator Testbed

The Dynamic Radioisotope Power System (DRPS) Testbed is a configurable laboratory test article designed to demonstrate the latest topology of a dynamic radioisotope power system generator. It utilizes an array of Stirling convertors arranged around a centrally located heat source that is radiantly coupled to the convertor hot ends. The Testbed is designed to dissipate all the waste heat through the housing and is outfitted with means for auxiliary cooling methods as well. During the past three years, the team at NASA’s Glenn Research Center (GRC) has been designing and analyzing the various aspects of the DRPS Testbed. Currently, the parts for the Testbed are being manufactured, and the team is focusing on developing the test stand, supporting hardware, and assembly and operation procedures in preparation for the anticipated first operation of the DRPS Testbed in summer of 2022.

Generator↗

NASA NTRSDate not supplied

Design of a Dynamic Radioisotope Power System Generator Testbed

The DRPS Testbed is a configurable laboratory test article designed to demonstrate the latest topology of a dynamic radioisotope power system generator. It utilizes an array of Stirling convertors arranged around a centrally located heat source that is radiantly coupled to the convertor hot ends. The Testbed is designed to dissipate all the waste heat through the housing and is outfitted with means for auxiliary cooling methods as well. During the past three years, the team at NASA’s Glenn Research Center has been designing and analyzing the various aspects of the DRPS Testbed. Currently, the parts for the Testbed are being manufactured, and the team is focusing on developing the test stand, supporting hardware, and assembly and operation procedures in preparation for the anticipated first operation of the DRPS Testbed in summer of 2022.

Ernestina Wozniak↗

NASA NTRSDate not supplied

Conceptual Integration Studies of Localized Active Flow Control on the Wing of a Commercial Aircraft

A study of conceptual integration and performance of localized active flow control technology onto wings of short-to-medium-range project passenger airplanes is summarized. Using predicted aerodynamic performance improvement opportunities on a computational fluid dynamics reference aircraft, this paper presents the estimated performance opportunities for conceptual implementation of studied wing localized active flow control technology for low-speed (takeoff and landing) application on a Project Research Aircraft configuration. Using conceptual active flow control systems and structural integration weight penalties for studied concepts, potential relevant net performance benefits can be obtained with reliable active flow control in takeoff and landing. The conceptual integration study identifies potential localized wing active flow control application opportunities for high-lift conditions using energy sources available on modern aircraft. Material benefits are estimated for takeoff and landing configurations for selected localized wing active flow control applications. The study concluded that substantial low-speed Maximum Lift and Lift/Drag related performance improvements may be possible with localized wing high-lift active flow control systems powered by auxiliary power unit, engine bleed, or electrical compressors - with due consideration of integration and weight impacts as well as availability requirements of such systems.

drag reduction↗

NASA NTRS1973

Aeronautical fuel conservation possibilities for advanced subsonic transports

The anticipated growth of air transportation is in danger of being constrained by increased prices and insecure sources of petroleum-based fuel. Fuel-conservation possibilities attainable through the application of advances in aeronautical technology to aircraft design are identified with the intent of stimulating NASA R and T and systems-study activities in the various disciplinary areas. The material includes drag reduction; weight reduction; increased efficiency of main and auxiliary power systems; unconventional air transport of cargo; and operational changes.

Braslow, A. L.↗

NASA NTRS1973

Construction and testing of a gas-loaded, passive-control, variable-conductance heat pipe

A methanol heat pipe using nitrogen gas for temperature control has been constructed and tested. The system was run over a power ratio of 15 (2 to 30 watts) with the heat source near ambient temperature and with the heat sink at a nominal value of 32 F. Control was obtained with a metal bellows gas reservoir which was actuated by an internal liquid-filled bellows. The liquid bellows was pressurized by expanding liquid methanol which was contained in an auxiliary reservoir in the evaporator heater block. It was demonstrated that the temperature variation of the heat source was reduced from 36 F for the heat pipe with no control to 7 F with the actuated bellows control.

Depew, C. A.↗

NASA NTRS1973

Transmitter and receiver antenna gain analysis for laser radar and communication systems

A comprehensive and fairly self-contained study of centrally obscured optical transmitting and receiving antennas is presented and is intended for use by the laser radar and communication systems designer. The material is presented in a format which allows the rapid and accurate evaluation of antenna gain. The Fresnel approximation to scalar wave theory is reviewed and the antenna analysis proceeds in terms of the power gain. Conventional range equations may then be used to calculate the power budget. The transmitter calculations, resulting in near and far field antenna gain patterns, assumes the antenna is illuminated by a laser operating in the fundamental cavity mode. A simple equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn which display the losses in antenna gain due to pointing errors and the cone angle of the outgoing beam as a function of antenna size and central obscuration. The use of telescope defocusing as an approach to spreading the beam for target acquisition is compared to some alternate methods.

Klein, B. J.↗

NASA NTRS1973

Design and testing of a passive, feedback-controlled, variable conductance heat pipe

A passive feedback system, which stabilizes the heat source temperature (T sub s) of a gas loaded heat pipe, was designed and tested. The control of T sub s is accomplished by an auxiliary liquid that senses the heat source and actuates a metal bellows system due to the liquid's thermal expansion. The movement of the bellows varies the gas reservoir volume and leads to a corresponding change of the condensation area of the heat pipe. With methanol as the heat pipe working fluid and perfluoro-n-pentane as the auxiliary liquid, the control capability was found to be T sub s = 31.5 + or - 1.5 C in a power range from 3 to 30 W, compared to T sub s = 33 + or - 3 C with methanol as auxiliary liquid. The change in T sub s was 35 + or - 5.5 C with the bellows held in the closed position.

Schlitt, K. R.↗

NASA NTRS1978

Inductive storage for quasi-steady MPD thrusters

Experiments in which a quasi-steady MPD thruster is driven by a large inductor demonstrate the feasibility of using inductive energy storage to couple an intermittent high power plasma thruster to a lower power steady state supply, such as a thermionic converter. Switching between inductor charging and MPD thrusting phases of the current cycle occurs smoothly, with the voltage spike generated during switching sufficient to initiate the arc discharge in the thruster without an auxiliary starting circuit. Further, the current waveforms delivered by the inductor are of a shape suitable for the quasi-steady thrusting process, and they agree with analytical estimates, indicating that the interaction between the thruster impedance and the inductive source is dynamically stable.

Clark, K. E.↗

NASA NTRS2010

Core-Noise

This presentation is a technical progress report and near-term outlook for NASA-internal and NASA-sponsored external work on core (combustor and turbine) noise funded by the Fundamental Aeronautics Program Subsonic Fixed Wing (SFW) Project. Sections of the presentation cover: the SFW system level noise metrics for the 2015, 2020, and 2025 timeframes; the emerging importance of core noise and its relevance to the SFW Reduced-Noise-Aircraft Technical Challenge; the current research activities in the core-noise area, with some additional details given about the development of a high-fidelity combustion-noise prediction capability; the need for a core-noise diagnostic capability to generate benchmark data for validation of both high-fidelity work and improved models, as well as testing of future noise-reduction technologies; relevant existing core-noise tests using real engines and auxiliary power units; and examples of possible scenarios for a future diagnostic facility. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The SFW Reduced-Noise-Aircraft Technical Challenge aims to enable concepts and technologies to dramatically reduce the perceived aircraft noise outside of airport boundaries. This reduction of aircraft noise is critical for enabling the anticipated large increase in future air traffic. Noise generated in the jet engine core, by sources such as the compressor, combustor, and turbine, can be a significant contribution to the overall noise signature at low-power conditions, typical of approach flight. At high engine power during takeoff, jet and fan noise have traditionally dominated over core noise. However, current design trends and expected technological advances in engine-cycle design as well as noise-reduction methods are likely to reduce non-core noise even at engine-power points higher than approach. In addition, future low-emission combustor designs could increase the combustion-noise component. The trend towards high-power-density cores also means that the noise generated in the low-pressure turbine will likely increase. Consequently, the combined result from these emerging changes will be to elevate the overall importance of turbomachinery core noise, which will need to be addressed in order to meet future noise goals.

Hultgren, Lennart S.↗

NASA NTRS1947

A Preliminary Study of Ram-Actuated Cooling Systems for Supersonic Aircraft

An analysis has been made of the characteristics of several cooling cycles suitable for cockpit cooling of supersonic aircraft. All the cycles considered utilize the difference between dynamic and ambient static pressure to actuate the cooling system and require no additional power source. The results of the study indicate that as flight speeds become greater, increasingly complex systems are required to reduce the altitudes above approximately 35,000 feet, a system composed of an externally loaded expansion turbine in conjunction with a supersonic diffuser would maintain tolerable ventilating air temperature, at least up to a flight Mach number of 2. The most complex system considered,composed of compressor, intercooler, and expansion turbine with the intercooler cooling air decreased in temperature by expansion through an auxiliary turbine is capable of maintaining a ventilation air temperature less than ambient temperature up to a flight Mach number of 3.7.

Stalder, Jackson R.↗

NASA NTRS1978

Preliminary design study of an alternate heat source assembly for a Brayton isotope power system

Results are presented for a study of the preliminary design of an alternate heat source assembly (HSA) intended for use in the Brayton isotope power system (BIPS). The BIPS converts thermal energy emitted by a radioactive heat source into electrical energy by means of a closed Brayton cycle. A heat source heat exchanger configuration was selected and optimized. The design consists of a 10 turn helically wound Hastelloy X tube. Thermal analyses were performed for various operating conditions to ensure that post impact containment shell (PICS) temperatures remain within specified limits. These limits are essentially satisfied for all modes of operation except for the emergency cooling system for which the PICS temperatures are too high. Neon was found to be the best choice for a fill gas for auxiliary cooling system operation. Low cycle fatigue life, natural frequency, and dynamic loading requirements can be met with minor modifications to the existing HSA.

Strumpf, H. J.↗

NASA NTRS1989

Requirements and designs for Mars Rover RTGs

A typical Rover mission, its requirements, the environment it imposes on the radionuclide thermoelectric generator (RTG), and a design approach for making the RTG operable in such an environment are described. Specific RTG designs for various thermoelectric element alternatives are presented. The results of studies show that current multifoil-insulated GPHS (general-purpose heat source) RTG and Mod-RTG designs can be modified to operate in an environment with an external atmosphere (e.g., Mars). This can be done while the helium generated by the fuel's alpha decay is vented to the external atmosphere. The use of novel selective vents and high-capacity getters is not required. The Rover RTGs can be built from standard, proven GPHS modules and standard SiGe unicouples or SiGe/GaP multicouples, using demonstrated thermoelectric material performance parameters. Rover's 500-W power requirement can be satisfied with two 250-W or four 125-W RTGs, whose sizes are compatible with currently envisaged Rover designs. An auxiliary cooling loop (e.g., water and antifreeze) will be required to cool the RTG while it is within the Rover's aeroshell during launch and transit to Mars.

Schock, A.↗

NASA NTRS2008

Aquarius's Instrument Science Data System (ISDS) Automated to Acquire, Process, Trend Data and Produce Radiometric System Assessment Reports

The Aquarius Radiometer, a subsystem of the Aquarius Instrument required a data acquisition ground system to support calibration and radiometer performance assessment. To support calibration and compose performance assessments, we developed an automated system which uploaded raw data to a ftp server and saved raw and processed data to a database. This paper details the overall functionalities of the Aquarius Instrument Science Data System (ISDS) and the individual electrical ground support equipment (EGSE) which produced data files that were infused into the ISDS. Real time EGSEs include an ICDS Simulator, Calibration GSE, Labview controlled power supply, and a chamber data acquisition system. ICDS Simulator serves as a test conductor primary workstation, collecting radiometer housekeeping (HK) and science data and passing commands and HK telemetry collection request to the radiometer. Calibration GSE (Radiometer Active Test Source) provides source choice from multiple targets for the radiometer external calibration. Power Supply GSE, controlled by labview, provides real time voltage and current monitoring of the radiometer. And finally the chamber data acquisition system produces data reflecting chamber vacuum pressure, thermistor temperatures, AVG and watts. Each GSE system produce text based data files every two to six minutes and automatically copies the data files to the Central Archiver PC. The Archiver PC stores the data files, schedules automated uploads of these files to an external FTP server, and accepts request to copy all data files to the ISDS for offline data processing and analysis. Aquarius Radiometer ISDS contains PHP and MATLab programs to parse, process and save all data to a MySQL database. Analysis tools (MATLab programs) in the ISDS system are capable of displaying radiometer science, telemetry and auxiliary data in near real time as well as performing data analysis and producing automated performance assessment reports of the Aquarius Radiometer.

Source record↗

NASA NTRS1972

Study of radioisotope safety devices for electric propulsion system, Volume 1: Summary report

A new reference design was prepared for the 5 kW(e) thermionic power supply. The safety equipment in this design is a passive containment system which does not rely on the operation of any mechanisms such as a launch escape rocket or deployment of parachutes. It includes: (1) a blast shield to protect against the explosion of the launch vehicle; (2) a combination of refractory thermal insulation and heat storage material to protect against a sustained launch pad fire; (3) a reentry body with a spherical nose and a large conical flare at the aft end to stabilize the reentry attitude and lower the terminal velocity in air; (4) composite graphite thermal protection to sustain the reentry heat pulse; (5) crushable honeycomb behind the nose to limit the deceleration of the radioisotope source due to impact on land at terminal velocity; (6) a double-walled secondary containment vessel surrounding the isotopic capsules; (7) neutron shielding to reduce external dose rates; (8) an auxiliary cooling system employing redundant heat pipes to remove the radioactive decay heat from the heat source and reject it to the surroundings or to a forced convection loop.

Bradshaw, G. B.↗

NASA NTRS1947

Report on Rocket Power Plants Based on T-Substance

In the search for an energy source independent of air for the propulsion of underwater craft, attention was early concentrated on T-substance. It was possible to convince the OKM [NACA comment: Navy High Command] very quickly of the importance of this material. In 1934, the first experiments were undertaken. A difficulty was at once presented by the limited concentration that had been attained. At first only 60 percent T-substance could be supplied; this amount was later increased to as much as 85 percent. Decomposition and combustion experiments conducted on the grounds of the CPVA in Kiel-Dietrichsdorf led to the first practical information as to the technical feasibility of the use of T-substance. New perspectives soon developed because a method of concentrated energy production had been found here, which was capable of many applications. The idea of using this energy for the propulsion of missiles either in guns or as rockets suggested itself and appropriate proposals, which quickly led to the construction of the first experimental devices, were made to the official quarters concerned. In January 1937, the first flight of a DVL aircraft with T-substance auxiliary propulsion took place at Alimbsmuhle in the presence of Colonel Udet, who piloted the third flight. In June 1937, the first T-substance rockets were fired (Altenwalde). Then in rapid succession take-off auxiliary, main propulsion, and other rocket drives were brought out in experimental versions. Hydrogen peroxide is a well known chemical, which is widely used in the textile industry. Its chemical and physical properties as well as the processes of manufacture and use are familiar and have been described in voluminous books and papers, Nevertheless, much developmental work was required to open the way for T-substance as a usable oxygen carrier. In fact the utilization of hydrogen peroxide as the oxygen carrier for energy production had hitherto been the subject only of isolated suggestions, which have never been developed beyond the stage of theoretical discussion.

Walter, Hellmuth↗