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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Remote lightning monitor system

An apparatus for monitoring, analyzing and accurately determining the value of peak current, the peak rate of change in current with respect to time and the rise time of the electrical currents generated in an electrical conductive mast that is located in the vicinity where lightning is to be monitored is described. The apparatus includes an electrical coil for sensing the change in current flowing through the mast and generating a voltage responsive. An on-site recorder and a recorder control system records the voltages produced responsive to lightning strikes and converts the voltage to digital signals for being transmitted back to the remote command station responsive to command signals. The recorder and the recorder control system are carried within an RFI proof environmental housing into which the command signals are fed by means of a fiber optic cable so as to minimize electrical interference.

Lennon, C. L.↗
NASA NTRS1983

Inherent overload protection for the series resonant converter

The overload characteristics of the full bridge series resonant power converter are considered. This includes analyses of the two most common control methods presently in use. The first of these uses a current zero crossing detector to synchronize the control signals and is referred to as the alpha controller. The second is driven by a voltage controlled oscillator and is referred to as the gamma controller. It is shown that the gamma controller has certain reliability advantages in that it can be designed with inherent short circuit protection. Experimental results are included for an 86 kHz converter using power metal-oxide-semiconductor field-effect transistors (MOSFETs).

King, R. J.↗
NASA NTRS1992

A genetic algorithms approach for altering the membership functions in fuzzy logic controllers

Through previous work, a fuzzy control system was developed to perform translational and rotational control of a space vehicle. This problem was then re-examined to determine the effectiveness of genetic algorithms on fine tuning the controller. This paper explains the problems associated with the design of this fuzzy controller and offers a technique for tuning fuzzy logic controllers. A fuzzy logic controller is a rule-based system that uses fuzzy linguistic variables to model human rule-of-thumb approaches to control actions within a given system. This 'fuzzy expert system' features rules that direct the decision process and membership functions that convert the linguistic variables into the precise numeric values used for system control. Defining the fuzzy membership functions is the most time consuming aspect of the controller design. One single change in the membership functions could significantly alter the performance of the controller. This membership function definition can be accomplished by using a trial and error technique to alter the membership functions creating a highly tuned controller. This approach can be time consuming and requires a great deal of knowledge from human experts. In order to shorten development time, an iterative procedure for altering the membership functions to create a tuned set that used a minimal amount of fuel for velocity vector approach and station-keep maneuvers was developed. Genetic algorithms, search techniques used for optimization, were utilized to solve this problem.

Shehadeh, Hana↗
NASA NTRS1970

Load cell for thermionic converter tests

Stable, low duty cycle transistorized emitter follower load cell controls and absorbs large currents at low voltages. The use of energy storage in capacitors reduces auxiliary power source requirements. Low duty cycle pulse mode of operation reduces the average power handling requirement of all components.

Breitwieser, R.↗
NASA NTRS1987

A laser sounder for U.S. Navy helicopters

The design and operating principles of the laser sounder developed for use in airborne coastal-zone bathymetric surveys with a U.S. Navy P-3 aircraft are described and illustrated with diagrams. The sounder components are listed and characterized, including the Nd:YAG transmitter (operating at 532 nm for bottom ranging and 1.064 microns for surface ranging), the scanning transceiver, the 10 x 6-inch-aperture controlled-FOV receiver/digitizer, the constant-fraction discriminator, the time-to-digital converter, the navigation and data-recording subsystems, and the parallel distributed processing computer (comprising a data collection and control system and a real-time processing system). Consideration is also given to the phase-I and phase-II data-reduction software being developed to process the approximately 228 million soundings to be obtained annually. The sounder can be used day or night to sound clear ocean water up to 20 m deep.

Harris, Michael M.↗
NASA NTRS1985

The Controlled Ecological Life Support System

A Controlled Ecological Life Support System (CELSS) is needed which would convert waste water to usable water, waste products to food, and CO2 to O2 to permit long duration space flight. Algae, representing the autotroph, and mice, representing the heterotroph are placed together in a controlled, gas closed environment to examine the gas exchange rate of O2 and CO2. The eventual goal is to develop biological controls that can stabilize atmospheres.

Ko, K.↗
NASA NTRS1973

Operations manual for the patient assist device

Quadriplegic patients and multiple amputee patients are almost totally dependent on nursing personnel for any activities or interests in which they participate. A patient assist device is reported which provides patient control over electrical devices in his environment. The patient operates three switches to acquire control over a desired electrical appliance. The type switches employed are chosen to conform to patient capabilities, even when such capabilities are as limited as eye or head movements. The switch operations are sensed and converted into command signals by the patient assist device to control ten electrical appliances simulataneously and independently.

Schrader, M. A.↗
NASA NTRS1982

Pressure Measurement

Pressure Systems, Inc.'s DPT 6400 is a system designed to increase productivity in industrial processes where there is a need for making multiple pressure measurements quickly and with high accuracy. It is applicable in controlling industrial processes in plants that are being upgraded to automated status. In order to automate such plants the pressures at the many loops must be measured, converted to digital information and transmitted to the plant's process control computer. The DPT 6400 serves that function. By employing solid-state pressure sensing transducers whose errors are automatically corrected by a microprocessor, it is capable of highly accurate pressure measurements. Basic DPT 6400 has 64 channels, but the system can be expanded to 256 channels by the addition of "slave" units.

Source record↗
NASA NTRS1976

A general unified approach to modelling switching-converter power stages

A method for modeling switching-converter power stages is developed, whose starting point is the unified state-space representation of the switched networks and whose end result is either a complete state-space description or its equivalent small-signal low-frequency linear circuit model. A new canonical circuit model is proposed, whose fixed topology contains all the essential input-output and control properties of any dc-to-dc switching converter, regardless of its detailed configuration, and by which different converters can be characterized in the form of a table conveniently stored in a computer data bank to provide a useful tool for computer aided design and optimization. The new canonical circuit model predicts that, in general, switching action introduces both zeros and poles into the duty ratio to output transfer function in addition to those from the effective filter network.

Middlebrook, R. D.↗
NASA NTRSDate not supplied

Source Contaminant Control System Design, Operation, and Testing for the Trash Compaction and Processing System

The Trash Compaction and Processing System (TCPS) aims to reduce volume, biologically safen, physically stabilize, manage effluents, and recover resources from astronaut trash in the International Space Station (ISS). This process involves heating the trash to high temperatures, which in turn releases gaseous contaminants. Effluent management scenarios involve releasing these gases back to the ISS cabin after processing and/or directly venting these gases out to space via the Vacuum Exhaust System (VES). Concerns for recovering the gases back to cabin are crew health, safety, and spacecraft environmental impact. The Heat Melt Compactor (HMC) at NASA Ames Research Center (ARC) serves as a test system that supports TCPS development by conducting risk reduction activities associated with an ISS flight demonstration. Previous gas effluent studies were conducted on the HMC. The results consisted of contaminants from the trash exhaust to exceed Spacecraft Maximum Allowable Concentrations (SMAC), which are selected airborne contaminants that can elicit toxicity symptoms to crewmembers via exposure. The Source Contaminant Control System (SCCS) aims to reduce that risk by converting the contaminants into carbon dioxide (CO2) and water (H2O) vapor. The SCCS is composed of a carbon adsorbent bed, to avoid catalyst poisoning, and a catalytic oxidizer (CatOx), which promotes oxidation of the contaminants to CO2and H2O. In turn, the gases coming out of the SCCS should be compatible to the ISS cabin and systems such as the Trace Contaminant Control System (TCCS). Preparation for SCCS testing alongside the HMC Gen 3 are currently underway at ARC. The main objectives are to evaluate CatOx efficiency by CO2conversion and characterize effectiveness of removal by comparing contaminant results before and after CatOx. This paper will report on the SCCS design, operation, and testing with results.

TCPS↗
NASA NTRSDate not supplied

Source Contaminant Control System Design, Operation, and Testing for the Trash Compaction and Processing System

The Trash Compaction and Processing System (TCPS) aims to reduce volume, biologically safen, physically stabilize, manage effluents, and recover resources from astronaut trash in the International Space Station (ISS). This process involves heating the trash to high temperatures, which in turn releases gaseous contaminants. Effluent management scenarios involve releasing these gases back to the ISS cabin after processing and/or directly venting these gases out to space via the Vacuum Exhaust System (VES). Concerns for recovering the gases back to cabin are crew health, safety, and spacecraft environmental impact. The Heat Melt Compactor (HMC) at NASA Ames Research Center (ARC) serves as a test system that supports TCPS development by conducting risk reduction activities associated with an ISS flight demonstration. Previous gas effluent studies were conducted on the HMC. The results consisted of contaminants from the trash exhaust to exceed Spacecraft Maximum Allowable Concentrations (SMAC), which are selected airborne contaminants that can elicit toxicity symptoms to crewmembers via exposure. The Source Contaminant Control System (SCCS) aims to reduce that risk by converting the contaminants into carbon dioxide (CO2) and water (H2O) vapor. The SCCS is composed of a carbon adsorbent bed, to avoid catalyst poisoning, and a catalytic oxidizer (CatOx), which promotes oxidation of the contaminants to CO2 and H2O. In turn, the gases coming out of the SCCS should be compatible to the ISS cabin and systems such as the Trace Contaminant Control System (TCCS). Preparation for SCCS testing alongside the HMC Gen 3 are currently underway at ARC. The main objectives are to evaluate CatOx efficiency by CO2 conversion and characterize effectiveness of removal by comparing contaminant results before and after CatOx. This paper will report on the SCCS design, operation, and testing with results.

Janine Young↗
NASA NTRSDate not supplied

Design of a High Power Density, High Efficiency, Low THD 250kW Converter for Electric Aircraft

A high efficiency, high power density, low distortion 250kW motor controller is being developed at NASA Glenn Research Center. Future electric aircraft require motor controllers which achieve the needed key performance parameters required to show benefit in increasing overall aircraft efficiency. Through a combination of carefully considered electrical topological choices and through the use of recent advancements in power switches and magnetic materials, a converter is designed which meets these requirements. A multilevel and interleaved converter architecture is chosen to meet the voltage, current, and THD requirements. The enclosure and thermal designs meet their weight targets and enable high altitude operation.

Matthew Granger↗
NASA NTRS1979

Optimal control of sun tracking solar concentrators

Application of the modern control theory to derive an optimal sun tracking control for a point focusing solar concentrator is presented. A standard tracking problem converted to regulator problem using a sun rate input achieves an almost zero steady state tracking error with the optimal control formulation. However, these control techniques are costly because optimal type algorithms require large computing systems, thus they will be used mainly as comparison standards for other types of control algorithms and help in their development.

Hughes, R. O.↗
NASA NTRS1978

Thermal energy storage

The general scope of study on thermal energy storage development includes: (1) survey and review possible concepts for storing thermal energy; (2) evaluate the potentials of the surveyed concepts for practical applications in the low and high temperature ranges for thermal control and storage, with particular emphasis on the low temperature range, and designate the most promising concepts; and (3) determine the nature of further studies required to expeditiously convert the most promising concept(s) to practical applications. Cryogenic temperature control by means of energy storage materials was also included.

Grodzka, P. G.↗
NASA NTRS1972

Closed loop dynamics of in-core thermionic reactor systems.

Use of a point model of an in-core thermionic converter to investigate alternative schemes for providing closed-loop reactor control. It was found that schemes based on variable-gain power regulation buffers which use the reactor current as the control variable provide complete protection from thermionic burnout and also provide a virtually constant voltage to the user. A side benefit is that the emitter temperature transients are small; even for a complete electric load drop the emitter temperature transient is less than 100 K. The current regulation scheme was selected for further study with a distributed parameter model which was developed to account for variations in thermionic and heat transfer properties along the length of a cylindrical converter. It was found that, even though the emitter temperature distribution is about 200 K along the converter length, the dynamic properties are unchanged when using the current control scheme.

Sawyer, C. D.↗
NASA NTRS1972

Adaptive position control loop

Design of attitude control system for a sounding rocket is established by using a control loop which incorporates a lead network to convert position output into a feedback signal that is approximately proportional to position, plus a constant times rate.

Keltz, W. L.↗