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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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New family of fast-recovery high-voltage power diodes compatible with D60T and D7ST transistors developed. Have wide range of applications in spacecraft and aircraft electrical distribution equipment, dc/dc inverters, and ac motor controllers for high-horsepower electric motors operating from 480-volt ac lines. Fast-Recovery 1,200-V Power Diodes use chip of hexagonal geometry to maximize effective silicon area.
Proposed regenerative snubbing circuit substituted for dissipative snubbing circuit in inverter based on silicon controlled rectifiers (SCR's) commutated by gate-turn-off thyristor (GTO). Intended to reduce loss of power that occurs in dissipative snubber. Principal criteria in design: low cost, simplicity, and reliability.
A 1 MW dc-dc power converter has been designed which has an input voltage of 5 kV +/-3 percent, an output voltage of 100 kV +/- 0.25 percent, and a run time of 1000 s at full power. The estimated system mass is 83.8 kg, giving a power density of 11.9 kW/kg. The system exceeded the weight goal of 10 kW/kg through the use of innovative components and system concepts. The system volume is approximately 0.1 cu m, and the overall system efficiency is estimated to be 87 percent. Some of the unique system features include a 50-kHz H-bridge inverter using MOS-controlled thyristors as the switching devices, a resonance transformer to step up the voltage, open-cycle cryogenic hydrogen gas cooling, and a nonrigid, inflatable housing which provides on-demand pressurization of the power converter local environment. This system scales very well to higher output powers. The weight of the 10-MW system with the same input and output voltage requirements and overall system configuration is estimated to be 575.3 kg. This gives a power density of 17.4 kW/kg, significantly higher than the 11.9 kW/kg estimated at 1 MW.
A set of necessary and sufficient conditions under which a general H2-optimal control problem has a unique solution is derived. It is shown that the solution for an H2-optimal control problem, if it exists, is unique if and only if (1) the transfer function from the control input to the controlled output is left invertible, and (2) the transfer function from the disturbance to the measurement output is right invertible.
The Advanced Electrical Systems Development Branch at NASA Glenn Research Center (GRC) has been involved in the research and development of high speed flywheels systems for satellite energy storage and attitude applications. These flywheels will serve as replacement for chemical nickel hydrogen, nickel cadmium batteries and gyroscopic wheels. The advantages of using flywheel systems for energy storage on satellites are high energy density, high power density, long life, deep depth of discharge, and broad operating temperature ranges. A flywheel system for space applications consist of a number of flywheel modules, the motor/generator and magnetic bearing, and an electronics package. The motor/generator electronics package includes a pulse-width modulated inverter that drives the flywheel permanent magnet motor/generator located at one end of the shaft. This summer, I worked under the direct supervision of my mentor, Walter Santiago, and the goal for this summer was to characterize motor generator and inverter attributes in order to increase their viability as a more efficient energy storage source for space applications. To achieve this goal, magnetic field measurements around the motor/generator permanent magnet and the impedance of the motor/generator three phase windings were characterized, and a recreation of the inverter pulse width modulated control system was constructed. The Flywheel modules for space use are designed to maximize energy density and minimize loss, and attaining these values will aid in locating and reducing losses within the flywheel system as a whole, making flywheel technology more attractive for use as energy storage in future space applications.
Electronic systems and components are often exposed to high temperature environment in space-based applications, nuclear power facilities, and geothermal energy extraction fields. A key requirement for these systems is, therefore, to withstand the high temperature exposure while maintaining efficient and reliable operation. Efforts were taken to design and develop a high temperature power inverter capable of 200 C operation. A 1 kW, 20 kHz Mapham inverter was designed and evaluated as a function of temperature at different load levels. The inverter system, excluding its input, control, and logic circuits, was characterized at temperatures from ambient to 200 C at 0%, 50%, and 100% resistive loading. With an applied input voltage of 75 VDC, the inverter produced an output of 250 VAC. The results obtained, which indicate good operational characteristics of the inverter up to 200 C, are presented and discussed.
This paper presents an approach to large-angle rotational maneuvers of a spacecraft-beam-tip body configuration based on nonlinear invertibility and linear feedback stabilization. A control law u sub d is derived for the decoupled control of attitude angles, lateral elastic deflections, slopes due to bending and angular deflection due to torsion at the tip of the beam using torquers and force actuators. For the stabilization of the elastic modes, a linear feedback control law u sub s is obtained based on a linearized model augmented with a servocompensator. Simulation results are presented to show that large slewing and elastic mode stabilization can be accomplished.
The objective is to set up and analyze benchmark problems on multibody dynamics and to verify the predictions of two multibody computer simulation codes. TREETOPS and DISCOS have been used to run three example problems - one degree-of-freedom spring mass dashpot system, an inverted pendulum system, and a triple pendulum. To study the dynamics and control interaction, an inverted planar pendulum with an external body force and a torsional control spring was modeled as a hinge connected two-rigid body system. TREETOPS and DISCOS affected the time history simulation of this problem. System state space variables and their time derivatives from two simulation codes were compared.
Oscillator generates symmetrical triangular waveform when inverting and noninverting inputs are equal. Oscillator portion of circuit has integrated circuit, high-performance operational amplifier wired as differential integrator, and two silicon controlled rectifiers.
The Pioneer F/G spacecraft is the first to use radioisotope thermoelectric generators (RTG's) for a long duration interplanetary mission. This paper describes the design of the spacecraft power subsystem which meets the unique requirements of such a mission. The primary power source consists of four SNAP 19 RTG's. The 4.2 volt dc outputs of the RTG's are inverted to higher voltage ac by four inverters which are connected in parallel at their outputs. A power control unit (PCU) regulates the ac output of the inverters such that the RTG's are operated at near maximum power voltage throughout the mission. The PCU also contains charge and discharge controls for a silver cadmium battery which supplements the RTG's if load requirements temporarily exceed RTG power output. Battery reliability is enhanced by overcharge and cell reversal protection electronics which are provided for each cell. Multiple, low voltage, regulated dc outputs which supply power to the spacecraft subsystems are provided by a central transformer-rectifier-filter unit (CTRF). The CTRF operates directly from the regulated ac bus.
Several studies have been performed to determine the effects on computer and direct manipulation task performance when viewing conditions are spatially displaced. Whether results from these studies can be directly applied to remote manipulation tasks is quenstionable. The objective of this evaluation was to determine the effects of reversed, inverted, and inverted/reversed views on remote manipulation task performance using two 3-Degree of Freedom (DOF) hand controllers and a replica position hand controller. Results showed that trials using the inverted viewing condition showed the worst performance, followed by the inverted/reversed view and the reversed view when using the 2x3 DOF. However, these differences were not significant. The inverted and inverted/reversed viewing conditions were significantly worse than the normal and reversed viewing conditions when using the Kraft Replica. A second evaluation was conducted in which additional trials were performed with each viewing condition to determine the long term effects of spatially displaced views on task performance for the hand controllers. Results of the second evaluation indicated that there was more of a difference in performance between the perturbed viewing conditions and the normal viewing condition with the Kraft Replica than with the 2x3 DOF.
Response surface methodology, an alternative method to traditional tuning of a fuzzy controller, is described. An example based on a simulated inverted pendulum 'plant' shows that with (only) 15 trial runs, the controller can be calibrated using a quadratic form to approximate the response surface.
A thermal vacuum power processor for the NASA Lewis 30cm Mercury Ion Engine was designed, fabricated and tested to determine compliance with electrical specifications. The power processor breadboard used the silicon controlled rectifier (SCR) series resonant inverter as the basic power stage to process all the power to an ion engine. The power processor includes a digital interface unit to process all input commands and internal telemetry signals so that operation is compatible with a central computer system. The breadboard was tested in a thermal vacuum environment. Integration tests were performed with the ion engine and demonstrate operational compatibility and reliable operation without any component failures. Electromagnetic interference data were also recorded on the design to provide information on the interaction with total spacecraft.
The inclusion of electric thruster systems in spacecraft design is considered. The propulsion requirements of such spacecraft dictate a wide range of thruster power levels and operational lifetimes, which must be matched by lightweight, efficient, and reliable thruster power processing systems. Electron bombardment ion thruster requirements are presented, and the performance characteristics of present power processing systems are reviewed. Design philosophies and alternatives in areas such as inverter type, arc protection, and control methods are discussed along with future performance potentials for meeting goals in the areas of power process or weight (10 kg/kW), efficiency (approaching 92 percent), reliability (0.96 for 15,000 hr), and thermal control capability (0.3 to 5 AU).
The potential of achieving up to 30 per cent more spacecraft payload or 50 per cent more useful operating life by the use of electric propulsion in place of conventional cold gas or hydrazine systems in science, communications, and earth applications spacecraft is a compelling reason to consider the inclusion of electric thruster systems in new spacecraft design. The propulsion requirements of such spacecraft dictate a wide range of thruster power levels and operational lifetimes, which must be matched by lightweight, efficient, and reliable thruster power processing systems. This paper will present electron bombardment ion thruster requirements; review the performance characteristics of present power processing systems; discuss design philosophies and alternatives in areas such as inverter type, arc protection, and control methods; and project future performance potentials for meeting goals in the areas of power processor weight (10 kg/kW), efficiency (approaching 92 per cent), reliability (0.96 for 15,000 hr), and thermal control capability (0.3 to 5 AU).
A laboratory design facility for digital microprocessor implementation of linear-quadratic-Gaussian feedback compensators is described. Outputs from user interactive programs for solving infinite time horizon LQ regulator and Kalman filter problems were conditioned for implementation on the laboratory microcomputer system. The software consisted of two parts: an offline high-level program for solving the LQ Ricatti equations and generating associated feedback and filter gains and a cross compiler/macro assembler which generates object code for the target microprocessor system. A PDP 11/70 with a UNIX operating system was used for all high level program and data management, and the target microprocessor system is an Intel MDS (8080-based processor). Application to the control of a two dimensional inverted pendulum is presented and issues in expanding the design/prototyping system to other target machine architectures are discussed.
The paper describes a laboratory design facility for digital microprocessor implementation of Linear-Quadratic-Gaussian feedback compensators. Outputs from user interactive programs for solving infinite time horizon LQ regulator and Kalman filter problems are conditioned for implementation on a laboratory microcomputer system. The software consists of two parts: (1) an off-line high-level program for solving the LQ Ricatti equations and generating associated feedback and filter gains, and (2) a cross compiler/macro assembler which generates object code for the target microprocessor system. Application to the control of a two dimensional inverted pendulum and expanding the design/prototyping system to other target machine architectures are discussed.
Ninety-six parallel MOSFET devices with two-stage feedback circuit form a high-current dc voltage regulator that also acts as fully-on solid-state switch when fuel-cell out-put falls below regulated voltage. Ripple voltage is less than 20 mV, transient recovery time is less than 50 ms. Parallel MOSFET's act as high-current dc regulator and switch. Regulator can be used wherever large direct currents must be controlled. Can be applied to inverters, industrial furnaces photovoltaic solar generators, dc motors, and electric autos.