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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Magnetostrictive direct drive motor

Highly magnetostrictive materials such as Tb.3Dy.7Fe2, commercially known as TERFENOL-D, have been used to date in a variety of devices such as high power actuators and linear motors. The larger magnetostriction available in twinned single crystal TERFENOL-D, approx. 2000 ppm at moderate magnetic field strengths, makes possible a new generation of magnetomechanical devices. NASA researchers are studying the potential of this material as the basis for a direct microstepping rotary motor with torque densities on the order of industrial hydraulics and five times greater than that of the most efficient, high power electric motors. Such a motor would be a micro-radian stepper, capable of precision movements and self-braking in the power-off state. Innovative mechanical engineering techniques are juxtaposed on proper magnetic circuit design to reduce losses in structural flexures, inertias, thermal expansions, eddy currents, and magneto-mechanical coupling, thus optimizing motor performance and efficiency. Mathematical models are presented, including magnetic, structural, and both linear and nonlinear dynamic calculations and simulations. In addition, test results on prototypes are presented.

Naik, Dipak↗
NASA NTRS1990

Induction motor control

Electromechanical actuators developed to date have commonly ultilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilized induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high-frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high-frequency power distribution and management techniques developed by NASA for Space Station Freedom.

Hansen, Irving G.↗
NASA NTRS1992

Mathematical modeling of bent-axis hydraulic piston motors

Each of the DSN 70-m antennas uses 16 bent-axis hydraulic piston motors as part of the antenna drive system. On each of the two antenna axes, four motors are used to drive the antenna and four motors provide counter torque to remove the backlash in the antenna drive train. This article presents a mathematical model for bent-axis hydraulic piston motors. The model was developed to understand the influence of the hydraulic motors on the performance of the DSN 70-m antennas' servo control system.

Bartos, R. D.↗
NASA NTRS1993

Development and testing of 11- and 24-inch hybrid motors under the joint government/industry IR&D program

Establishment of a test facility and associated 11-in.-diameter motor for hybrid propulsion technology development at NASA's George C. Marshall Space Flight Center is discussed in this paper. Results of twenty 11-in.-diameter motor tests with a UTF-29901 (60 percent polycyclopentadiene, 40 percent hydroxyl-terminated polybutadiene)/gaseous oxygen propellant system are presented. Tests at this scale have developed fuel regression correlations for comparison with results of yet-to-be-completed, 24-in.-diameter motor tests; demonstrated combustion efficiency levels in the 95 percent range for both single- and multiple-port grain configurations; have shown smooth and stable throttling characteristics over flight-type throttle ranges; and have begun to establish criteria for stable combustion in hybrid motors. The testing of 24-in. motors has not as yet been initiated and is not addressed.

Boardman, T. A.↗
NASA NTRS1994

A preliminary analysis of low frequency pressure oscillations in hybrid rocket motors

Past research with hybrid rockets has suggested that certain motor operating conditions are conducive to the formation of pressure oscillations, or flow instabilities, within the motor combustion chamber. These combustion-related vibrations or pressure oscillations may be encountered in virtually any type of rocket motor and typically fall into three frequency ranges: low frequency oscillations (0-300 Hz); intermediate frequency oscillations (400-1000 Hz); and high frequency oscillations (greater than 1000 Hz). In general, combustion instability is characterized by organized pressure oscillations occurring at well-defined intervals with pressure peaks that may maintain themselves, grow, or die out. Usually, such peaks exceed +/- 5% of the mean chamber pressure. For hybrid motors, these oscillations have been observed to grow to a limiting amplitude which may be dependent on factors such as fuel characteristics, oxidizer injector characteristics, average chamber pressure, oxidizer mass flux, combustion chamber length, and grain geometry. The approach taken in the present analysis is to develop a modified chamber length, L, instability theory which accounts for the relationship between pressure and oxidizer to fuel concentration ratio in the motor.

Jenkins, Rhonald M.↗
NASA NTRS1995

High performance stepper motors for space mechanisms

Hybrid stepper motors are very well adapted to high performance space mechanisms. They are very simple to operate and are often used for accurate positioning and for smooth rotations. In order to fulfill these requirements, the motor torque, its harmonic content, and the magnetic parasitic torque have to be properly designed. Only finite element computations can provide enough accuracy to determine the toothed structures' magnetic permeance, whose derivative function leads to the torque. It is then possible to design motors with a maximum torque capability or with the most reduced torque harmonic content (less than 3 percent of fundamental). These later motors are dedicated to applications where a microstep or a synchronous mode is selected for minimal dynamic disturbances. In every case, the capability to convert electrical power into torque is much higher than on DC brushless motors.

Sega, Patrick↗
NASA NTRS1995

Dynamic neural networks based on-line identification and control of high performance motor drives

In the automated and high-tech industries of the future, there wil be a need for high performance motor drives both in the low-power range and in the high-power range. To meet very straight demands of tracking and regulation in the two quadrants of operation, advanced control technologies are of a considerable interest and need to be developed. In response a dynamics learning control architecture is developed with simultaneous on-line identification and control. the feature of the proposed approach, to efficiently combine the dual task of system identification (learning) and adaptive control of nonlinear motor drives into a single operation is presented. This approach, therefore, not only adapts to uncertainties of the dynamic parameters of the motor drives but also learns about their inherent nonlinearities. In fact, most of the neural networks based adaptive control approaches in use have an identification phase entirely separate from the control phase. Because these approaches separate the identification and control modes, it is not possible to cope with dynamic changes in a controlled process. Extensive simulation studies have been conducted and good performance was observed. The robustness characteristics of neuro-controllers to perform efficiently in a noisy environment is also demonstrated. With this initial success, the principal investigator believes that the proposed approach with the suggested neural structure can be used successfully for the control of high performance motor drives. Two identification and control topologies based on the model reference adaptive control technique are used in this present analysis. No prior knowledge of load dynamics is assumed in either topology while the second topology also assumes no knowledge of the motor parameters.

Rubaai, Ahmed↗
NASA NTRS1996

Development of a hermetically sealed brushless DC motor for a J-T cryocooler

This development was sponsored by Ball Aerospace for the Cryogenic On-Orbit LongLife Active Refrigerator (COOLLAR) program. The cryocooler is designed to cool objects to 65 K and operate in space for at least 7 years. The system also imports minimal impact to the spacecraft in terms of vibration and heat. The basic Joule-Thompson cycle involves compressing a working fluid, nitrogen in this case, at near-constant temperature from 17.2 KPa to 6.89 MPa. The nitrogen is then expanded through a Joule-Thompson valve. The pure nitrogen gas must be kept clean; therefore, any contamination from motor organic materials must be eliminated. This requirement drove the design towards sealing of the motor within a titanium housing without sacrificing motor performance. It is estimated that an unsealed motor would have contributed 1.65 g of contaminants, due to the organic insulation and potting materials, over the 7-year life. This paper describes the motor electrical and mechanical design, as well as the sealing difficulties encountered, along with their solutions.

Joscelyn, Edwin↗
NASA NTRS1995

Plume Particle Collection and Sizing from Static Firing of Solid Rocket Motors

Thermal radiation from the plume of any solid rocket motor, containing aluminum as one of the propellant ingredients, is mainly from the microscopic, hot aluminum oxide particles in the plume. The plume radiation to the base components of the flight vehicle is primarily determined by the plume flowfield properties, the size distribution of the plume particles, and their optical properties. The optimum design of a vehicle base thermal protection system is dependent on the ability to accurately predict this intense thermal radiation using validated theoretical models. This article describes a successful effort to collect reasonably clean plume particle samples from the static firing of the flight simulation motor (FSM-4) on March 10, 1994 at the T-24 test bed at the Thiokol space operations facility as well as three 18.3% scaled MNASA motors tested at NASA/MSFC. Prior attempts to collect plume particles from the full-scale motor firings have been unsuccessful due to the extremely hostile thermal and acoustic environment in the vicinity of the motor nozzle.

Sambamurthi, Jay K.↗
NASA NTRS1995

PZT Thin Film Piezoelectric Traveling Wave Motor

With the development of micro-electro-mechanical systems (MEMS), its various applications are attracting more and more attention. Among MEMS, micro motors, electrostatic and electromagnetic, are the typical and important ones. As an alternative approach, the piezoelectric traveling wave micro motor, based on thin film material and integrated circuit technologies, circumvents many of the drawbacks of the above mentioned two types of motors and displays distinct advantages. In this paper we report on a lead-zirconate-titanate (PZT) piezoelectric thin film traveling wave motor. The PZT film with a thickness of 150 micrometers and a diameter of 8 mm was first deposited onto a metal substrate as the stator material. Then, eight sections were patterned to form the stator electrodes. The rotor had an 8 kHz frequency power supply. The rotation speed of the motor is 100 rpm. The relationship of the friction between the stator and the rotor and the structure of the rotor on rotation were also studied.

Shen, Dexin↗
NASA NTRS1995

SRM Internal Flow Tests and Computational Fluid Dynamic Analysis: RSRM Full Scale Motor Analyses - Volume 2

The purpose of the RSRM Nozzle Slag Ejection Precursor Test is to investigate the effect that slag ejection from the RSRM nozzle has on the chamber pressure and trust of the SRB's. In past firings of the Reusable Solid Rocket Motor (RSRM) both static test and flight motors have shown small pressure perturbations occurring primarily between 65 and 80 seconds. A joint NASA/Thiokol team investigation concluded that the cause of the pressure perturbations was the periodic ingestion and ejection of molten aluminum oxide slag from the cavity around the submerged nozzle nose which tends to trap and collect individual aluminum oxide droplets from the approach flow. The conclusions of the team were supported by numerous data and observations from special tests including high speed photographic films, real time radiography, plume calorimeters, accelerometers, strain gauges, nozzle TVC system force gauges, and motor pressure and thrust data. A simplistic slag ballistics model was formulated to relate a given pressure perturbation to a required slag quantity. Also, a cold flow model using air and water was developed to provide data on the relationship between the slag flow rate and the chamber pressure increase. Both the motor and the cold flow model exhibited low frequency oscillations in conjunction with periods of slag ejection. Motor and model frequencies were related to scaling parameters. The data indicate that there is a periodicity to the slag entrainment and ejection phenomena which is possibly related to organized oscillations from instabilities in the dividing streamline shear layer which impinges on the underneath surface of the nozzle.

Source record↗
NASA NTRS1995

Effects of Slag Ejection on Solid Rocket Motor Performance

In past firings of the Reusable Solid Rocket Motor (RSRM) both static test and flight motors have shown small pressure perturbations occurring primarily between 65 and 80 seconds. A joint NASA/Thiokol team investigation concluded that the cause of the pressure perturbations was the periodic ingestion and ejection of molten aluminum oxide slag from the cavity around the submerged nozzle nose which tends to trap and collect individual aluminum oxide droplets from the approach flow. The conclusions of the team were supported by numerous data and observations from special tests including high speed photographic films, real time radiography, plume calorimeters, accelerometers, strain gauges, nozzle TVC system force gauges, and motor pressure and thrust data. A simplistic slag ballistics model was formulated to relate a given pressure perturbation to a required slag quantity. Also, a cold flow model using air and water was developed to provide data on the relationship between the slag flow rate and the chamber pressure increase. Both the motor and the cold flow model exhibited low frequency oscillations in conjunction with periods of slag ejection. Motor and model frequencies were related to scaling parameters. The data indicate that there is a periodicity to the slag entrainment and ejection phenomena which is possibly related to organized oscillations from instabilities in the dividing streamline shear layer which impinges on the underneath surface of the nozzle.

Whitesides, R. Harold↗
NASA NTRS1996

Correlation of Slag Expulsion with Ballistic Anomalies in Shuttle Solid Rocket Motors

During the Shuttle launches, the solid rocket motors (SRM) occasionally experience pressure perturbations (8-13 psi) between 65-75 s into the motor burn time. The magnitudes of these perturbations are very small in comparison with the operating motor chamber pressure, which is over 600 psi during this time frame. These SRM pressure perturbations are believed to he caused primarily by the expulsion of slag (aluminum oxide). Two SRM static tests, TEM-11 and FSM-4, were instrumented extensively for the study of the phenomena associated with pressure perturbations. The test instrumentation used included nonintrusive optical and infrared diagnostics of the plume, such as high-speed photography, radiometers, and thermal image cameras. Results from all of these nonintrusive observations provide substantial circumstantial evidence to support the scenario that the pressure perturbation event in the Shuttle SRM is caused primarily by the expulsion of molten slag. In the static motor tests, the slag was also expelled preferentially near the bottom of the nozzle because of slag accumulation at the bottom of the aft end of the horizontally oriented motor.

Sambamurthi, Jay K.↗
NASA NTRS1997

Speed Sensorless Induction Motor Drives for Electrical Actuators: Schemes, Trends and Tradeoffs

For a decade, induction motor drive-based electrical actuators have been under investigation as potential replacement for the conventional hydraulic and pneumatic actuators in aircraft. Advantages of electric actuator include lower weight and size, reduced maintenance and operating costs, improved safety due to the elimination of hazardous fluids and high pressure hydraulic and pneumatic actuators, and increased efficiency. Recently, the emphasis of research on induction motor drives has been on sensorless vector control which eliminates flux and speed sensors mounted on the motor. Also, the development of effective speed and flux estimators has allowed good rotor flux-oriented (RFO) performance at all speeds except those close to zero. Sensorless control has improved the motor performance, compared to the Volts/Hertz (or constant flux) controls. This report evaluates documented schemes for speed sensorless drives, and discusses the trends and tradeoffs involved in selecting a particular scheme. These schemes combine the attributes of the direct and indirect field-oriented control (FOC) or use model adaptive reference systems (MRAS) with a speed-dependent current model for flux estimation which tracks the voltage model-based flux estimator. Many factors are important in comparing the effectiveness of a speed sensorless scheme. Among them are the wide speed range capability, motor parameter insensitivity and noise reduction. Although a number of schemes have been proposed for solving the speed estimation, zero-speed FOC with robustness against parameter variations still remains an area of research for speed sensorless control.

Elbuluk, Malik E.↗
NASA NTRS1960

Flight Performance of a Spin-Stabilized 20-Inch-Diameter Solid-Propellant Spherical Rocket Motor

A successful flight test of a spin-stabilized 20-inch-diameter solid-propellant rocket motor having a propellant mass fraction of 0.92 has been made. The motor was fired at altitude after being boosted by a three-stage test vehicle. Analysis of the data indicates that a total impulse of 44,243 pound-second with a propellant specific impulse of approximately 185 was achieved over a total action time of about 12 seconds. These results are shown to be in excellent agreement with data from ground static firing tests of these motors. The spherical rocket motor with an 11-pound payload attained a velocity of 15,620 feet per second (m = 16.7) with an incremental velocity increase for the spherical motor stage of 12,120 feet per second.

Levine, Jack↗
NASA NTRS1999

An Instrument for Real-Time Measurement of Solid Rocket Motor Insulation Erosion

An instrument (eroding potentionmeter) has been designed to measure real-time case wall and inhibitor insulation char depth within a rocket motor during firing. Thus measurement can be close to the real-time recession of the insulation surface. The eroding potentionmeter consists of two small (3 mils 9in diameter) twisted resistive wires that are polyimide insulated. The wire pair form an electrical circuit and will recede with the erosion of the rocket motor internal insulation. A constant current applied along the wires will detect the resistance change via a voltage drop across the wires as the wire pair recedes with the decomposition fo the insulation. The eroding potentionmeter, as presently designed, can be an effective tool for real time measurement of internal insulation recession of a solid rocket motor. This tool will provide a way to accurately measure inhibitor performance or to measure flight effects of insulation erosion on a flight test. The eroding potentiometer has been verified on a plasma torch test and two static tests of a small solid rocket motor. There are some irregularities in the measured date, but the data remains useful in determining the real-time performance of internal insulation during a motor firing.

McWhorter, B. B.↗
NASA NTRS2001

Real-Time Inhibitor Recession Measurements in the Space Shuttle Reusable Solid Rocket Motors

Real-time char line recession measurements were made on propellant inhibitors of the Space Shuttle Reusable Solid Rocket Motor (RSRM). The RSRM FSM-8 static test motor propellant inhibitors (composed of a rubber insulation material) were successfully instrumented with eroding potentiometers and thermocouples. The data was used to establish inhibitor recession versus time relationships. Normally, pre-fire and post-fire insulation thickness measurements establish the thermal performance of an ablating insulation material. However, post-fire inhibitor decomposition and recession measurements are complicated by the fact that most of the inhibitor is back during motor operation. It is therefore a difficult task to evaluate the thermal protection offered by the inhibitor material. Real-time measurements would help this task. The instrumentation program for this static test motor marks the first time that real-time inhibitors. This report presents that data for the center and aft field joint forward facing inhibitors. The data was primarily used to measure char line recession of the forward face of the inhibitors which provides inhibitor thickness reduction versus time data. The data was also used to estimate the inhibitor height versus time relationship during motor operation.

McWhorter, Bruce B.↗
NASA NTRS2002

Test Platform for Advanced Digital Control of Brushless DC Motors (MSFC Center Director's Discretionary Fund)

A FY 2001 Center Director's Discretionary Fund task to develop a test platform for the development, implementation. and evaluation of adaptive and other advanced control techniques for brushless DC (BLDC) motor-driven mechanisms is described. Important applications for BLDC motor-driven mechanisms are the translation of specimens in microgravity experiments and electromechanical actuation of nozzle and fuel valves in propulsion systems. Motor-driven aerocontrol surfaces are also being utilized in developmental X vehicles. The experimental test platform employs a linear translation stage that is mounted vertically and driven by a BLDC motor. Control approaches are implemented on a digital signal processor-based controller for real-time, closed-loop control of the stage carriage position. The goal of the effort is to explore the application of advanced control approaches that can enhance the performance of a motor-driven actuator over the performance obtained using linear control approaches with fixed gains. Adaptive controllers utilizing an exact model knowledge controller and a self-tuning controller are implemented and the control system performance is illustrated through the presentation of experimental results.

Gwaltney, D. A.↗