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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 163 records · Page 9

Aligning for Innovation - Alignment Strategy to Drive Innovation

With the sudden need for innovation that will help the country achieve its long-term space exploration objectives, the question of whether NASA is aligned effectively to drive the innovation that it so desperately needs to take space exploration to the next level should be entertained. Authors such as Robert Kaplan and David North have noted that companies that use a formal system for implementing strategy consistently outperform their peers. They have outlined a six-stage management systems model for implementing strategy, which includes the aligning of the organization towards its objectives. This involves the alignment of the organization from the top down. This presentation will explore the impacts of existing U.S. industrial policy on technological innovation; assess the current NASA organizational alignment and its impacts on driving technological innovation; and finally suggest an alternative approach that may drive the innovation needed to take the world to the next level of space exploration, with NASA truly leading the way.

Johnson, Hurel↗

Compact, Efficient Drive Circuit for a Piezoelectric Pump

A switching circuit that drives a piezoelectric pump at a high voltage with a polarity that alternates at the desired mechanical pump frequency is described and depicted. This circuit offers advantages of (1) high energy efficiency relative to conventional direct-drive circuits and (2) compactness relative to conventional resonant drive circuits.

Matice, Chris↗

Improved Gear Shapes for Face Worm Gear Drives

Shapes different from the traditional ones have been proposed for face worm gears and for conical and cylindrical worms that mesh with them. The proposed shapes are based on the concept of generating a face worm gear surface by use of a tilted head cutter instead of by the traditional use of a hob. (As used here, head cutter is also meant to signify, alternatively, a head grinding tool.) The gear-surface-generation equipment would be similar to that used for generation of spiral bevel and hypoid gears. In comparison with the corresponding traditional hob, a tilted head cutter according to the proposal would be larger, could be fabricated with greater precision, and would enable the generation of gear surfaces with greater precision and greater productivity. A face worm gear would be generated (see figure) by use of a tilted head cutter, the blades or grinding surfaces of which would have straight-line profiles. The tilt of the head cutter would prevent interference with teeth adjacent to the groove being cut or ground. A worm to mesh with the face worm gear would be generated by use of a tilted head cutter mounted on the cradle of a generating machine. The blades or grinding surfaces of the head cutter would have a parabolic profile and would deviate from the straight-line profiles of the head cutter for the face worm gear. The shortest distance between the worm and the cradle would follow a parabolic function during the cycle of meshing in the generating process to provide a parabolic function of transmission errors to the gear drive. The small mismatch between the profiles of the face-worm-gear and worm head cutters would make it possible to localize the bearing contact in the worm gear drive. The parabolic function of transmission errors could absorb discontinuous linear functions of transmission errors caused by errors of alignment; this could afford a significant benefit, in that such errors are main sources of noise and vibration in gear drives. The main advantage of using tilted head cutters is that cutting speeds are independent of the shape-generation processes, making it possible to choose cutting speeds that are optimum with respect to requirements to minimize temperatures and deformations during fabrication and improve the quality of finished parts.

Litvin, Faydor L.↗

Helical Face Gear Development Under the Enhanced Rotorcraft Drive System Program

U.S. Army goals for the Enhanced Rotorcraft Drive System Program are to achieve a 40 percent increase in horsepower to weight ratio, a 15 dB reduction in drive system generated noise, 30 percent reduction in drive system operating, support, and acquisition cost, and 75 percent automatic detection of critical mechanical component failures. Boeing s technology transition goals are that the operational endurance level of the helical face gearing and related split-torque designs be validated to a TRL 6, and that analytical and manufacturing tools be validated. Helical face gear technology is being developed in this project to augment, and transition into, a Boeing AH-64 Block III split-torque face gear main transmission stage, to yield increased power density and reduced noise. To date, helical face gear grinding development on Northstar s new face gear grinding machine and pattern-development tests at the NASA Glenn/U.S. Army Research Laboratory have been completed and are described.

Heath, Gregory F.↗

The Effect of Drive Signal Limiting on High Cycle Fatigue Life Analysis

It is common practice to assume a Gaussian distribution of both the input acceleration and the response when modeling random vibration tests. In the laboratory, however, shaker controllers often limit the drive signal to prevent high amplitude peaks. The high amplitudes may either be truncated at a given level (socalled brick wall limiting or abrupt clipping), or compressed (soft limiting), resulting in drive signals which are no longer Gaussian. The paper first introduces several methods for limiting a drive signal, including brick wall limiting and compression. The limited signal is then passed through a linear time-invariant system representing a device under test. High cycle fatigue life predictions are subsequently made using spectral fatigue and rainflow cycle counting schemes. The life predictions are compared with those obtained from unclipped input signals. Some guidelines are provided to help the test engineer decide how clipping should be applied under different test scenarios.

Kihm, Frederic↗

Partially Turboelectric Aircraft Drive Key Performance Parameters

The purpose of this paper is to propose electric drive specific power, electric drive efficiency, and electrical propulsion fraction as the key performance parameters for a partially turboelectric aircraft power system and to investigate their impact on the overall aircraft performance. Breguet range equations for a base conventional turbofan aircraft and a partially turboelectric aircraft are found. The benefits and costs that may result from the partially turboelectric system are enumerated. A break even analysis is conducted to find the minimum allowable electric drive specific power and efficiency, for a given electrical propulsion fraction, that can preserve the range, fuel weight, operating empty weight, and payload weight of the conventional aircraft. Current and future power system performance is compared to the required performance to determine the potential benefit.

turbogenerator↗

Results of NASA Technical Challenge to Demonstrate Two-Speed Drive for Vertical Lift Vehicle

Currently, manned vertical lift vehicles are flown in a manner such that the rotors operate over a narrow range of rotating speed regardless if the vehicle's flight condition is one of vertical takeoff and landing, hover, or forward cruise. The propulsion systems are optimized for operation at the same, corresponding narrow range of rotor speed. However, certain missions and markets benefit greatly if the rotor speed can be adjusted over a wide range of speed to match demands of different missions and flight regimes. A vehicle that can operate with a wide range of rotor speeds would address key barriers to enable new markets and missions for vertical lift vehicles. Key barriers addressed by the wide-range of rotor speed include noise reduced via lower rpm rotor, increase of maximum forward flight speed, increased payload and range, reduced fuel burn, and lower operating costs. A new paradigm for the propulsion system is needed to enable these key benefits. One viable approach is to make use of a two-speed ratio drive system such that the engine can continue to operate over a narrow speed range, whereby engine performance is optimal, while adjusting the rotor speed as needed using the two-speed drive system. Motivated by such needs and by results of several system studies, a NASA Revolutionary Vertical Lift Technology Challenge was established to develop and demonstrate required technologies and designs for achieving a 50% reduction in rotor rpm via a two-speed drive system that incurs less than 2% power loss and maintains current power-to-weight ratios. The technical challenge work was completed and the technical objectives were achieved. This report describes the motivations, the research approach and the significant outcomes.

Transmissions↗

Gate Drive Technology Evaluation and Development to Maximize Switching Speed of SiC Discrete Devices and Power Modules in Hard Switching Applications

To understand the limitation of maximizing the switching speed of SiC low current discrete devices and high current power modules in hard switching applications, double pulse tests are conducted and the testing results are analyzed. For power modules, the switching speed is generally limited by the parasitics rather than the gate drive capability. For the discrete SiC device, the conventional voltage source gate drive (VSG) is not sufficient to maximize the switching speed even if the external gate resistance is minimized. The limitation of existing current source gate drives (CSG) are analyzed, and a CSG dedicated for SiC discrete devices is proposed, which can provide constant current during the switching transient regardless of the high Miller voltage and large internal gate resistance. Compared with the conventional VSG, the proposed CSG achieves 67% faster turnon time and 50% turn-off time, and 68% reduction in switching loss at full load condition.

Handong Gui↗

Investigating Pyroclastic Volcanism in the Taurus-Littrow Valley (TLV) Using the Station 3 Double Drive Tube 73001-73002

Well over 100 pyroclastic deposits have been identified on the Moon. Eruptive processes such as represented by these deposits transported endogenous volatiles from the Moon’s mantle to its surface. Debris from pyroclastic deposits has been identified in all Apollo and Luna samples. The high-Ti pyroclastic de- posit sampled at Shorty Crater by the Station 4 double drive tube (74001-74002) is our best sampling of these types of deposits. Samples 78500 and 78526, NAC images of fissures in the Sculptured Hills, ash identified in 70001-7, and other green volcanic glass indicate that very low-Ti basalt (VLT) erup- tions also occurred in TLV. The double drive tube core being investigated by the ANGSA initiative provides an- other view of TLV pyroclastic eruptions. The regolith in 73001-73002 and the regolith breccias therein have nu- merous pyroclastic beads. Some individual regolith brec- cia fragments have abundant pyroclastic beads (>50 in a polished surface). In this work, we address the following questions. Do these glass beads overlap in composition with those sampled elsewhere in the TLV or do they rec- ord another episode of pyroclastic eruption? Are the magmas associated with pyroclastic eruptions petroge- netically related to the crystalline mare basalts in the TLV? Finally, is the volatile record of the pyroclastic eruptions better preserved in the newly opened and spe- cially contained Station 3 double drive tube core?

C.K. Shearer↗

The Lower Thermospheric Winter-To-Summer Meridional Circulation: 1: Driving Mechanism

In this study, the mechanism driving the narrow lower-thermospheric winter-to-summer meridional circulation is thoroughly investigated for the first time using the Specified Dynamics configuration runs of the Whole Atmosphere Community Climate Model eXtended (SD-WACCMX) simulations and the TIMED Doppler Interferometer (TIDI) observations. The mean meridional circulation in the SD-WACCMX is qualitatively consistent with the TIDI measurements, though the magnitude in the SD-WACCMX is about 50% weaker. The lower-thermospheric winter-to-summer circulation is mainly driven by the resolved wave forcing, including the tides and internally generated inertia gravity waves (GWs). The momentum forcing from the parameterized sub-grid scale GWs is not as significant as the resolved wave forcing in driving the lower-thermospheric meridional circulation. The GW parameterization scheme in the SD-WACCMX only includes GWs with phase velocities in the range of ±45 m/s, which might result in most of the parameterized sub-grid GWs dissipating and breaking in the mesosphere and hardly impacting the lower thermosphere. Only including slow GWs in the SD-WACCMX parameterization could potentially lead to the underestimation of the meridional wind in the model. Analysis also indicates the lower-thermospheric meridional circulation is stronger in the summer hemisphere, which is attributed to the hemispheric asymmetry in the resolved wave momentum forcing. This study underlines the importance of the whole atmosphere coupling through wave propagation and dissipation. This understanding can guide the model development with an accurate representation of underlying physical processes in the mesosphere and lower thermosphere which drives the lower-thermospheric circulation as well as the overall dynamics of this region.

Jack C. Wang↗

Extended Investigation into Fault-Tolerant Integrated Motor Drive for a Quadrotor Urban Air Mobility (UAM) Aircraft

Electric propulsor machines and their associated power electronics have been identified in past studies as low-reliability components in emerging Urban Air Mobility (UAM) Vertical Takeoff and Landing (VTOL) vehicles that raise their predicted catastrophic failure rates. This research effort extends previously presented work investigating the use of fault-tolerant (FT) motor drives in quadrotor aircraft as a promising approach to significantly increase their mean-time-to-failure (MTTF). In particular, fault-tolerant modular motor drives (FT-MMDs) are identified as strong candidates for closing the electric propulsor reliability gap. These FT-MMDs divide a machine drive into multiple redundant modules, each consisting of three phase stator windings and power electronics units, enabling continued machine operation after a module failure. Achieving the highest possible isolation between modules (physical, magnetic, thermal, electrical) is critically important in FT-MMDs to prevent the propagation of any failure between modules. Key additional requirements for achieving the highest possible reliability characteristics with FT-MMDs are high repair rates and aggressive suppression of all single-point failures.

quadrotor↗

Motor Configuration Selection for A New Technical Challenge to Develop A 5 MW Cryogenic Motor and Drive

Due to aviation’s appreciable and growing share of humanity’s impact on our environment and estimates that CO2emissions only account for 34% of aviation’s total effective radiative forcing [1], there is a need to reach beyond climate goals that focus only on CO2emissions, such as the US Aviation Climate Action Plan’s [3] goal to reach net-zero carbon emissions by 2050.There is motivation to develop technology that pushes toward future large transport aircraft with net zero climate impact that are highly electrified (i.e., have higher power electrical propulsion system components). This paper describes a new, 6-year technical challenge to address this need by developing a 5 MW superconducting motor and cryogenic drive. Section 1 will detail the motivation for this work. Section 2 will describe the technical challenge and the selected specifications for the motor. Section 3 will present the results of a motor configuration trade study and the down selection of one configuration to develop a detailed design for. The technical challenge focuses on the design of a5 MW superconducting motor and cryogenic drive and demonstration of it at a 2+ MW scale to achieve TRL 3. Both fully superconducting (superconducting stator and rotor) and fully cryogenic (superconducting rotor and cryogenic stator) machine configurations will be explored. An emphasis will be placed on addressing the key tall poles for high power superconducting machines. Further details will be included in the full paper. The requirements and goals of the motor will be detailed. The rated speed (2,000 to 3,000 rpm) is defined to be appropriate for directly driving multi-MW fans or propellers. A range of rated speed is permitted because the motor is not designed for a specific aircraft and to provide design flexibility if AC losses in the stator winding are found to be a significant constraint (i.e., a lower speed can be selected to reduce electrical frequency). Relatively conservative requirements for efficiency (99%) and specific power (20 kW/kg) are defined, because TRL advancement and pushing toward flight readiness is emphasized over performance optimization. However, more aggressive efficiency and specific power goals are specified (99.9% and 40 kW/kg). The 3rd section will present the results of a motor configuration trade study. The study started with a qualitative assessment of sixteen motor configurations based on geometric, mechanical, thermal, and electromagnetic criteria. This assessment has been completed with three evaluators scoring all nine criteria. A configuration down select was made by prioritizing the sixteen configurations into four tiers based on each configuration’s total score and consideration of manufacturability, complexity, and support hardware (e.g., rotary vacuum seals, bearings). Configurations in priority A and B will be further evaluated through quantitative assessments, whereas those in priority C will only be further evaluated if time permits and priority D will not be further evaluated. Eight of the sixteen configurations were down selected for quantitative assessment, which will include analytical calculations and low-to moderate-fidelity finite element analysis to produce a preliminary Pareto front of efficiency versus specific power for each configuration. This assessment emphasizes the calculation of AC losses in the stator winding and an exploration of thermal management approaches to remove that heat and maintain cryogenic temperature. The final paper will include a description of each motor configuration that was considered. The quantitative assessments are underway, and an assessment of one configuration is complete for multiple stator conductor options. The remaining assessments are scheduled to be completed by late March so that the final down select to one configuration can be included in this paper.

Net Zero↗

Design Techniques for Lightweight Aircraft Motor Drives

Electric aircraft require a propulsion system with a high specific power. Designing electric motor drives for aeronautics applications is a multidisciplinary effort which requires complex design and construction techniques to achieve the desired performance metrics. This presentation explains some of the electrical, mechanical, thermal, and magnetics design techniques used in these motor drives. The presentation also shows how the techniques are used in two ongoing NASA EAP projects.

Aircraft Motor Drive↗

Quick-acting clutch disengages idle drive motor

Positive-drive, no drag, over-running clutch is developed to conserve power of idle motor in a low-power system using multiple drive motors. This device is useful where a number of shaft speeds are required with frequent shifting.

Stark, K. W.↗

Compact cartridge drives coded tape at constant readout speed

To facilitate storage and repetitive reading of short-program coded tape, a cartridge case, containing mechanical drive and readout assemblies, has been fabricated. The drive transports the tape past a conventional pickup device during the reading function.

Austin, D. C.↗

Modified power tool rapidly drives series torque bolts

Feeder attachment, which fits on a standard power driver, drives a series of longitudinally attached torque bolts into place with great speed. It allows loading of a series of bolts and then positions individual bolts in the driving head for assembly. The attachment contains a socket gun which may be modified to accommodate different types and sizes of bolts.

Source record↗

Motion drive system is accurately controlled in the 1-micron range

Motion drive system has been developed for use with interferometers where accurate control of minuscule distance in the 1-micron range is of prime importance. The drive system is applicable to any device that requires extremely accurate positioning control.

Morecroft, J. H.↗